OPPENHEIMER LECTURE: The Higgs Particle: Pivot Of Symmetry And Mass

welcome to the 2012 J robert Oppenheimer lecture I'm Marvin Cohn and it's been my great pleasure to serve on the Oppenheimer lecture committee since its inception in 1998 I've also enjoyed the opportunity each year to give you an extended introduction with some personal comments about physics or Oppenheimer or about the subject of the lecture we've been privileged to have some of the world's outstanding physicists delivering lectures to us in this series Murray gell-mann Kip Thorne Freeman Dyson Channing yang Robert Laughlin Bruno's Amina who's here tonight edward witten martin rees michael fisher stephen hawking david merman claude cohen-tannoudji frank will check Lisa Randall in this evening professor Gerard a tooth will deliver the 15th Oppenheimer lecture professor a tooth is our sixth Nobel laureate in this series and we are delighted to have him here today on behalf of the physics department they'll be repeat my yearly invitation to you to see the Oppenheimer's displays that the department has covering the time when he was here from 1929 to 1943 you are welcome to visit the area in old LeConte Hall there are historical artifacts letters a plaque a number of memorabilia and on the fourth floor of old LeConte there are showcases with various things his old office was 435 LeConte Hall for those of you who would like to learn even more about Oppenheimer there is considerable information on the web his picture was up is up there and there is there are many books there's television documentaries there's dramas at least one play and at least one opera so his legend lives on and we continue to celebrate his Berkeley connection last year i speculated about what Oppenheimer would have thought about our series of lectures I divided the previous subjects of lectures into two groups the first group had complexity emergence statistical physics the spookiness of quantum mechanics the quantum behavior of atoms interacting with light these subjects can be roughly grouped into the branches of physics called condensed matter physics in an area called amo that covers the physics of atomic molecular and optical phenomena the second group covers gravity black holes cosmology particle physics and string theory and the subject of our lecture tonight belongs in the second group although I concluded last year that I thought that our coverage would have pleased Oppenheimer I have been reminded by colleagues that tonight's lecture and the last two by Frank will check in Lisa Randall have focused on research connected with the Large Hadron Collider the LHC with considerable emphasis on the search for the Higgs particle and then the question was posed to me about whether this area is really that important well I feel that it is first of all currently there is significant public interest in this area of physics once Eve's many articles on this subject in the press and even in popular magazines for example there is the recent Time magazine article hunting the Higgs which has quotes from our own colleague professor bethe Hyneman and one new thing that I learned from that Times Time article was and I hasten to say that I haven't checked this out so I can't confirm it but this is what time says they said that when Leon Letterman was complaining about the difficulty of finding the Higgs particle he nicknamed it the goddamn particle time goes on to say his publishers clean that up for his popular 1993 book the god particle in and then they say that's a name widely used by everyone except physicists that's according to Time magazine well Peter Higgs is an English theoretical physicist and an emeritus professor at the University of Edinburgh he is best known for his 1960s proposal of broken symmetry in electroweak theory this so-called Higgs mechanism which had several inventors besides Higgs around the same time like Robert Brout and Francoise and glare predicts the existence of a new particle the Higgs boson it's called the boson because it is a particle without spin particles without spin are called bosons there is considerable crossover in this area of particle physics in the field I work in condensed matter physics in fact when I was at Bell Laboratories we called it the Anderson Higgs mechanism after Phil Anderson but you have to remember there's an old saying that success has many fathers but failures are orphans so the Higgs by that measure is a success at least as a theory so far now since symmetry will be part of Professor tooth's lecture let me take this opportunity to acknowledge the great contributions in this area of a not so well-known woman mathematician scientist Emily nurture almost all and perhaps all areas of physics incorporate symmetry considerations as a tool to gain insight into physical phenomena the study of symmetries and how they are broken is a central area in theoretical physics in the March 27th science times section of the New York Times there is a nice article about the career of Emily nurture spelled noe th er the question is raised about whether her work on symmetry is more important than Einstein's theory of relativity they quote Einstein as saying that nerd er is the most significant and create a female mathematician of all time and the New York Times goes on to say that others of her contemporaries were inclined to drop the modification by sex they should have said gender but as you know the copy editors these days of the New York Times are not what they used to be nerd er unified symmetry in nature with conservation laws when there is a symmetry or a homogeneous property of a physical system there is a conservation law of some kind associated with it we all know that energy is conserved it can be changed into mass it can change in form but you don't lose it despite what is stated in the opening lines of the opera about Oppenheimer called dr. atomic where they actually violate this principle but anyway nurture associated conservation of energy with the fact that physical processes are independent of time that is the same physics applies to physics events whether it's a Monday or a Tuesday for another example the radial symmetry of a rotating top or a bicycle wheel keeps angular momentum conserved or constant so that symmetry results in a conservation law and as a result these objects don't fall and there are many other examples if you break a symmetry there can be important consequences when you hear more about this in today's lecture please remember amine urder is some of the path breaking work while she dealt with difficulties because of her gender I hope her example will encourage more young women to choose scientific careers the Higgs boson make the Higgs bosons make up a vac all around us according to Higgs it is the coupling to this boson that is responsible for giving mass to particles and hence the larger objects like us so if you're having weight problems if maybe you're coupling to the Higgs that should be turned down but before I leave the details about the properties of the Higgs - professor the - let me make a few comments people often ask what are the chances that the Higgs boson will be found and if it is will it solve a lot of problems the trouble with producing and finding a Higgs particle is that it has no charge it has no spin and it's therefore very difficult to couple - and Peter Higgs equations describing these particles they don't pin down the mass they don't give you the exact value of the mass you don't know where to look so finding one Higgs will be a great achievement and that's the simplest scenario if finding the Higgs mass if they find this Higgs mass in a certain range it might open the door for many other symmetries in particular other theories for example supersymmetry and that would make many of us happy since our colleague Bruno's Meno is one of the fathers of the theory of supersymmetry however it may turn out that there are several Higgs bosons with different masses and that would make the search much harder and if no Higgs particles are found at the LHC that would be something because we would need some creative retooling on the theory side but let's assume that at least one more one Higgs particle is found given that I would like to repeat what I said last year which was to assure our students that even if the LHC verifies some of the so-called ultimate laws don't stop your studies and research in physics there is still an enormous amount of exciting and fundamental work left for you to do I emphasize again that if the theorist LHC dream are all realized future researchers like our graduate students will in some sense have a better alphabet to create physics in their own words using this alphabet physics will not be finished well Gerard the tooth was born in Den Helder in the Netherlands he is an emeritus professor it attract University where he received his PhD in 1969 he shared the 1999 Nobel physics prize in with his thesis adviser Martin Veltman for elucidating the quantum structure of electro weak interactions professor with to work his work concentrates on gauge Theory black holes quantum gravity and fundamental aspects of quantum mechanics his contributions to physics include a proof that gauge theories are renormalizable which was an incredibly important achievement works on dimensional regularization in the holographic principle after obtaining his doctorate the tooth went to CERN in Geneva where he had a fellowship CERN is where the LHC is now in 1974 he returned to attract where he became an assistant professor he then took some visiting positions and after spending some time at Stanford and Harvard he returned to attract in 1990 1977 where he was made full professor and he became an emeritus professor last July in the past I usually add a personal note when introducing the Oppenheimer lecturer but professor tooth is the first Oppenheimer lecture I hadn't met previously we met just today however let me remark that because of his unusual website I feel then I know much more about him than just about his physics accomplishments he's a proud grandfather with pictures of his family and other information about them on his website mixed in with articles and physics and pictures of physics events I found considerable information about his life and some discussion of his writings including his published books fairytales and some discussions of his recent book playing with planets from the web website which I recommend that you visit one quickly realizes that Gerard a--to is a multi-dimensional person with many interests and accomplishments and now I'm very happy to be able to leave the internet virtual world and to have the opportunity of presenting professor tooth to you in the flesh his lecture is titled the Higgs particle pivot of symmetry and mass [Applause] just came back along all right thank you very much for this very kind and generous introduction so I'm gonna help me with this so it is indeed my honor to be invited here and to give a lecture in the name of such an important and influential scientist of course you all know from the history books a great deal him being associated with a military project and the sort of Manhattan Project reminds you of a military man who explained to his officers how to give a good lecture and his his recommendation was as follows first you tell them what you're going to tell them next you tell them and then tell them what you told them and so here is what I'm going to tell you but I'm not going to read doing this all this list I might not even each further than a little bit beyond halfway because then my time will be over and use that chaplain that should stop so I'll see how far I'll get the main message however that I think is very important I want to say right now the main message is that the Higgs particle as such has nothing to do with God or anything like that and it isn't even a particle that generates mass that is folklore it has been invented much later when in the early days we all talked about Higgs mechanism and the importance of fine Higgs particle nobody was saying that the Higgs of generating Mass it was a particle needed for our theories to work it is that simple we have explanations of everything in a theory and in particular we have a very delicate theoretical construction called quantum field theory and it was in my time that quantum field theory suddenly made a bit a big search in importance you all realize this is the way to describe and understand fundamental particles and when we look at the particles around us and we the analyzed very carefully all the experimental data we discover a data is an important notion missing and there is a problem with the mass of many particles that problem is not only a problem is there mass but also problem with their spin and antiparticles do something that all objects in the physical world do is you hang them around in free space they rotate somehow gets faster rotates slowly but planets and stars rotate soccer balls and tennis balls when you play games they rotate and when you play snooker or are curling these all these things they always rotate elementary particles also rotate and it is when we try to Skype the role played by their location it's very important all by the way you know very well that if some place soccer or football and if this ball rotates very fast it affects its orbit it also affects in case of tennis it affects the way it bounces against other objects so spin plays an important role in the way things behave it ways things move so by studying carefully how elementary particles in a subatomic world how they move how to collide you can say something about how they spin and the real message I want to explain to you is that this spinning motion is so essential in our theories describing how these particles exert forces upon one another the it was discovered that to describe their mass while they are spinning gave rise to a problem and how to solve that problem well the what we now call the Higgs particle turns out to be a solution of that so does the Higgs generate mass I would say no but it certainly is very strongly related to the mass that all the particles have and that I want to explain so my story begins with the landscape way above the region what happened oh it was good now here it is ok so my story begins with the landscape high as seen from high above that is a boy less along the boundary between Switzerland and France well you see at the back of the background is the Alps while the highest peaks there is a moon blow one of the highest peaks in Europe it's the highest peak of Western Europe and more informed you see a lake that's Loch Lomond the lake of Geneva here there's a very famous fountain here near this lake this is a town of Geneva right here and when you are in a plane and you look down at the countryside below you there's one thing you will not see and that is that red circle that I drew there the reason why you will not see it is that it is underground some hundred meters at some places of 300 yards underneath the ground other places while depending on the shade on the height of the landscape it is less heat but and the surface very slightly tilted and it has a circumference of over 26 kilometers and that is over 16 miles what you definitely don't see from Appling is that inside this the this underground tunnel there are bunches of particles going in opposite directions hitting each others at various places so design is such the dis particles usually miss each other except when they come in one of those six points around the circle that's why these particles are actually made to collide and it is there that we are studying what happens what this thing actually is is a gigantic microscope it looks at smaller distance scales than anything else you can make in the physical world now since these things on the ground the locals here will hardly notice that as anything special happening beneath their feet oh I should first say that the machine here started out in 1989 as a large electron positron Collider electrons are they charge the carries of electric charge in any substance the positrons are there under particles they were first made to collide at gigantic energies anything already acted as one of the world's biggest microscope but then later it the lab was taken out of the tunnel and autonomous replaced by a different machine called LHC the Large Hadron Collider it didn't have electrons and anti electrons or positrons to collide against each other but it had protons instead now protons are nearly two thousand times heavier than electrons collide trying them selling them around in circles gives rise to collisions that have correspondingly more energy when you when they hit each other and they can be made to collide a such great force that this became an even more powerful microscope now what I want to say just before was that the local population will notice very little of what happens beneath the feet and they will not notice anything I check every now then some gigantic tons for comes by their homes and this is just one of those little devices that is neat and sound to analyze the particles that go through you see everything is big in this machine the tunnel is enormous in size if you look inside the tunnel you see something like this this is actually taken by Taylor lens because you already see the curvature of the tunnel but the tunnel is very long so so this is seen at a distance actually in these blue monsters that you see in front I magnets each of them being 15 meters long and weighing 35 tons or some saw something of that order and the whole thing is filled with nearly 2,000 such magnets those methods are needed to force the particles to go around and not to just move straight on what you sure to need motorized transport if you want to go somewhere in the tunnel so yes this thing is a gigantic microscope investigating the features of the particles and trying to improve our understanding of what happens in the subatomic world now to explain what we like to investigate I have to go back a bit yesterday now I like to go back to the year 1969 for two reasons one is that it was a time I started to become a professional physicist studying the subatomic world and the other is that it's a very interesting moment in the history of particle physics when life looked very different for particle physicists in those days than it does now in those days in 1969 we have a fairly simple picture of subatomic particles we had a particle that generates the electric force and that just one single quantum particle called the photon indicate America clatter gamma it is a boson that was a one little thing I had to correct from my introduction not all bosons have spin zero but all bosons have integer amount of spins or zero or one or two this foot these photons also boson that has spin one now other particles have non integer spins been integer plus one half those are called fermions at a specific group that we've called leptons you see the Atlantic particle physicists in those days did the same things as biologists botanists and zoologists do then they see an animal they try to place it somewhere in the landscape of animals so they give animals names and they group them in families and genera and such we do the same thing with the particles so let bones formed a family there and among those families are even closer related levels we draw a box around them indicate that they are close are related so the electron indicated by the letter e is closely related to a neutrino and they have particular coordinate we know of the electron type it means the electrons can make it very easily transitions into those dirty nose and back there was another Latin called muon which was 200 times heavier than the electron and it comes with its own route we know that was what we knew in those days about the particles and we had another group of particles other genes say like plants and animals and so we had the Ayden's like animals among the subatomic particles they are strongly interacting particles and the Haden's came again to families the Mazen's which are bosons have integer spin and the baryons which a family owns because they have half odd integer spend either spin 1/2 or some of them have spin three-halves and actually what you could also do is not immediate here you could put those particles in an excited state when they were colliding very hard they and spin particles would either spin harder or they would carry some intrinsic extra vibrational energy so that we go heavier because of that those particles are not indicated because they are clearly excited states of these particles they would very quickly decay back into this basic form and the other thing not yet mentioned I'll do that now is that every particle comes an anti particle so the model also tells the model also says that the Panthers have other particles not the mesons they are their own antiparticles so the PI plus is the anti particle of Pi - so no need to indicate those separately but the proton had the antiproton neutral have antineutrons Omega minus has the anti Omega which the Africare is a positive electric charge rather than negative and so on and all and those things have spin three halves and apart from those excited states which were very short-lived this was the entire picture of the subatomic world and these thought that was complicated enough but now we know this was a great simplification there was much more to come and in a very short time but the physics expanded enormously both from theory and from experiment but in those days the experiment was still very close together when we theorist made some prediction experimentalist would merely try to verify whether production was correct and the converse is experiment experimental search found something new we serious all jumped upon it to try to explain that in terms of our newest theories unfortunate today the situation is quite different theorist thinking of things that no experimentalist usually can investigate in as much detail as the world but as experimentalist do very interesting sparin to work with only a few theorists are dying interesting that they mostly say well you know we don't understand exactly what you're seeing but we are actually interested something else and many theorists is really addicting apart but of course still there is a lot of connect direct connection as well between series and experiment and the LHC is definitely something which you're extremely interested in because they hope hopefully it will open up a new domain of the physical world the the energy by which the particles being accelerated in LHC is nearly an order of magnitude more than what has been accelerated before and because of that we hope to uncover a new domain of the physical world not known of before astronomers all always tell us that don't worry you'll discover things because when we make a telescope and suddenly a new telescope comes which is sometimes the resolving power we make new discoveries all over the place you live is very large but of course if you make a telescope ten times as powerful the universe becomes ten times as large if we make an accelerator ten times as powerful our universe becomes ten times smaller because you're looking at smaller things so it's not obvious that you'll make new discoveries but you all are very much in our favor so first thing you have to understand when you describe and investigate subatomic particles is the way that forces among these particles act so one of the first forces that we investigate would be electromagnetic forces but there are other forces as well so and Oh Eddy in 1969 we knew that basically there are four kinds of forces the electromagnetic force which we all understood pretty well as being an example of a force that you also see in daily life electric forces you feel and when the weather is drying you try to comb your hair and you see that hair is attracted to the comb that's electricity magnetic forces of course you also are familiar with we all know what it feels like ever methods to magnets in your hands you feel the magnetic force the other two forces strong and weak only reserved for the subatomic particles they are only important in the subatomic world but they are actively never seen beyond that and then there's gravity which is game very very general so because gravity and electromagnetism are also aspects of our world at large they have been investigated much deeper and much more slowly than those other forces so we knew those best in those days those other forces were still very very mysterious well the first force about which he obtained a more detailed picture was the weak force and actually to be honest already a lot was known about the weak force among elementary particles what was not yet quite understood was whether exists only one weak force or maybe the weak force could be a collection of many phenomena this we did not know in those days but there were some very striking features suggesting that the weak force was something fairly Universal among these subatomic particles here is an example of how you notice the weak force we do an experiment you may notice that a particle such as a electron may hit one of the subatomic particles called a new particle which is now one of the quirks I McDougal I'm a little anachronistic here because coax actually understood also later but now we know the electrons can hit against a you quark you quark will change to a down quark the electron change into a neutrino that happens with a certain probability that has been measured many times so we know precisely how strong this force is and you could quantify that very precisely by using the experimental results now what you can do with this interaction you can replace electron by its cousin the muon the Greek letter mu what happens in that case the viola also transmuting tantino but of the muon type and always fans found that if you change one you also change the other so it change the electron into a muon you also change like Latino tuna to Tino of you'll type in fact you would do something else we'd also replace them by yet another quad like a D goes back into you that way and you could make the same substitutions downstairs as well so and this is just basically bookkeeping your edges to all the weak forces take place and you find they always go in this sort of logic that there's positioned ourselves at position upstairs according to certain rules certain strengths that you can measure and then it looks as if the interaction causes of up part and the lower part knowing this or earlier 1969 many investigators suspected that a weak force takes place two steps it's a very logical conclusion you can draw that imagine that the index takes place in two steps there's one interaction on the top side of the diagram where either electrons going to Latinos or mules going to new munity knows or D goes to you and there are other possibilities downstairs the same thing and all you have to assume is that a particles being exchanged the exchange takes place in a very very short amount of time so short that all seams happen at one point you can explain that if you assume that exchanged particle the easy part of the problem is to give the name it was called W for a carrier of the weak force but the fact that the interaction took place in one point only indicated the weak carrier had to be very heavy particle if it is very heavy lots of energy is needed to create it it can only have a very very short virtual lifetime the other interactions that take place very very near and you compute these things in detail in in problem few theory and conclude that the mass or W had to be heavier than a certain limit which in those days was not yet very good later we could calculate the mass measure the mass of the W much more precisely so this was the suspicion but now how do we continue from here oh yes I should add that when you measure how these particles interact you notice that W would have to have spin this has to do with what I said earlier about spinning particles if a particle spins its other particles in a different way than if it doesn't spin so already we know that from the daily lives a little bit when you are good at tennis or soccer or whatever you know that spin has an effect again that effect could be measured and it could be concluded that the W had to be a boson with spin one if it if this all pictures going to make any sense those other particles by the way has spin 1/2 most of them have spin 1/2 although you could also have zero spin objects take part in this interaction as well now when you investigate the most fundamental particles and how they interact among the weak interactions you always find that they arrange a logical doublets an electron forms a doublet together with electro Latino the muon forms a doublet with the mute we know the proton forms a doublet is a neutron so the proton can make a weak interaction into the neutron but it was also observed every now and then a proton made the weak interaction with an other subatomic particle called capital lambda k lambda so these interactions were observed and something very striking was verse here's something very in PE which was at each of these interactions took places about the same strength so the weak force is a weak but his weakness is quantified and namely saying for all these four transitions except the last one the last one was only 5% of the other forces and the next two last one was nearly but not quite the same there was a slight discrepancy between theory what you expect and what you found the the proton Neutron transition rate was a little bit less you might expected from this universality principle so the weak interactions were universal but not quite this was a very mysterious feature of the weak force in those days but as my thesis advisor likes to tell me a story that he was working at CERN in Geneva summit before 69 and he was good friends with Nikola khabib Oh another Italian theorist who was also working at Sun at the time and he told me that one day Nikola Kabir came running into his office all excited shouting teeny which is first name of my adviser Timmy it's an angle it is that what do you mean and Kabira explained the following thing the electron to neutrino interaction is a fundamental basic weak interaction of a force that drives all electrons - neutrinos all muons are driven into muon neutrinos or the other way around if the weak force takes place backwards you have cannot both things now if you look at the forest that drives the proton into a neutron then that force is not quite oriented in the right direction it drives a proton to a neutron but 5% of the time it drives a portal to a lab done all you have to assume that this force is a vector and that the vector is rotated a little bit and if you take that angle to be 13 degrees then you can explain why the proton - love the transition is what 5% that goes to the sine of that angle theta which is about 0.05 if you square it and the cosine square is point 95 so that means that explains why the proton to love the force is a little bit weaker than the mutant neutrino force and the proton are reported to Newton force liquid weaken the portal's love that is a lot weaker because this angle is very fairly small the sine of the angle is much bigger than the cosine angle it is much smaller than the cosine makes us difference if you assume this thing to be in a located vector the total length of the vector very precisely matches the total length of these other forces what this result of n is the notion that the weak force is not approximately Universal it is exactly Universal but something very fundamental going on with a force and so now let's a lot of or yes I guess indicate those percentages here so from that moment on my thesis advisor Flatman was all convinced that we had to understand the riddle of the weak force how come that this is such a fundamental force and you also notice of course the importance of the carry of the force having spin one because the photon is also parted with spin one and it's also universal the photon the thing that the phone can be exchanged is direct proportion to the electric charges of the particle so photon photons are particles exchanged when the other object between which has been exchanged each carry electric charge so that's why a positive charge attacks a negative charge I mean repel another positive charge it's all because of the actions of the photon and all elementary particles carry the same amount of likely charge or perhaps sometimes twice that or three times that or zero times that if it's neutral but this like a child is seen to be very universal and fundamental so now I said look the weak force is just like that a weak particles being exchanged just like a focal also carrying spin one the only difference being that now the particle undergoes a change electron changes into a neutrino when a weak particle be exchanged whereas if a photons being exchanged it just means the same so that one got very intrigued by this similarity it seems as if nature is trying to tell us something about the weak force now Veltman knew about a very important looking theory that had been launched nearly a decade earlier in 1954 in 1954 Young and his collaborator Robert Mills were sharing an office and so they got to talk to each other and young had a splendid new idea about generalizing the concept of electromagnetism he said you could imagine a electromagnetic field that is just like ordinary electromagnetism except a partner goes who would field let's take a proton going through that field the proton will transmute into a neutral Margaret field in other respects the field just looks like electricity and magnetism conversely if you let a neutral go to that field is might change into a potent again so young startled and together his collaborator Mills they struggled to get the equations right in the beginning they made all the errors that we now don't allow graduate students to make but that was because they are pioneers and pioneers when this investigate something totally new they don't know what they are doing and so you tie everything and Jung showed me his notes when he was struggling with this concept don't know why he showed him to me because there's not contained but full of mistakes but what what did he know I mean this is the way it goes our science if you see the theoretical papers by someone who pioneered something new then make all the mistakes you can make but then finally got everything cleared up beautifully and the paper was published it was a marvelous paper and they got all the mistakes ironed out gotta complete generalization of the old laws made way back in the 19th century banned James max Maxwell Maxwell vote was the first to see what the complete set of equations are of electromagnetism Jung and Mills now did the same but to generalize it the introduced more kinds of electromagnetic fields which had different properties of transmuting particles into other particles and they found they obeyed basically the same equation so for instance they try to quantize the theory the quanta gain the lis bosons of spin 1 but you may ask a question if a neutron changes to a proton or a program change it to a neutron what happens to the electric charge of this particle how does it disappear I thought charge was conserved well the animals realized that the particles in this field ought to be quantized energy packets so they are said conversely the energy in the field ought to be quantized in packets of energy and thus particles so there are particles in this field photons but now if you shown that charged particles change neutral particles it means these generals photos themselves must carry electric charge and so that means that you not only have these diagrams there are photos being exchanged but now when a photon carries a charge one side to the other side the diagram then it means these things themselves are charged so they might exchange the photon themselves now so this diagram at the right is something totally new oh yes raise it so this diagram is something new and a complication in a theory eight complication indeed because this makes that the theory has novel features that you ought a theory electromagnetism definitely did not have so the question was how does it all work and now I want to focus attention on a subtlety that this irritation of the Earth days did hardly notice and that is that there is a property that yang-mills fields have in fact electromagnetism has that as well it's a property with spin if a spinning particle goes through a young mills field its spin is conserved it keeps operating in same way the particle might change direction because it's attached or repelled by this electromagnetic field but it doesn't change its spin or more precisely it doesn't change the spin if you measure the spin along an axis which is parallel to the direction which a party was going so soon butter goes goes straight upward then it's the horizontal rotation amount of rotation that remains the same and but the partner can change direction because it feels a force under the energy Amiens it would change the direction it's been with respect to its new dash of motion will remain the same spin in the action of motion recall that olicity it's like a helix and the helix remains the same and particles who yarn will shift it could have been otherwise other bosonic fields who change the olicity of a particle but the young males field doesn't in fact I'll say right now the Higgs field is an example field which changes the olicity of a particle but I'll leave that for later so history remains the same but this argument only holds that yes so again I think I think I've spin as a soccer ball rotating this property only holds if these particles are truly massless so for massless particles indeed when the spin is voting to the left that is a property which is separately conserved and so may be particles that rotated left all altogether interact differently for particles of the rotate to the right and this left-right asymmetry might explain an observed phenomenon which is that the weak interactions are not the same when you look at them in the mirror a very striking discovery made long ago by Lee and Jung well theoretically the detrimental discovery was made by CS Wu one other female physicist has a great reputation but the discovery that the weak forces left right asymmetric could easily be fitted into the yang-mills theory by saying management when a father spends in the left it stays spinning to the left but it can make a certain transition if the same part of the spins to the right it cannot make it yang-mills transition so the yang-mills fields might act totally differently on left rotating particles then it does not right rotating particles and this feature is necessary she won't understand why the weak force is right left ASA method so this probably would later turn out to be very important now this important property is only shared among particles which are massless because if they came us then the whole picture doesn't work anymore if this part was carrying mass you can't always define the spin along an axis by which the particle ISM is moving because their partner is mass it can move slower than the speed of light in fact it can stand still and what's the direction motion of a particle standing still as ill-defined yet that patter can spin you can spin all sorts of directions and that makes that this whole argument about spin being conserved in the yang-mills field breaks down if this part is carry mass so you can do this provided that you only talk about massless particles this is why the original yang-mills theory actually should have been described only for massless particles going through a young males field it's a massive the weak force doesn't act on them now we know it particularly all particles are sensitive to the weak force so this theory added that neutrinos can only rotate to the left right rotating tinos wouldn't exist at all I say wouldn't exist because laters found that yes neutrinos can rotate in the other direction but very rare in that case they don't do anything at all in the yang-mills field as well so the extremely in earth but the left rotating between OHS do exist and electrons can make transitions into left rotating three noes but then also those electrons must fall left and that explains why in the early investigations to week force in asymmetry was found in left and heart rotating particles the electrons involved in the weak interactions were observed to rotate also the left and the neutrinos work was much more difficult to observe with Valentino made in electron again that like there would be a left rotating electron so his left-right asymmetry was something that forces us to think of all certain particles to be massless so something was wrong and actually two things which are wrong one thing was about the range of the interaction electromagnetic particles lack of other forces have a gigantic range now I remember one of us in a fortunate position to witness how far magnetic fields range in the universe I could see with my own eyes that the net fields go further much further than the size of the earth what does that well I was in a fortunate position to watch a solar eclipse and I can recommend you even if you know precisely the theory of solar eclipse is extremely simple the moon moves in form to the Sun that's all that is just a geometrical effect so why is it interesting at first I thought I won't go to see this Eclipse but it took place fairly close to where I live so last moment I decide to go loo have look anyway and I saw the solar eclipse it was so beautiful because the moon shines of home to City from the Sun the only thing to see is the corona of the Sun and you not only you see the corona but you see very long lines leaving this Crona lines well where the shade really gets a little bit different somehow this is obviously a magnetic or electromagnetic effect and you see that those electromagnetic fields or some the range for several diameters of the Sun now the Sun is thousands of times more bigger than the earth so you could see so clearly you could see that these magnetic lines were ranging over enormous distances in space so this is a marvelous sight and obviously then it means that like the magnesium is a long-range force but I also explained that the weak force is a very short range force in fact it's so short-range it for a long time it was sort of the weak force takes place in one point only Fermi's original theory of the weak force was a one-point force where everything happens at one point that's because the weak force is such a short range so it's total different from electromagnetism in this respect this was not anticipated by young and Mills they treated the fields as if it's also a long-range field this is totally wrong theoretically we realized immediately because it's a very fundamental theoretical law what that implies for the force carrier the force carrier must be a particle with a high amount of mass called W boson and the table also must be so heavy that takes so much energy to transplant this weak force that it can only move a very short distance and theoretical it works beautifully so all we had to say is that the yang-mills that the the Bo zone that exchanged the weak force is young Mills particle but for some reason it carries mass this mass was not in young and Mills original equations and in fact when young once gave is similar it was Perry who milli in realize of something wrong with theory us what about the mass with his particle and young had to confess that he couldn't he didn't stand where the mass comes from the other thing I was wrong is that all particles of which the weak force acts actually do carry mass as well so they are light usually but I do carry mass and because he carry mass the augment of the left-right asymmetry cannot be exactly right because a last rotating electron is not people who are automating light all we have to do is is satisfaction still and then left and arrived means the same thing so how come that the electron in the weak force nevertheless has a preference of rotating to the left there was something very still is going on and theoretically we couldn't understand that there were not no proper equations to get this thing figured out so there was something that had been overlooked so so the mass of the week for us carry instead of very large as what I said so something has to be done to remedy this and then felt mom did the same thing as some way famous other physicist ed Hyman and Raja they all agreed that well Jana Mills had a beautiful theory but his equations their equations were not quite right you have to modify them as sort of said just además to them because you have to add all you want term to the equations that describes the mass of the carrier and everything will be alright so they had a new theory the yang-mills theory with modified young Mills equations and then we just sit down and calculate what happens so yes you can calculate that particles get exchanged on wheels photons and everything seems me in order this was a beautiful theory for the weak force but theoretically we knew that if you postulate that a photon can be exchanged you can also have multiple exchanges taking place at the same time so for instance while the fault will be exchanged an other photon can be exchanged as well and doing this that means that the diagram that describes in fact is false is a more complicated diagram complications can become even more case even several photos I exchanged at the same time in particular situation here is very complicated because a photos being exchanged while this other photo be exchanged and a third photo comes along and metals with a whole lot in a complicated way so what felt on a particular realize is that the theory they had would not describe the situation right automatically you have to wait and see and do the calculation the calculations were so complicated that felt bound saw the necessity to do this by computer in fact computers in his day were not at all as well developed as computers are nowadays so he had to read to invent to the first time how to do mathematical symbolism on a computer had not been done before he was the first to ride down and mathematical a computer program that does mathematics mathematics of all the equations that you need to solve in this case is a tremendously complicated case now first final and well found very excited because they discovered something beautiful if you look at the first complication that you get if you have a multiple particle exchange like to spin one particle spindle half particles exchanged or to both himself exchanged they form a final diagram with one close loop in it and developed on discovered that all diagrams one close loop beautifully arranged according to the expected rule so he can calculate what happens and everything is fine and beautiful so he was stubbornly continuing with his calculations because he realized that it doesn't mean that if you have multiple loops that this thing is still correct so this is a page of all of his papers where he attacked the multi loop problem you see that he was struggling with something he was inventing new other kind of ghost particles to handle the multi loop situation much to his dismay is covered it doesn't work these diagrams do not give the desired results the calculations violate very important principles of nature in particular conservation of probability and other such properties positive positivity of energy and locality and all these properties they seem to be going down the drain so this theory is bound to fail so how come you think you're on the right path in the last moment everything goes wrong well the theory isn't right we and the reason why the theory wasn't right was that they missed something they missed that we actually need a new particle what was that why did we need a new particle now I have to explain the concept of symmetry breaking what had we overlooked well a theory with massive particles is sometimes fundamentally different from the theory of massless particles the modification a 12 on a final made in yang-mills equations was more profound than they realize themselves the reason is that when a particle has mass and has spin 1 it can rotate in 3 different rotation modes all atomic physicists know this if you have a spin one atom if you have okayed in three different ways with the particles mass less like a photon it can only rotate in two different ways the fact that the photon can rotate in two different ways actually and can easily be checked whenever you have a Polaroid sunglasses or rather you have two sets of Polaroid sunglasses and you hold one against the other and then you rotate and discover that in some mold you get lights to both Polaroid glasses and when you rotate 90 degrees all light is being filtered out and and no light gets through so so photons have a property that changes when you rotate the source that means there are two kinds of photons and not three so actually the same holds for yang-mills photons because they are massless they can only rotate in two ways when you give them a mass take a suddenly rotated in three ways this gives an axial degree of freedom in the equations which wasn't handled correctly so to handle it correctly you have to do something in this discretion of spin so spin is a central theme my talk in the popular account with Hicks theory nobody talks about spin well now I talk about spin even though it's complicated and people who are not very familiar with playing tennis they hate spin because the ball lands somewhere else and expectantly lose the game and same is true for particles if you don't know much about them you might neglect that they rotate and everything lands in the wrong direction this has to do with symmetry electrons turning the neutrinos poles into neutrons all these are symmetry transformations in the answer to the question what did he do wrong is he didn't take the symmetry of the problem sufficiently seriously and this goes indeed back to Emmeline another who was the first to rely has symmetry has to do with conservation laws nowadays in particle physics we interchange those when we talk about symmetry sometimes you talk particles of a shoe law we talk about the conservation laws sometimes we mean symmetry it's fast not become the same thing due to a marine odor in a sense so what what is the symmetry well think of the electron and in 1802 be one part of the same field but the field is some vector field if the vector is oriented in horizontal direction we call this thing an electron if the vector is vertical we call it a neutrino horizontal and vertical in some imaginative imaginary space not an ordinary space within the measure space as a horizontal directions electron vertically it because in neutrino the young male system treats those things identically and Yana Mills would further require that both particles are massless and then you can make this rotation now not only does the electron carry a mass we didn't know whether Newton who carries a mass or not in 1969 we thought it was massless it's very nearly massless but the Latin K is a mass and of course it also carry electric charge versus neutrino is no is neutral so this particle totally different how can you make a symmetry transformation at these things about the same so what had to be realized that the symmetry is broken so the city transformation as some different particles requires something that you call symmetry breaking and here comes mr. Peter Higgs Peter Higgs realized that symmetry breaking can take place in two different ways in particle physics actually the discovery that he made was goes back to earlier discoveries in condensed matter physics when you can study a superconductor or a magnet you also talk about symmetry being spontaneously broken within a piece of solid material now Higgs realize that you can have the same phenomena of symmetry breaking in particle physics but to be fair and that's also mentioned about as a gram that I should also mention is our two names for Swat and Blair and Robert Brout who both physicists were a bit annoyed that always Peters Higgs his name is mentioned whereas they discovered the same thing but they made the error of not emphasizing that there's also a Higgs particle a massless a massive spin zero particle that they predicted they are not concentrating on the phenomenon symmetry breaking itself which is very very important when Nambu the the first person actually realized that spontaneous symmetry breaking takes place both in particle physics and elementary and in condensed matter physics when none received his Nobel Prize he asked his younger collaborator to give his noble speech because number I think of somewhere in the ninety is 90s when you see it in Nobel Prize he didn't feel like he could give his speech but he left that to his collaborator Johannes Inyo and Jana Xenia gave a beautiful exposition about spontaneous symmetry breaking is is that imagine a vertical pole and is a perfect cylinder but from very minor decent details on the surface it's a perfect cylinder suppose you have there's a certain amount of force you push the cylinder down then it is made of soft material it will Shankly the viscose here you are squeezing it now that's all right but if you squeeze it too hard the cylinder will buckle but in which direction will it buckle well you don't know and it doesn't matter it can buckle any direction but it suddenly chooses one particular direction into which it should buckle we call that spontaneous symmetry breaking the symmetry is rotational symmetry of these two earlier settlers and the rotation symmetry is broken by the cylinder that buckles because you your force is still great that is spontaneous symmetry breaking and the same phenomenon happens in particle physics as well we like to think of other analogy think of a particle falling in a Mexican hat his Mexican hat is a symbol symbolizing a potential field that might frequently appear the physical world and you put a particle in the middle of the Mexican hat now will it stay there forever well all's I know it will one day it'll fall in the rim of that with where in the remnants fall you don't know it might fall that direction might fall in the other direction we don't know it is a spontaneous breakdown of the rotational symmetry of the Hat now the Hat is no longer symmetric and Mexican riot where I had to feel the hair tube for one direction so this we call spontaneous symmetry breaking and now suddenly this ball here has a new degree of freedom it's going to run around in the Hat in the hem of the Hat and this running around gives rise to a new degree of freedom and that degree of freedom could actually in our theories be described such where it describes the missing degree freedom of this rotating W particle the W particle now suddenly has actually freedom given to it by this Higgs field and so now the W patter can located three directions and now it can get a mass so to get a mass you have add this new field that we call the Higgs field and so it turns the vector particle the gauge particle the W boson into a massive bottom so you need spontaneous symmetry to get that done now in the same senses higgs field will give a preferred direction in this electron neutrino space suppose that we say all particles that are parallel to the Higgs we call that the three no and since the IG's is little Latino will be neutral as well but everything or thought of that will carry electric charge that's the electron so now we can distinguish the electron from the three no because the say the Higgs has spontaneously obtained some length it's there whatever length is whatever is parallel to that it could be just one name if the thorah no it gives another name the orthogonal object will be slightly different equations from the object which is parallel so this is why the electron can become different from the neutrino so we actually need protein is seem to break down they have an action definitely no and never less have it interact with the yang-mills field so this actually also allowed the electron to get a mass it also meant that electron could go for a list electricity right because gas and mass now here comes in not a set about is new spin zero particle when a spin zero particle interacts something having spend the spin tends to flip so in left pathetic particle cannot go into a right pathetic particle so now the electron doesn't have to choose only one way to spin now the electronegative ass so duties extra field the Latin you get a mass as well so I said W buzzing at the mass the Latin get some ass so just by the press of the field we can accommodate from massive particles and this is the way which is object generates a mass I've said all this and now again this transparency ends with word but but there's one aspect of this vector field which have not yet touched upon which is what is the length of this vector is it it itself the vector can be used as a coordinate frame it prefers coiled frame in a journal space what does the length of this vector do the length of the vector does nothing by way of symmetry breaking but the length is vector can fluctuate can oscillate those fluctuations will carry energy quanta and those energy quanta collagen will correspond to a particle and that is the Higgs particle now comes a very important question and this crashes is rarely touched upon in a public talk I dare to ask it anyway because physicists do ask this question very frequently say yes but why do we have why can't we keep the length of this vector fixed why can't we say well it always has length one and that's it it's a field with length 1 it always has length 1 so there is no degree of freedom with that life so why do you need a 6 particle really yeah so that is go to higher energies going to higher energies means you are going to small distance scales you are probing nature even further at very high energies this field start oscillating much much more strongly than otherwise if it oscillates told me you have hell of a time of keeping its length fixed it wants to oscillate it has two degrees of freedom horizontal vertically it can oscillate in Ozone the direction also the vertical direction it oscillate so much that you can't stop it from four also its length from oscillating if you try to do that you will read you require such a strong force that our ability to make theories that make a prediction somewhere breaks down such a theory will not give you any predictions the higgs particle will run out of control a theory where things runs out of control is usually not the theory favored by theoreticians we keep on to keep everything under control the only way to do it is to allow the Higgs to oscillate how much should we allow it to oscillate well you're free to choose that means you're free to choose the mass of this Higgs particle massive it will be because it's length is fixed but how massive we don't know and this is why the Higgs particle itself is a particle whose mass we don't know we know exactly how generates mass for the other particles but you don't know its own mass so talk and gain but in that about the Mexican Hat we said that this was the actually if we don't give to the W bosons this is a new degree of freedom corresponding to the Higgs quantum itself this is the Higgs particle that we wanted that you're not predicting so this is the nature of prediction this is also by the way the most difficult part of my talk that's will be easier so people then start to make models I think I have to speed up a little bit because my time is going to run over and I'm going to run over time and see about that unless someone stops me and I'll just continue so this is a new model that was based on this principle a model by the way that was independently discovered by people who were actually practically their roommates a glass shower while they were sitting in the same building while the independently made their own model but while they in particular worked on a model and he he explained that left rotating leptons are in doublets right sitting Latins iron singlets that's why they interact differently in the arnelle's field you have two W particles and you needed a third one a neutral object for a weak force that was a basic new prediction of the theory and the other baisemeaux prediction is this Higgs particle so why am I go down this most explicit model while there was a smart man why was he so smart he said it's a model for leptons I'm not going to include the hedonic particles all the others say why not wait a minute Hayden's also sensitive to the weak force why don't you include them while I said I don't understand the head ones he was right about that he didn't on send Hayden's something was missing but that was something he couldn't have known the chimed quack was a new invention yet to be made without chant quacks indeed the head-ons are impossible to to force in the forge in the same model because while I realize immediately if you try to do that his model will predict things that weren't true and actually eventless knew with certain transitions do not take place which he would have predicted with his model so I said I don't understand they don't so lead them out that is perfectly correct the leptons are described this model the Halen's are only collecting this card if you add new quarks to the hydraulic world that were not yet known about now the counting goes right at very high energies Higgs field fluctuates so much that you don't notice symmetry breaking so basically you have four few components of the Higgs I cheated a little bit when I do it in two dimension space I should have a four dimensional screen describe the Higgs completely it has four components nuclear accounting the yang-mills field each of only two components they'll be like massless particles so there are three of them so three times two is the yang-mills particles four times one is the Higgs field altogether ten degrees of freedom if you do arithmetic fast enough and at lashes you do notice the spontaneous symmetry breaking then the young males fields all become massive each of them can rotate in three directions you have these pieces of them all together nine components of the armies field and the Higgs only the neutral particle field survives as a physically observable particle so one next particle and nine young males walks again ten degrees of freedom now the counting matches down the theory works the equations can be understood and there's no internal discrepancy anymore so now we understood how to do this lap had one major reason of existence which is to discover the double particle explicitly by blue explicit measurements this is so-called cross-section of electrons Claudia against antielectrons the cross-section had been measured before in other machines notably in Germany Doris and Petra and then other laboratories joined in to measure the cost section effect of cross-sections electron when it collides and gives head-ons or when it collides and gives muons or when they'll act as a process try to get photons they measured those amplitudes and let's continue to measure samples and found gigantic Peaks gigantic because as left is a logarithmic scale so you see that the peak increased by more than a factor hundred the effective cross-section of the electron gets a positive that peak is called is at 90 GeV exactly the mass of the so called Z particle the new particle predicted in the winder Salam model then lack then people got so excited I said maybe you'll see the Higgs as well if we go to high energies so left came in lap to version which is twice energetic and then measure the curve and you see how beautiful the new data of lab to the colored dots at the right fit the mag experimental curve without Higgs particle so there's no expertise in the lab to so this is when the additions urge at relentless to go to higher energies and find the Higgs they realize that you have to do headphones to go to higher energies in the tunnel this is a famous plot that you see all over the pages in your day's lap and other machines had excluded the existence of Higgs below about 100 GeV and mass but very heavy masses were allowed this parabola this year was actually the best fit describes the best fit to all the precision measurements that could be done in those days and the best fit is where line touches the horizontal axis you actually leave it below 100 but actually when the best fit is better than about number two the theory is still credible so the Higgs mass could a pencil be 200 or 300 or 300 or so GeV it was heavier than that a game of this experiment because and precision measurements and calculations becomes less good but maybe someone roofs somewhere and maybe the haters have here but then you have to explain why these calculations do not agree so well nowadays situation improved a lot and with the new machines both Fermilab and and some have also exclude other domains with expose there's a very tiny wide region around 125 which is kept white because it saw a slightly enhanced signal in that region which tells you that we cannot exclude the possibility the Higgs sits there it's still possible that if she is running again today at higher energies than ever before so we hope that very soon Alice IVA managed to close this gap either with or without discovering the Higgs particle to explain a little bit how difficult this music is expect to do the experiments here you see that while the detectors at CERN being built it's still largely empty because the whole thing is got later going to be filled with electronics to illustrate how big this machine is you have to realize that are actually some people standing here there's a man standing here so competitor man you see how gigantic a big these machines are again the machine is big because it's a bigger machine you can detect much more than a small machine this holds for astronomy for all branches of physics holes the bigger the machine is that you make the more sensitive it will be so creatures I think is also explains Reinbold biology animals we've got bigger and bigger bigger so dinosaurs became so big because there are big eyes they have much more sensitive detection organs then smaller animals have a fly can see another fly not more not sharper than we can affect out flies see other flies much less well than we can so for instance a fly doesn't see a spider's web because the eyes aren't so good so that's why every spider can catch flies but that's because the eyes are so small our eyes are bigger and so we can see the spirals that we don't understand why the fly goes into the web anyway but the bigger the machine the better the detection so that their biggest machines are needed to look at the very tiniest particles this is the assimilative event if X is found it looks something like this and gigantically complicated interaction process somewhere in all these tasks are the degrees of Hick's decaying you can show that the Higgs will be very short-lived particle if it exists is a decay immediately we have to find its decay products some are hidden in here you need gigantically strong and fast computers because sound is providing millions of collisions per second and all these collisions look as complicated as this they have to be analyzed in real time as fast as possible because you can't keep all those data in your computer that would be hopeless far too many so you have to analyze as fast as you can where a possibility could be Higgs or something else of interest in there now I talk about a little thing that happened and Georgia after LHC or switched on for the first time and I see you getting impatient so the story story of the accident will have to be kept very short but I liked our story because it illustrates how well cells being managed and very proud of being European in this particular respect not what way Europeans handle finances but the way to handle mishaps like here is is very admirable and this while you see that something happens here is not so good actually an explosion took place what was the explosion well the next picture shows that there was a bad contact these 2000 magnets ok dozens and dozens of contacts where long temperature leads have to contact the temple valley divided 1.9 kelvin those contacts have to be flawless it is not flawless they they will show some resistance then things will melt and the contact will be broken now if you have a magnet K mega joules of magnetic energy you can try to break the contact and stop the cart but that means you stop the method the magnetic field and there which carries mega joules of energy that current can't be stopped instantly it comes will go on for another minute or so no matter where it comes from so a spike has made the spark continues the current in spite of the original contact being broken the spark will do the same thing as in their science fiction movie it will start to do this and finally this spark at something which was not anticipated by the CERN designers which was it hit a helium pipe now there are many impacts in this method all be very fragile and that made sure around these fragile paths breaks there is no big problem but it had not anticipated that the spark of a bad contact would hit while the main healing path besides the magnet this helium is super cooled to 1.9 Kelvin but when the spark hits the helium pipe it suddenly is heated beyond this transition temperature so it's evaporation temperature so the helium entity evaporates when helium evaporates its volume increases by a factor thousands if that happened instantly that's a definition of an explosion and what explosion took well this 35 tonne weighing magnets till lifts it up by half a meter or so and put it down somewhere else that is not good for an accelerator and in fact then the next magnet and the vent problems as well although some 60 magnets in a row are being damaged by this event and had to be replaced the replacement itself was not that terrible it took them only a few months to have everything back in working condition again what took - over a year was this incident came unannounced and unexpected it was the factor was unexpected which caused him to worry we made a calculation we want to make sure this error doesn't take place again so it took over a year to fill all these magnets with new detectors to make sure that that what happened then doesn't happen again they investigated all magnets they found another magnet where the same mistake had be made but that method had not yet exploded could have done but it didn't so but they analyzed and found the origin of the error and then they are now making sure that air doesn't take place again but it's still not quite sure that's why a taxi today still around not quite at design energy but a little bit lower just to be on the safe side in 2013 for the first time LHC will run at the full design capacity some statistics here some superlatives many superlatives but well I think I should actually stop this is the competition Fermilab and in good science you have competition collaboration going side by side so we collaborate with Fermilab we competed at the same time but now Europe is in a better position and Fermilab to do the higher energy measurements so that machine is not closing down and still analyzing some of its data but otherwise it's no longer in operation at that high energy firm enough each only one TV Western has four TV in its beams now and it will continue ought to go all the way to seven what the Higgs is not found well our theories will be in serious trouble but maybe we just have to modify them maybe they exist more than one Higgs could be than finding that those Hicks's will be much more difficult there will be several particles which which share a job of doing this into baking among all five of them or so and that makes each single atom more difficult to detect that could happen there could be very many Hicks's there could be an infinite number of fixes even or something else could happen absolutely no Higgs at all that unlined you began the theory would be entirely wrong but the see ourselves is so well in previous years that not many theaters think that is unlikely it's not totally impossible but then weave of roots something much more serious and glad to do a homework all over again we don't mind doing that so if experimental is tell us there is no Higgs period well I'm sure the additional final answer sooner or later but that means lots and lots of work so to go with this there's no way we can lose it as I said here to go with this look this is a military guy I should tell you what I told you [Applause] we have time for just a couple of questions so if you would line up over here afternoon even if those who have questions please come to this microphone and form a line oh yes you said higgs generates mass asking because I can't see foster off yeah oh I'm in front um you said that right here yes yes you said the the higgs generates mass but but one say an object has mass it has a whole bunch of other properties including of in general relativity it'll warp time-space it will also generate inertia it'll also bend the light ray so does is the Higgs responsible for all these multiplicities of properties of once you have mass well as an emphasis in my talk I would rather not say that Higgs is responsible for mass that are giving it too much honor it is just in heated in a theory necessary to Skype massive particles now you know probably very but well that general relativity is a theory of the gravitation force today we do not quite understand how to incorporate general relativity in particle physics as well as a major outstanding problems in theory today so we can't answer your question completely but we do know as a fact that mass okay mass in the sphere is inertial mass so we always talk about inertial mass we rarely talk with gravitational mass but according to Einstein and all belief he has basically correctly that mass a cavitation mass inertial mass is the same thing so we believe this is to which means that when the Higgs interacted particle giving it effectively a mass then that same mass also be the source of gravity it goes against ein that happens automatically in fact are much more forms of energy in our theory such as kinetic energy which also contributes to mass in saying atom electrons and other particles move in atom that kinetic energy also controversial mass but also contributes to the gravitation that's the same way I cried to Einstein we have to take that we had take Einsteins word for it we haven't yet fully understood how his theory has to be incorporated in particle physics thank you thank you have you written this talk up or are you going to write it up someplace and and where are you gonna write your stock because well this story has been told by many people in different ways I this is my version of the talk I actually wasn't planning to write it down in this way I'm talking about not mainly my own research my own researches on different topic but this is what I'm confronted with fairly frequently today because I'm member of us science policy committee and we discuss all these things in detail that's why I love to talk about it that's not my own research so I'm hesitating hesitating a little bit to write it down I'll just mention that the talk itself will be available on the physics department website in about a week so we record that see a little registration of this talk will of course be available yes since elementary particles can have only particular values of their rest mass is that an example of energy quantization we would love to think that way but no energy is quantized with only depending on frequency so but so the quantum comes automatically with the frequency if you change the frequency you change the quantum of energy and they're also the mouse effectively this means it means that particles can have any mass in principle there is no obvious restriction to the mass apart can have for instance neutrinos are known to be very very light the lightest particles which are nonzero in mass focus zero mass the teen is a very very light but how light we don't really know but today there is no theory that tells you the mass so that you know must be quantized we don't believe that although in the future maybe one day something like this comes out this will be a major discovery at all but today we have no good mechanism to quantize mass this energy is quantized proportional to frequency of the source okay let's let's thank professor who talk again thank you [Applause] [Music]

Channel: UC Berkeley Events

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Length: 95min 36sec (5736 seconds)

Published: Wed Apr 11 2012