1 00:00:05,879 --> 00:00:08,159 Okay, Can people see the slides now? 2 00:00:08,489 --> 00:00:11,399 Yes, it works perfectly fine. So please go ahead. 3 00:00:12,750 --> 00:00:17,490 So, so thanks for the introduction. As I said, I will be talking about probes of 4 00:00:17,490 --> 00:00:23,370 perturbative qc D with vector bozos photons and Jetson Atlas. Today I'm going 5 00:00:23,370 --> 00:00:28,380 to focus on two topics. The first is have a heavy flavor production in association 6 00:00:28,380 --> 00:00:34,020 with z bozos, and in particular, z greater than one is greater than to be jet cross 7 00:00:34,020 --> 00:00:38,160 section and differential distributions. The second is measurements of isolated 8 00:00:38,160 --> 00:00:43,980 photons plus to jet production, distributions and direction fragmentation 9 00:00:43,980 --> 00:00:48,390 has features like correlations. Just wanted to point out that there are 10 00:00:48,390 --> 00:00:51,540 additional measurements that I'm not discussing today that will be presented in 11 00:00:51,540 --> 00:00:55,980 other kcd sessions that were precision probes of jet substructure that will be 12 00:00:55,980 --> 00:01:03,000 presented by Matt LeBlanc on Wednesday and yesterday You heard about z and draw em 13 00:01:03,000 --> 00:01:08,910 cross sections and P t distributions. Okay, so let me get to my first topic B 14 00:01:08,910 --> 00:01:15,510 production in association with C bozos. z plus b production is an important test to 15 00:01:15,570 --> 00:01:20,760 determine if QC D the calculations have been done to nll accuracy. They just both 16 00:01:20,760 --> 00:01:25,560 in the four and a five flavor number schemes. The five flavor scheme, by 17 00:01:25,560 --> 00:01:30,810 definition uses be quirks in the PDFs that means that you have to have massive, 18 00:01:30,990 --> 00:01:36,870 massive speak works in the in the hard scattering although masses are used as 19 00:01:36,870 --> 00:01:42,240 part of the showering of the events. In the for flavor scheme. The B corpse come 20 00:01:42,240 --> 00:01:47,010 from blue on splitting and it's possible to include massive fees. It's a benchmark 21 00:01:47,010 --> 00:01:51,090 process for testing performance for MonteCarlo generators and an important 22 00:01:51,090 --> 00:01:57,270 background for many bsm searches. The performance of the calculations in both 23 00:01:57,270 --> 00:02:02,430 schemes and for different generators has been Compared for a large number of 24 00:02:03,240 --> 00:02:08,670 different distributions, both the one and the two, tag bhujette selections, and 25 00:02:08,700 --> 00:02:14,400 unfolded differential distributions are available. So let me begin just by showing 26 00:02:14,400 --> 00:02:19,500 you what the fiducial cross sections look like. The selection cuts for the fiducial 27 00:02:19,500 --> 00:02:24,660 region are listed on the left, I'm not going to bother to read those. Also, I 28 00:02:24,660 --> 00:02:29,130 know it's a bit tomorrow, I apologize, you can see the different MonteCarlo 29 00:02:29,130 --> 00:02:34,380 configurations that are used for the calculations. So as as shown, they're both 30 00:02:34,380 --> 00:02:39,510 for flavor and five flavors in calculations. And the labels make are a 31 00:02:39,510 --> 00:02:43,080 little difficult to understand because many of these are matched and merged 32 00:02:43,080 --> 00:02:47,220 calculation. So listed on this table, not only do you see the order of the 33 00:02:47,220 --> 00:02:52,920 calculation, you also see for the multi leg cases, how many legs are in the 34 00:02:52,920 --> 00:02:58,110 calculation in particular, let me point out the cases of Sherpa where there's a 35 00:02:58,110 --> 00:03:03,090 merging process so the lads no For small numbers of Park towns merge together with 36 00:03:03,330 --> 00:03:09,480 lowest odor calculations for for more park on legs, the PDF sets used in the 37 00:03:09,480 --> 00:03:14,910 calculations are also indicated here, shown on the right hand side, the cross 38 00:03:14,910 --> 00:03:21,210 sections for at least one and at least to be just satisfying the fiducial catch on 39 00:03:21,210 --> 00:03:26,820 the left, as you can see from this flap before flavor scheme tends to 40 00:03:26,820 --> 00:03:31,050 underestimate the cross sections and the region was with at least one beach yet, 41 00:03:31,110 --> 00:03:35,400 but it's consistent with the data for at least to be jets. The five flavor scheme 42 00:03:35,400 --> 00:03:40,230 predict the cross cross sections reasonably well in both of these regions. 43 00:03:40,500 --> 00:03:44,430 You should also note that the statistical uncertainties are quite small there the 44 00:03:44,430 --> 00:03:50,400 yellow band, so the data are totally dominated by a systematic uncertainties at 45 00:03:50,400 --> 00:03:57,210 this stage. Okay. Let me quickly show you a few distributions. And typically in this 46 00:03:57,210 --> 00:04:00,660 talk, what I'll do is first I'll show the distributions and then I'll have A summary 47 00:04:00,660 --> 00:04:06,210 slide giving some some overview of what's seen. So here you can see in the case of 48 00:04:06,210 --> 00:04:10,800 at least one v jet kinematics, the distributions for the PT and the Z and for 49 00:04:10,800 --> 00:04:17,130 the leading v jets that PT on the top of the distributions themselves, the cross 50 00:04:17,130 --> 00:04:21,480 section as a function of the variable being measured, and on the bottom are a 51 00:04:21,480 --> 00:04:27,060 number of predictions of MonteCarlo divided by data. They're just put on 52 00:04:27,060 --> 00:04:32,670 several in sets, because there are too many points to show on a single insert. As 53 00:04:32,670 --> 00:04:38,040 is often the case, it's difficult to reproduce the bpt as a GPT distribution, 54 00:04:38,040 --> 00:04:42,360 very low up PT, that's a region where non perturbative effects and retardation are 55 00:04:42,360 --> 00:04:46,200 important and in particular, regeneration matters a lot in that region. 56 00:04:47,850 --> 00:04:52,980 Well, one would expect better preservative production at the high end. The overall 57 00:04:52,980 --> 00:04:57,090 levels of course, just reflect the differences in the MA predicted cross 58 00:04:57,090 --> 00:05:01,350 sections on the previous page of particular notes. is a case of a lead 59 00:05:01,380 --> 00:05:07,980 leading BGP t, where you can see that, that the multi leg calculations, do a 60 00:05:07,980 --> 00:05:13,260 reasonable job all the way out, perhaps beginning to disagree as you get to very 61 00:05:13,260 --> 00:05:17,820 high PTs and then typically do better than no calculations that don't involve 62 00:05:17,820 --> 00:05:23,190 matching emerging. If we move on to the region of greater than to be jets, then we 63 00:05:23,190 --> 00:05:26,550 can start looking at some more interesting distributions. In particular, the 64 00:05:26,550 --> 00:05:34,620 correlations between your server will show here, the correlations between the two B's 65 00:05:34,620 --> 00:05:39,570 in the left and five, and in the end the rate for the invariant mass of the two 66 00:05:39,570 --> 00:05:44,850 B's. The five distributions between the two B's seem to be reasonably well 67 00:05:44,850 --> 00:05:49,740 reproduce the shapes are similar for all of the MonteCarlo predictions. In the case 68 00:05:49,740 --> 00:05:56,310 of MBB. One can see that none of the MonteCarlo is over a good job at the 69 00:05:57,000 --> 00:06:02,730 invariant mash of the bees being quite large. Okay, so just to summarize what we 70 00:06:02,730 --> 00:06:08,520 see for these equal speed results. In general, the five flavors game and flow 71 00:06:08,520 --> 00:06:13,380 calculations predict uncouth cluesive cross sections for both the one and the 72 00:06:13,380 --> 00:06:18,990 two jet regions while the four flavor schema underestimates the values, 73 00:06:19,170 --> 00:06:25,050 multiplex calculations model the region of large bpt better than the piano postpartum 74 00:06:25,050 --> 00:06:30,960 shower. The sharper nll five flavor scheme with up to two port times at low anello 75 00:06:30,960 --> 00:06:33,870 and up to four partitions at lowest though, to describe most of the 76 00:06:33,870 --> 00:06:38,070 differential distributions within the experimental uncertainties. And all of the 77 00:06:38,070 --> 00:06:44,220 generators disagree with the data at large in various massive a big bar. Now, let me 78 00:06:44,220 --> 00:06:51,000 move on to the second analysis. photons was to jet production. I've shown the 79 00:06:51,060 --> 00:06:57,420 examples of the Fineman diagrams from the two categories of production here. And 80 00:06:58,830 --> 00:07:02,400 just to give you a little bit An introduction from photonic was to jet 81 00:07:02,400 --> 00:07:07,680 production is a rich system to discuss perturbative q CD. Because we have three 82 00:07:07,890 --> 00:07:11,850 particles in the final state, it's possible to look at a variety of Angular 83 00:07:11,850 --> 00:07:16,590 Carlo simulations as well as P t distributions, and a particular lowest 84 00:07:16,590 --> 00:07:21,210 order. There are two production mechanisms. Of course, it mlo talking 85 00:07:21,210 --> 00:07:25,950 about separate production mechanisms doesn't make any sense. However, this 86 00:07:25,950 --> 00:07:30,930 lowest odor structure will still reflect itself in the peaking region to the 87 00:07:30,930 --> 00:07:37,260 kinematics. So those two or photons from a hard scattered self and photons from 88 00:07:37,260 --> 00:07:43,290 fragmentation those are shown in a and b above. And of course, the treatment of 89 00:07:43,290 --> 00:07:47,970 this fragmentation is one of the things that is traditionally made understanding 90 00:07:47,970 --> 00:07:56,400 direct photon production, a difficult and specialist phenomenon. Here on the next 91 00:07:56,400 --> 00:08:03,000 slide, you can see the definition of the fiducial regions Because of the trigger 92 00:08:03,000 --> 00:08:09,240 the photon 80 is required to be greater than 150 gV. There is an isolation 93 00:08:09,240 --> 00:08:15,660 requirement this isolation requirement is is placed on the on the truth and the 94 00:08:15,690 --> 00:08:19,890 experimental data are corrected to match that isolation requirements and all the 95 00:08:19,890 --> 00:08:26,490 Jets are required to be greater than 100 gV weather affinity less than 2.5. The 96 00:08:26,490 --> 00:08:32,520 separation between the photon on the Jets is also good. comparisons are made with 97 00:08:32,550 --> 00:08:38,670 three separate MonteCarlo predictions. The first is almost a straw man it's a it's a 98 00:08:39,000 --> 00:08:43,110 patio where opinion itself is doing the hard scattering so it's a lowest odor 99 00:08:43,110 --> 00:08:49,530 calculation as compared to using a lowest odor PDF. The second is emerged lowest 100 00:08:49,530 --> 00:08:55,350 odor calculation from Sherpa 2.1 or the merging is done in a two to N process 101 00:08:55,350 --> 00:09:01,170 where n can be between two and five part times and the final state here. PDF is C 102 00:09:01,170 --> 00:09:07,830 tech 10. And the final is SharePoint 2.2 point oh, this involves an nll merging for 103 00:09:07,830 --> 00:09:12,540 two or three jets, together with a lowest order emerging for three and four and the 104 00:09:12,540 --> 00:09:18,870 whole thing's done in a consistent way with an nll PDF. as one would expect the 105 00:09:18,870 --> 00:09:23,460 lowest order calculations have a large scale uncertainty they therefore always 106 00:09:23,460 --> 00:09:29,400 displayed using a K factor to take into account the fact that the actual choice of 107 00:09:29,400 --> 00:09:33,780 scale leads to larger uncertainty in the rate and the values of the K factor that 108 00:09:33,780 --> 00:09:40,350 give them the best data are shown on the class. In the theory to data comparisons, 109 00:09:40,590 --> 00:09:46,470 the shaded area so it shows the NLL theoretical uncertainty so that's the 110 00:09:46,470 --> 00:09:47,310 uncertainty 111 00:09:48,600 --> 00:09:53,400 obtained with a Sherpa and a low calculation. The uncertainty shown in the 112 00:09:53,400 --> 00:09:59,970 error points include both the statistical and systematic uncertainties on the data 113 00:10:00,000 --> 00:10:08,940 themselves. So just as an example, this shows the plot for all of the data for the 114 00:10:08,940 --> 00:10:14,130 end of the photon. As you can see, aside from the very highest CTS, the 115 00:10:14,130 --> 00:10:19,080 calculations all do a reasonable job on that. So one of the interesting things 116 00:10:19,080 --> 00:10:24,090 about this measurement is the fact that that regions of direct and fragmentation 117 00:10:24,090 --> 00:10:30,150 contribution are selected. Now, of course, that's only an enhancement because the mo 118 00:10:30,150 --> 00:10:35,880 diagrams don't separate in that case, but you can still pick regions where one or 119 00:10:35,880 --> 00:10:40,350 the other diagram dominates. The fragmentation enhance region is selected 120 00:10:40,350 --> 00:10:45,600 by requiring the photon at the less than the end of the sub leading jet while the 121 00:10:45,600 --> 00:10:51,540 direct enhanced region has a photon eta greater than the 80 of the of the leading 122 00:10:51,540 --> 00:10:57,240 jets. The total includes both of these reagents as as well as the additional 123 00:10:57,240 --> 00:11:03,420 reagents not covered by either one. So let me just show a variety of distributions 124 00:11:03,420 --> 00:11:09,540 from this. This slide here, you can see the distributions for again the total 125 00:11:09,540 --> 00:11:13,980 phase space, the fragmentation enriched and the direct enriched region for the ETA 126 00:11:13,980 --> 00:11:22,350 of the photon and PT of the jet. Again, the three calculations are shown here. And 127 00:11:22,350 --> 00:11:28,080 these single variable cases, aside from the highest at all of both versions of 128 00:11:28,080 --> 00:11:32,970 Sherpa do a good job, you can already begin to see that the lowest odor pythia 129 00:11:34,320 --> 00:11:41,280 perhaps not unexpectedly, does not do as well. Moving on to more interesting 130 00:11:41,280 --> 00:11:47,400 distributions, shown here, the angular distributions comparing the two jets in 131 00:11:47,400 --> 00:11:52,800 the event if one compares the fragmentation rich and the directed, 132 00:11:53,040 --> 00:11:57,780 enriched regions you can see there are quite significant differences in shape 133 00:11:57,780 --> 00:12:04,620 here. As expected that fragmentation and rich Do you see peeking in the digestive 134 00:12:04,920 --> 00:12:10,170 region refer close to being at the back. That's because the photon is essentially 135 00:12:10,170 --> 00:12:14,580 coming from a broom strolling off of one of the initial parkins. While in the 136 00:12:14,580 --> 00:12:21,390 direct enhance region, you see much less peeking and it's enhanced, basically in a 137 00:12:21,390 --> 00:12:28,140 region of smaller delta phi. Again, the two sharper calculations which are matched 138 00:12:28,140 --> 00:12:34,890 and merge do a reasonable job and both of these regions and there's no real 139 00:12:34,950 --> 00:12:39,360 improvement with the envelope calculation in terms of the shape, and the pythian 140 00:12:39,360 --> 00:12:43,710 does a rather poor job. The bottom shows similar distributions in the case of the 141 00:12:43,710 --> 00:12:50,130 delta phi between the two jets. And here you can see a delta y excuse me between 142 00:12:50,130 --> 00:12:54,180 the two jets and here you can see that especially in the fragmentation region, 143 00:12:54,450 --> 00:13:00,120 none of the predictions do a particularly good job at Delta. Watch I 144 00:13:02,429 --> 00:13:04,859 have about three minutes left. So 145 00:13:04,860 --> 00:13:12,630 the next slide shows similar distributions for the case of m j, j and m gamma j j, 146 00:13:12,630 --> 00:13:17,520 the invariant mass of the two jets and the invariant mass of the of the three part 147 00:13:17,550 --> 00:13:23,190 argon system. Again, for the total Face Face on the left the fragmentation and 148 00:13:23,190 --> 00:13:27,960 rich region in the middle and the director and rich region on the right hand side. 149 00:13:29,400 --> 00:13:35,220 Here one sees a significant discrepancies between the data and all three of the 150 00:13:35,220 --> 00:13:40,350 generators in particular in the case of large m JJ, and in the case of large, 151 00:13:40,410 --> 00:13:46,920 gamma and JJ none of them do a perfect job. It's interesting that the Sherpa 152 00:13:46,950 --> 00:13:53,100 lowest odor merge sample appears to do the best job among the three generators. One 153 00:13:53,100 --> 00:13:59,040 wouldn't necessarily expected that but, but it seems to be a fact when prepared 154 00:13:59,040 --> 00:14:04,710 the data to the To the generators. And again, we see that there's a rather poor 155 00:14:04,710 --> 00:14:14,700 job that's being done by Pipi on its own. Just to summarize the results on the 156 00:14:14,700 --> 00:14:19,680 photon plus two jets, the measure distributions and direct and fragmentation 157 00:14:19,680 --> 00:14:24,240 enhance regions exhibit features that are expected from the underlying processes. 158 00:14:24,540 --> 00:14:28,800 The tree level lowest Oda Sherpa gives a good description of the shape of the data, 159 00:14:29,130 --> 00:14:36,240 except at high et gamma, delta y j, j and m, gamma j, j. And of course, because it's 160 00:14:36,240 --> 00:14:40,470 a lowest order calculation, a K factor needs to be applied to get agreement in 161 00:14:40,470 --> 00:14:45,510 the overall rate 58 where the sub leading gender originates from part time shower 162 00:14:45,510 --> 00:14:50,220 does not describe the distributions well. The mlo Sherpa describes they've 163 00:14:50,220 --> 00:14:57,060 adequately both in terms of shape and normalization accepted Hi, ET gamma, delta 164 00:14:57,060 --> 00:15:02,010 y j, j and m gamma j j. Although the lowest started Sherpa seems to do a 165 00:15:02,010 --> 00:15:06,900 slightly better job in reproducing the shapes and theoretical uncertainties 166 00:15:06,900 --> 00:15:11,880 rather than experimental ones dominate all of these measurements. So let me just 167 00:15:12,030 --> 00:15:17,490 summarize with some conclusions. Recent Atlas results on jets photons and bozos 168 00:15:17,490 --> 00:15:23,100 probe perturbative. qc with high QC D with high precision c greater than one v jet 169 00:15:23,160 --> 00:15:27,750 and greater than two B jet kinematic distributions probe sensitivity of the 170 00:15:27,750 --> 00:15:32,790 predictions to the flavor number scheme. The prompt photon was to jet measurements 171 00:15:32,790 --> 00:15:37,740 test nll calculations and regions where direct and fragmentation photons dominate 172 00:15:38,160 --> 00:15:42,120 the ability of the theoretical calculations and MonteCarlo generators to 173 00:15:42,120 --> 00:15:47,640 model complex UCB systems in general good, but some discrepancies with the data 174 00:15:47,640 --> 00:15:52,890 remain, and a wide range of observables available to tune MonteCarlo generators 175 00:15:52,980 --> 00:15:57,420 and to explore regions where theoretical calculations are difficult or problematic. 176 00:15:58,590 --> 00:15:59,970 And that's the end 177 00:16:01,260 --> 00:16:07,170 Many things module for very nice and clear presentations. We don't have some applause 178 00:16:07,170 --> 00:16:13,470 function here in zoom. But can you imagine that you have received this? And now it's 179 00:16:13,470 --> 00:16:20,070 time for questions. So I will remind you that the attendees can ask questions using 180 00:16:20,070 --> 00:16:24,240 this raise hand function in in zoom. 181 00:16:34,920 --> 00:16:36,420 Please don't be shy. 182 00:16:44,760 --> 00:16:50,520 Otherwise, the panelists and the hosts can also ask questions they can directly 183 00:16:50,550 --> 00:16:51,900 unmute themselves. 184 00:16:56,070 --> 00:16:59,970 So I see Tomas, so 185 00:17:01,140 --> 00:17:02,820 Please go ahead. Yes. 186 00:17:03,120 --> 00:17:10,590 I think I'm unmuted now. Okay. When you say, for mutation in rich and static in 187 00:17:10,590 --> 00:17:18,330 rich samples in the photons, isn't there a perspective that you may actually from 188 00:17:18,360 --> 00:17:24,510 from this data on, more and more refined measurements with higher statistics have 189 00:17:24,570 --> 00:17:29,610 an independent measurement of the proctor for permutation functions because all that 190 00:17:29,610 --> 00:17:35,190 we have now is still dating back to lead times and is not of that terrific point. 191 00:17:37,170 --> 00:17:43,290 that's a that's a good question. I, I'll try and answer but if there's anyone else 192 00:17:43,290 --> 00:17:50,430 from Atlas, who would like to give a more detailed answer about this, I think if one 193 00:17:50,430 --> 00:17:54,360 were going to do it, it of course would have to be done within the context of one 194 00:17:54,360 --> 00:18:03,870 of the MonteCarlo generators. You Because one needs to, of course use those in order 195 00:18:03,870 --> 00:18:10,410 to do the unfolding. Do I have a good answer to this question? So I don't think 196 00:18:10,410 --> 00:18:14,820 the issue is statistics. There's plenty of statistics here. I think the the issue is 197 00:18:14,880 --> 00:18:24,240 is whether or not one could reliably model the transport translation between this 198 00:18:24,240 --> 00:18:29,910 isolation cut in the data and in the MonteCarlo. And perhaps someone else from 199 00:18:29,910 --> 00:18:36,480 Atlas who would like to comment in more detail whether or not they see your 200 00:18:36,480 --> 00:18:42,660 prospect to do that unfolding in a in a reliable and consistent way. 201 00:18:44,579 --> 00:18:49,919 I'm not especially expert or expert on this topic, but what I know is that we 202 00:18:49,919 --> 00:18:55,079 have some ongoing effort to try to harmonize as much as possible this 203 00:18:55,079 --> 00:19:00,599 definition between the truth level and the reconstructed level and this is is somehow 204 00:19:00,599 --> 00:19:06,839 related to minimizing the modal dependence that we have when doing the unfolding and 205 00:19:06,839 --> 00:19:12,749 also minimizing the sensitivity to this model dependence when doing the data to 206 00:19:12,779 --> 00:19:19,169 theory comparisons later on. So I know that there's some context with the 207 00:19:19,619 --> 00:19:22,739 theories to try to make some developments on this. 208 00:19:24,119 --> 00:19:27,869 Yeah, I believe the hardest part will be understanding how to how to do the 209 00:19:27,869 --> 00:19:35,189 unfolding. And and to what extent the unfolding is different for different 210 00:19:35,189 --> 00:19:39,689 showering Monte Carlos. So one of the things that might make it more possible 211 00:19:39,689 --> 00:19:45,449 than it would have been a few years ago is the fact that the MonteCarlo generators 212 00:19:45,449 --> 00:19:51,149 now have many more switches to allow you to change the shower in itself. So the 213 00:19:51,149 --> 00:19:58,559 ability both to change the new scale within the shower, and also to switch the 214 00:19:58,589 --> 00:20:02,759 type of shower and so forth. Jacqueline in her wanting to be able to switch between 215 00:20:02,909 --> 00:20:07,529 Angular and dipole or in the case of pythia to be able to switch between dire 216 00:20:07,529 --> 00:20:14,729 and and standard 50 on string fragmentation well at least allow one to 217 00:20:14,729 --> 00:20:21,359 understand the sensitivity to the systematic uncertainty so but certainly 218 00:20:21,359 --> 00:20:28,649 the first thing I see is in the shower, how much it affects the unfolding Yeah. 219 00:20:29,639 --> 00:20:37,049 Well, I can see the generator side of it if you if you really after the after 220 00:20:37,049 --> 00:20:42,239 fragmentation function, then the extraction should be largely insensitive 221 00:20:42,269 --> 00:20:47,189 on the on the generator that you're that you're using for the unfolding. 222 00:20:48,480 --> 00:20:51,090 I would hope so. But I don't know if anyone's check that 223 00:20:51,569 --> 00:20:52,169 okay. 224 00:20:53,609 --> 00:20:59,369 This is more space for for for work, I guess. Yeah, I think I think you're 225 00:20:59,369 --> 00:21:02,849 perfectly right. I mean, this is something that requires some careful checks in any 226 00:21:02,849 --> 00:21:11,819 case. Okay, thanks. Thanks for the question. Any further questions now? 227 00:21:18,630 --> 00:21:24,600 I don't see any. So you can also think about questions during the following talks 228 00:21:24,600 --> 00:21:30,240 and that said, we will have another discussion at the end of the session. So 229 00:21:30,240 --> 00:21:36,030 many things. Many things Marjorie again, so we move now to the