Beyond Higgs: The Wild Frontier of Particle Physics

[Music] good afternoon everybody you know we began the festival with a celebration of the hundredth anniversary of the confirmation of Einstein's general theory of relativity which was on the 29th May 29th and that moment in the history of science is a pivotal one a beautiful one because it really shows the optimum way for signs to progress we have a body of thinkers in this particular case it was design Stein himself but more generally it's a community of theoreticians who use mathematics to try to figure out some deep insight about the nature of reality but importantly that insight needs to come with predictions and those predictions then can inspire other physicists other astronomers or experimentalist to go out and try to confirm the prediction and see whether the mathematics is actually describing true aspects of reality now for Einstein it was a wonderful confluence of the mathematics and the technology necessary to check the mathematics because he wrote down his equation of the general theory of relativity in November of 1915 and the observations that confirmed his ideas happened in 1919 so just four years between the theory and the observation oftentimes in physics the timescales are longer the irritations will come up with the ideas perhaps they're difficult to test perhaps it will take building new equipment perhaps it will take in fact countries to come together to put their resources together to combine the resource in order to even be able to build the machines necessary to test these ideas and that is going to be part of what will drive our conversation here today but whereas Einsteins ideas and his confirmation was all about sort of looking up into the sky thinking about gravity thinking about big things the focus here will be on the other end of the spectrum for the most part thinking about small things particles because we have four you can really trace the history back thousands of years asked ourself the question what is stuff made of what are the fundamental ingredients and we have thought about this over the course really of many many centuries but that program of trying to figure out the basic ingredients of matter really picked up in the middle of the 20th century and it was a wonderful time where the theorists and the experimentalist really worked hand and glove back and forth playing off of each other and Steven Weinberg one of the great scientists of our era summarized the excitement in a really wonderful ways it was a time when graduate students would run through the halls of a physics building say they discovered another particle and it fit the theories and it was also exciting back and forth between the mathematical ideas that inspired the experimentalist to look for certain kinds of particles they find the particles come back the theorists would then update their equations with the new insights and back and forth it went and as this unfolding occurred there was one sticking point which is really going to be part of the focus of our conversation here today which is there was a very basic question why is it that these particles that were being found have heft have mass in essence if you had one of these particles fundamental particle in front of you it could be an electron it could be a cork whatever as you push on it where does its resistance to your push come from where does its hef where does its mass originate and a mathematical idea was put forward that we will discuss in the 1960s by Peter Higgs and other scientists as well and it was a strange idea to solve this conundrum because it required the universe to be filled with something that we physicists often referred to as a cosmic molasses some stuff that would be filling space moreover it came with the prediction that if you kind of banged on this molasses sufficiently in the right way you could sort of have a little Fleck that would come off and that little piece of the molasses would be a particle called the Higgs particle or the Higgs boson and on July 4th of 2012 if you weren't out celebrating and doing whatever we Americans do on Independence Day for actually paying attention to something some of us consider to be much more important you might have seen the following press conference if we combine the ZZ and gamma gamma this is what we get they line up extremely well and in the region of 125 GeV they combine to give us a combined significance of five standard deviations [Applause] [Music] so the emotional gentlemen taking off his glasses wiping his eyes you might guess that was of course Peter Higgs the gentleman whose mathematics was put forward in the 1960s and about half a century later was confirmed through the observation of this Higgs particle and of course this excited the world it was picked up by newspapers television shows around the world because this is again one of those iconic moments in the history of deep understanding but at the same time the discovery of exactly what we expected to find based upon the mathematics raised a certain kind of challenge which is what's next and that's what we are going to have a discussion about here today and we have some of the world's leading thinkers on these ideas of particle physics so let me now bring them out to you our first participant this afternoon as a theorist at the Institute for Advanced Study a member of the National Academy of Sciences he was an inaugural recipient of the breakthrough prize in fundamental physics please welcome Nima Carney Hamed [Applause] also joining us is an experimental high-energy particle physicist working on the Atlas detector at the Large Hadron Collider at CERN please welcome Monika Dunford all right finally please join me in welcoming the deputy director of research at the Fermi National Accelerator Laboratory he's a fellow of the American Physical Society and the American Association for the Advancement of science please welcome Joel Icahn I've known all you guys for many years probably known Joe the longest of all I think we probably go back 30 years but whoever wrote my little notes here probably didn't know that fact because they have told me that your name is pronounced lickin just like finger-licking good so so let's begin the discussion by just going way back for a moment way back to you know ancient Greece when there were thinkers who began to ask the question you know what is matter made of what is the stuff around the world made of and so we have this this fellow right here sanema who is this end and what role did he play in your mind this is mister Democritus apparently I don't know how we made it look like that but anyway but now Democritus is widely credited as being the person who suggested that the world is actually made up out of atoms that matter is made out of some fundamentally smallest building blocks and just tell us your view of that I think he's a single most over credited individual in human history because there's absolutely no evidence one way or the other whether this idea was right you know you're just sitting around in ancient Greece hey you think matter you know you keep cutting it up it goes all the way down forever I don't know yeah I do know I don't and you know there's absolutely no reason to believe either one either way the guy who said that it stops somewhere I he's famous for 2500 years let me ask you one thing though so we certainly tell our students and I think it's a real truism that asking the question is often oh yeah as important as finding the answer so perhaps maybe it's worth crediting him with at least thinking about the possibility that this is a worthwhile the question to investigate what you said it's true but I'm not historian of science I don't so so the idea that that he had of course was presumably you take a piece of matter and you start to sort of pound on it or cut it up in some we have an example here is Iraq and so what have we found in the past you know 2,000 years if we easily start the journey with Democritus yeah so I think a little over a hundred years ago I mean in the mid-1800s I guess chemists or back in the time when there was not such a distinction between the different physical sciences but anyway people started suspecting that there might be atoms that ultimately different kinds of material were made out of different sort of building blocks we have the system of the periodic table of elements and so on and already back then there are people who are skeptical that you were talking about these teeny teeny tiny things that no one can actually see but they're started to be more and more in direct evidence that atoms actually exist of course today we see them in various ways directly but that's where the sort of journey began that you know big hunks of matter are made out of molecules or in turn collections of atoms and atoms maybe you know a a 100 millionth of a centimeter across so it's a very it's it's it's very very very small but then the atoms themselves were built out of other constituents we have the electrons we all heard about in school that were around the nucleus of the atom the nucleus of the atom in turn is around a million times smaller than the size of the atom itself so these kind of pictures are not really to scale right the nucleus is around a million times smaller than the atom itself then we go into the nucleus we see that the nucleus is made out of particles like protons and neutrons which are now around 10 to the minus 14 centimeters big and around 56 years ago we started peering inside gradually these apparently elementary objects protons and neutrons that turned out not to be elementary at all and built out of still more point-like constituents so that's that's where the journey has been taking us young in this at least in this building blocks of matter perspective on what it is that we do and hopefully we'll come back and talk about some other perspectives on what it is that we actually do but anyway in this in this very fundamental aspect of what we do that's that's the journey that we've been on we're now at a distance around what we're probing at the largest experiments in the world like the large the largest accelerators in the world like the Large Hadron Collider are distances around a thousand times smaller than that a thousand times smaller than the nucleus of the atom and there's a lot of drama that has unfolded there and so Monica you know when we show a picture as we began there with whatever a sledgehammer smashing into rock it suggests the most brutish way of figuring out what's inside of Maddie just sort of smash it apart and see what the constituents it's like a five-year-old just smashing things together to see what's in there is that what we do at the Large Hadron Collider or would a more refined way be to make you say of equals mc-squared sort of the most famous of all formula so you know are we using energy to create stuff or we just sort of smashing things to bids I think pretty much it's one of the same I think it's just a question of whether or not you want to speak elegantly or or not so yes I mean in essence what we do is we take two things and we smash them together and what we want out of that of course there's a lot of energy right and at any collision you want a lot of energy and as Einstein says energy is equal to matter and so therefore we can produce heavy things and that's our goal but but a key part of them the point which I probably didn't say clearly was if you only are smashing things you're only gonna find the stuff that was literally there whereas that's not quite what we don't exactly know that is absolutely not what we do it's sort of like it would be more as if you took two let's say cheap cars and you smash and you got yourself a Ferrari right that would be more the equivalent of what we're doing I mean it's you're really creating something new out of what you had and what you had is is now no longer and you've got this you know elegant it's hard to find status symbol that you're really looking for so that that is more along the lines of what we do so so from that way of looking at things energy is sort of the the basic currency from which you can buy the status symbol energy is money in our case right so the more energy you have the more options you have for the things that you can buy or we get off this metaphor which perhaps is a good idea the greater the mass of the particles that you're able to create through these collisions so the idea behind any sort of what we would call frontier Collider is that it needs to be as energetic as you can as you can by really literally give me we want a big you want it powerful you want tons of particles you want tons of energy you just you want it all so what's our the most powerful Collider of that sort that we have today I gather is very large work so and and so give us some sense of what it can do and the energy that it has and so on so the Large Hadron Collider yeah it's in a tunnel it's about 27 kilometers located near Geneva Switzerland and probably some of the most expensive real estate in the world so probably in future colliders Wow you wouldn't have designs what's it in Switzerland now let's say but it's where we have it and the idea is you've got two protons that are running around in this ring in opposite direction they're being celebrated by superconducting magnets they are you know getting to very very high energies energy is currency here so the higher the better this one runs about 13 TV soon to be 14 and then you collide them together you have a tremendous amount of energy in that collision and you basically build this gigantic detector we have four two such detectors you build these gigantic detectors around that collision point you know the Atlas detector which is a sector that I work on is a five-story building so it's humongous and that basically takes a snapshot of the collision and the collision is messy it's not like you know a couple of particles here or there right I mean it's how many protons are in these these bunches that are slams I mean the protons you have you have many many protons in a bunch so the button the beam is it's not a continuous beam as you might think it's not like a stream of protons that are coming in the beam is designed such that you have like little packets of protons you know well 10 to the 11 around and you have these little packets of protons and they're kind of colliding every 25 nanoseconds which means that it's like your camera your detectors a camera and it's taking pictures every 25 nanoseconds so 40 megahertz speed and these collisions are so big and are happening so often that we actually cannot record all of the data and we have to make a very difficult decision quickly within a microsecond about whether or not this event is interesting or not and this is a very challenging thing for us experimentally because if you know NEMA comes to me a year from now and he says oh you know what I think I saw a new signature would be something totally different and it would have looked like this and if my trigger system that system that makes that decision wasn't looking for that yeah or couldn't the data's lost I didn't record it so I can't go back to the data and say oh I can look for that so theory really guides the experimental approach it's not as though you approach it as a blank slate and say let's slam these things together and just see what happens well it's it's absolutely and it's also a very difficult challenge experimentally because in one hand you need to be ready for everything your detector cannot record everything so you can't take everything so you want to be ready for everything however you need to have made a decision so you need to sort of have some sort of idea about what you're looking for and to get that idea of what we're looking for then yes of course we rely heavily on theory and tell us that because otherwise done you know you're at sea we're at sea you're absolutely at sea so Joe you of course also have spent your career working at a facility that undertakes these kinds of experiments as well Fermilab and over the course of decades both through Collider experiments but also through other kinds of experiments that we won't go into any detail in cosmic ray experiments and other things of that sort we have built up what we think may be the fundamental ingredients making a at least the stuff that we interact with in an everyday sense and that's the standard model of particle physics so I just wanted to go through the particles that were predicted and ultimately found giving us our most complete understanding to date of what things are made of so it's in the early days of looking for particles maybe just sort of take us through sure some of these particles here so that's that's a familiar one electrons everybody those electrons everybody knows photons the muon was an example of a particle that wasn't predicted but was discovered and we still don't know why they exist but they are also fundamental particles similar to electrons neutrinos even stranger there we know they exist but they're they're very different from the particles that you're made out of but that's one of the things we're still trying to figure out and they what they have no electric they don't have any electric charge they're very difficult to detect and and they're very very different from from other particles quarks american murray gell-mann who just recently passed away invented the the idea of quarks you are made out of actually only three of these particles the electron and two of those quarks the up and down U and D courts that's what all of leave that's what all of you are made out of it but there are more quarks there's the strange quark you see there was discovered later and charm quarks bottom quarks top quarks were discovered at my laboratory Fermilab we're very proud of them and what year was that that was in 1997 with the what was then the world's biggest particle collider the the Tevatron before the LHC and we don't know why there are so many of these elementary particles as you there's way more than you need to make us so that's one of the things that's still a big mystery and we don't know why they're so different from each other we have some ideas for that but it's it's part of the the big mystery of this whole picture of the standard model is is why is it so complicated in some sense and also why is it so simple there are simple principles that hold it together so so we see here two collections of particles if you will the ones on the green you know in the far right hand sides are distinct you know in a fundamental way from those on the left-hand side you just draw that this thing yeah so the particles that you are made out of are called fermions since when we talk about matter particles matter particles are fermions and and they're one of the ways of distinguishing them is that they they carry a little unit of spin which is not really spinning around like balls cuz they're point-like particles but they carry a little bit of spin like angular momentum so you're made out of fermions on the other hand the forces that hold you together and hold the universe together are carried by these bosons these green particles of which the photon is the most obvious example for electromagnetism but the gluon and the w and z also carry fundamental forces of nature and those are particles that have a different spin they have spin that's actually twice that the unit of what fermions heaven they're called bosons and they behave very differently they behave like forces instead of behaving like matter now nema so when we actually begin to look at the mathematics behind this one of the curious features that people recognize even before the theory was fully in place was that it was challenging to give mass to these particles and it's challenging to describe why it was difficult to give mass to these particles I'm gonna ask you to try to do it oh okay yeah good it's actually it's actually it's actually a piece of cake in fact what what we're about to talk about is a very large part of the conceptual drama of the 20th century in fundamental physics and we're just gonna have to count on our fingers a a little bit so um maybe before getting to it I just want to make one just general comment about this this picture is that you might um and it's echoing something that it's been said a couple of times already on the one hand it looks a little bit complicated it's not the most complicated thing you could imagine but there's there's many particles and it seems a little haphazard and random perhaps but one of the aspects of our of our subject think that the the deepest aspect of our of our subject is that all of these things are somehow completely governed and there are their properties the broad properties are almost entirely dictated by big general principles these these two revolution principles in the earlier that we learned in the early part of the 20th century of the laws of relativity and of quantum mechanics it turns out that these laws are almost incompatible with each other there's not at all remotely obvious that you could come up even with you know toy universes that were compatible the principles of relativity and of quantum mechanics but you just barely can and if you a hand sufficiently competent theoretical physicists these laws and lock them up in a room and refused to let them look outside and just say what could you come up with that's conceivably consistent with these principles then this is the kind of thing that that comes out in a sense out of pure thought once you put in of course these two big facts that we've observed experimentally that relativity and quantum mechanics are both true and a very big aspect of this and a very big reason why it's so constrained is exactly this business about the difference between being massive and being massless so let me try to describe this we just talked about the photon and as Joe mentioned one of the properties of the photon has is it has a little spin if you're familiar from just thinking about light as a wave sort of classically is an electromagnetic wave sometimes we talk about it having polarization okay it can spin around one way it could spin around the other way well what's really going on the underlying photons that make up a light to have a little spin so they can spin either in the directions they're moving or opposite to the direction they're moving and this is a crucial fact that they can spin in two directions now the other particles like the W and Z particles there are sort of massive cousins of the photon but the mass is not a tiny correction you see if you're very naive you would think especially when we go to these huge accelerators we smash particles into each other at incredibly high energies surely when the energies are enormous you can kind of ignore their mass so that the e is so much bigger than the M so that you could really just basically ignore the mass and you can and get incredibly high energies you can think of the masses a little tiny perturbation and just talk about massless particles but it's not true it's not true because massive particles that have spin one that that I've spin twice to spend of the electron we say it's spin one like the W Mzee they have three ways that they can spin while the photon has to and what's this difference between this 3 and this 2 it's no matter how quickly this W particle let's say is moving around you can always catch up with it you can always move and catch up with it let's say it was spinning up this way well by tilting your head you could see it spinning that way or the other way as well catch up with it because massive exactly exactly that's right that's the crucial point because it's massive no matter how quickly it's moving it's not moving at the speed of light and so you can catch up with it whereas the massless particle like the photon is moving zipping around at the speed of light you cannot catch up with it and therefore you can't play this game where you tilt your head and see it the spin in every possible in all of the three possible directions in fact all you can do is conclude that it's either spinning in the direction that it's moving in or opposite to the direction that it's moving in this to not equal to three business is really profound it means that you can't think of mass as just a little correction the things that are massless already and in fact precisely because of this point if you attempt to describe the the possible composition types and interactions of massless particles then it's essentially a mathematical theorem it follows from the again the following from the general physical facts about the presence of both relativity and quantum mechanics but the types and interactions of massless particles that you're allowed to have have to come in a minuscule variety okay so the menu of particles that you're allowed to have that can interact in a way compatible with the principles of relativity and quantum mechanics are the following the particles can have spin zero one-half that's the unit that the electron has it's just a convention so one three-halves and two that's it that's all you can have furthermore there can only be one of those massless spin-2 particles so we're not going to talk about it much today but you can only have one of them and if you study its properties that are sort of forced on you by relativity in quantum mechanics you would find that it makes massive particles go around in orbits and so on it's gravity okay and then all the properties are sort of dictated by these basic principles of Einstein's special theory of relativity and of quantum mechanics then the spin zero particles okay you can have as many of them as you like to spend a half you can have as many as you like the massless spin-1 particles have two very special properties and interact with each other in very special ways you can have massive spend three have particles they have to be even more special we might come to that later and as I said the massless spin-2 are are associated with gravity so that's it there's a sort of tiny menu of possibilities that you're allowed to have and nature is making use of that menu as far as we can tell so we've seen of the set of possibilities before July 4th 2012 we had seen nature make use of some of these possibilities it had used particles of spin 1/2 particles of spin 1 and of course this has been - associated with with the gravity one of the most exciting and important things about the Higgs is it's the first example of an elementary particle that has no spin at all that we've that we've ever seen so that's been added to the that's been added to the to the mix but the reason why the Higgs had to be there is that something has to account for this - not equals to 3 business ok something has got to explain where mass comes from not just not merely to add this number of the actual mass of the particle but to account for this extra stuff this extra spin ways that the the extra ways that things can spin when you give spinning particles a mass and that's the entire story of the Higgs is to account for that for the for the for the origin of these extra degrees of freedom they did quite a piece of cake yeah but it's all just about counting it really is all just about this - not equals 2 or 3 business so with that as it preamble to the motivation that you had to have something fundamentally new added to the story Monica can you take us back to the 1960s when Peter Higgs and others who shared the Nobel Prize with him as well and glare and so on what was the approach that Peter Higgs took to add this crucial profound new ingredient that would fix up the two not equal to three puzzle that Nia articulated well so Peter Higgs postulated the Higgs particle and well I wasn't there in the 60s so I can't really tell you a whole lot about exactly what was going on when that was but it was it was a pretty revolutionary idea you know it was we were stuck in the sixties this point where we needed to you know you you you had suddenly in the sixties this this huge explosion of particles right suddenly I mean the 60s was this period where it was like every week essentially new particles were being we were being discovered and not not maybe elementary particles like quarks and and you know muons but more like we were seeing mesons which are combinations of two quarks or hadrons which are combinations of three and you know every week and so suddenly our kind of picture of what the world was went from very small you know what what made us up to a whole fleet of particles it didn't really seem to fit into anything we didn't really meet them what why why do we have a while suddenly all of these extra particles and certainly you know how do they all fit together you know what's the bigger picture and then also as you said what gives them mass and so Higgs was you know part of that which was sort of to say well postulated that there was the actual and what was unique about his paper was that he postulated that there was the actual Higgs particle yeah and that it could be something that we could then discover and detect so tell us about so the Higgs particles that keep part story tell us also about the higgs field which ultimately is a key part of getting a sense of how particles acquire mass in this dimension this phrase cosmic molasses I think this is good a way of picturing it as anything else but it's really a daring idea right you're saying that all of space all the whole universe is filled with this cosmic molasses whose effect is to give the particles that were made out of another particles mass so that's a really daring idea and and in fact Higgs original paper on this was rejected for publication it was considered a little bit a little scene right here again so these are the dots here meant to be the molasses that you're referring to and then one of these particles is meant to be masses like the photon I guess and the bottom one is meant to be massive so what's happening to the guy in the bottom so if if you're an electron and you're moving through the molasses you'd like to move at the speed of light like a photon and the only thing that stops you is the fact that there is a Higgs field everywhere and and you can't avoid it on the other hand for the photon the photon is not interacting least directly with with the Higgs field and so it does if through the speed of light and that's the difference between those particles so so for this crazy sounding idea to be true we'd have to accept that empty space is not empty and it's not even a quantum mechanical notion of fluctuating fields that people may have heard of this is just there's actually a something there permeating all of space obviously it's invisible because we don't see it's tasteless right like when I move my hand am i touching it in some sense you you are interacting with it all the time because part of the resistance I feel as I try to move my hand would be the electrons and the quarks in some sense moving against this molasses so it's it's a far-out idea he puts forward this paper and it gets as you say rejected yes now many of us if we have a paper rejected we kind of back off this is not what Higgs did right he actually went around and lectured on this and crosslet eyes and discussed this and ultimately I'm you know I've said it before but when I was a graduate student and first learned about these ideas the class that I took the professor taught it with such certainty that I had no idea that the Higgs was a hypothetical idea there was a time in our community by probably the mid 80s early 90s it was almost a foregone conclusion that this crazy mathematical idea from the 60s which had now somehow permeated the consciousness of particle theorists around the world that it was it was right but still you gotta you gotta try to confirm it so we start to look for it through these kinds of collisions so mark I guess you were you were were you were there when this was actually happening so what was it like and what exactly were you looking for in those collisions well in the beginning it was very intense I mean at first when we first turned on the accelerator we weren't really thinking about the Higgs right then we were thinking about my god please let it work you know I mean it was it was 15 years to build this detector you're working on collaborations that are you know 3,000 people the days leading up to the start of the beam no one was sleeping and so forth and so I think in the beginning you were more concerned with the technical challenge and the Higgs was sort of a far-off dream and we certainly at that time when we first turned on the accelerator and and also you know just collecting up the data you know we you've got a brand new detector it's five stories tall it involves you know millions of electronics channels that all need to be understood and calibrated and so forth and the Higgs I remember people always to say what are you gonna discover the Higgs theorists you know like Nemo would tell anyone when he gonna discover it and I was like you know give me give me five years you know I've got to discover I've got to figure out this detector we've got to collect enough data and I think for us we were really amazed may be very happy with ourselves at how fast the discovery was made actually I mean we were not no one was predicting that we would have discovered the Higgs in 2012 particularly nice it did it was it was it was very nice spot for us it's very easy well you say spot you mean it's mass presumably it's mass and and therefore because of its mass it has many it has the maximal possible ways in which it came decay the Higgs do you find it so so you smash these protons together what happens matches protons together you get a lot of energy and in that energy you produce your Ferrari which is your Higgs yep the Higgs then decays it falls apart it falls apart not exactly a Ferrari yeah well the Higgs Higgs falls apart and you know and it Hicks will fall apart too it prefers to couple the mass which means that it prefers to fall apart to the heaviest things that can that it can so depending on the Higgs mass if the Higgs is extremely massive then it will prefer to follow it apart to two top quarks if it's at 125 which is where it's at 125 times the mass of the proton exactly 100 25 times the mass of the proton then it falls apart then it can fall apart and a whole bunch of things which is in essence an experimental dream right right because it means that it can fall apart to Z bosons and you can look for for the decay of the two Z's it can fall apart to two photons it can fall apart to two W bosons and so you have a variety of different ways experimentally you can test and that for us was really key because it allowed us to be able to to say okay I looked in to I looked at the decay of the Higgs to two Z's I see exactly where it should be I looked at the decay of Higgs to two WS I see exactly where it should be because from an experimental perspective we don't actually measure the Higgs right never measure the Higgs so all we knew at that time was we had measured something new whether or not it was the actual Higgs boson we then had to compare the rate of decay to two Z's the rate of decay to two w's of which the theory once you know it's mass is predicted exactly so if you if there's an announcement in like July 4th when did you know that you had or when were you fairly certain that you had it is it is it months before is it six months before the day before I mean you I mean statistics is such that you know we were collecting data and and if you if you see some sort of statistical signal you should expect that it's more and more data you know the size of the Signet of the size of your you know Higgs peak let's say it starts growing and growing and growing yeah but that's not actually usually how we ecstatic we usually get it in chunks even though the accelerator is kind of working continuously over the day you know we have to calibrate our detector and we we tend to data just kind of comes to us in chunks well do this calibration try to understand it okay that's trunk' will do this calibration and that's kind of chunk B so we're kind of looking at it kind of in chunks at a time and because a false discovery is worse than death let's let's put it that way death would be better so a false discovery is yes you're gonna do anything anything we we oftentimes do is we blind the data from ourselves right so we will we will do the entire analysis chain where we have and we can do blinding and a variety of different what there's several strategies but what means is either we withhold from looking at a particular data or we screw with the data such that we can't actually get the right answer and we so we make sure that everything is correct our calibrations our analysis selection so forth and so on and then we unblind and it's extremely stressful that moment when you get the you get it's a collaboration of 3,000 people and then they agreed unblind and you you know someone hits the you've got a computer program someone starts it you know you're watching the data being processed watching it being process to get the plots is it there is it not is it there is it not I mean so it's in that sense it was semi instantaneous and and now that you have the Higgs and we're gonna now turn to the question of like going beyond this this major discovery you or actually at the World Science Festival about I think was 10 10 years ago having a conversation prior to the discovery of the Higgs and I thought I'd just show you a little little clip from that if you don't mind so can you just run that that little the worst scenario as far as I'm concerned would be that the LHC sort of completes the standard model and and doesn't do anything more so in the standard model as it stands we need this cosmic molasses that was mentioned we don't know what it's made out of the simplest idea is that it's made out of one new particle is so-called Higgs particle and that could be true and then you've accounted for the missing ingredient of the standard model and that would be it and that would be horrifying Monica well I think there's there's pretty much two scenarios where I would end up at McDonald's and that is that if we discover the Higgs and Higgs only which is Frank's worst case scenario and also mine so far every Collider experiment we have is really you know has predicted this and we measure it its predicts animal predicts this and we've measured it animal and so success is our curse yeah a success is our curse exactly and and so I think from the experimental perspective we're really sick of the standard model so just continue to measure the standard model which would be a Higgs and Higgs only scenario would be frustrating so so you said there's a scenario you'd wind up at McDonald's you're not at McDonald's so I'm assuming that in the second part of our discussion so let's let's think about how we go beyond and how we've tried to go beyond these ideas and to sort of start that discussion you know nimi you pointed out that the standard model has a sensible simplicity and complexity sort of depending on how you look at it and we were looking at it just graphically with the particles arranged a nice little rows and columns if you actually look at the equations underlying the standard model of particle physics you just like write them all out this is what the equation looks like which certainly has a sense of complexity associated with it it's sort of hard to imagine that you know after you know certain number of days and nights the Lord simply said let there be the standard model Lagrangian you know so now you can also tell me this is misleading because this is the most naive way of writing out the equations and what we have found over the course of many decades is that symmetry is sort of an important way of being able to repackage our understanding in a way that really simplifies and allows us to shine a light going forward so Jo can you say a little bit about symmetry sure and and and and how for instance it helps us to understand this better and illuminates the path going forward yeah so it's symmetry of course is something we're familiar with in everyday life snowflakes of interesting symmetries a diamond is a good example of symmetry in physics you know what's the difference between a diamond and the graphite in the pencil they're both made out of carbon but the difference is that diamond is in a beautiful crystal lattice symmetry and that's what gives diamonds its special properties and so symmetry in in the physics world it it's controls the physics properties of the things that you're talking about this happens in the subatomic world as well and and and what we're talking about symmetry in the standard model we're actually talking about principles that control how the standard model works and actually make it much simpler than it could otherwise have been and that's why those complicated equations can actually be expressed almost in words in terms of a few symmetry principles in fact you can even use that simile chics to put those equations on a coffee exactly as has their job I think it's worth it's worth really stressing that these it's a kind of an unusual sort of symmetry that we're talking there are some important differences we don't have time to really get into it but but this very simplicity and the fact that there's a certain kind of symmetry that is useful for theorists to describe the physics has everything to do with this - not equal to three BS absolutely everything to do with the fact that we're only allowed this tiny menu of elementary particles when they're massless and that that mass is a big is a big perturbation so yes trying to describe massless particles which we think we should be doing in some approximation when we go to very high energies that's what forces you to do these incredibly simple compacts looking formulas and these formulas are really directly reflecting the underlying principles of space-time and quantum mechanics that govern everything so so it's there's there's not very there's no real veil between these these remarkable simple formulas and these grand underlying principles of 20th century physics and to draw the connection to two Higgs and others who were working along the same lines in the 60s one way of describing what they found was a powerful way of including mass in a manner that didn't spoil the beautiful underlying symmetry in fact I would say that I mean that there isn't this molasses analogy is it's probably the sort of best the metaphorical analogy that when when one can use it raises various questions that probably occur to you if you're a kid in the audience you know is this like the ether all over again you know physicists don't learn anything they're so dumb you know they didn't do not have the ether yeah the ether hundred years ago and it's gone now all we can say is that this is something but it's not like the ether it sounds like either but it's not like either and but I suspect the most fundamental way of saying what the Higgs is about the way that you know people will still be talking about in two or three hundred years after maybe robots have come up with better metaphors and analogies is that is sort of precisely what what Brian just said the world of massless particles is completely prescribed and sort of fixed by general principles of space-time and quantum mechanics the world around us appears to have massive particles in it and so you have to somehow take the stuff that you see that slow and massive and low energies and as you collide them at higher and higher energies be able to continuously interpolate to a to a world with massless elementary particles smashing into each other at very high energies and if you if you just finish this counting that we talked about you went through it a little bit more detail you would find that there's you just can't do it with the elementary particles that we knew of before the Higgs you just have to have something else in order to be able to take massive low-energy particles and interpolate them to massless high-energy ones the incredible thing and this is part of the sort of cognitive dissonance and the real irony about the Higgs you just described it for example is something people knew ought to be there for 50 years you know so that's like it's very amazing that people predicted it but it's sort of boring that it's the thing that we expected all along but it's in fact something it's actually quite shocking well welcome to come to it later in the discussion it's quite shocking that all it took was one stinking little elementary particle just one extra thing was needed to allow us to be able to interpolate smoothly and continuously between this world of massive particles at low energies and this very sharply prescribed world of massless particles at very high energies and it's shocking that it was so simple that's the that's the irony about the Higgs that we all come to it is that nowhere else in physics when this rough type of phenomenon happened did anything remotely as simple as the Higgs happen and it's a it's a feature of the of an a mysterious feature of our world that the simplest possible answer ended up being wrong so along those lines you know as we've tried to push our understanding of the world further using this idea of symmetry particles that in some sense are the different tips of the snowflake to use Joe's metaphor that can kind of be rotated into each they're in some sort of abstract sense we have come upon other symmetries mostly from mathematical studies not really from observations of the world and the most prominent among those is supersymmetry so can you tell us a bit about supersymmetry and what it implies for what we should find out there in the real world if nature abides by this particular symmetry so supersymmetry is actually an idea that relates not the tips of the snowflake but it actually relates the kinds of particles that we said we were made out of these fermions of matter particles to the bosons like the particles that carry forces so so that's a found like a very profound relationship and it is a very profound relationship it was first noticed by a bunch of physicists in the 1970s and immediately got the whole community that we belong to excited because it sounds like it's a it's a theoretical breakthrough it also makes predictions it predicts a bunch of new particles now the way you framed it let me just say the way you framed it was it takes the particles that make us up and it relates us to the particles say that and make up light like the photon yeah that sounds very economical yes it's it's not quite as economical as you might have thought because for example the electrons you have in your body are related to a boson and supersymmetry but it's not the photon and it's not any of the other bosons you showed on your chart it would be a new particle we call it this electron in fact I think you see it up that hasn't been discovered yet yeah so it's in that sense it doesn't sound economical because it's postulating a whole bunch of new particles that nobody had seen on the other hand there's historical analogy for why this might be reasonable which goes back to what Nima was talking about was the early days of quantum mechanics when we're trying to understand how quantum mechanics can be made compatible with relativity and as Nima said that that is a very very difficult mathematical understanding which was part of it was first put together by Paul Dirac one of the great Giants of our field and he found in making that work it just in the mathematical basis that that predicted also a bunch of new particles what we now call antimatter anti particles which also seems pretty out there and in fact direct it took him a long time to convince himself that this Eve was reasonable but he was right and in fact he was super lucky because the first antiparticles discovered about a year after his his prediction came out we now know that antiparticles exists we can make them and they're part of our standard model so in some sense supersymmetry is if you like the next phase of that it's saying yes there's anti particles and then there should also be these superpartner particles and you just have to go out and find them so so well so let me just make sure we have the full playing field so the idea then is we see a pattern playing itself out over the course of the last 100 if not more years where you invoke some notion of symmetry embodied in mathematics and make some statement about the world you resisted at first because it's something I haven't yet seen but then you go out and you look for it and you happen to find it in fact there's a beautiful quote I think it's Steven Weinberg where he said the problem with steers is that not that we don't take our equations seriously enough is that it's not that we take them too seriously that we don't take them seriously enough yeah good we have it right here and and and so if you sort of take this to heart it does suggest that if there's just beautiful new symmetry then as you say seems to in some sense be the final symmetry that you could ever invoke because it puts sort of everything together there's a strong mathematical motivation to look for all those particles you know that this symmetry implies but that I mean how do you then make the argument to the governments and the funding agencies right because this is not a small undertaking right I mean this is part of the motivation for the Large Hadron Collider as well as with the Higgs how much does that machine did that machine cost what was the cost of the LHC in the end I mean it's it's hard to do you remember them what's the final number of the LHC it's you know it's billions of dollars number two to quantify I mean because in that number you have you know like my salary and Joe's salary you know I'm sure it's a very small fraction out to 12 billion but you know yeah it was but you know I think that's the time that the LHC was built was was a very unique time in particle physics and it's exactly like it's a unique time like we're at right now so there's a great symmetry between you know the start at the LHC and the start of what's going to happen next which was you know we had a tremendous amount of evidence is the wrong word but we had a tremendous amount of consensus that there was going that we would discover something at this energy this energy is very unique to the standard model so the energy at which the LHC can probe let's say the energy of particles at the LHC has is has enough to produce is it's a very key energy to the theory itself and so if you expected supersymmetry to appear you would have expected it to appear at the LHC energy did you did you expect it in fact I'd like to ask all three of you because there's a lot of rewriting I find of history post facto that happens and we're just a small group of friends intimate gathering here I mean how many of you really would have argued and thought that supersymmetry those other particles that we saw briefly on the right-hand side of the screen would be found by now at the Large Hadron Collider nema I mean what did you well I I think and then look over yes or no here just so I can like actually because it's not just about supersymmetry yes there is an intent only something will we'll come to in a second there's a sort of whole paradigm yes that goes around the existence of the Higgs particle how strange it is how bizarre would be to have the Higgs is a lonely beast accompanied by anything else that's something even when we've seen roughly this kind of phenomenon elsewhere in physics before we've never seen something like that for very good theoretical reasons that perhaps will become too so there's a whole sort of paradigm built around what it would take to see something like the Higgs particle yeah and it's that whole pursue per symmetry being the sort of best developed a version of and most concrete and and and and well put-together version of that paradigm and by the way it's not broadly the idea of supersymmetry I mean the as it's been said a couple of times supersymmetry is just the very last thing nature can do compatible with its grand principles that we've not yet seen it do yeah and but this is at the level of massless particles right however there is mass in nature and so so we have to go to high enough energies where where we see all the relevant particles in order to be able to see the asymmetry from that point of view supersymmetry could show up you know anywhere it'll be relevant for nature but there's a specific problem associated with the Higgs particle which we'll talk about more in fact we can do it right now well yeah so I think the all the drama about about the Higgs and has to do with this with this with this basic fact for all the other elementary particles there's a difference between them being massless and being massive so for example if you ask the question why is the photon massless in this kind of in this analogy you imagine that that that space is filled with these violent quantum mechanical fluctuations that are that are going on everywhere while the photon is zipping through this this kind of medium why isn't it begging into all this crap all the time and and picking up some inertia just like the kind of molasses picture that we going on all over the place right you know there and those quantum mechanical fluctuations get more and more violent as you go to shorter and shorter distances higher and higher energies because of the Heisenberg uncertainty principle so why does the photon sort of impervious to this go zipping through through through space at the speed of light and the reason is that two is not equal to three okay because if the photon did have a mass if it's somehow picked up a mass with all these interactions that's not you can't be a little bit massive it's like being a little bit pregnant it's not possible right those those extra than the extra way that it can span has got to come from somewhere and that's the deep reason why particles that have spin like the photon of the graviton electron everything else there's a good understanding for why they could be massless in some approximation you've got to do something to them to make the masses here okay and and that's something has everything to do with the Higgs that's the huge irony is that the thing that solves the that gives us the understanding for why all the other things can be consistently massive and there's a good reason why the mass of all the elementary particles is pegged to the scale associated with the Higgs we don't understand why the Higgs itself has them as kin has it mass or what could be massless in some approximation because the Higgs has no as spin zero that's that's the strange thing about it's a simplest elementary particle we've ever seen it has no spin no charge no kind of properties of any sort other than having a mass and the difficulty is that unlike photons for which massless guy has been as two degrees of freedom massive has three the Higgs has spin zero and one is equal to one there's no difference between the the the number of ways namely none that a massless or a massive Higgs particle can have and therefore the Higgs is zipping through this complicated quantum mechanical vacuum there's absolutely no reason why its interactions with all the this virtual crap couldn't give it a huge inertia and in fact if you do a simple back of the envelope estimate for where the Higgs should end up it would be orders and orders and orders of magnitude more massive than then naively then then then we've actually seen it to be so you need some explanation for why the Higgs didn't pick up a lot of mass going through all this flux exactly and and and and it's really important to stress this point it's not inconsistent for it not to do so we can perfectly do in fact we've done it right Higgs did it before ever having thought about any of these things but when you think about it more deeply you would not expect the Higgs to be right and in fact nowhere else in physics where similar phenomenon have shown up has something like the Higgs ever been seen or ever been been in something as simple as the Higgs been the correct explanation so if there is a mechanism if there's a reason that we can we can understand that shows up right around as has happened for 400 years in the history of physics where to find him explanation for a phenomenon that that takes place in some at some scale you don't have to look at what's going on you know 500 million times smaller than that scale and that's a sure opposite of right around the scale of the mystery itself if that mystery if the if the origin of the mass of the Higgs was explainable in that way that which has been the trajectory we've been on for centuries essentially the reductionist paradigm if the reductionist paradigm that we've been on for a century is it holds the way it has before then we would have expected to see something come along with the Higgs it's like I've used this analogy many people use this analogy the sort of difficulty is like walking into a room and seeing a pencil standing on its tip and it's not inconsistent it's perfectly allowed for a pencil to stand on its tip and it's okay it's not violating the laws of physics but if you saw it you would probably try to find an explanation right maybe it's hanging from a string right there's a string hang from the ceiling maybe you look there's a little hand holding it up right you need to find some mechanism to explain it and it's that mechanism a supersymmetry and the other ideas that people have talked about for it for decades were trying to look for a hand holding it up so just to give a quick summary so the idea is supersymmetry provides an approach that at least on paper allows the mass of the Higgs to stay relatively small like ten or a hundred times the mass of the proton but not billions and trillions of time for NASA it's very much related to what to how we were just talking about what what supersymmetry is about you see supersymmetry relates particles a different spin and and and if the particles have a spin we have no difficulty understanding their mass that's just what we have to do so by relating something that has no spin to something that does you we get to inherit the clean understanding we have so all of this gives some confidence even if you're not willing to say it directly but give some confidence that we thought that supersymmetry was going to be found I mean Joe did you I mean just to show frustrated yes is at least in the simplest version of using supersymmetry to do this job you can actually deal calculation that says the Higgs boson can't be heavier than a certain amount and that amount was calculations actually done by my colleague Marcela Karina who you saw in the clip there it and that the answer was a hundred and thirty in these units that we've been using so when we found the Higgs at 125 in those units it's like okay the supersymmetry must be right but it's right on the corner right but it's been a really big corner so far so as we turn the corner we have found what happens on nothing we find right I mean certainly from the experimental community it was a pretty heavy romance with supersymmetry much more be honest because I mean from the experimental perspective it was the experimentalist dream I mean it was gonna be one new particle for every particle that we already have right I mean I remember when I showed up at the LHC and I was it's just very young postdoc at that time and I was working on the trigger system so the system that you know helps us keep events versus rejecting them and I remember you know senior physicists coming up to me and saying like you know you got to be really careful supersymmetry is gonna is gonna overload the trigger and I remember thinking myself like yeah I'm happy with that problem you know like I'm okay with that but that was kind of the feeling was that that that you know that this age of discovery was it was gonna be this age of discovery again and I think that we you know I agree with you that I think many people you know there were many problems with supersymmetry you know that were but we didn't want to hear it at the time but even it's not just experimentalist of course I mean I haven't done a calculation of it but a significant fraction of every single paper I've ever written has supersymmetry at its core the assumption that these ideas deep theoretical idea it's a very deep theoretical mathematical idea which is driven even mathematical discovery not even just just discoveries or non discoveries in physics but the bottom line is here we are sitting in 2019 we built this massive machine in Geneva it found the one thing that we were really certain about the Higgs particle and it has not found the other particles that we thought would come along for the party because they're so as you've articulated directly related to the Higgs as well as the record added to this deep idea of symmetry so the question is what do we do from here and we can continue to follow our mathematics as we will do but in the end of the day we're going to need data and we have to convince people to build new machine so can you give us a sense of where we are on the frontier of building new machines that will have higher energy be able to probe yet other domains and perhaps maybe these supersymmetric particles are there they're just heavier so what's going on and that's in that space so there is let's say a roadmap right now but I think there's no there's no money yet let's say in part of this and there's two projects that let's say if money was not a question what would we do in particle physics well we would build two things we'd build two new accelerators one of which is would be a linear collider Japan has expressed a lot of interest in building such a Collider and hosting such a Collider let's say and this would be where you instead of colliding electrons and protons you would be colliding sorry instead of writing colliding protons you'd be colliding electrons and positrons it's a it's a linear machine so you've got extremely long and you basically collide them into each other and why is it good idea to do those particle as opposed to proton so they vanish'd electrons is that their point like and therefore they're just clean the problem is when you take two protons and you smash them together you you what you're doing actually is you're smashing two quarks from inside those protons but the actual how much energy those quarks have inside the proton is very difficult to model and then on top of that you've got the rest of the proton that breaks up and it just leaves if you look at pictures I think we have some pictures of what a collision looks like for example and in one of the detectors you'll see there's just huge amounts of particles coming out and we see here like what you see here so here in this event you actually only have two particles that you're actually interested in this would be kind of what you kind of see with these these big red blue clusters of energy those would be the two particles that you're interested in and music tracks and these are all green is all tracks of particles and so forth and so on and most of this is just crap from from that's actually that is the 10th week we use that a lot of publications yes yeah so you know that's just the crap that comes in in an electron positron collision everything's clean you don't have this breakup of the of the and you know exactly what the electron energy is so from a precision measurement perspective its superior absolutely superior however if you want to really go high energies then you've got to go protons protons are what gives you your power in terms of the energy aspect and so in addition to a linear collider in in the ideal world it's what we would have so we'd have an ideal Clutton linear collider to really measure her top and Higgs extremely precisely and then in the ideal world we would have another Hadron Collider which was you know the well the next generation the FCC future circular Collider or there's a where might that be and that would be at CERN this is a picture of what it looks like it's actually very it would be a hundred kilometer ring and we just pointed out it's clear up there but disappointed the LHC is a smaller ring here and what's actually interesting about the circular collider is that God apparently put mountain ranges exactly perfectly such that you could build such a tunnel I'd would have to go underneath Lake Geneva and it would it would just pass right before the Alps pass right before the celeb coming back so it's just perfect going under the lake is actually not a problem everyone will always ask about going underneath the lake but you know the thing about a lake because I always worried that it's gonna be a leak you know think about a lake is that there's never a leak in the lake because if there was you wouldn't have a lake so going underneath underneath the lake is no problem but but it is a problem in the sense that you do have mountains and mountains lead to a lot of water drain so the energy scale of that machine so this would be hundred kilometres and I thought yes a hundred TV machine it's roughly not quite but maybe eight times eight times what we have now the LHC here was 14 and then you had the temperature on which was which was lower and so this would be your real discovery machine right which would be go out to to 100 TeV and you would you know be head again it would be proton proton Joe let me ask you a question just so we have those numbers up there so NEMA was describing how the energy scale that the Higgs was at and supersymmetry in its most conventional formulation it all seemed to come together it was all happening at the right energy scale now when we go say from 14,000 times you know the mass of the or you know 14 TeV to a hundred even factor of eight in there is their theoretical motivation at that particular slice of energy space is going to really hold something new or we just simply saying let's go bigger because we haven't found anything yet well of course it's a combination of those things because there's never a guarantee that any particular Collider is going to discover anything we didn't we didn't know that the LHC would discover anything so you're always making a gamble but there is motivation that if the idea is that we've been talking about have any validity at all if they're not totally wrong yeah that that may be what we were we're missing is we didn't quite have a powerful enough tool to see them and and you know what's the probability of that nobody knows this is why it's discovery science you're always taking risks and Neema can a few broad points I mean first of all we go to the frontier because it's the frontier so that's that's the zeroth-order thing and but I think it if if you think that that particle physics is about discovering new particles and so you're only going to build a machine if you know for a fact you're gonna discover a new particle and you have some idea where it's going to be and so on then this is a perfectly good time to take your ball and go home and do something else with your life okay because we have absolutely no guarantee I cannot stress this enough absolutely zero guarantee that that a new machine is going to produce a new particle there are some indications for a new phenomenon that would happen at scales you know having to do with gravity and things like that or does in orders of magnitude removed from where we are but we had lots of theoretical arguments that something should happen right around the scale of the LHC we haven't seen them and they were in any case there were circumstantial indirect arguments anyway so we there's no guarantee that there are new particles however this entire and that's why I alluded to this earlier when we were talking about the building blocks of matter picture of the world it's maybe a little a little funny that's certainly not what drew me personally yeah into fundamental physics I don't care that much about the building blocks of matter it's a lot like chemistry I sucked very badly at chemistry in school and I don't care that much about the building blocks of matter I care about the structure of the fundamental laws of nature yeah and we've learned that that that the that the elementary particles are the are the letters of the novel that we're interested in the novel we're interested in the in the structure of the laws of nature and they're what we really care about a new new principles new phenomenon and from that point of view the Higgs is damn new it's very strange we've never seen anything like it before and so I think the main to me and I think the most people proposing these future machines the main thing we'll learn for sure from doing these new experiments are fundamental facts about the Higgs we've never seen an elementary particle like the Higgs before we have to put it under a very powerful microscope more powerful microscope than we have at the LHC and that the main drama about the Higgs is whether it really looks elementary or not whether it really looks point-like or not from the LHC we're gonna get a pretty fuzzy picture of how point like the the Higgs looks you really have to put it under and and in fact it's fuzzy enough that we've seen roughly analogous things to it elsewhere in particle physics most of you probably haven't heard of this particle there's a very important particle known as the PI on that also at first blush looks like it might might be kind of an elementary particle of spin zero but very quickly you see that when you just put it under a magnifying glass with magnification five you see that it's actually made up at a little quarks held together with glue on so whew all the theoretical drama that could have been there with the Higgs was actually not there with the PI on well that's the resolution we're gonna get on the Higgs from the LHC more or less that same kind of factor of five resolution that we had with the PI on we need another factor of 10 on top of that to know if it's something really really new if it's point-like as we expect actually in the standard model or if it has some sub sub sub structure and so there there are two kinds of experiments that we can do one is to see whether it looks quite like two other things like if you literally want to see that it looks point like you want to see what happens when a photon bounces in into the Higgs of course the Higgs doesn't actually live very long so um analogous so if proven dueño hates decays the two photons or into other things and then you see whether that interaction of the Higgs with other stuff is compatible the higest looking point like that's what these so-called Higgs factories will do the linear machine that Monica was talking about is is a great machine to do this it would produce millions of Higgs particles in a very clean environment actually these circular 100-kilometer machines could do exactly the same thing if you collide in them the same electrons and positrons so that's one of the great things about these circular machines is that they could do double duty you could first collide electrons and positrons produce millions of Higgs particles and and see whether it looks point like to external probes like photons and the other things that it could run into and then ultimately if you go to the hundred T V colliders if you collide protons and exactly the same machine you can ask and settle the question whether the Higgs looks point like ultimately to itself and that's kind of a sort of a fascinating thing the very simplest interaction elementary particles can enjoy is with three of them meet at a common point in space and time and it turns out no other elementary parts Engle elementary particle actually has this interaction every other thing that we know there's something that changes some some property changes the Higgs is the only elementary particle that can have as its dominant interaction this interaction with itself and therefore by looking for this interaction not only for the first time seeing the sort of simplest possible interaction in nature but you're checking to see whether the Higgs actually looks point like even to itself the LHC is not even going to tell us with confidence whether this interaction even exists but the hundred T V Collider will produce billions of Higgs particles and by doing that will not only tell us if exist but I'll measure it to a few percent accuracy so I've just told you what I think of and I think most most of the people pushing for this next generation of accelerator they're not promising oh we just barely met supersymmetry might be right around the corner that might be true okay but that's not the logic of the argument at this point the logic the argument has to do with the fundamental kind of paradigm shifting paradigm challenging nature of the Higgs itself and the fact that theorists are confused 40 years of ideas for what might be associated with the LHC but what the Higgs have certainly not been have not been amply confirmed at the LHC not even close when theorists are confused you need more experiments and you need to do experiments on the thing that's confusing the Higgs is the thing that's confusing so we have to put it under a very powerful magnifying glass very well said now when when we look at the big principles so one thing to do is to smash harder to magnify greater to try to see fundamental structure that we may have missed and so on but in terms of overarching theoretical paradigms that will guide us forward so supersymmetry is not ruled out it could still be part of the story but what I mean maybe just go down the line a little Joe what would you say I mean obviously there are things that people have string theory people which have supersymmetry there are other things like Technicolor that people have spoken about do you feel that we've got the guiding theoretical structure to really give us a clear path going forward as to what we should be looking for I think we're in one of those periods of physics history where we really need guidance from data it's we have ideas some of them I'm sure are good ideas but we need we need more we need nature to tell us more about what's really going on and this has actually been more the typical situation in the history of physics then then you know having confidence and you know Dirac was as I said was the lucky guy where he had the idea and then the experiment came right along that this is the typical situation where we're we have some ideas part of it's probably right part of it's probably wrong there's probably something missing and we need data to sort that out and that's what these more powerful instruments are really for there's a nightmare scenario that you described for the the LHC imagined some next machine is built what would your nightmare scenario be there well actually I think that you know coming back having looked back now nine years later and you know lots of data later we didn't have any data at that time right so we were sort of in a you know I definitely have also sort of had let's say eye opening experience out of the whole thing and I think that you know basically supersymmetry basically did us experimentally a disservice let's say because because it sort of set this expectation that I think that you know that that the LHC was going to be the discovery machine in the sense of discovering particles and the LHC has been a discovery machine and I think that you know because we have learned a tremendous amount the LHC has given us many many precision measurements of the standard model the detectors that we have are beautiful they're stunning the amount of precision we can get out of these detectors is amazing it's really been an absolute success in terms of what we've been able to measure and as I said we discovered the Higgs in 2012 no one expected that our detectors would be at that precision at that time we've been making measurements that we never thought I mean Nima says we won't be able to measure the the Higgs self coupling but you know already we're doing studies that show that we could maybe start to access it so forth so on so I think that we have made tremendous progress in technology we've made tremendous progress in precision measurements of the standard model and I think this idea that that you know physics particle physics was about new particles was really a disservice to us and in this comment that I made you know ten years ago saying would be Higgs and Hicks only it's the worst case scenario is it's absolutely a reflection of that time I think is a reflection of how how we were viewing progress at that time and I think we've all there has been a big emotional shift in in physics in the sense that exactly as joe says that we need the data we need to know the standard model better before we can really say you know let's go in direction a B or C and that we're really despite its successes despite how much we know about the standard model we've all discovered that it's not enough yeah and and these next-generation machines are exactly that so in that sense my worst-case scenario would be pretty much a you know a fire in the cavern I think so you know yeah real a real disaster I think we're we're at a moment the the the most important thing is that we've seen this phenomenon that we've never seen before and so I think it's it's it's it's very funny that in a sense seeing the Higgs and nothing else so far is by far the most shocking thing that could have happened that could have come out of the LHC experiment it's the biggest challenge to theorists it shakes the conceptual grounds under us more than had we seen these things that we expecting for a decades it's actually funny when I was a grad student there was such an expectation that something like supersymmetry was right and that was an idea that people came up with 70s and 80s and the job of my generation was to clean up the details and figure out how precisely it broke and worked out and so on and that's definitely not how it's worked out in fact the challenge just got greater got much greater the the stakes went became more more structural rather than about this or that detail or this or that additional particle like that I can't stress that enough I think that that the last time a whole community of theoretical physicists have been so perplexed by something and have had experimental results not aligned with what they expected was when we expected the universe was filled with an ether and the absence of the ether a null experiment was the was the harbinger of the revolutions to come this idea that a whole generation of particle physicists grew up with that what glory looks like was the 1960s with a particle every week it's true was a wonderful period but that was not you know in 200 years this will not be the the great thing about the 20th century the great thing about the 20th century was the relativity and quantum mechanics and there's lots and lots of very important details after that but these very revolutionary kind of conceptually earth-shaking discoveries don't have that character yeah they had their they have their surprising they involve things that that that that happened that that you wouldn't expect and so I think we're a nut we're in another one of those periods today and the heat is not the only you know you've talked in these programs eloquently or many many years there have been there's one other very important experimental shock to the system in the late 1990s when we discovered the universe is accelerating okay and these are two different ratings the expansion of the universe is actually accelerating and rate these are two very theoretically from a theoretical money but they're very closely related shocks our astronomer colleagues want to go measure the heck out of the expansion of the universe and our part of his experiments we're gonna go measure the heck out of the Higgs and these are actually very closely related conceptual mysteries I believe I'm certainly not the only one but I definitely believe that we're at another one of these periods that comes around every 100 years or so where the where the issues at stake go up one order of magnitude in sort of structural significance and in many ways the Higgs is the most important experimental actor in the story because it can be put under scrutiny have okay can be put under a powerful microscope be put under put under scrutiny yeah so all this talk of disappointment and nightmares and so on is I think kind of crazy you know just because you're in these conversations I need to sort of play devil's advocate but in you know 2010 or 2011 I wrote an op-ed for The Times in which I wrote about finding nothing unexpected at the LHC as being one of the most potent possibilities that could emerge as opposed to this standard frame of mind that you're articulating which is particle find more products and more particles so I fully agree but I want to finish on one point related to the the note that you just made about accelerate expansion cosmological ideas I just want to finish on a cosmological question so Joe you have written about a curious feature of the Higgs phenomenon which is that you know in the very early universe at least in many conventional formulations the Higgs field wasn't actually permeating space then it was only a little bit later on that the universe kind of went through a transition yes where the Higgs then permeated everything so it went through a phase transition a change of a very radical sort the particular ask for the Higgs field that we found suggest at least the possibility that we could be facing another such cosmological change in our future so since that's a very bright note to conclude on maybe you can describe what it is that we're referring to at the end of the universe yes exactly so as you said that we believe the cosmic molasses wasn't always there it actually turned the Higgs turned itself on if you like at some point in the early universe that's the phase transition talking about and so you can ask the question well is is the cosmic molasses just going to stay the way it is forever or at some point will something else happen that involves this and there is a calculation that you can do at least with with those standard model equations that we have now that we know the Higgs boson and its mass we have all the all the numbers that you need to do a calculation like that and some of our colleagues have done these calculations very carefully and and interestingly enough we seem to be right on the borderline of the universe that will eventually want to change into something else it seems that our universe is slightly unstable - at some point a little bubble of something else where the Higgs is doing something else will appear siyou or a different value and once that bubble appears it will expand at basically the speed of light and eventually it'll get to get to us and I'm gonna get to us way and that'll be the end of us though it'll be a different universe but we won't be there anymore now the chant even if this calculation is right you would expect this to happen incredibly far in the future so it's not it's not I think it's more it's on the order of ten to the hundred years from now so even in the billions of billions of years it's it's a very long time so you shouldn't actually worry about this I have got an email from people saying I can't sleep at night because I'm worried about this I always reply you you know you have many other things you should be worried about but this is not one of them but two two particle physicists this is an incredibly profound thing it's a question of what is is the Higgs really forever and if it's not forever what what does that mean and one possibility is again this leads back to ideas like supersymmetry if you think yeah that nature should make stable universes then you need some some ingredient that we need to add and what is that ingredient right know what one thing we presume you could also write back to people with that concern is since this bubble of sort of a new phase is expanding at the speed of light by the time you see it it's upon you yeah you don't have to have to worry you won't see it coming you'll just be looks like inside this bubble you know because what's going on is the heat gets a lot bigger inside the bubble so that means that every particle in your body that has a mass gets way more massive inside so anything massive go splat well right you know it's stars you me everything would go splat on this except light light goes sailing right through so if you if you or some progeny of yours manages to make it inside the bubble and run at the speed of light to sort of keep up with the width of all the bubble it's literally like being on the inside of a car with flies on the windscreen right you know the whole rest of the universe is just going splat on this bubble as it as it goes goes through you so it's a very cheering thought indeed a couple minutes to go and I just want to give you all a chance for sort of a final word compared to where we were say 10 15 years ago are you do you think that we've gotten to a more exciting place do you think that we've kind of gone through the doldrums I mean what would you characterize the state of particle physics to be today maybe just right I always remember when I was having a really frustrating time as a graduate student a senior graduate student and my group saying if it was easy it would have been done already and I think that pretty much really describes where particle physics is right now there's absolutely nothing about particle physics that's easy and I think I don't know a single particle physicist who went into this field because they wanted it to be easier so in that sense I'm personally excited about the challenge it's going to be hard as hell to build experiments for these new coal lighters bring it on I'm ready and I'm ready to take on the measure the Higgs as well as we can all right NEMA well III tell him my grad student said if I could go back in time and control when I'd be born I would wish that I was entering grad school today III really think I really think this is from my point of view it's the most exciting time in fundamental physics in certainly in 50 or 60 years maybe going back to the to the time when relativity and quantum mechanics ended up coming into existence and um and it might sound crazy I mean you know that there again there's there are other people were wandering around they're sort of depressed we have seen the Higgs and nothing else so who's right you know I might just on drugs or they aren't drug what and and I think it really depends on why you got into this business if if what really drives you is is trying to understand something deeply conceptually new about the world that kind of opportunity does not come along every ten or 20 years or so most people don't get to experience that and I think we're now at the point after slogging through all kinds of easier questions where you know in science you're you're motivated by gigantic questions but you have to work on the next question you have no choice but to work on the next question well we're finally at the point where the next questions are these gigantic ones are these sort of existential ones what space and time what's the origin and the fate of our enormous universe why can there be large macroscopic structures when there are the enormous quantum mechanical fluctuations that seem to want to destroy them and so on these questions even seem to be interrelated to each other in some way potentially and our generation of people are the generation we will get to work on these questions responsibly it's meaningful for us to work on them because there isn't like ten other questions in between us and then and so I'd like to say it's like you want to climb Mount Everest first you have to you know get in a plane go to Kathmandu find Sherpas foothills all kinds of stuff finally we get the base camp right and you get to see the beast for the first time then decide what you want to do you want to wait for oxygens be oxygen masks be invented otherwise it might go up and die or do you start trying to climb in some way that's where we are I think we're at a point where finally staring at these most profound questions about the nature of reality and we get to work on them and we get to work on them as theorists and we get to you know take on the mighty sort of generation scale challenge of attacking some of these questions as experimentalist so I think it's a fantastic time to be a a physicist but you have to have the understanding that that you have to be in this business for the long haul and and you may well go 3040 years you may easily die without having made substantial progress on the questions that you are interested in but that's what you have to do if you're interested in this kind of thing Joe yeah along the same line speaking to somebody that's at a big national lab if you look at what our young people are doing now at these labs they're motivated by the big scientific challenges they're trying to develop new technologies to build us these better microscopes that we know we're going to need to make these discoveries and and so those those technology challenges are equally fascinating and interesting as these scientific questions that are motivating them and I think that sort of cycle of this big science questions motivating us to push the technology so that we can do the experiments that we haven't been able to do yet I think that's a very virtuous cycle and it's one of the things that that we do for society that that's really important grateful it's been a fascinating conversation please join me in thanking everybody [Applause] you [Music]

Channel: World Science Festival

Views: 640,664

Rating: 4.803103 out of 5

Keywords: Higgs, Higgs Boson, LHC, god particle, Brian Greene, Michael Dine, Andrew Strominger, Marcelo Gleiser, String Theory, particle physics, dark matter, Standard Model, black holes, superstring theory, supersymmetry, quantum gravity, Einstein, extra dimensions of space, Bekenstein, Calabi-Yau, holographic worlds, multiple universes, supersymmetric quantum field theories, mathematical physics, Superstring theory, best science talks, New York City, World, Science, Festival, 2020

Id: no3qLqUYBLo

Length: 90min 8sec (5408 seconds)

Published: Fri Apr 10 2020