EF06 Contributions
Huey-Wen Lin
>> All right. On that note. Let's go to our next talk. HueyWen.
HUEYWEN: Yes.
>> We see your slides. They're not full screen, though. Yeah. Thank you.
HUEYWEN: All right. Okay. So, today I'm going to talk about the EF06 contribution and just remind everybody, I will we're focusing on the hadronic structure and forward QCD. And this talk is given by me, but in preparation with Pavel and Christophe. So, EF06 have a number of the focus questions that we see in the beginning of the Snowmass process. And I don't everybody to read this all. I have a link to the page with all the existing questions. But point out a few things that are going to be representing in the talk later today. We have a lot of PDF interests. And then we have there are some facility overlap with EIC and some other forward facilities as well. And not only are we studying the distribution function, we are also interested in the three dimensional structure for not on nucleons, but also nuclei. And some with the computational here interested in using artificial intelligence to really improve our knowledge to the nonperturbative hadronic structures.
So, the beginning of the process, we in total received about 64 LOIs. And here's the word cloud that was made. I made some modifications to it. It's interested that the topics that people are interested in. We have about 31 of the LOI that's primarily EF06. We have about 22 that's overlapping with the theory frontier, about 10 with the computational frontier, 12 "cosmos, and so on. And some of this you will also see in other presentations as well.
And so, here are the list of the white papers that we have received. That's currently on the Wiki page. So far. So, a lot of them are on the PDF. The information with some xFitters. And we will talk a few of these white papers into this presentation. So, the way we organized this is different from the other presentations you saw so far. We are trying to get the each of the contribution white papers have a chance to kind of highlight what's really important in their topics. And we try to orient in the rest of the presentation that way.
And so, another thing I want to point out is that it looks like, you know, we don't see or we have originally a huge amount of LOI. And then the white paper number have been reduced. And this is because a lot we really appreciate a lot of our participants actually working really hard. For example, one of the white papers that's currently on the Wiki page is actually a combination about 15something LOI contribution. And people do spend their time working really hard to some of them even try to condense. It could be easily over a hundred pages of white paper. But they try to keep the message at the high level, some of them become 20 pages, some are still very long. So, it's really a lot of hard work that we don't see as we talk about in this presentation. But there's a lot of work that has been going on behind the scenes that we kind of unfortunately only have time to talk about a couple slides in this talk.
And so, one of our big topics is about the parton distribution functions. And so, I took the liberty to get some of the slides from Maria from our earlier 06 meeting. And it was huge importance that we talked about this importance of getting the precisions of the PDF as well as the alpha S that has been mentioned in Michael's talk. Especially we want to get to the precision functions. And then going beyond not just NLO, but also the N3LO as well.
Here is a slide from Pavel. We are showing we used the category that was listing in the last Snowmass exercise. And at the time the status right now. And a lot of progress has been made since. So, here's the table listing where we are. They allow more data and they are more interesting experiments coming along. And they are more extending to the traditional nuclear, nuclei and meson, and a lot of people have been talking about the transversemomentum dependent PDFs. But also the us in tasks coming along which was in this precision PDF white paper that focused on a lot of new tests ahead of us that we need to continue improving and they will help develop some of this improve some of this precision calculation.
And one of the motivations that was given in terms of being able to reduce the error in the PDF and others, we are able to further reduce some of the crosssection measurements a lot further if we would be able to reduce some of this. And they are also calculations, the process that's taken from the order over here. And the importance of being able to reduce some of the as you go on to the higher and higher order, the error would be significantly reduced in the cross sectional measurement. This is all very important for us to this precision PDF white paper would be addressing.
And there would be also, again, the upcoming HLLHC and then other finding DIS that will significantly improve the presuggestion of the PDF. And as well as reduce the not just experimental error, but also help us understand on the theoretical side and other semantic as well.
And so, this is a really like, as Pavel put it, a $10 million question on the precision of PDF analysis. How do we get from here, where the crosssection ratios of the correlation between the Z and the gluongluonHiggs cross sections the LHC, and 95%, and predicted recent PDF analyzes. it's spread out a little bit to somewhere that we can we would like to be going somewhere here around late 2030 also to be really significantly reducing the current to that much.
On the xFitter PDF side, we have an update with this open source QCD analysis framework. And having some newer features on the photon PDF including QED. Also some other and PDF and TMD analyzers. And here are the slides from them. And I think this is the group pictures. And so, they also point out not only their interest in PDF, but also have impact in other subfields such as neutrino physics frontier where the improvement on the PDF nuclear correction could be important to the minimize the systemic error in DUNE. Or even very small, it's going to be repeated. Very small S could improve some of the high energy neutrino and other kinematic regions as well.
So, on the lattice side, since the last Snowmass, there have been actually quite a lot of active development from the latest calculation to start to be able to calculate the next xdependent PDF directly. And not only there was the first calculation up here roughly in late mid to late 2013 that use large momentum theory. And since then there have been a lot of other calculations. Not only new cases, but accessing the PDF. They use something called pseudoPDF. And here, and studying the structure that had been done before. And there's gonna be a talk on Wednesday. I don't want to get into too much of the technical detail here. But just want to let you know that the lattice is actually making a lot of progress. Not just the calculation itself. But also the methodology.
And just kind of give a really quick overview on where lattice are. So, usually lattice calculation starting many happier than physical pion computation. We don't spend a lot of physical time. And by about 2019 also, there are actually the groups that kind of evolved from that and be able to do the calculation directly at the physical pion mass. And here's some of the calculation or the updown flavor differences PDF with the polarized PDF, and transverse PDF. And in comparison with the available global fitting at the time. And then not quite yet as precise. But in terms of transversity, the polarized lattice can become quite comparable. And keep in mind all these errors are limited bit computational resources available to the latest calculations. They can be further reduced if there are more computational resources available dedicated to this calculation.
We discussed there's a great synergy between one can use some of the latest inputs spatially in the data region when we don't have a lot of data to constrain the PDF. It can be quite complementary along with all the other efforts. And there are some of the earlier work accounts have been done in the transversity case. One can use the latest charges to give you the area of the of the quark PDF distributions. But combining with the experiment data, and combine the constraint quite significantly.
And there are also a lot of other ongoing. There are some attempts to start to study the flavor dependence. And calculations that move into the NNLO levels. And there are a lot of young colinear PDF calculations, pion distribution function, GPD. And the transverse, and TMD might interest some of you. And go to twist3 PDF and GPDs. And also some detail of some of the things we need to overcome in the upcoming 5 to 10 years to really improve some of the problems that we run into. And again, the computational resources are going to be important here. And there will be a talk on Wednesday in the parallel section.
So, there's going to be there's also a lot of connection with the EIC physics. I don't think I have time to get into that. Here's the slide from the team a while ago. But generally a lot of discussion that we talked about, the connection between the EIC and HEP. We hear from the EF07 talk. But we want to emphasize on the GBT that the EIC would also be a very effective facility to explore that uncertainties. And the one of the examples, one of the contributions. Talk about the TMD gluon distributions that they are starting to make some of this structure here.
And not there's also forward physics white paper. Again, this is another giant white paper that had many, many individual LOI. People worked together to summarize a few of these very small acts physics, BFKL submissions. And with the defection events and electro physics. And this is going in the parallel session as well. This is another sections that complementary with the EIC and also with the upcoming LHC measurements.
And there are also interest we saw this similar slide in Michael's talk. We're just going to emphasize that this is a this is a white paper to cover many frontiers. And also have a dedicated QCD study. And there's, again, we're going to be able to put on very, very small X and low Q region as well.
>> You have about 5.5 minutes left.
HUEYWEN: Okay. Last one. And this is a very unique white paper talking about potential TFE facility at muon collider. Muonion collider. And in this white paper, they talk about two potential schemes of such a facility. Built either on top of the the existing EIC and will have inside. Or possibly on top of the LHC. So, it's still at the preliminary stages. As they discuss this in detail in the white papers. But it's quite interesting. They show above the connecting regions which actually it's quite complementary between the high the upcoming LHC and the MuIC. They in between this region allow interest that's not currently available. And not only precision QCD it's one of the main goals. It could also allow us to study electroweak measurements and lepton flavor violation. And all the interesting physics in that. Not only interesting to particle physics, but also the community as well. Whoops. It's not moving. All right.
So, apologize. For those contributions we didn't have time to cover. And thanks for many of our participants that sent us the slides to cover this talk. I just wanted to also mention that we have a lot of activity Wednesday. There is a parallel section that also topical group plenary discussion. So, there will be a lot more chance to discuss some of this white paper in detail. Thank you.
>> Thank you for that very nice talk. Do we have any questions or comments from Zoom while I give folks a chance to raise their hands? I'll just point out as a followup to the last talk we have a comment from the on the subject. So, make sure you don't miss that in the chat. And I don't see any hands up now. I assume that means there's no question from Zoom and I'll hand it over to Phil.
>> Questions in the room? Don't see any questions. So, actually, I have a comment. So, or question, actually. For this muonion collider, how many luminosity can they project? Can you really go beyond the LHC, building a physics facility at the LHC and probing the region?
>> Perhaps I can answer it. So, again, you know, well first of all you see the luminosity projection on the slide, right? And the idea is that this collider will be quite competitive with LHeC in some aspects. Furthermore, you can vary the energy. Therefore, you can get access to different ranges with different sensitivity. So, therefore, I think okay. The visibility of having one muon beam rather than two muon beams. And using the existing infrastructure that was that would be for the election of the collider connection. Would be a very nice steppingstone towards the next generation of precision hadron structure studies. That, again, will be more build more incrementally. Therefore, you could imagine that after this muon beam is probed at Brookhaven, you can build the full collider with both mu plus and mu minus with very high precision electroweak physics there.
>> And I see we have a couple hands up now on Zoom. Was either of those a response? Or new questions?
>> I think Darin can respond in more detail.
>> One very direct question. If you were to build this let's say like and let's say you ran it at EIC and then you say made a muon beam. Beyond center of mass energy, is there a qualitative gain? Do you probe things that are fundamentally different than EIC?
>> Darin can answer.
HUEYWEN: Yes.
>> Yes, thank you. You did a great job. And the initial estimate based on the parameters, at the EIC photon ring with the expectations for a muon beam we got to 5 to 10 with the luminosity. It's hard to see because they almost completely coincide. But it turns out that 1 TeV beam would almost completely overlap the same, the same physics reach. Different lepton. Most are by the boson exchange. But the kinematics are different. The muon scatters at very, very small angles. So, that's a difference. On the other hand, the hadronic system can be pulled more into the central region. Particularly if you start talking about the particle physics aspect of creating standard model particles. There's complementary kinematics. I don't know if that answered all the questions.
>> Yeah, almost at least from my end, it makes sense. There's obviously BSM component which is interesting. I was just wondering if there's things that you gain beyond just like a electron LHC collider, EIC.
>> Classically with the EIC, you go to a much higher reach. From an electron beam to muon beam. You have a much higher reach. For the LHC beam, you have to create a 50 or 60 GeV electron accelerator. But that would be weighed against a novel muon accelerator. We found one thing interesting if you look at the highest marked reach with the LHmuC. If instead we had a collider instead of the electron, you go beyond the center of mass reach. You get to 6 center of mass, versus a 50 GeV of proton range. Trying to get to high DIS, you don't need the a new ring. Of course, if you take the TeV beam and collide with a 50 proton, you get a higher one. Just interesting numbers coming out.
>> Do you have a question?
>> Yeah. This is about PDFs. And especially the lattice calculation of PDFs. Is it possible to foresee how these things will develop on a say 10 or 15year time scale? Lattice is new to the game. We have been doing experimental studies for decades. Is it possible that lattice one day will simply supplant the measurements we do with all the these different processes and that we won't really rely on these complicated analysis of a wide variety of processes in order to tells about the PDFs? Is that possible?
HUEYWEN: So, currently it's a little bit hard to see. We can reach a lot of really small regions that people are very interested about. So, there have been quite a lot of white papers talking about the 10 to the minus 5 or minus 7s. And so far we haven't seen way to reach that small X yet. So, it's it's not easy to see how we would do there. That would require some new idea of where you would be able to reach that small X. And it's due to various difficulty that we run into in the calculation. There's some technical issue that we need to overcome with the latest calculation with the signal to the noise issue. We haven't seen a way to reach there yet.
So, I would say this is before the next Snowmass, we are still looking for new. This is a complementary tool. We will probably be able to use our resources on the to focus on the that such as flavor PDF or strange charm. Maybe we can contribute, save some constraints. And some of the polarized PDF that's not so strongly constrained by existing data yet. And that's something we have proceeding. Something we can envision right now. Beyond anything beyond 10 to the minus small X requires more ideas which we don't know where that comes from yet.
>> Okay. Thank you.
>> Yes, just a comment. So, the idea that we are pursuing in our group is that precision determinations of PDFs at colliders for unpolarized processes will serve as a benchmark for latest QCD calculations. And in term latest QCD calculations can predict combinations of PDFs or types of PDFs that are not easily accessible in the experiment. And so, therefore clearly there is a complementarity out there, precision analysis of former PDFs in latest experiments and the latest calculations for the new types of PDFs.
>> Okay. Very interesting.
>> Pavel: Now, if I could comment on Michael's question about the EF05 about support for QCD calculations in the United States. What seems to be equally important or more important at least in the PDF start is to support development of what is called the broad theory infrastructure. Where all kinds of errors are controlled to the same level of accuracy is the precision of the QCD calculations for hard cross sections. That's a very challenging problem. I don't know how it will develop. But clearly if we want to support let's say progress towards 1% accuracy for either alpha S or PDFs, that direction is very important. And we need to put more attention to it as opposed to what's been happening in the past.
>> All right. Any more questions in the room? Comments? If not, our next speaker is
>> Phil, just before we move on. I did get a request to read the comment that was submitted so that those in the room know what's being talked about on Zoom. So, David d'Enterria followed up on Michael's comment from the previous talk saying that for high precision alpha_s they did identify them in a white paper. And there's a big list, order alpha_s to the fourth, QCD corrections, full order alpha cubed, electroweak corrections to W/Z hadronic widths, mixed QCD, et cetera. If you want to get more information on this, he gave an archive reference. It's 2203.08271. Okay. Sorry, Phil, go ahead.