How to Know a Neutrino - with Art McDonald

how many people here have ever heard of Tim Hortons how about Tim bits Tim Hortons is everywhere in Canada Tim bits are the holes in a doughnut that are sold as individual items hang on to that piece of information that will come up later okay so how to know Anna trina from a hole in the ground that actually came from an advertisement that international nickel company put in magazine called Saturday night which used to be a major Canadian publication they put it in there in 1990 international nickel company was the owner of the hole in the ground and it is their mine is now owned by valet but it was their mine in Sudbury Ontario and they provided us with an opportunity to do something that is really unique we were able with first of all the snow experiment which you see on the left and I'll tell you all about that but with that we were able to do the science that was for which the Nobel Prize was awarded trying to figure out how I end up being able to look at that look at you and point the things as well and I think I'm going to come a little bit to the side of the table if you if you don't mind there's the snow experiment we use that experiment to study tiny particles called neutrinos the most microscopic particles we know about and we are now with something called snow lab which is an expansion from that snow area to a much larger area studying other things that penetrate through the two kilometers of rock that are above us basically what we're able to do is to study everything from the most microscopic particles through things the scale of our Sun and we learned a lot about our Sun in this experiment all the way to things that are affecting the largest reaches of the universe and in fact how the universe began and evolved and in fact in our next experiments we'll be studying neutrinos that are produced in the earth so we have a wide variety of measurements that are done and they're done because by going two kilometers underground we're able to create the lowest radioactivity location that has been yet created we avoid the cosmic ray particles that produce the Northern Lights which were very familiar with in Canada by making the atmosphere glow by going two kilometers underground they stopped in the rock and do not thereby make our detectors glow other particles that we can study that I'll mention in a moment enable us to observe and address questions like how to stars like our Sun burn and that's where a lot of the elements from which we are created are made it's our basic source of energy here on earth very important questions that we can study we also study whether the basic laws of physics for these very fundamental particles and what is the composition of our universe and how has it evolved the way it is at present we do it by studying unusual particles that are not affected by that two kilometers of rock above us first of all particles called neutrinos and I'll tell you more about in a in a moment but come from the core of the Sun and that we are able to observe in our detector about one an hour and so you can understand why we don't want that detector glowing like the Northern Lights do in order to see these faint bursts of light one an hour we now having studied neutrinos in detail are moving on to ooh a next class of particles if we think fill those spaces you see on a dark night when you look out there it turns out there's five times as much matter in the spaces between the stars as there is in the stars themselves and it's something new it's something we've never seen in any experiment here on earth up to this point referred to as dark matter particles we think we have a great opportunity to observe them and I'll tell you a bit about those that's what we're doing in our new laboratory it's no lab we also can measure the ultimate in rare radioactive effects we're now looking for a rare form of radioactivity called neutrino is double beta decay that's expected to only have a what they call a half-life in other words one probability of decaying once in 10 to the 26th years and we can do this because we can get rid of all other forms of radioactivity that would obscure our ability to observe it so let's start with study of the Sun it turns out that the reactions that power the Sun fusion reaction produce first of all about 16 million degrees in the core of the Sun and also produce an enormous number of neutrinos and these neutrinos are highly penetrating and so they penetrate out through the Sun without any problem at all and eventually reach our detector underground neutrinos are very unusual particles and yet they're very basic along with electrons and quarks they're the basic particles that we don't know how to subdivide any further they come in three flavors muon electron and tau neutrinos and in the standard model of elementary particle physics which you've heard a lot about in recent years particularly with the discovery of the Higgs particle which is the last element in that particular model we have something that explains particles on a very basic level very completely and that model predicted that these particular particles would not change from one flavor to another and did not have a finite mass they were a mass of zero and always traveled at the speed of light these particular particles neutrinos only feel the weak force out of the set of forces that we we know weak force strong force electromagnetic force and gravity they only feel the weak force so they only hit they only stop if they hit the nucleus of an atom or the electron going around it head-on and so as far as they're concerned matter is open space they can go through the distance that light travels in a year of lead and have only a 50% chance of hitting something and so they're extremely penetrating which is great if you're trying to get information from the core of the Sun it's not so good when you're trying to detect them and hence this one an hour in the detector the size of a 10-story building which is what we built two kilometers underground just to put you in a little bit more detail as to where they fit these days we think that a description of those particles we can't subdivide any further includes quarks up and down quarks are the things that we're made up there are more energetic versions that are called charm top strange and bottom there are neutrinos which is what our topic is for today and also other particles called electron muon and tau particles and there's a one-to-one relationship between neutrinos and those particles so we have an electron neutrino muon neutrino and a tau particle turns out that what we're made of is atoms in the nucleus of an atom there are protons and neutrons most protons and neutrons are made of three of the up and down quarks producing a positive particle in the case that proton and a neutral in the case of the neutron an atom as those in the nucleus and an electron going around the outside and so basically we are composed in our universe is predominantly composed of these things there are higher energy things that involve these other particles these are the force carriers they along with the pig boson in the graviton for gravity make up a full description of things the neutrinos are produced in certain forms of radioactivity if you might guess that if they only stop once an hour and something the size of a 10-story building they're not going to very often stop in you there so it penetrate so little or affect things so little it only once in the course of your lifetime will one neutrino stop in your body and change one atom into another atom and only if your eye happens to be closed as many of them are in the room by the time I get to the stage in the talk what's the time and it hits you right in the eye will you be conscious of anything and you might see that little burst of light at that point but basically neutrinos are well it turns out that if you eat a banana you are exposed a little bit more to neutrinos because regular beta decay so-called which is potassium one element of one isotope of potassium does gives you a little bit more neutrino flux striking you than otherwise but in general the neutrinos that affect you are the ones that come from the Sun and those neutrinos are such that in one second you will have about five million of the type we were measuring coming from the Sun going through something the size of your thumbnail one square centimeter so there are a lot of them and they very seldom interact so why do you care it's not as though as I was once asked they were a breakfast Ciril they're not even though the name might suggest something attractive for an advertiser I mentioned earlier that the elements from which we are made particularly carbon nitrogen and oxygen are made in nuclear reactions in stars like our Sun and in fact what we're doing is studying in detail how the Sun burns so in a sense we're studying our origins it turns out actually that the elements heavier than iron are made in collapsing stars and stars typically that end up singing in on themselves after they've finished burning and and then there's an explorer that collapse into minimum density and then they they explode back out and bounce back out as they say and it turns out neutrinos are essential in order for that to happen and it is in that subsequent process that all of the elements heavier than iron are produced and so basically our essence the elements from which we're produced arise from processes in which neutrinos have a fundamental part it turns out you can calculate them then factors of four or five the abundance of all the elements in the universe starting with a few made in the Big Bang some made in the stars like our Sun and the rest made in processes like supernovae now the Sun itself as I said by our measurements we're able to understand how the Sun burns in great detail and that's a value in the sense that it's the basic physics of a process called fusion but it's large-scale this extremely hot core of the Sun is held in place by gravity but otherwise it is full scale generation of fusion energy up to temperatures of 15 million degrees that's the same thing we're trying to do here on earth in fusion power plants but in this case typically what happens is you can't build a bottle that's going to hold this very hot plasma and so what you do is you build something in which as these charged particles try to get out they're turned back in by magnetic fields and they never touch the wall of the bottle that's turning out to be extremely difficult and so it's still a number of years before we have fusion energy but we know and we have tested in the case of the Sun that the calculations that go into calculating how fusion works full scale are very accurate so it's a prime example of how the more you understand about basic science the more you're eventually able to have confidence in what you do in developing things for mankind neutrinos if they have a finite mass actually have an effect on how the universe evolves in the early days formation of structure stars galaxies and so on are affected by that and neutrinos are now being used in large detectors like one under the South Pole that enable you to look at the farthest reaches of the universe by seeing these very straight line messengers they aren't affected by enter by space in between anything else you can look well outside our galaxy and are not affected by magnetic fields and so you can look for very distant parts of our universe using these neutrinos and they're very high-energy so let's talk about the Sun a little bit further it was said I think by Sir Isaac Newton probably in this very town that we stand on the shoulders of giants there have been a tremendous number of people that have developed our understanding of how the Sun burns Hans bethe and Willi Fowler who happened to be the actually the professor who led the research group that I participated in at Caltech in the in the 60s that's 1960s was that great great scientists and and Willi Fowler is actually the person who developed this understanding of how elements are created in stars in the 1960s ray Davis experimentally and John Bacall theoretically attempted to understand how the Sun burns ray Davis made measurements of neutrinos from the Sun with a gigantic tank of cleaning fluid underground in South Dakota John Bacall made calculations of how many neutrinos he should observe and what was found is what came to be known as the solar neutrino problem as leaves mentioned earlier on only 1/3 of the expectation of the expectation was observed it was suggested back then by Bruno Pontecorvo a very famous physicist who had some great ideas and one of them being that perhaps neutrinos can change from one flavor to another outside the standard model but if it were to happen then what you'd find is that the other experiment that was sensitive only the type of neutrinos produced in the core of the Sun would find too few because they had changed into something else undetectable by that previous experiment so the solar neutrino problem be solved either by those calculations of how many were being produced being wrong because you were relying on them in order to know how many left the Sun in the first place or those electron neutrinos were changing into another flavor and they would elude the previous experiments so here are the set of reactions where which which in fact create the light elements in the in the Sun you start with a couple of protons you produce something called deuterium and some neutrinos at that point it continues on until you have neutrinos produced by this boron element that's decaying and producing high-energy neutrinos now in 1984 after this solar neutrino problem had been going on since the late 1960s herb chen from the university of california irvine asked the question of a friend of his and at national research council in Ottawa and Canada of whether it might be possible to borrow enough heavy water which I'll tell you about in a moment too absurd for a special experiment which would enable you to tell whether or not exactly what was happening in terms of solving this solar neutrino problem he said you think I could borrow 4,000 tons of heavy water to do this experiment now at that point he was saying do you think I could borrow 1.2 billion dollars worth of heavy water and it turned out that was not possible surprise surprise but we were able to borrow 300 million dollars worth for about 10 years for $1 now that's pretty good leverage in any market we had to pay about a million dollars a year in insurance for it but we returned it at the end of the experiment without losing a drop turns out if you have this material called heavy water and it turns out that 1 in 7,000 of the molecules of water that you drink in this glass or any glass one in 7,000 has an extra Neutron in the nucleus of the hydrogen and the h2o so it's d2o instead of h2o one of my colleagues at one point when we were trying convinced the people in Sudbury that this was a benign safe experiment I went to the City Council and drank a glass of heavy water to show that it's non radioactive and perfectly safe of course he as he was drinking it he poured a little bit of whiskey in and said nothing improves the taste of heavy water like a little bit of teachers but that's uh that's history and here's some more history in 1984 a collaboration of 16 people came together in Canada this actually shows 1986 still approximately the same number of people herb Chen is here and George Yuen from Queens University your alma mater was a very central individual in beginning this project project as well he had scoped out this underground location where this could be done turned out that it was possible for us to borrow that 300 million and by 1986 we at least had approval in principle and we were preparing the experiment us in the UK there forward from the beginning do you US and Canada I should say we're in from the beginning the UK came in very shortly thereafter through David Sinclair at Oxford joining the project and so we said about doing the experiment and and seeking peer review and seeking the money unfortunately and it's really a shame when you look at that picture six months later herb Chen had died from leukemia at that early age and so that really set us back but everybody in the project decided that this was such a good idea we would pursue it at that point I was a professor at Princeton and I took over as the US spokesman for the project & herb's place and then came back to Canada on sabbatical in 1988 and stayed on as the project director when we receded in 1989 turns out that as I said with heavy water you have some unique ways of studying neutrinos now this sort of equation like thing here shows what happens when an electron neutrino come in and strikes this deuteron with an extra Neutron in the nucleus in the in the D of D to O when it strikes the neutron it changes it into a proton and there's a fast moving electron that's going faster than the speed of light and water and you get kind of a sonic boom in this case it produces light called shrink off process so that's rather distinctive and specific to electron neutrinos there's another reaction such that any flavor of neutrinos can come in and just break apart then the deuteron giving you a free Neutron and we worked out three ways to detect those neutrons in three different phases of the project now what's significant about having those two reactions is now by comparing how many electron neutrinos and you know it's only those doing this with all neutrino types you can thereby figure out whether or not they're changing from one type to another in fact what we observed was that only 1/3 of them one third of the total detected by the second reaction were still electron neutrinos and so thereby we could show without trying to figure out how many were being produced in the first place that in fact neutrinos had change from one flavor to another now it was very important for us to control the radioactivity because it turns out that uranium and thorium emit gamma rays of an energy that could also do the same thing here and produce a free Neutron in the experiment and so we had to control radioactivity to a great degree in the middle of our heavy water we had less than one radioactive decay per day per ton of water and the center of the detector billion times more pure than tap water and that was essential in order to do the experiment safely we also had to do it deep underground to avoid the radioactivity that represents those particles coming in from interstellar space and so we did it in Canada the icon of course is is the CN power and so we're for CN towers down I really should be dealing with the empire with the Eiffel Tower suppose perhaps here or one of the London landmarks in the United States I usually use the the entire State Building as the as the thing and you may think I thought I mispronounced that but I had a from my seven-year-old eight-year-old I guess he was at that point son when we lived in Princeton he took a trip to to New York City with his class and he came back and told us he had seen the entire State Building so whatever icon it's a long way down and we had to bring everything that we use to build a detector down in this shaft same shaft that the miners travel in and that they take thousands of tons of ore a day out on the other side of the shaft so this is what we built as I said size of a ten story building about 34 meters high I should have translated it to feet I'm sure it's a hundred and some feet high and and two kilometers underground and this is 22 meters across 70 some feet across in the middle is the 300 million dollars worth of heavy water and kind of the biggest Plexiglas Christmas tree ornament that anybody's ever built it literally was the biggest thing of that nature that anybody had ever built from acrylic or Plexiglas and what the manufacturer or the contractor learned to do in the process of producing this has resulted in you having aquariums around the world which you can for example the ones that you can walk through and have the water all above you those were techniques that they developed after having learned trial and error we had to suffer through some of the error at that point in building this but we eventually built it it was all secure in the heavy water is looked in that by nine thousand five hundred light sensors each of them about that big and each of them capable of observing a single photon of light with about a twenty five percent probability so we someone calculated that you could see a candle on the moon with this if you applied it to that process I didn't have any background ultra-pure water surrounding the whole thing in a water and radon tight covering this is sort of the ultimate in in deep basement you get advice to check the radon in your basement that's what comes from the decay of uranium it's a gas you don't want to be breathing it in this case we didn't want it anywhere near our detector so we had about a hundred thousand factor suppression of radon in our detector you'll see there's a person that's to scale and everybody who came in to work in the project took a shower put on clean lint-free clothing and we maintained a something cleaner than a hospital operating room in the hole detector as we were that we were doing the project we had less dust on the surface of that detector than you could pile in your thumbnail so imagine that you're a neutrino starting in the you're produced in this reaction and the Sun and here you go you're easily clear out of the Sun you're now heading to the earth you happen to be the one that's heading towards Sudbury and you go past a beautiful snow lab building and on down past the operating cage and into the center of the detector and you produce a burst of light that's the way in which we observe neutrinos but in order to do it we had to build something was pretty unusual we had to put together this steer within a sphere within a cavern we built the top half of the photo of the light sensor system we built the top half of the acrylic sphere we built the bottom half you can see the last of the hundred and twenty pieces being bonded together here it is after it has been completed with respect to the acrylic sphere and they're just putting in the last part of the photo tubes or light sensors and this is after it's all cabled up and connected to our computers that have the ability to observe a neutrino and transmit them to our store them and also transmit them to our collaborators around the world including collaborators from Oxford who in fact contributed significantly to the project by contributing an extra ability to collect light surrounding each one of the light sensors this is an actual picture looking up from the bottom of that sphere and there's the acrylic sphere and those are the light sensors looking in at it there was also a lot of work done by the Oxford people on purity of water and on the computing software necessary to understand the experiment both when we simulated it in the first place and when we collect the data later on the water systems were as I described earlier on capable of a billion times purer than tap water when we brought Stephen Hawking down in 1998 for a visit that he was very interested in we had to take a different approach taking him down and having a shower just didn't work and so Inco built a special mind cage for him where he could be vacuumed off above-ground and then brought underground and and just go out into the clean area that way fascinating an inspiring individual asking lots of questions of our students at this point you can see he actually has a clicker in his hand and later I'll show you a picture when he came back in 2012 when the only thing he could move was his right cheek but still the same spirit of trying to to deal with a handicap and in a very effective way he's a an excellent scientist and also someone with a fantastic spirit that really impressed us all so good sense of humor he said that he thought that he was telling us about how after the Big Bang the world had cooled off to its present present temperature in terms of the light emitted in the Big Bang that's about two degrees above absolute zero or as he put it almost as cold as Sudbury in the wintertime so by and large things went pretty well the final phase of the project we had to install 400 meters of very low radioactivity detectors that were capable of observing a single Neutron that's the way we did that second reaction in the last part of the project you can see them being installed here here is one of these detectors being pulled down by a submarine and it went very well except at the very beginning is the original sub well if you had a chance to specify the color of your submarine right what would you specify so we did and the only problem of course is that paint was far too radioactive so we ended up with this very prosaic green turned out that nobody over about the age of 23 or 24 was capable of flying that submarine at all we needed the video game generation in order to be able to to have this happen so after all of that it all came together in the following way here you have a plot of on this side the numbers of neutrinos that were observed with that first process for observing them to sensitive only two electron neutrinos and on the right-hand side the other process that is sensitive to all neutrino types so it turned out there were only a third of the total that are still electron neutrinos the total which is the original set of electron neutrinos that had not been transformed matched very well with the calculations of how many are produced in the Sun but only 1/3 survived as electron neutrinos there was less than a chance in 10 million or as we call it five standard deviations possibility that neutrinos had not changed into other types muon or tau neutrino types and that was regarded as as a discovery as a sensitivity adequately plane discovery in particle physics and it is that that basically enabled us to as a collaboration to receive this nobel prize so why does that happen well here's the most complicated part of the whole talk it's a quantum mechanical effect turns out that electron mu and tau neutrinos are not specifically one mass their combinations of three masses quantum mechanics allows you to do that when you make an electron neutrino you get that combination of mass one last two and minus three that combination when you make a muon neutrino and that combination when you make a Tau neutrino then as they propagate through space these fractions change because it's the mass that determines the process of how they well how they change as they pass through space and then later on you say okay I'm going to make a measurement and I'm going to ask what fraction of the time does it still look like this the thing that has propagated through our detector on earth and the fraction is only one third of the time the rest of the time it looks like either this or this that's a quantum mechanical process that enables you to have an explanation for how neutrinos change from one type to another as a result of having mass another thing that you can say is if neutrinos do that if they oscillate then they must have mass because if they travel if they do not have mass then they travel at the speed of light and in that circumstance if they're traveling through a vacuum then it is not possible for them to keep track of time things traveling at the speed of light don't have the ability to track time in what we call their rest frame therefore they can't be traveling at the speed of light and also do that they don't travel at the speed of light it's because they have a finite mass and therefore that's the relationship between observing the trainers to change from one flavor to another and having a finite mass but as I said earlier it's not easy to explain this so let me try I got some help from this hour has now from Cape Breton the nobel prize here to explain why he's the best in the world among us is our diversity 2015 we demonstrated the flavor change into one of the commentators you are and pound as in travel the core of the Sun amazing we don't know how to suffer by any further then we need to is smaller they developed that script by actually listening to me trying to explain to people all of the things that they had in the first part of it just as I was trying with you earlier on but okay a little bit of fun one has to have a bit of fun in doing science here is the set of agencies and countries involved and all of the institutions including a very substantial contribution from Oxford here in the UK as I mentioned earlier on and here are the 273 names of people who were authors on all of our scientific papers and I know you can't read those names but it's very important to me that those names are up there because those are really the people that did the work in in this experiment and also because no we started with 16 people they were essentially all faculty members at that point and we may have added somewhat similar and the numbers of faculty members since then but the difference between that 30 or 40 people and the 273 are students and postdocs who got their PhDs or their postdoc training working on this experiment and so it really was a major educational expert major educational experience for all of these people there are faculty members at Queen Mary and that world Holloway and at Lancaster and at Liverpool and that and at Sussex and probably some others that I'm forgetting right now but they they are all here in the UK and four of those are women so we're really pleased about the way in which things have materialized for people who worked with us so let me switch a little bit to a discussion of snow lab where we have the opportunity to go beyond simply an understanding of neutrino to make other measurements of things that are are now on our radar and in fact are the subject of discussion substantial discussion at what's called neutrino 2016 a major conference that's happening at Imperial College here in London 700 neutrino physicists from around the world in fact neutrino physics has become such a big part of particle physics now that it it really is a growing area for example Fermilab the major highest energy accelerator in the United States is doing essentially nothing but neutrino physics at this point and so what we're doing at this laboratory and actually the director of the laboratory Nigel Smith is with us here tonight is looking for other things that arise from the sorts of things that we learned about neutrinos but in order to do so we needed an entire laboratory that had the properties I described earlier of being 2 kilometers down and also ultra-clean you can see here that we're repurposing the the snow experiment called snow plus that we have a number of experiments here that are predominantly looking at for dark matter particles that I mentioned earlier or in the space between the stars but also in one case looking for the detection of supernovae the laboratory is ultra clean as you can see here the various cavities that have been excavated are enormous as was the original snow cavity and here Stephen Hawking again surrounded by his fans having a look on his second visit in this case again something that he really wanted to do in in 2012 and again an inspiration for our students and for all of us actually so what are we trying to do well we're trying to get as complete a picture as we can of how the universe has evolved since the Big Bang we started out we think in this universe with an enormous conversion of energy into two particles those fundamental particles electrons quarks and and in neutrinos and also their anti particles we think that the energy was converted into equal amounts of matter and antimatter you may be familiar with positrons that are the anti particles from for electrons they're used in medical diagnosis of a positron finds an electron it will annihilate and create energy it also can happen in the other way energy can Bruce equal amounts of positrons and electrons but somehow subsequent to that we've ended up with predominantly things that are like matter rather than equal amounts of matter and antimatter that process of transition in the early universe we don't understand but we think that neutrinos have something to do with it and we think that in fact by studying this double beta decay I mentioned we'll be able to understand that so we started with these particles away back in the early universe I mean you'll see it's 10 to the minus 32 seconds after the start of the of the Big Bang by the time you get to ten to the minus six seconds you're forming protons and neutrons the universe is cooling off as it expands by three minutes you're starting to get to a point where light can shine through after three hundred thousand years electrons combine with those protons and neutrons and you form atoms mostly hydrogen and helium back then and then later that starts to coalesce into stars and galaxies and it's at this point that the absolute mass of neutrinos begins to have an effect on how that formation occurs and at the same time dark matter has an influence as well on how the universe has formed as it evolved so in snow lab we have what I mentioned this neutrinoless double beta decay where we're refilling the snow detector with what's called linear alkyl benzene it's a something that gives out about a hundred times as much light as the heavy water that we have used before we're putting tellurium in it and we're studying a prime case of neutrino let's double beta decay and snow plus is one of the most sensitive experiments the world for doing that and is being reported at this conference in order to do that we had to put ropes in to hold it down because the stuff in the middle is lighter than water now so it tries to bob up unlike the heavy water and we're hoping to start next year here you can see the biggest example of macrame I think that's ever been been done but it's in place and and ready to go the other thing we're interested in is dark matter we think we have a number of known unknowns the older members of this audience might remember Donald Rumsfeld's discussion well this is a prime case of known unknowns we have three things that we think make up our universe there's us the more ordinary matter there's dark matter which we think is about five times as extensive in terms of total mass and then there's a quantity called dark energy that really is an inkling the implication of its existence comes from the observation that the universe is actually accelerating a little bit as though gravity has a slight repulsive term as well as it's normal attractive term but the dark matter is what we're particularly interested in because we know that it's there and we think we can see it by having the best case of getting rid of everything else at CERN at the Large Hadron Collider they're trying to create this dark matter for the first time by having enough energy finally to make these particles that have never been seen before and so what we do is very complementary with what they do one of the reasons we think that that dark matter is there is if you look at how fast the stars in a galaxy like ours are traveling and you you look out along well let's say along a distance out towards the radius that's this is actually the speeds you measure whereas the speed that would be appropriate to hold them in place with just the glowing matter is here so there's something else in the middle here in the spaces between the glowing stars that's holding it from flying apart and so we know that there are extra there is extra matter and and there are other reasons why we think they are small slightly interacting articles and what we're trying to do is to put weakly interacting massive particles that come through the two kilometers of rock so that we can put in our detectors things that will enable us to observe them and in particular they are to banging we try to have them bang into other atoms and nuclei those atoms and that's the signal we look for these are the set of experiments that we're doing I'll tell it tell you a little bit about the deep experiment that uses liquid argon to detect them what happens is you have the weakly interacting massive particle come in and hit an argon atom it makes a short burst of light if it's just the nucleus at recross because one of those wimps headed on the other hand other forms of radioactivity have almost a thousand times longer light output and so you can discriminate against those rather readily and what we're what the form of our experiment looks like is a tank of thirty six hundred kilograms of liquid argon in the middle again in an acrylic sphere made by that same company that's a lot better at making them now after their previous experiments experience on snow we have light sensors looking in in the center and this is what it looks like just before this outer shield was put on and right now we have about 1,000 of those thirty six hundred kilograms installed and so everybody in the project is extremely excited because we're about to within the next month be able to get this data this is a complicated diagram but let me tell you that right now limits on the observation of dark matter are at this line here in terms of the probability of interacting with the nucleus versus the mass of the of the weakly interacting massive particle and I can just show you that for our experiment this deep 3600 we're going to be about a factor of 10 better than anything that has been done so far there's another experiment called the super CDMS experiment which is that one of the top experiments from the US that's coming starting next year to snow lab and it's going to cover the remainder of this region here this is a limit which ironically is set by neutrinos interacting with your detector and messing up the signal for Dark Matter so that's the science it was suggested that maybe I tell you a little bit about some of the things that have happened in the last year related to the Nobel Prize and so on just for fun just for a little personal description of some of the things that occurred that are kind of interesting we won the breakthrough prize last November it's awarded by a whole set of well we shared it with four other neutrino experiments it's awarded by a set of interesting individuals including Mark Zuckerberg the founder of Facebook Sergey Brin the creator of Google his wife Anne Wojcicki was the creator of 23andme the genomics company yuri milner and his wife yuri is a again a Silicon Valley entrepreneur and they're trying to create a prize to interest young people in science and so these are Prize winners along with me and we had lunch at marks hooker Berg's very unassuming Palo Alto home but as I was sitting there at the dinner table I was thinking there's a hundred billion dollars in net worth sitting around this table but these are perfectly ordinary genuine individuals who are interested in the science asking us questions and so on and it's their motivation for doing it and we had a very similar experience in in Stockholm we have we were sent a couple of books one is a booklet that on the right that describes the set of events in the weekend in Stockholm which is absolutely incredible set of things that you do all of which are done in a wonderful way Nobel lecture Nobel Concert reception prize ceremony fall over the banquet and a ball afterwards and then the students Nobel note night capital thirty in the morning over at the University everybody in white tie and Tails banquet of the Royal Palace the next day and then finally Lucci a dinner and ball at the end of the day all of that is described in a book called reindeer with King Gustav which is the King's name of course written by the wife of a what is it subtitle is what to expect when your spouse wins a Nobel Prize this is the wife of a Nobel Prize winner in 1998 which my wife Janet and I hope attended is here too we had a it was a wonderful guidebook it even told you to not rent the shoes that go with the tuxes they rent in Stockholm because they hurt take your own shoes things like this but we just had a great time one of the Rice's things about having a great time was that we were able to bring in addition to our family which you see here which I'm very proud of we have four children and eight about to be nine grandchildren was that I was also able to bring 15 of our collaborators to Stockholm which include from Oxford Nick Shelley and Dave wark who is here and Steve biller and their wives and so we had a party in Stockholm for that week it was very formal and wonderfully done the Swedish royal family participates very extensively in this we shared with the other Nobel Prize winners particularly my good friend Takaaki kajita and his wife Michiko from Japan here you see us at the royal banquet we came into the major banquet down this enormous long flight of stairs and I was together with the Crown Princess Victoria who was quite pregnant at this point about to have a baby in a couple of months and I don't think I looked up for one moment coming down that stair if I tripped on her dress I was that was it so this is what the banquet itself looked like thirteen hundred people in their big banquet hall there's where Jenna and I were seated and a wonderful banquet beautiful beautifully done served by students in in wonderful white uniforms we were seated I was seated between the two princesses Jenna was seated between their husbands as I said genuine people and you know the sort of you get the feeling that these are people who are placed in a certain situation but are very genuine I asked Victoria who actually has a four year old daughter how do you raise a four-year-old who will be Queen someday and she said well we we try to treat her as normally as we can taking her to daycare and so on but every now and again we get her to come and stand still for an hour at a formal formal ceremony just to learn what she's going to have to do eventually he had a a not a shake and then finally at the end of the week there was the Lucia ball and this was put on by the students on Lucia day the the day in which the days start 13th of December when the days start to 12th I guess as they start to get longer and here everything was to be the antithesis of the formality and so on of the of the Nobel banquet etc and so my fellow laureate Ozzie Shankar and I were inducted into the Supreme order of the ever junk jumping and laugh at smiling green frog everything was to do with frogs that day and so they they asked us to give make some relationship between frogs and what we had won the prize for so tell us about the relationship between neutrinos and frogs so I explained to them that Petrino's penetrate through everything and maybe once in your lifetime one neutrino will hit one atom in your body change it into another element and you won't even notice it unless of course you happen to be a frog in which case it changes you into a prince so so fun is a part of science I was very privileged to work with a very highly skilled group of collaborators here in Canada and internationally including an excellent group in the UK and it's no lab were able to carry this on and there's still a substantial number of UK collaborators on experiments at at snow lab when I had to write up the lecture for the Nobel Prize I looked up the lecture that was given by Willy Fowler as I mentioned was my mentor way back and at the top he had a little a little Latin phrase ad astra per aspera at per Ludum to the stars with hard work and fun and so if you can keep fun in your science and enjoy what you're doing as I think our collaboration tried to do throughout it can even if you have to spend over 20 years trying to do it it can be an enjoyable exercise so thank you very much why can't the neutrino be detected going fast and light insane heavy water on its own rather than with collision

Channel: The Royal Institution

Views: 101,408

Rating: 4.8384199 out of 5

Keywords: Ri, Royal Institution, physics, neutrino, science, lecture, art mcdonald

Id: eWc0jywR-H4

Length: 53min 32sec (3212 seconds)

Published: Wed Sep 07 2016