 All right, I'm gonna go ahead and get us started here so we can enjoy the full benefit of the presentation today. So I'm Steve Sikulich here at the physics department. It's nice to see everybody here in person and online again. One announcement I wanted to make here at the beginning if that's okay for the department is that our final colloquium of the semester, the winter colloquium is kind of a culminating event of the semester. And I'm very pleased to announce that David Nigren from UTA will be here to talk to us about sort of some historical perspectives of the field, the time projection chamber and then the future of neutrino physics as well. And we're currently planning to have a reception and an event that evening. So there'll be food and a chance to mingle a little bit on the night of December 6th. So mark your calendars. If you haven't done it so already last colloquium of the semester, December 6th, we'll have the colloquium here and then six to 8 p.m. We'll have a social event nearby and details will be coming out soon once we get everything kind of firmed up for that, okay? All right, so without further ado, let me introduce our speaker for today. So Professor Darren Acosta has come over from Houston today to talk to us about a subject that's of great interest, not only because many people in the department are now excited about the electron ion collider, but because it gets an even more interesting idea involving colliding muons with stuff. Professor Acosta received his BS in physics from the California Institute of Technology in 1987 and his PhD in physics from the University of California, San Diego in 1993. He was a postdoctoral researcher at the Ohio State University. I was there too, so you're practically obligated for like to say the B. And afterward became a faculty member in the physics department at the University of Florida in 1997. In 2013, he was elected as a fellow of the American Physical Society. In the fall of 2021, he joined the faculty of the Department of Physics and Astronomy at Rice University. His research in experimental high-energy physics spans the search for new lepton quark couplings and compositeness that could arise from new forces and symmetries, searches for supersymmetric particles, standard model measurements, and searches for rare processes, such as the Higgs decay into dye muons. Seeing a theme here, muons. He's currently a member of the CMS collaboration at the CERN Large Hadron Collider. He's an expert on electronic trigger systems of particle collider experiments that perform real-time analysis of collision data before storage on computer disk. He's also was, I told him this when we originally got him to say yes to coming here. He's been influential whether he realized it or not on some of the things that I did in the modern physics class here at SMU when I started reteaching it again a few years ago. And it's my pleasure to welcome him to SMU to speak to us today about a muon ion collider at Brookhaven National Lab. Let's welcome him. Well, I think atlas can detect muons as well and they're very proud of their toroidal system. So that's right. Well, so on the topic of Higgs to dye muons, that search, that was one analysis where I think CMS has an inherent advantage over atlas because we have the four Tesla or almost four Tesla central field to get better resolution on muons to get a narrower peak than the two Tesla central field of atlas. And toroids are good for bending the muons you can self trigger on them but it doesn't help on the much resolution. Anyway, but yeah, today I'm not gonna be talking about LHC physics. So, and it's a joy to talk to you in person. So thank you very much for the invitation to talk about a new idea still kind of at the hobby stage for me right now but I'm hoping to turn it into something because most of my day job is on the research at LHC or things like trigger systems. And also to say I'm a new transplant to Texas I'm not far from you here in Houston and it was actually in establishing that contact and that was me taking a position there that kind of led to this idea growing with my colleague Wei Li at Rice University. So let me tell you a little bit more about this idea. Well, I guess first I've kind of already said a little bit about myself and as did Steve but yeah, I've had a long time in particle physics I did work on the Zeus experiment at Hera which was an EP collider so some of these ideas kind of were digging back in my memory banks on that and Wei Li is a nuclear physicist but also on CMS but also participates on the heavy iron studies at the RIC accelerator, I'll say more about that. And he's joining as others here the EIC, the electron ion collider at Brookhaven. Okay, and anyway, it was in those discussions as I said that led to kind of like oh, maybe there's something here that'd be interesting to pursue between the two communities but one big caveat is neither of us is an accelerator physicist. Whether this is practical to do we still, that's where the work is, okay? All right, so we're definitely in a crossroads for the field of particle physics and probably also later for nuclear physics and Europe already approaches on where we're going to go after the LHC. There's a lot of options as you see on this table here borrowed from this talk by Shridharadazu. We can build large electron machines to make basically Higgs factories to study the couplings of the Higgs boats on even more precisely. We can go to the energy frontier, be build huge next generation hadron machines perhaps at CERN in Europe, going to 100 TV. And so there's kind of some representative timelines but another attractive idea which isn't so new, it was around there 20 years ago is the possibility to have a muon collider where the muon is an unstable particle of course you have only two microseconds in its rest frame to get it on average accelerated and collided. There's been growing interest there and to say a little bit why that's interesting, it could be a novel and compact facility to study the high energy frontier. And this is a plot taken from this archive article a group there that's studying muon colliders. And basically if you're gonna build 100 TV proton machine the reach in physics is very similar to what you could do with a muon collider at 14 TV much smaller energy and that's a more compact design. The reason being is you get all the energy of the muon in an annihilation, whereas a proton you only get a fraction of the energy from the partons that are in it. And this is kind of a diagram of how one might achieve that one of the possibility designs of having a proton driver feed to create your pines such decayed in muons. But there's still a lot of unknowns, but that's possible. Potential timeline is kind of shown here this from the international muon collider. And somewhere between 10 and 15 years to really see if this technology can be mature to really commit before building a muon collider which is getting a lot of the particle physicists is very excited, smaller facility so many kilometers around that could fit on a single site. But just to borrow from the punchline of this article who's gonna invest in all the money to prove such a design, it would be good to have some physics potential of some smaller scale machine to kind of demonstrate the muon technology or technology as a demonstrator. And so this is kind of fitting in that bullet point there to give you a science case to go ahead and build at least one muon TV, muon accelerator before going and jumping to the ultimate which would be a 10 TV order collider. Now some words about the electron ion collider of course some of the members here know this very well. The conceptual design report for that was just released. And as I understand the proto experiments are now being designed and we'll put out documents soon by the end of the year. The salient points of this machine is it has a hadron beam energy up to 275 GeV a slight increase from the relativistic heavy ion collider. It will add an electron beam energy up to 18 GeV giving you a center of mass collision energy between 20 and 140 GeV. But also with high luminosity 10 to 33 to 10 to 34 Hertz per centimeter. And you can have polarized electron proton and iron beams. Physics goals and I'll go over that deep and elastic scarring of electrons on protons or electrons on nucleons. Understand the nucleon spin structure with the polarized beams and study the saturation scale which I'll say a little bit more about but basically when it gets very dense at low moment of fractions inside the nucleon. And the idea is this right now at Brookhaven National Lab is the relativistic heavy ion collider Rick. It's been running since 2000 and still has a plan through middle of this decade. It's accelerating protons and colliding them with either protons a nucleon or two nucleons up to 500 GeV and center of mass. The idea is to upgrade that and add an electron ring to collide with one of the proton rings. So basically you're adding a new facility here a linac and an electron cooling system to be able to inject into an electron ring and that replaces one of the hadron rings of the Rick accelerator. So you're adding a polarized electron source to the linac, this rapid cycling cyclotron and the new storage ring. Cost is of order about $2 billion so it doesn't come cheap to do that. And to me, this is a successor to HERA. This was the electron proton accelerator that first had collisions back in the last century in the early 1990s. This is actually one of my drawings from some old slide back then of what it could do. There were two main experiments H1 and SUSE but basically that machine collided 27 and a half GeV electrons or positrons on an 820 up to 920 GeV proton giving you a center mass NG of close to 320 GeV. And what it did was it probed a completely new deep domestic scatter regime from earlier fixed target experiments. So this is a plot from the PDG. These were all the fixed target experiments here in the multiple colors and you've extended several orders of magnitude in Q squared scaling still behaves so there's still just individual fundamental quarks in the proton, but you can see some violations in the scaling. I'll tell you something about the gluon density. And basically that was one of the main bread and butter physics from that machine. It paved the way by measuring the part on densities inside the proton, how much up, down, strange, charm anti-quarks there were in the proton by doing those measurements allowed for precision calculations of cross sections at hadron colliders and namely for the LHC. I don't think we would have had as easy time establishing that the Higgs is following the standard model predictions if the predictions themselves were very uncertain on the cross section because we always normalize what we observed to what we predicted and if you had big on error bars, well, okay it could be serum I like the night might not be so we owe a lot to that kind of bread and butter physics. One of the things that did come out of here that was a little bit unexpected was it was a strong rise in the gluon density for low momentum fractions. This is the fraction of the proton momentum. So here's down to 10 to minus three and this is suppressed by order of magnitude. So this is growing, growing, growing at very soft momentum in the proton there's just lots and lots of gluon in there. And well, the point is does it keep growing? You know, you can't violate uniterity. So when do saturation effects come into play in the proton? And there's just how my cartoon from high X down to low X where he just have just a soup of all kinds of C quarks and gluons. Okay, so just to kind of set the scale here this is a plot of the delivered luminosity versus the center of mass energy started from some fixed target deep and less excretion experiments down here Hermes and compass, the new EIC sitting here so around up to 140 GV but you have several different energies you could run at but much higher luminosity than say the Hera experiments which were higher in center of mass put over 300 GV as I said, but lower in luminosity. So the EIC is a bit lower in energy than that. So for me as a high energy particle physicist like, wait, that's the wrong direction but much more luminosity and also with the polarization allows you to understand spin structures inside the nucleon. Now, what could come after the EIC? So there is a proposal I'll say a little bit more on one of the next slides, the Large Hadron Electron Collider but what this talks about is maybe there's another alternative this Muon iron collider and we've even targeted particularly this one at BNL where the EIC is, which could also offer polarization. So first on the known approach which has already been documented in a nice technical design report the idea is you've got the LHC experiments and the LHC ring here the seven TV proton beams that collide or nearly seven TV at the moment. And the idea is to add an electron ring it's not a new idea originally before LHC was LEP and it was always this idea of colliding electrons on protons and repeating the HERA experiments but here you would have a new facility basically a new electron accelerator ring composed of Linux that are obviously aligned to provide 50 to 60 GV electrons to collide on the seven TV protons which would give you a center mass energy in the neighborhood of 1.2 to 1.3 TV. So that's one idea and it's nicely documented in this report you can find there but this talk is about this other concept of Muon iron collider and just to steal from his or Robbie's famous quote who ordered that, right? So let me try to convince you why we're ordering this, why it might be interesting. The idea is to probe a new energy scale and nuclear momentum fraction deep plastic scattering to reach a center mass energy of order TV which allows you to study Q squared and deep plastic scattering up to 10 to the sixth GV squared and X as low as 10 minus six. So this is an order of magnitude beyond the HERA EP collider. So that gets me excited. It's like, oh, there's new territory. And at the same time since we're doing this with Muons we have to develop a Muon storage ring and accelerator. And so this is providing a science case for trying to do that. And what we'll let you do and I'll say more briefly later in the talk is you can study QCD quantum chromodynamics as well as understand the Hadron-Nucleon structure in these new regimes. But if given enough luminosity you might also be able to do Higgs boson physics top-quark physics and BSM physics. To do so, this could be a merger or at least collaboration of the nuclear and particle physics communities around this single new innovative machine. I mean, there's no reason these communities have to be separated. We share a common heritage. It's just we have different focuses. So such a facility would bring the communities back together as naturally maybe they should work together. There's no difference between a nuclear physics experiment detector and a particle physics experiment detector. It's still various detector technologies. And we can by placing it at BNL but if another laboratory would like to try to host it we can think about those often but we could reuse the existing facilities and basically be as a large upgrade to the EIC there. Okay, some details here. So here was that EIC in this diagram here. The idea is to replace the electron injector with the new muon beam injector. So replace the electron beam with the muon beam. Now we tried to work out what kind of energies one might get. So the bending radius of the rick tunnel at least in the bending sections because it's actually made of hexagon so there's bending sections in six places. There's 290 meters, good useful experimental equation the momentum is 0.3B times R, B and Tesla. And so if you take some assumptions for magnet technology for example, LAC has 8.4 Tesla dipoles. So we know that technology exists. We could accelerate muons with using that radius of curvature to 0.73 TEV. But the HLAC will deploy dipoles that have 11 Tesla strength in some regions. So that technology should be fairly safe to choose as well. And that gives us basically close to one TEV for the muon beam energy. Or if you are aggressive, the future circuit collider projects are trying to get dipoles that would reach a field of 16 Tesla, which would get us to 1.4. But we took just this middle of the road just what we think is realistic for a muon beam energy of one TEV which is a seven to eight times increase over the top electron ion collider energy. Now, this is just taking magnet technology. It's not saying that whether it meets the demands of ramping it quickly for acceleration. That's a different story. Again, that relies on the accelerator experts and magnet experts. One comment is these straight sections, muons are unstable, they decay, telelectrons and neutrinos. So these straight sections will lead to collimated sprays of neutrinos. So if there's interest in high intensity in trino beams and there are in the community, not necessarily at these high energies, this could be a facility to make use of those as well. And then there's one final caveat that if we were to use the same magnets, for example, for the Hadron beam and accelerate the Hadron's higher, then we could actually go from one TEV, sorry, it was one TEV center mass energy as well for the muon ion collider could go to two TEV roughly if we actually upgraded the Hadron beam. But at the moment we just proposed just adding the muon beam and reusing the known Hadron beam there. We try to make an estimate of luminosity at such a facility basically by taking the known parameters for the proton beam at the accelerator. So the top energy is 0.275 in TEV. And then for the muon beam parameters we took from this node here again here from this map consortium. And we took the sort of column here somewhere between the Higgs factory muon collider and the multi-TEV one. So these are the parameters we took there for things like the admittance, the transfer beam size and the repetition rate for injecting the muons. And if we do that and just punch in the numbers blindly to this luminosity equation, we could achieve in principle seven times 10 to 33 luminosity for such a machine. Now, of course the muons are constantly decaying. Basically the number of cycles they'll make is about 3,000, which is basically 300 times the field strength in Tesla. Clearly if you added more than one interaction region for the colliding, then you could get twice the data very expensively. Of course, cut your ability to another experiment but more interaction reasons makes the most use of those muon collisions. Okay, yeah, that was a number there. All right, so how does all solve compare? Let's look on one chart here. So this is a two dimensional plot of the Q squared reach versus the momentum fraction X in the proton and the max here is basically the center mass energy squared. So it's like a TV there. And so for the electron ion collider that's the region in green. This is the territory it maps out. Everything above Q squared of one is generally what's felt to be now hopefully fairly perturbed of QCD calculations. Anything below that's like really non-perturbative and it doesn't converge when you do those calculations. So you're kind of reaching up to Q squared of a few 10 to the four and X is down to 10 minus four, 10 minus five ish. The muon ion collider would be this red region and it's just barely taps but it's a really nice extension and upgrade beyond what the EIC is providing. And it also has gone beyond what the Hera collider reached which is this gold region there. We've extended here in the new territory. Interestingly enough, these parameters that we came up with actually give you very similar coverage to that proposed large hadron electron collider. That's the region in blue. Okay, it was slightly higher energy 1.2 TV and center mass but pretty much almost equivalent reach and equivalent science but done to a very different way. Lower energy hadron beam and a high energy muon beam. And this dashed line here is where in this model here by this author, sorry, GBW is this model and in this PRD document which they think below that Q squared region is this function of X here you would be start to see this saturation effects come into play inside the nucleon. And so you have a chance there to start to see it in a muon ion collider or the LHEC whereas you can see for the electron collider for in protons is probably not much region at least in the perturbative regime. But we'll see also on the nucleon case. The kinematics though even though it's similar coverage between the muon ion collider idea and this LHEC is similar the kinematics are different and I'll say more about that at the end of the talk. Basically if you took the center of mass system for muon of 960 GB on the proton 275 center of mass is moving in the muon direction the negative direction in rapidity about minus 0.6 so fairly central for the center of mass whereas the LHEC because it's much more in balance with seven TV proton it's boosted at eight of or rapidity of 2.5 roughly so very much in the proton direction. So the kinematics are different that means different detector designs to really maximize the potential. What kind of physics can you do? So this is just a cartoon of the types of physics you can do it you can measure as I said the structure functions which are measuring the part on densities you can also get at alpha S the parameter the basically dimensionless fine structure constant of QCD if you get to high Q squared and have enough luminosity you can make Higgs bosons top quarks I can study what's going on at very high X both gluons and also the partons and perhaps even see hints of beyond standard model physics but the low end it's the non-linear QCD regime that saturation region and you can even do tomography if you like of the nucleon and also study the spin structure of the nucleon but let me just try to come in a few of these in turn so starting with the structure function so this is kind of the same plot I showed you but taken in a different way so this is from the C-tech collaboration which is taking the world's data on things that can relate to part on densities and this is just the inputs so I just stole the plot on the inputs so a lot of fixed target deep mass scattering experiments the hair experiments and then these are the hadron colliders to have a tron and the LHC and the different data sets that are used it's I'm sure quite the business to fold all that data in and if I superimpose the muon ion collider reach it would definitely be in new territory you'd be just opening this area here as well as overlapping with now with the LHC coverage and why is that useful? I mean you might think well they actually covered it but these PDF measurements done in deep mass scattering are complementary to what you can do with a hadron collider yes the LHC data can also be used to extract part on densities and are from Drillian lepton production W production jets and top and so on but if you're also trying to calculate and compare to standard model those cross sections it's a bit circular if you're measuring the PDFs there and then using it to do your comparison of theory and also the measurements are convoluted with QCD effects because you're starting with a very colored system with quarks and gluons and quark flavor you're not always able to disentangle that so well deep in the last the scattering measurements can definitely more cleanly decouple the quark flavor and QCD effects. The other point I'd like to make is you know this me I see there it is overlapping there if for no other reason you can probe directly the structure function and part on densities at the scale for say Higgs production at the LHC or a future circular hadron collider so if I just kind of overlay two points roughly at the X values and Q squared scale these were these are sort of inferred from the earlier Hera measurements especially for the FCC it's all you have extrapolations and you know you have an estimate there but it's gonna have an uncertainty based on the how the lower energy data can was extrapolated out. If you directly measure then you can lower that uncertainty borrowing from the LHC report you can probably constrain those uncertainties to be less than a percent maybe a half a percent versus say several percents and that would be useful for doing precision physics at a hadron machine of course the motivation here is to demonstrate the case for building a muon collider but if in the end you find you're not gonna be able to fully achieve the goals of such a collider at least you have input now for a future hadron collider and I make the case that Hera was very useful for the LHC so the next generation high energy deep and elastic scattering collider would be useful for a future hadron machine. Okay one other comment about QCD is of course the coupling constant runs that's what leads to confinement because it gets stronger at the smaller the Q-scales Q-square scales this is just a collection of various different experimental measurements from the hadron colliders as well as deep and elastic scattering where you're measuring jet production and for example from that deep and elastic scattering of jets you can see some points here in green mapping out say this is now Q and not Q-squared from 10 to 100 GeV but if you had a muon ion collider you can principle reach out close to TeV so you'd be able to measure the strong coupling constant from jet production as well as indirectly inferred from the QCD evolution equations when you fit the deep and elastic scattering data the part time density data you can do that all in a single experiment map out that curvature which helps eliminate some inter-experiment uncertainties so I think that would be quite attractive in trying to do as if you like precision measurements of the strong coupling constant okay switching a bit first a bit now to the nucleon scattering so comparing the LHEC with the muon ion collider idea for lepton nucleon scattering there you kind of open up more that saturation region here this is this line there so even the EIC that was its main point for the design parameters they have you open up this territory to see saturation effects come into play in heavy ions this is taking a values of 110 the nucleon atomic number so you've opened up there but again it's opened up much further with the muon ion collider or the LHEC you'll have all this territory as well and as with the EIC which can accelerate and collide a wide range of ion species the same principle could then be done with the muon ion collider with the LHEC you're kind of limited you have the protons or whichever ions I think they've done gold and xenon and I can't remember what other not only a few they've done I am not a nuclear physicist so a lot of these I can't go into great details here but the things that get nuclear physics community community excited again I mentioned the blue on saturation understand what's going on there and when that transition happens but they also measure understanding the part tendency is not just in the longitudinal direction that X values in the direction of the proton momentum but also transverse for slices of the longitudinal momentum and so you can study that and basically the MuIC with IOT approach and measure these transverse dimensions or distributions in ever smaller values of that momentum fraction X and then there's also the spin of the nucleon you know naively in the quark part amount of we all learned that okay the three spin one half quarks make up the proton they all add up to spin one half looks great because that's how angular momentum rules work except that we learn that actually the quarks don't make up all of the spin of the proton it's also made up of orbital angular momentum and blue on contributing and that's complicated and probably you know not so well pinned down it's exactly going on there so the spin structure of nucleons is also a whole science program that to study and basically the mu and ion clatter allow you to study that also down to very low values of that momentum fraction X because it has the possibility of having polarized beams now going back up to sort of the high energy domain of particle physics what can we say if you have enough luminosity about say Higgs boson physics so you could you would primary diagrams would basically be vector boson fusion so basically W's or Z bosons emitted off the quark leg and the and the muon leg to produce a Higgs boson and this is a chart from one of the reports for the HLHC and future accelerators like the FCC and these are various bars for different decay modes of the Higgs boson and I just want to draw your attention to a few of them a few of them have basically smaller predicted uncertainties this is taken from the LHEC reports I'm just transferring that whatever the LHEC could do that the muon clatter could do smaller is better so for example if I look at the measurement of Higgs to BB bar that's the largest contributing the branching ratio to a species the BB bar 57% this is the predicted from the HLHC you know something like just under 4% 3.5% but in principle LHEC could do better on that but even more of the point charm so the reason it's harder to hadron colliders is lots of be quarks produced in proton collisions and trying to understand I mean the background is enormous to do that measurement precisely charm quarks are even harder is more of those and you also tell the difference between bottom and charm these busy environment but in a certainly in a lepton collider like a E plus E minus machine or a mu plus E minus machine but even at a mu hadron machine it's cleaner environment and you could get at the charm content and so the HLHC I mean else he's just not making any statement about charm least within the standard model level right now the limits are like 20 times but you can see here that yeah maybe the such a silly could do that providing making the feeds blows on so second generation we have hints now evidence for Higgs coupling to muons but yeah this would give you a hope to measure it into in the charm the other second generation particle and then just a few comments about kinematics so this is a distribution and pseudo rapidity for I'll just concentrate on the red curve which is where the Higgs bosons produced this is from the LHC reports it's produced rather forward here you know a to above two to the four and the decay parts are basically following that so that's rather forward whereas the scattered lepton is is you know fairly central for the muon ion collider idea it would shift basically by three units of rapidity so those Higgs decay products would actually be very central in the detector so very well measured region of the experiment but it's gonna be the scattered lepton the muon in this case it's very forward and I'll show you that a bit later okay so that's for Higgs physics what to say about BSM you know sorry model so you know the hints that are out there now that are still residing are come from G minus two where we have an anomalous measurement as well as anomalies in B maze on the case basically the penguin diagrams for B to S gamma or B to S dileptons and so there was a recently a nice workshop summarizing all the results from giving indications to anomalies in B decays at this flavor nominate implications workshop that I think was hosted by CERN virtually and so I stole a couple of slides from that as kind of motivation because they're trying to use that to scenario down what are the theoretical possibilities to maybe explain some of those anomalies and so just pulling two of them possible Z prime a new boson presumably a force carrying boson or leptoquarks and the idea here was that maybe the C prime couples to bottom and strange and then to muons or in the leptoquark case a leptoquark has both lepton and quark numbers it'd be a very odd object but maybe also could be indications of granification and the quarks and leptons and again but here it's a bottom and muon basically merging into a leptoquark and indicating say the stranger muon or the other way around and that said that looked interesting to me if that's what your hypothesis is well maybe that's something this machine could test because just take those diagrams this Feynman diagram and just turn them 90 degrees well it depends on the point of view how you read them but in this case rotated 90 degrees instead of producing muon pairs or having a pair of leptoquarks of the muons in the final state rotate 90 degrees and maybe you can have muon strange quark scattering via C prime going to muon and B or a leptoquark in the T channel so it would have the same well has the same possible initial and final states there so I mentioned the T channel here leptoquarks themselves because they have both lepto and quark number could be produced as a resonance in the S channel unfortunately though with this one TV center of mass muon ion clatter machine probably could only probe to very roughly 800 GV and leptoquark mass give or take although you could probably extend it to one FTV if we did also accelerate the hadrons higher to about a TV but that's to be compared with the limits coming from the LHC experiments where leptoquark mass limits are typically greater than about one TV depends on the exact leptoquark model at which final states you're going to some are closer to one and a half TV and some are maybe one TV or just below but that's probably interesting territory especially in this T channel where you're gonna look for a deviation in your differential distributions of deep plastic scattering with Q squared and X and it looks like the scenario for these possible extension to the standard model are in the range of one to 10 TV so at least in this slide from this author in that workshop probably within sensitivity of such a deep mass that's scary machine so but that's an open question the study would have to be done to see if we could really be sensitive so that would be interesting quick study to do just check out what we can say there with this machine but the other thing to mention is well you know if there's violations of lepton flavor universality you've got a muon beam coming in you know one thing that you should just look for is like how often does it disappear and become something else for example if it turned into a tau lepton that would be very striking evidence of beyond standard model physics so that might be something also interesting because we know less and less about the muon and tau couplings and say the electron couplings okay to sort of head toward latter part of this talk on the experimental side we can talk a little bit about the kinematics of such machine I've briefly gone over kind of the science cases so just to review deep elastic scattering you've got a lepton hadron scattering you can define the center of mass energy which is just as the usual at the full momentum squared of the incoming beams but then there's Bjorkane X which is that scaling variable mentioned to you that's basically the fraction of the momentum carried by the proton that's defined here in terms of q squared and then the dot product here of 2p dot q q squared is basically that full momentum transferred for the exchange boson between the lepton and the hadron the negative square that is you can find in textbooks or work it out yourself you can work out the kinematics to how to figure out q squared or the inelasticity y from the scattering angle and energy scattered energy of the lepton solely but you can also do it from the hadrons and just to say in this form of the state at the polar angle with respect to the hadron direction the proton direction so the lepton is going in the opposite direction so just by convention but you could do it also from the scattered hadrons or a mixture of the two it's over constrained at least at leading order and you can get an effective angle for the hadrons basically by summing up the energy flow I won't go over the details here but you can work out the energy flow transfers in parallel to the beam axis and work out basically for at least the argument for cosine of that angle and then use that in your formulas and I'll use that later I won't go into the details here so this is just to give you a flavor of what the final states would look like at such a muon ion collider where you have this TV muon beam coming in so this is plotting the muon scattered muon directions and energies in that q squared x plane and what we see here is kind of the staircase up here this is the pseudo rapidity of the final state muon at the very highest q squared in x it starts to become central eight of zeros probably right near the top there's negative one, two, three so this is already now within 10 degrees of the beam pipe and for a large part of the q squared x region you're very forward eight of less than minus four even down to minus seven so these muons are not scattered much at the low and medium q squared which has been opposed to its own experimental challenges because you're trying to tag very forward muons the energies though can be very large very low y then it's close to a TV but you can see even for a large ish y very close to this kinematic limit it's still hundreds of GV, half a TV so you're talking about half a TV to TV muons very close to the beam pipe for most of this q squared x range the good thing about muons because that can be very difficult first of all they're in the beam pipe at that low angle for a long time and then they have to escape the beam pipe and then they might hit some magnets and other things along the way but muons are minimum ionizing so they're very penetrating so that's good, if they were electrons we'd have a problem it starts showering what about the hadron kinematics so these are the hadron kinematics q squared versus x so the let's see so the eta values are here the diagonal lines now rather than the staircase here's central eta of zero so basically in the region where you expect to be able to do measurements only a q squared, large q squared and large x then the hadrons are fairly central but at low q squared x they also tend to be fairly forward or actually backward because it's in the muon direction but not quite as much as the muon still maybe eta of minus four here so scattering angles in that backward direction less so than the muons so the jet kinematics are more central from minus four to two interestingly the energies are very large typically from 20 GV up to maybe even half a TV so 20 GV is this curve which wraps around down there and then here's 250 and then 500 would be closer to the line so you have very energetic hadronic systems so very jetty final states from the scattered hadron system okay this is a busy slide trying to go through it the idea was basically how well can we measure where we are on these planes how well can we measure q squared and x because deep elastic scattering and so we try to do just a quick little toy study using the Pythia event generator for deep elastic scattering for a muon on a proton and then put in certain assumptions for building your dream detector and what would that be so starting from the muons high energy muons well that's difficult to measure they don't deflect much in a magnetic field but of course the spectrometer has to be designed so what we took is a tracking system which would grow with P as normally they do and just set a benchmark 10% momentum measurement at one TV and that kind of matches say for an LHC experiment how well they can measure the momentum for hadrons we took basically some numbers here 0.1% times momentum in GV plus 1% in quadrature and assume that we can measure amounts pretty far forward up to eight of five and the muons as I said had to get down to eight of seven and then other assumptions for photons and neutral hadrons as well hadrons being less full measured at least as the stochastic term in the energy resolution anyway this is a plot these are two dimensional plots of how you reconstruct on the left most column Q squared the middle column X and then the last column Y for different methods using the top row the left scattered up ton only so from the scattered muons we do pretty well at measuring Q squared from this detecting the angular measurement I didn't say anything about the angle but the it's where did I put that in there where did I forget to put it in there but we had a certain assumption on the angular resolution which I yeah, there it is. Sorry. Well, now that was in a moment I must have forgot it. He was sorry. We had a certain assumption on the angular resolution so we do pretty long reconstructing Q squared from the scattered muon assuming those measurements but if you look at X well the colors means that it's more than about 10% resolution so this is sitting more at 50% so it's not very good and even worse for Y. Sorry, there's a question. Yeah. That's right. There's no, no, it's not. This is a toy study just taking some assumptions on how what the resolution would be the work is okay, let's do a simulation of how it would drill through wherever and where it would come out. I'll come to a cartoon design what we're talking about but in a moment but yeah, that's if this is if the science case looks interesting compelling enough then yes, the hard work is in studying what would be needed to build a detector to do extract that science. Absolutely. But as I said, at least for TV muons they're gonna go pretty far. You're not gonna stop. They may scatter a bit or brimstrelog and that can disturb the measurement. Yep, yep. The hadrons I think are what's gonna be tricky if you try to go too far far because they will start to shower once they hit material. The hadrons actually do pretty well you can see like on Y it's down here in the 10%ish resolutions or even an X at high X because of those high hadron jet energies they're doing pretty well. And even Q-squared is not too bad it's just that low Q-squared you start to suffer a bit in hadrons. An approach I learned back when I was on the hair experiments was this double angle approach. So you're kind of independent of energy measurements and that works really well in principle. You see you're in the purple so a few percent resolution on Q-squared also an exit especially high X and also on Y even down to low Q-squared. So that looks the promising approach and the idea would be, okay we'll have a detector design and some physics process and then you can go through the exercise of how well you can measure either extract part time density measurements or whatnot or actually say structure function. Yeah, the question was how often can we what's the scattering rate very far forward? So that depends on the cross section here. And so this is, these are the studies I'd like to do beyond my hobby here just about finding what might be done now we need to do some serious work. But yeah, because that would tell you how much luminosity you really need. I'm just kind of relying a bit on if Hera could do these structure function measurements with over to 10 to 31 luminosity. Yeah, okay 1031, 1032 we're probably gonna be good shape but that's a hunch, right need to be borne out. And you have to detect these forward melons. Okay, so yeah, that was just to satisfy that looks like you could measure these with these assumptions we shouldn't be able to do while doing the measurements in principle of course the hard works and designing a detector. So yeah, about a detector. So this is a diagram pulled out of a document on the muon collider itself on mu plus mu minus machine and one thing that you have to worry about is along with the melons it's not just melons coming down your beam line it's also the melons that decay to electrons and a lot of neutrinos and neutrinos at least the experiment doesn't have to worry about they're gonna pass right through enough of them could be a radiation problem but the electrons are an issue and so there has to be some shielding of the incoming beam to prevent too many hits on your experiment or too much even radiation. So this is a symmetric design that I stole here because it's a mu plus mu minus machine coming in but in our case we would have a muon beam coming in and a hadron beam coming the other direction. I noticed from this diagram that the shielding cones these nozzles looking elements reached about eight of 2.4 well that's gonna start to block a lot of those forward hadrons. The melons I think will have no problem going through but there's some other material out here and so on. So that's the part you have to study but I'm guessing that with the melon beam it's coming from one direction I probably don't have to shield the same amount from the other direction from the melons right? So maybe I can get rid of a lot of that to help build my spectrometer in that lepton direction. And you will need that muon spectrometer because of small angles it's gonna be inside the beam pipe for a while and then come out. You might be able to put at least some milliradians of crossing angle. I mean, I think for the IC it's even up to 25 I remember that will help also get the melons out at least in one direction. Yeah, so that helps get it out sooner rather than many tens of meters downstream maybe it comes out in a few meters. So and actually also an overall tilt to the machine of a few milliradians also might be good to help control where those neutrinos come out of the earth as well. So this is just a cartoony diagram but the idea is that you kind of need a central detector you're close to four pi experiment although most things will tend to go in the muon direction for this type of collider as opposed to the electron ion collider where things are very central or even the hadron direction. But you're gonna need to tack on an LACB like spectrometer that goes to very forward rapidities to measure not just the muons but also any hadrons that you wanna recover out there. So I could imagine some kind of staging thing where you have muon detector centrally and then maybe some out here and you go further down the beam line and there's some more muon detector further down that you reach smaller smaller angles there. Okay, so just to wrap up then. So the path forward in our viewpoint we're trying to promote and we're trying to gem see if there's interest and to pursue further study that a muon ion collider could be a natural upgrade to the electron ion collider. That's basically set to start sort of in around 2030 I guess we'll see how well that schedule holds. So maybe in the decade after that we'd be ready for muon ion collider. I think that gives us the time that 10 to 15 years to let the major muon acceleration and storage ring designs come to some more maturity but perhaps even with a test facility to help feed into design for this muon ring at Rick. The same time here's the Heilemaus LHC program running here that should start up around 2028 now. And then it's like, what happens next? Maybe there will be a Higgs factory machine or electron machine or circular or linear. And well, then if the muon technology works out then perhaps you could have a muon collider sort of at this time scale but now we're talking several decades from now which we're talking about anyway, no matter what. This is trying to build the case to help make this more of a reality. So anyway, to conclude some of this key merits of this concept, try to build a compelling science case across the nuclear physics and energy physics energy frontiers and the intensity frontier even perhaps. So kind of this intersection of this Venn diagram intersection between the energy frontier and nuclear physics and then intensity frontier and latrinos. You can serve as a demonstrator or a staging option to establish muon collider technology toward the ultimate order 10 TV type accelerator and collider. It's maybe, I should have put the quotes around as affordable as an upgrade to the EIC by reusing the existing facility infrastructure and accelerator expertise. And I think it's probably our best chance at a unique muon collider sided on US soil with a clear design goal provided we get to join efforts between the energy and nuclear communities even attracting worldwide interest to come there. I think it's more realistic than trying to argue for a completely new collider facility on US soil at least in the particle physics side. The electrolyte collider, at least you haven't in principle agreed upon new collider. So this will be a staging off of that. And so the next steps, we're going around trying to talk to people, propose this idea of one of the future muon collider options in the US for the particle physics community that's the snow mass 2021 process that's going on and should give a community report by middle of next year and also provide to the nuclear physics community and their long range planning next year. The idea is to establish a dedicated R&D program we'll build on this concept and establish an R&D program along with the muon collider technology in the US evolving, as I said, the energy physics and nuclear physics communities and as well as working with the international muon collider collaboration is a lot of your a lot of Europeans as well studying muon colliders and engage BNL to consider muic as a possible future option of the lab there to start conceiving of a possible design and potentially established test facilities maybe even if this does take hold think about the detector designs and make sure they can be staged and upgraded to account for those high energy muons. And so yeah, my goal here is to engage the broader theoretical and experimental communities to explore the physics potential maybe seek some collaborations here on studies we can do and address the detector design requirements and challenges through workshops, collaboration and working groups. So thank you very much. Okay, so what I'm going to do is I'm going to switch to the handheld wireless mic. And let's just do another test here real fast. So, Krista, if you're still connected, I'm sorry to keep picking on you. Is this working? Can you hear me? Which is a silly thing to ask. I can hear you, yes. Okay, great. All right. So first of all, let's start with folks online. So are there any questions from anyone online? Go ahead and raise your hand in the participant window or just unmute and ask your question. Okay, I don't see anything there. So in the room. So Darren, thank you so much. This is a very nice and informative review of this very inspiring project. For spin physics, it is important to have polarization. And obviously, being able to measure the final state of missing energy will allow to use W plus, W minus bosons to very precisely resolve spin dependent PDFs. What are the prospects for measuring missing energy with higher accuracy at this facility? Yeah, that's an excellent question. So if I go back, well, let me go back to the Q-Spirits plane. Actually, this will kind of say, so if I imagine like a charge current reaction, just W exchange. So the muon now becomes a neutrino in the final state. If that was a question, that muon's going to follow where the neutrino will follow where the muon would have gone, which is very forward, which is going to be hard to measure missing ET. But at high Q-squared and X, actually, I should go back one more. High Q-squared and X, it is central. And that's also the region where I'm going to have a jet of order 100 GV. So I think its prospects are very good to measure, at least at high Q-squared and X, the missing ET of this machine. I think better than say at LHTC, although at high Q-squared X there, they have a pretty significant hydronic system as well. Where exactly that transition starts to fall apart down here, we'd have to do some definite modeling of that. But I think at least in this region, upper Q-squared and X, measuring missing ET shouldn't be an issue for deep molasses scattering. Can I quickly ask another question? So of course, you can reduce the energy of the beam. And then what are the prospects for that, for the hydronic and muon beam? No, I mean, I didn't have any specific results here, but yes, you can always presumably lower the energy, not ramp the magnets as high. And that will let you more, these kinemax will then morph and change with that. And that might put it, if you're interested in a specific region, you might want to lower the energy so that becomes in the region where you can say, for example, measuring missing ET better. But I don't have any particular quantity of comment to say about that right now. That's a good point. This is really interesting. I'm glad you're doing it, keep up the good work. Muon colliders have been talked about for a very long time. And it's so pie in the sky that this is a very pragmatic approach. And I'm really excited to see the ideas. You mentioned several times top quark physics, but then when you talked about things, you talked about Higgs, and do you have anything on special top physics that might be possible at the? Yeah, I'm pretty sure there was a section in the LHEC report. The point is you have up to that TV center mass energy. So you can make either single top production or even diet, TT bar production. And also, actually, maybe I meant to put it or I could have put it, I just didn't. But on the BSM topic, I mentioned you could have left on flavor violation beyond the towel, but you could also think about a top quark coming out and you would have enough energy to do that. So of course the LHEC had enough to make top quarks as well. And so I think there are some left to quark limits involved top quarks, but the question would be whether this could maybe perhaps be more competitive on specific models. And so I didn't put it here, but if I go away from these models that were inspired from those talks in that anomaly workshop, and just to think more generally, you could have a top quark in the final stage. That might be interesting just to look for it. So absolutely, yeah. And then in the case of BSM here, but whether it helps on the mass measurement, because that's kind of difficult to do with hydrogen car, especially ones that have lots of pilot because they're at lots of luminosity that the top mass measurements are difficult. Well, what about, probably you wouldn't do TTH, I guess, your tower coupling measurements. Yeah, so let's see, you're gonna be over half a TV mass. You're probably gonna start running out of phase space. It's probably not the limit, just see it. And you're probably better off doing TTH at the Hydrogen Gliders. But yeah, that's a good comment. We should emphasize more of the couplings to top, because that's something we couldn't do it here. I know we looked at one click, we had 300 TV and just enough to make a top work, but not sure we had any, I can't remember if we had any convincing evidence for top work there. Okay, any other questions online or in the room? All right, I have one. I'm gonna exercise chairs prerogative. Let's talk about the Higgs physics that you mentioned there. I missed it if it was on the slide, but did you have a rough estimate of the production cross-section for the VBF process at these energies? So that was one of the things we wanna be able to calculate the cross-sections. I can just, I remember in the LHEC report, there was a cross-section number there, 150-ish fifth bar and something like that. But first of all, don't rely on my memory. And two, we didn't do the calculation with a generator yet. I need to find some person power and some students. Well, actually I was gonna pitch, this might be an interesting area to co-collaborate on if you'd be interested, because certainly my ears pricked up when you started talking about doing Higgs to CC bar with this. And I mean, you already had me a deep and elastic scattering, but you completely sold me when we're talking about H to CC bar here, right? So if that's fertile territory for a study, maybe we should talk more, because I think this is a great intersection of things that I care about and certainly things that you care about too. So, okay. Absolutely, it's great. Okay, awesome. All right, any other questions? All right, well, if not, let's thank the speaker one more time and we'll go ahead and close up the event. Thanks, Aaron. Thank you very much. All right.