1.2. Prof. Klute’s Research

Key Takeaways

hello and welcome back to a20 special relativity in this little video i want to continue with my introduction and talk about the research i'm interested in but this is not strictly on the topic of special relativity but you will see some of the influences of my research in the class as well as we move along so what am i interested in and what i'm working on i work on the large hadron collider you see behind me here a picture of the cms detector cms detector is one of two omnipurpose detectors at the large hadron colliders there's also lhcb and release two more dedicated experiments the large hotron collider collides protons at the highest possible energies in some units 13 tv terror electron volt collision energy collision happen around 40 million times per second in this machine when it's operational um and we have made great progress in understanding nature uh using this machine in the last about decade uh the large hadron collider started operating in 2009 we are currently in a shutdown phase but we hope to restart next year with even higher center of mars energies available for for our studies so why do we need a machine like this um colliding particles at higher energies allows us to probe the structure of matter um like with the big microscope and so we we can look very deeply into into the structure of the proton at the very same time we can this high center of mass energies and collisions produce perhaps new particles unexpected particles we will later see e equal m c square as a result of special relativity that when you have enough energy you might be able to produce a new particle of high mass and so that's kind of the holy grail and what we're trying to do and the other thing we do here is by colliding protons and sometimes even lead ions um we are able to create a very hot and dense form of matter similar to the environment after the big bang and we are able to study this this new form of of matter let's see how mars and mata are being built if you take the table in front of you and you start looking in detail you start seeing molecules and atoms the atoms are built out of electrons and the nuclei the nuclei itself is built of protons and neutrons and if you look more precisely drill deeply into the structure you see that a proton you know on the surface is built out of quarks up quarks to up quarks and a down clock if you further investigate the structure of the proton you see that there's much more going on there's gluons particles holding the quarks together and there's also bunches of quarks and antiquarks this is by now well understood if you ask what is the mass of the proton it's about one giga electron volts or 938 mega electron volts um but where does the mass come from the mass of the proton comes in parts of the mass from the mass of the quarks but in most parts uh from the gluons or the fields which holds the quarks together that's kind of surprising but if you had eight or two already you know that there's energy stored in a field and that energy again is equivalent to the mass so the energy stored in the gluon field holding the quarks together gives mass to the proton and this works quite well there's a theory which describes all of this it's called qcd quantum chromodynamics and you know if you with some assumption you can calculate the masses of a bunch of particles so this this plot here shows the lightheartron spectrum which can be calculated using the squishy event what i'm actually interested in is the mass of elementary particles so this discussion so far uh was a brief overview and how composite particles like your table becomes massive but how does the quark itself acquire mass how does an electron acquire mass or a neuron in ital this picture here shows you all known elementary particles um we can put them in three boxes quarks those are the particles the up quarks and the dunk rocks we found in the proton the electron um makes uh together with the proton makes a hydrogen atom there's neutrinos those are called electrons and then there's force carrier and we just met the gluons but there's also a photon the w and the z boson and the w z both on they are themselves also mass masses particles how do they acquire mass the answer was found passed about eight years ago with the discovery of the higgs boson a new particle and the underlying theory explains how particles acquire mass and so basically solve right not quite so this is really mysterious to see how different the masses of those elementary particles actually are you see this on this logarithmic table here again here our friends the down quarks the up quark and the electron and if you compare this for example with the heaviest known elementary particle the top quarks you see many many orders of magnitude different yes so how does this actually work and then you see some of the bosons the force carriers are massive others like the photon and the clue ones are mass less the answer to this was the higgs mechanism and a very simple explanation how the the fix mechanism actually works for fermions for those quarks of the electron for example is given in this cartoon um so the idea is that a field fills all of space it's basically a property of the vacuum and then you travel as an elementary particle through this vacuum you interact with this field and the stronger you interact the more drag you kind of get some sort of you feel an inertia and this inertia is what we we know as the mass of the elementary particle so there is an equivalence between how strongly you couple to this to the vacuum to the higgs field and your mass and so a top quark is coupled strongly to the sixth field while an electron only so lightly great um so we have understood everything so we you know the question is why do we uh still and you know collide protons important at the lhc um is there anything else to be discovered so it turns out that we have a very sophisticated theory describes those particles and their interactions but this theory fails to explain the observe all of the observations we have in nature and so that is kind of the driving force behind the experiment i'm conducting right now and so for example we know that there's dark matter when we look at the rotation of stars in galaxies we find that they don't behave um as you would expect simply all based on the distribution of matter in those galaxies there must be something else out there and that's what since it's not visible it's called dark matter and those dark matter um that dark matter could be a particle we might be able to produce at the lhc so that's an interesting question um also when we look out in the universe we see a lot of matter you don't see a lot of anti-matter so there must be in the symmetry behind between how matter and antimatter is being produced and so that is also not fully understood yet and then there's more question for example those neutrinos they're really really light you know on this leg scale i had a cut off um and then the neutrino masses do neutrinos acquire mars as an electron does as a top quark does or is a different mechanism we don't know um gravity is not even included in the standard model and the fact that the higgs boson was discovered at a specific mass which is rather small is also a little bit unnatural and so there is this entire list of questions and unresolved mysteries which we're trying to uh to answer and the way we do this is with big cameras so this is cms detector a similar picture as behind me um it's a you can think about it as a big camera looking at the interaction of of the collision of two protons and it starts off with around this interaction region with the pieces of silicon which we use to track charged particles going through we put all of this in a magnetic field and if if you listen to 802 already you know the charged particle in magnetic field they follow a curvature and from the radius of the curvature we can um calculate the momentum of those particles and then we stop the particles in order to measure the energy so we do this in calorimeters and what we use here is the lead tungsten electromagnetic calorimeter and a second calorimeter for particles which are harder to stop um so those are called hydronic calorimeters and then the silver part in the middle here gives the cms detector it's its name it's the as a solenoid it's a two-part a 3.8 tesla superconducting magnet and then we have more detectors out there to see whether or not some particles might to escape and we try to measure those as well there's another very nice picture after opening the detector you see this silver thing in the middle here is the pipe in which the protons zoom through the detector and are brought into this car and to collision in the very center part of it all right and then we take those pictures here's one and this is a very famous one it's a higgs candidate event where the higgs boson might have decayed into two z bosons and then the z bosons themselves decayed again into a pair of electrons shown here and a pair of muon here and then we can use those individual particles to reconstruct the property of the exponent here's another candidate where there's two photons being reconstructed and again those two photons can then be used in order to reconstruct for example the mass of the particle which is the origin first two protons so we have done this for the last years and i collected quite some data and if we look at the entirety of the data we can make this plot here and what this plot here shows is the mass of the particle and the coupling of the particle to the hex field and what you see there is a linear relationship in this log-log plot between those two and that gives us some confidence that the elementary particle like a muon here like a [Music] tau laptop here like the top quark here they acquire mass through the coupling of the higgs field and so there's this linear relationship the correspondence between mass and coupling to the x field great so we have this all together and it gives us a complete theory again there's a large number of open mysteries and questions we'd like to to answer and the way i look at this is a little similar to you know the exploration of for columbus so what we are trying to do is we go to higher and higher energies to higher and higher intensities to find out whether or not we find first hints of something new and unexploited so we made this discovery we made the discovery of the higgs boson but whether or not this particle is really the higgs boson is still out there we are trying to measure it's this more and more position maybe we find deviations from its expected properties to the ones we observe similarly christopher columba when columbus when he sailed off from spain he tried to reach the indies or asia and in his lifetime he never figured out that he didn't actually accomplish this and similarly maybe we have discovered a new project which helps us to understand you know more about the inner structure of particles you