1 00:00:00,930 --> 00:00:05,640 Okay, so today I'm talking about precision QCD the measurements on behalf of these 2 00:00:05,640 --> 00:00:13,050 four, fine collaborations. And so of course, we know that the LHC is a QCD 3 00:00:13,050 --> 00:00:18,060 factory, and that pretty much every event we see has some element of QCD within it. 4 00:00:18,660 --> 00:00:22,800 And indeed, QCD is at the center of the standard model. And by studying it, we 5 00:00:22,800 --> 00:00:27,810 understand nature itself better. Of course, it's crucial as well to understand 6 00:00:27,810 --> 00:00:32,310 QCD if we're going to understand the rest of what we see at the LHC. And so today, 7 00:00:32,310 --> 00:00:38,790 I'm going to look at a variety of measurements that probe QCD at exciting 8 00:00:38,820 --> 00:00:43,440 levels of precision, and I'll take a look at a wide variety of different energy 9 00:00:43,440 --> 00:00:47,400 scales and I've got these different processes that I've been asked to cover. 10 00:00:48,210 --> 00:00:55,740 And I'll try and touch on on some of these today. So let's start by looking at Drell-Yan 11 00:00:55,740 --> 00:01:02,730 physics and vector boson plus jet physics. So I thought I'd start with this 12 00:01:03,000 --> 00:01:09,600 lovely analysis from CMS, where they take the measurements of W and Z boson 13 00:01:09,600 --> 00:01:15,750 production cross sections of the Drell-Yan process that were made using the run one 14 00:01:15,750 --> 00:01:21,600 datasets. You can actually see these results from these two plots as the horizontal 15 00:01:21,600 --> 00:01:27,360 bands in gray. And you can use these to extract values of alpha_s. As I say, these 16 00:01:27,360 --> 00:01:32,940 happen to pick out the W and Z boson cross sections at 8 TeV: W plus boson I should say 17 00:01:33,180 --> 00:01:37,980 there are other plots like this. And then you've got a joint probability 18 00:01:37,980 --> 00:01:45,840 distribution function for the different PDF sets, showing the one sigma 19 00:01:45,840 --> 00:01:50,370 favoured regions. And of course, you can do this and then say, what is the favoured 20 00:01:50,370 --> 00:01:55,380 value of alpha s and on the left hand plots, you've got the curves for different 21 00:01:55,380 --> 00:01:56,940 PDF sets considered 22 00:01:58,409 --> 00:01:59,969 and the analysis takes onboard 23 00:02:01,709 --> 00:02:08,549 And uses CT and mmht14 - it claims that these are the most robust in the context of this 24 00:02:08,549 --> 00:02:13,949 analysis. And indeed you can see the value of alpha s just in these measurements is 25 00:02:13,949 --> 00:02:22,289 extracted, which is really quite precise. This is an impressive achievement. We can 26 00:02:22,289 --> 00:02:28,499 also ask, what do these W and Z boson events look like. So CMS have recently 27 00:02:28,499 --> 00:02:34,349 published this run two analysis considering rapidity, PT, distributions of Z bosons 28 00:02:34,349 --> 00:02:41,459 and more, and comparing these to a wide variety of theory predictions. On the left 29 00:02:41,459 --> 00:02:48,989 hand side of the plot here, I show the ratio of different predictions to data, 30 00:02:49,079 --> 00:02:53,759 including the low PT region where there is clearly a continuing challenge in terms of 31 00:02:53,759 --> 00:02:59,729 modeling. And then you've got fixed order predictions on the right hand side, 32 00:02:59,729 --> 00:03:04,109 you've got FEWZ and so on, and indeed again these show reasonable agreement 33 00:03:04,109 --> 00:03:13,139 across a variety of PT scales. And ATLAS have measured the Z boson 34 00:03:13,139 --> 00:03:18,299 PT distribution, I show here (they also measure far more in this this paper that's 35 00:03:18,299 --> 00:03:20,159 recently accepted in EPJC) 36 00:03:21,449 --> 00:03:22,769 you can see again that 37 00:03:24,539 --> 00:03:30,239 pythia eight is here doing well at low PT but obviously being leading order 38 00:03:30,389 --> 00:03:37,229 struggles at higher PT, Sherpa does well a high PT and indeed radish, NNLO plus N-cubed-LL 39 00:03:37,229 --> 00:03:41,309 describes the entire spectrum well, which is pleasing to see. 40 00:03:44,639 --> 00:03:47,699 And CMS have put out recently this very nice 41 00:03:49,710 --> 00:03:56,430 analysis where they consider the 13 TeV data set and make a measurement that is 42 00:03:56,430 --> 00:04:00,000 a double differential cross section measurement 43 00:04:00,000 --> 00:04:06,030 in terms of rapidity and PT. And again picking out the different left 44 00:04:06,030 --> 00:04:10,230 handed and right handed helicities of the W boson. And this is a high precision 45 00:04:10,230 --> 00:04:16,290 study of QCD. It gives key sensitivity to and ability to constrain PDFs. But of 46 00:04:16,290 --> 00:04:20,430 course, it's also a crucial step towards an MW measurement it's its own right 47 00:04:20,430 --> 00:04:27,480 and I'm sure we'll hear more about this in the electroweak plenary. Overall, we see 48 00:04:27,480 --> 00:04:33,000 reasonable consistency between data and predictions from QCD once you account for 49 00:04:33,030 --> 00:04:41,700 correlations between the different bins in data. And CMS have also produced this new 50 00:04:41,700 --> 00:04:46,230 measurement, which I'm delighted to be able to show, with differential cross-sections 51 00:04:46,230 --> 00:04:51,780 of Z plus jet and photon plus jet. The measurement considers the 52 00:04:51,780 --> 00:04:55,500 differential cross sections for Z plus jet, photon plus jet. It also considers 53 00:04:55,500 --> 00:05:00,000 the boosted topologies, so here we see separation of the Z and the closest jet 54 00:05:00,630 --> 00:05:10,110 for high PT jets. And you can see that this is a nice measurement, extending this idea 55 00:05:10,110 --> 00:05:14,160 of making precision measurements of standard model processes, but it extends 56 00:05:14,160 --> 00:05:19,830 this idea into extreme regions of phase space. So that's that's also very pleasing 57 00:05:19,830 --> 00:05:25,860 to see. And indeed, good agreement is seen with theoretical predictions throughout 58 00:05:26,100 --> 00:05:32,820 throughout this analysis. And CMS have also done a dedicated study of a triple 59 00:05:32,850 --> 00:05:37,320 differential cross section for isolated photon plus jet using the 8 TeV 60 00:05:37,320 --> 00:05:43,410 data set. And this analysis gives sensitivity to the gluon PDF. And indeed, 61 00:05:43,470 --> 00:05:52,740 good agreement is seen with predictions at next to leading order. And ATLAS have probed 62 00:05:52,740 --> 00:05:57,600 photon plus two jet and this measurement picks out a variety of regions in phase 63 00:05:57,600 --> 00:06:02,700 base where you can pick out sensitivity to different processes, direct processes, 64 00:06:02,700 --> 00:06:08,220 fragmentation processes, and many different differential distributions have 65 00:06:08,220 --> 00:06:13,440 been considered. And in all of them good agreement is seen with theoretical 66 00:06:13,440 --> 00:06:19,680 predictions from QCD, except potentially high dijet masses, as you see 67 00:06:19,680 --> 00:06:26,820 on the right most plot, or indeed where the, the, there is significant separation. 68 00:06:26,880 --> 00:06:31,530 And so in the middle plot, you can see the jet-jet separation, the data somewhat 69 00:06:31,530 --> 00:06:38,220 undershoots the theoretical predictions. So, it's these more extreme 70 00:06:38,220 --> 00:06:45,390 regions of phase space where we still need to understand what's going on. And CMS 71 00:06:45,390 --> 00:06:53,130 have produced the first measurements of associated vector boson plus heavy flavor jets 72 00:06:53,490 --> 00:06:58,800 at 13 TeV we have from the LHC. It's really nice to see these these analyses. And 73 00:06:58,800 --> 00:07:04,440 again, they've considered b jets, c jets and the ratio and throughout there is 74 00:07:04,470 --> 00:07:13,980 reasonable agreement with the next leading order predictions. And ATLAS have 75 00:07:14,010 --> 00:07:18,120 considered Z plus b jets and they've considered both Z plus one b jet 76 00:07:18,120 --> 00:07:23,220 inclusive and Z plus two b jet inclusive. And they show here, essentially 77 00:07:23,220 --> 00:07:28,380 a plot: the first plot is from the one b jet case, and the plot 78 00:07:28,380 --> 00:07:34,050 on the right hand side is from the two b jet case. And the analysis is a tour de force 79 00:07:34,050 --> 00:07:40,560 it considers a large number of different predictions, including this sherpa fusing 80 00:07:40,560 --> 00:07:45,090 scheme that enables predictions to be combined using the four flavour number 81 00:07:45,090 --> 00:07:50,010 scheme and the five flavour number scheme. And broadly the next leading order 82 00:07:50,010 --> 00:07:56,460 predictions using the five flavour number scheme seem to describe the data well. And 83 00:07:56,460 --> 00:08:00,510 indeed the fourth flavour number scheme predictions do agree with the data in the 84 00:08:00,540 --> 00:08:04,680 two b jets case so if you look at the right hand plot you see the four flavour number 85 00:08:04,680 --> 00:08:11,370 scheme does does well here. So that's kind of a whirlwind tour of some of the 86 00:08:11,400 --> 00:08:17,490 analysis that has been done looking at vector boson final states. I'm now going 87 00:08:17,490 --> 00:08:22,920 to look more at physics that can be done using the jets themselves either using 88 00:08:23,130 --> 00:08:28,230 looking at events that contain jets or then going on and looking at jet 89 00:08:28,230 --> 00:08:32,220 substructure and and what happens the evolution inside the jet. 90 00:08:34,020 --> 00:08:39,570 So let's start by looking at event shapes. So this is a new measurement from ATLAS of 91 00:08:39,570 --> 00:08:46,260 event shape observables. This is done in bins of jet multiplicity and ht2. It probes 92 00:08:46,290 --> 00:08:51,810 multi jet energy flow, at TeV scales, and there are a variety of different 93 00:08:52,980 --> 00:08:58,050 observables the analysis considers. Here I'm just going to pick out this tau 94 00:08:58,050 --> 00:09:02,880 perpendicular variable which is essentially related to the transverse 95 00:09:03,720 --> 00:09:05,370 thrust within the event. 96 00:09:08,250 --> 00:09:11,040 And what you can see, if we look at these plots, 97 00:09:12,690 --> 00:09:13,980 we take the top plot. 98 00:09:15,420 --> 00:09:22,020 This is a bin of ht2 between one and 1.5 TeV, the bottom is ht2 above two TeV, 99 00:09:22,350 --> 00:09:28,740 but then you've got the different lines comparing to predictions of the 100 00:09:28,770 --> 00:09:33,390 three jet case, the four jet case, the five jack case and so on. And you can see that 101 00:09:34,890 --> 00:09:41,340 for lower jet multiplicities the shape seems to not be perfect in Monte Carlo - it seems to 102 00:09:41,340 --> 00:09:46,650 not be perfectly describing the data. As you move to the higher multiplicity, so 103 00:09:46,650 --> 00:09:53,940 these are the lower plots that you see, we find that the shape seems to now be picked 104 00:09:53,940 --> 00:10:02,220 out reasonably, but we see discrepancies in the normalization still. Moving on, we 105 00:10:02,220 --> 00:10:06,060 can consider inclusive production from ALICE, it's nice to show this, this result 106 00:10:06,060 --> 00:10:11,490 from ALICE. Here ALICE study the dependence of the inclusive production 107 00:10:11,490 --> 00:10:17,010 cross section on the distance parameter are used within the anti kT algorithm, 108 00:10:17,280 --> 00:10:21,000 ie the extent of pase space, you're going to end up clustering into jets. Now 109 00:10:21,000 --> 00:10:25,380 there's much more within the paper as well, of course, this is a study performed 110 00:10:25,380 --> 00:10:30,630 using p p data and lead lead collisions. And what I'm showing here are the ratio of 111 00:10:30,630 --> 00:10:37,920 these cross sections for values of this anti kT R between point one and point 112 00:10:37,920 --> 00:10:46,560 six. And you can see that the data and the different theoretical 113 00:10:46,560 --> 00:10:50,640 predictions are all right on top of each other. These next to leading order predictions, 114 00:10:50,850 --> 00:10:58,440 which show that the jet shapes, the size of the jets that dependence of the cross 11500:10:58,440 --> 00:11:04,260 sections on that seems to be reasonably well understood. Excuse me. A similar 116 00:11:04,260 --> 00:11:09,120 study has been made by CMS using 13 TeV data here taking the ratio of the 117 00:11:09,120 --> 00:11:14,610 inclusive cross sections measured in steps of this radius parameter between point one 118 00:11:14,730 --> 00:11:21,300 and 1.2. And here CMS report that they see much better agreement with NLO 119 00:11:21,300 --> 00:11:26,670 predictions than leading order predictions. We look at this bottom plot 120 00:11:26,670 --> 00:11:33,960 on the right hand side, we can see as well that we also see that non perturbative 121 00:11:33,960 --> 00:11:38,760 effects are also crucial. That's also clear on the top plot on the right hand 122 00:11:38,760 --> 00:11:42,600 side that it really is the the non perturbative effects as well that 123 00:11:42,600 --> 00:11:49,470 really lead to the data prediction agreement. And CMS and totem have also 124 00:11:49,500 --> 00:11:53,190 looked at dijet events where there's a rapidity gap between the two leading jets, 125 00:11:53,490 --> 00:11:57,390 and also potentially where there's a gap and then there's also you see a 126 00:11:57,390 --> 00:12:03,390 forward proton. And this is sensitive to hard collar singleness exchange. And the 127 00:12:03,390 --> 00:12:09,720 fraction of these dijet events that you see that have this 128 00:12:09,720 --> 00:12:17,250 gap is plotted here, you can see that the data as a function of the azimuthal 129 00:12:17,250 --> 00:12:22,950 separation of the dijet system shows reasonable agreement with with these 130 00:12:22,950 --> 00:12:29,610 predictions. The BFKL predictions. The middle plot is interesting it shows that 131 00:12:29,610 --> 00:12:36,330 there is some evolution with energy we see with this. You can see the results, CDF and 132 00:12:36,360 --> 00:12:41,490 DZero at different energies in red and then green and then coming down to the 133 00:12:41,490 --> 00:12:46,500 LHC, but actually the results at the LHC from CMS at 7 and 13 TeV are broadly 134 00:12:46,500 --> 00:12:51,450 similar. And again, on the right hand plots, you've got the Totem results, we 135 00:12:51,450 --> 00:12:55,770 use Totem is shown in red, and that's just picking out where you pick up this gap and 136 00:12:55,770 --> 00:13:06,090 then a forward proton. We can also consider jet substructure using the soft drop 137 00:13:06,090 --> 00:13:10,650 algorithm, which is essentially a clustering technique that removes soft and 138 00:13:10,650 --> 00:13:14,910 wide angle radiation in the jet, and really enables you to find the hardest 139 00:13:14,910 --> 00:13:21,600 one to two splitting within the jet. ATLAS study here, the jet mass, the momentum carried 140 00:13:21,600 --> 00:13:28,770 by subjets and much, much more. I'm just showing here essentially, the mass of this 141 00:13:28,800 --> 00:13:34,620 soft-dropped jet system, normalized, it's shown here on the right hand side and there's 142 00:13:34,620 --> 00:13:38,100 good agreement between predictions and the unfolded measurements, and indeed, this 143 00:13:38,100 --> 00:13:41,070 is a common feature in this this recent paper. 144 00:13:43,830 --> 00:13:46,410 We can also consider the evolution of jets 145 00:13:47,940 --> 00:13:52,380 as characterized by the Lund plane. So you've got these kind of variables 146 00:13:52,380 --> 00:13:57,330 where you can use similar clustering techniques to follow kind of 147 00:13:57,330 --> 00:14:03,330 proto jets and emissions and track back through the, through the evolution of the 148 00:14:03,330 --> 00:14:08,190 jet, how the the emissions occurred. And you can look and see, well what fraction 149 00:14:08,190 --> 00:14:12,000 of the momentum was carried by the emission, what was left in the core, what 150 00:14:12,000 --> 00:14:16,860 was the separation of the emission from the core. And you can plot these out and 151 00:14:16,860 --> 00:14:21,270 you, you map out this Lund plane as shown schematically here on the right hand 152 00:14:21,270 --> 00:14:21,660 side. 153 00:14:23,190 --> 00:14:24,840 And you can pick out here, 154 00:14:26,280 --> 00:14:30,420 some measurements, you can, in different bins, you can pick up different bins with 155 00:14:30,420 --> 00:14:34,260 these measurements. And so you can see the schematic you've got your triangle shown 156 00:14:34,260 --> 00:14:38,940 on both of these plots, and this is showing the relevant bin. So on the left 157 00:14:38,940 --> 00:14:43,800 hand side, we've got this bin in separation that we're picking out and then 158 00:14:43,800 --> 00:14:53,460 we're showing multiple bins in this z variable, which is how much of the PT 159 00:14:53,460 --> 00:14:58,350 is carried out by the emitted particle. On the right hand side we're then binning in that; 160 00:14:58,380 --> 00:15:02,880 we've picked out one bin in that variable. And then we're considering bins. 161 00:15:02,910 --> 00:15:09,180 The plot itself shows the Delta R of the emission and the core. And again, there are 162 00:15:09,180 --> 00:15:14,250 comparisons, so all of these different predictions that that we've just heard 163 00:15:14,460 --> 00:15:22,050 some information about. And here we find that herwig 7.13 angular ordering gives, 164 00:15:22,680 --> 00:15:26,010 broadly speaking a very good description across the Lund plane. 165 00:15:28,500 --> 00:15:30,000 And another result from ALICE. 166 00:15:31,740 --> 00:15:39,180 We know that emissions are suppressed within an angle of roughly mq over EQ. And 167 00:15:39,180 --> 00:15:44,400 this is going to be more significant for charm and beauty jets where you have the quark 168 00:15:44,400 --> 00:15:49,050 mass. So ALICE consider these D0 tagged jets and inclusive jets and they treat 169 00:15:49,050 --> 00:15:54,150 them as similarly as possible. And you can see here essentially the ratio of cross 170 00:15:54,150 --> 00:16:00,420 sections you see as a function of this angle of the core and the radiator. You can 171 00:16:00,420 --> 00:16:07,890 see that as one over theta increases, you get the suppression of the D zero 172 00:16:07,890 --> 00:16:14,040 tagged jets relative to just general inclusive jets. In other words, this is an 173 00:16:14,040 --> 00:16:19,440 observation of this dead cone effect, which is very nice to see. And the effect 174 00:16:19,440 --> 00:16:24,210 becomes more pronounced with hard cuts on kT, this is just the difference between 175 00:16:24,210 --> 00:16:29,940 the blue the green and the red. The idea is that these are then introducing an 176 00:16:29,940 --> 00:16:34,080 ability to reduce the impact of non perturbative physics such as hadronisation 177 00:16:34,080 --> 00:16:40,140 effects or reducing the impact of a decay of your D zero, but you can see that 178 00:16:40,140 --> 00:16:47,670 the dead code effect is clearly there. And LHCb have considered jet fragmentation 179 00:16:47,670 --> 00:16:53,910 and hadronisation. So LHCb considers we've got a jet that's recoiling against 180 00:16:53,940 --> 00:17:00,390 Zed boson can we measure the content of that jet? What are the charged hadrons in 181 00:17:00,390 --> 00:17:06,240 the jet, what, what's the fraction of the jet momentum carried by 182 00:17:06,240 --> 00:17:10,650 these, these charged hadrons. So this is shown on the left hand side, we're 183 00:17:10,650 --> 00:17:15,600 comparing LHCb against pythia8 data, and in the bulk of the distribution 184 00:17:16,410 --> 00:17:22,800 it's broadly compatible. But as you see, as you get to high values of z, or 185 00:17:22,800 --> 00:17:28,860 indeed low values, instead, you start to see the data overshoot the the Monte Carlo 186 00:17:28,860 --> 00:17:33,960 prediction. And on the right hand side, I'm comparing this measurement from LHCb 187 00:17:33,960 --> 00:17:38,100 to an earlier measurement of inclusive jets from ATLAS. And indeed, you see that 188 00:17:38,100 --> 00:17:42,690 there are differences in this distribution. And it is hypothesised that 189 00:17:42,690 --> 00:17:47,610 this comes from the fact that the LHCB Z plus jet sample is dominated by light quark 190 00:17:47,610 --> 00:17:52,350 jets, whereas this ATLAS sample is potentially dominated by gluon jets. 191 00:17:54,450 --> 00:18:00,630 ATLAS, Have I said before done this measurement at 8 TeV, this is now the thirteen TeV 192 00:18:00,630 --> 00:18:06,840 measurement considering similar properties. On the left hand plot, we've 193 00:18:06,840 --> 00:18:11,730 got the expected number of charged particles, on the right hand plot we've got 194 00:18:11,730 --> 00:18:16,860 momentum fraction carried by those charged particles. And you can see that the data 195 00:18:16,860 --> 00:18:24,630 theory agreement in the jet multiplicity and the energy composition of the jet is 196 00:18:24,630 --> 00:18:29,040 pretty reasonable. Between them pythia 8, herwig plus plus and Sherpa are all 197 00:18:29,040 --> 00:18:39,000 accurate to about 20%. So leaving jets to one side now: having looked at vector boson, 198 00:18:39,000 --> 00:18:44,970 vector boson plus jets, jets, evolution of jets, and how we go through the event, 199 00:18:45,360 --> 00:18:52,380 we can also consider what about the production of hadrons. So ALICE have 200 00:18:52,380 --> 00:18:58,980 measured the D meson production cross section. This is a measurement that is 201 00:18:59,100 --> 00:19:06,630 sensitive to the low x gluon content of the proton. So it's picking out the low x 202 00:19:06,630 --> 00:19:12,780 gluon PDF. And ALICE compare the data to a wide range of theoretical predictions 203 00:19:12,780 --> 00:19:17,970 with reasonable agreement. But another item in the paper - I've not 204 00:19:17,970 --> 00:19:23,820 shown it here - is that ALICE also compare their results to the LHCb results in a 205 00:19:23,820 --> 00:19:27,120 different rapidity interval. It's very nice to see so it means that you've got 206 00:19:27,120 --> 00:19:33,630 very similar measurements so they're just picking out different regions of rapidity, 207 00:19:33,840 --> 00:19:38,370 different values of x and really getting some nice complimentary physics analysis 208 00:19:38,370 --> 00:19:39,000 going on there. 209 00:19:41,460 --> 00:19:42,960 ATLAS have also considered 210 00:19:44,880 --> 00:19:47,340 production of J/psi and pi(2S) 211 00:19:49,410 --> 00:19:50,580 we see here, 212 00:19:52,559 --> 00:20:00,689 this is done a high pt. So this is for pts of 60 gev and above, and measuring prompt and 213 00:20:00,689 --> 00:20:04,229 non prompt contributions. And actually something that's quite interesting is that 214 00:20:04,229 --> 00:20:09,899 the non prompt fraction of J/psi is relatively flat as a function of PT and 215 00:20:09,899 --> 00:20:15,089 rapidity. And then you can take that non prompt contribution and compare it to the 216 00:20:15,089 --> 00:20:23,129 fonll model. And indeed you see agreement in the low PT region. But actually, the 217 00:20:23,129 --> 00:20:31,229 prediction ends up overshooting the data at higher PT. And so those are just a 218 00:20:31,229 --> 00:20:36,479 couple of recent hadronic production cross section measurements that I just wanted to 219 00:20:36,479 --> 00:20:42,629 pick out. And so I thought I'd spend the last few few moments of the talk just 220 00:20:42,629 --> 00:20:50,729 covering hydronic spectroscopy. So LHCb has looked at the lambda_c k minus mass 221 00:20:50,729 --> 00:20:59,519 spectrum in run two data and it sees various structures over a smooth 222 00:20:59,519 --> 00:21:04,499 background. And reports new states and makes precise mass and width 223 00:21:04,499 --> 00:21:10,469 measurements and of these the two lowest mass states are definitively observed for 224 00:21:10,469 --> 00:21:15,629 the first time. The higher mass state requires further study to confirm it is separate 225 00:21:15,629 --> 00:21:24,119 to the already known cascade_c 2970 but it's nice to see these these new 226 00:21:24,119 --> 00:21:24,989 resonances seen. 227 00:21:25,470 --> 00:21:27,150 Will, you have three minutes. 228 00:21:28,260 --> 00:21:31,680 The LHCb also looks at 229 00:21:33,630 --> 00:21:40,200 new excited omega b resonances. And this uses the entire LHCb data set. And we see 230 00:21:40,200 --> 00:21:49,920 here on the bottom plot, the contribution that you would get from (excuse me a second), you 231 00:21:49,920 --> 00:21:59,640 would get from the combination of k plus and if you took the k minus you get the top 232 00:21:59,640 --> 00:22:03,750 plot, you recover this peaking structure. And I say these are the local 233 00:22:03,750 --> 00:22:11,790 significances I've put on the top plot. And these are between 3.6 and 7.2 sigma. 234 00:22:12,120 --> 00:22:15,840 And then when you account for the look elsewhere effect, the two lowest mistakes end up 235 00:22:15,840 --> 00:22:20,430 with a significance below three sigma. But the two high mistakes have significance as 236 00:22:20,430 --> 00:22:28,830 above five sigma still. LHCb and CMS have both reported in the last year new excited 237 00:22:28,830 --> 00:22:33,930 lambda_b resonances, measuring the lambda_b pi plus pi minus mass spectrum, 238 00:22:34,200 --> 00:22:40,020 three states have been observed. These are separate analyses I should be clear from 239 00:22:40,020 --> 00:22:47,190 CMS and LHCb. And these analyses make use of different decay modes. But the key 240 00:22:47,190 --> 00:22:51,810 feature is that the excesses are seen at both experiments. And again, you can see 241 00:22:51,810 --> 00:22:57,030 the pi plus pi minus combination at the top with the pi plus pi plus and pi minus pi 242 00:22:57,030 --> 00:23:03,930 minus blow and you only see these excited estates in the pi plus pi minus 243 00:23:03,930 --> 00:23:07,500 combination. And there's a suggested interpretation, a doublet of states that 244 00:23:07,500 --> 00:23:13,770 correspond to the lambda_b (1D). And then you've got the lambda (2S) observed 245 00:23:13,770 --> 00:23:22,080 as well. There's also a measurement from LHCb of the BC mass using multiple decay 246 00:23:22,080 --> 00:23:25,590 modes. And what's quite nice here is that there's an improvement on the current world 247 00:23:25,590 --> 00:23:31,950 average by a factor of roughly two. And indeed, this is already far more precise 248 00:23:31,950 --> 00:23:39,510 than the prediction from unquenched lattice QCD. And then the final result I 249 00:23:39,510 --> 00:23:44,280 want to share is another new result. This one from LHCb. This is the first 250 00:23:44,310 --> 00:23:51,420 measurement that the X(3872) has nonzero width. It's the most precise determination 251 00:23:51,420 --> 00:23:57,150 of mass and binding energy to date from this channel. There are actually two analyses 252 00:23:57,150 --> 00:24:02,850 here that are both in preparation: one uses an inclusive selection, one uses an 253 00:24:02,850 --> 00:24:08,730 exclusive selection. And the analyses make an extensive study of branching fractions 254 00:24:08,760 --> 00:24:15,060 and the line shape of the state considering modeling using flatte and 255 00:24:15,060 --> 00:24:21,690 Breit-Wigner distributions. And indeed, the first pole of the complex amplitudes 256 00:24:21,690 --> 00:24:27,840 found within this extensive study of line shape implies results consistent with 257 00:24:27,870 --> 00:24:34,650 bound dates. So just to conclude, I've kind of done a rapid whirlwind tour of 258 00:24:34,650 --> 00:24:40,590 studies of QCD at the LHC, which covers scales, from high momenta to lower momenta 259 00:24:40,800 --> 00:24:45,330 and probes a range of phenomena. There are stunning levels of precision achieved by 260 00:24:45,330 --> 00:24:49,680 ALICE, ATLAS, CMS and LHCb with new and exciting measurements in the last year. 261 00:24:50,100 --> 00:24:59,820 And of course, I've had to sum up the entirety of a parallel session in one 262 00:24:59,820 --> 00:25:03,960 plenary talk. So do connect to the parallel sessions to learn more, or if you just 263 00:25:03,960 --> 00:25:09,540 want to ask some more questions or chat to me, then I can be found at this link after 264 00:25:09,540 --> 00:25:13,350 the plenary sessions are over today. Thanks for listening. 265 00:25:14,549 --> 00:25:18,959 Thanks a lot Will for this impressive summary of research results from the 266 00:25:19,319 --> 00:25:21,689 LHC experiments. Questions. 267 00:25:23,190 --> 00:25:24,150 Bogdan? 268 00:25:26,550 --> 00:25:27,180 Okay. 269 00:25:28,559 --> 00:25:34,979 Hello. Do you hear me? Yes I hear you. Yes. Hello. Very nice. Very nice talk. I have a 270 00:25:35,009 --> 00:25:41,759 question/comment. Two measurements from ALICE and from CMS 271 00:25:41,789 --> 00:25:49,709 concerning the ratio between jet cross-sections for different jet sizes. So I 272 00:25:49,709 --> 00:25:55,859 would like to to know how the authors comment about the two important 273 00:25:55,859 --> 00:26:00,599 systematics: the modeling system metrics that are involved in the calibration when 274 00:26:00,599 --> 00:26:06,089 extrapolating between different jet sizes, and also how the correlations of the 275 00:26:06,089 --> 00:26:10,349 uncertainties are therefore taken into account when computing those ratios. 276 00:26:12,240 --> 00:26:17,820 So unfortunately, I'm not a member of either of those collaborations so I can't 277 00:26:17,910 --> 00:26:21,300 give an extensive comment on this. 278 00:26:24,359 --> 00:26:28,619 More for someone's from CMS or from ALICE, I mean, if they are, yeah, if someone wants 279 00:26:28,619 --> 00:26:30,269 to speak up, please feel free. 280 00:26:34,290 --> 00:26:37,770 I don't see any hand: if you want to speak up, please raise your hand. 281 00:26:42,540 --> 00:26:47,100 I would also be happy to follow up on this topic offline if someone is available. 282 00:26:47,280 --> 00:26:51,030 Yeah, it's clearly interesting to know the degree which you can expect 283 00:26:51,030 --> 00:26:57,390 systematics to cancel in this kind of measurement; to what degree as you change 284 00:26:57,390 --> 00:27:02,250 your jet size, your systematic effects actually do cancel or to what 285 00:27:02,250 --> 00:27:06,210 extent they are clearly correlated with the collimation of the jet. 286 00:27:08,250 --> 00:27:09,000 My concern. 287 00:27:10,260 --> 00:27:14,070 Yeah, sorry. My concern is mainly related to the modeling dependence. I mean, this 288 00:27:14,070 --> 00:27:18,120 extrapolation and I think it is quite large. So this is what I wanted to hear 289 00:27:18,120 --> 00:27:18,360 about. 290 00:27:20,430 --> 00:27:25,170 Yeah, this probably really needs the experts. So maybe if there is an expert in 291 00:27:25,170 --> 00:27:30,300 the audience, you can join the chat room of Will afterwards after the plenary 292 00:27:30,300 --> 00:27:30,750 session. 293 00:27:32,069 --> 00:27:33,959 We have time for one more question. 294 00:27:40,410 --> 00:27:47,280 No hands up. Okay. Then we move to the last talk of today. So we move to the low 295 00:27:47,280 --> 00:27:48,000 scales.