1 00:00:05,910 --> 00:00:07,260 Can you see the full screen? 2 00:00:08,519 --> 00:00:09,719 Yes, go ahead. 3 00:00:10,349 --> 00:00:15,629 Alright, so, once again, thanks to the organizers, and thanks for having me here. 4 00:00:17,309 --> 00:00:23,249 So I'm going to be talking about dark photons at elite cb. And so there are many 5 00:00:23,249 --> 00:00:27,179 theoretical attempts of tackling this problem of the nature of dark matter, 6 00:00:27,179 --> 00:00:31,769 right? A lack of discoveries both at the IHC direct detection experiments suggest 7 00:00:31,769 --> 00:00:36,479 that we should explore other scenarios beyond a simple extension of the standard 8 00:00:36,479 --> 00:00:42,419 model. So what if there's a Dark Sector that can be rich in quarks and leptons, 9 00:00:42,449 --> 00:00:47,009 but there's no connection between the standard model and the Dark Sector, not 10 00:00:47,039 --> 00:00:51,509 case dogmatic could easily evade detection and particle physics experiments at the 11 00:00:51,539 --> 00:00:56,309 energy frontier? Even if there is a Dark Sector particles are relatively light. So 12 00:00:56,309 --> 00:01:01,529 what do we do here? A simple possibility is that die Matter interacts with itself 13 00:01:01,559 --> 00:01:07,559 by a new force. This force is similar in structure to the non forces. A loop can 14 00:01:07,559 --> 00:01:12,599 create a so called Portland direction that allows us to probe this dark matter. This 15 00:01:12,599 --> 00:01:16,679 loop can be due to particles of that charged under both the standard model and 16 00:01:16,679 --> 00:01:20,969 Dark Sector forces, but it can have arbitrary monsters all the way up to the 17 00:01:20,969 --> 00:01:27,629 point scale. And also you can have an exchange to get those on in there. So the 18 00:01:27,659 --> 00:01:32,609 vector portal with the dark photon portal is the most valuable of the four portals 19 00:01:32,609 --> 00:01:37,979 for thermal models of light dark matter. And when the dark photon is light decays 20 00:01:38,069 --> 00:01:42,839 to standard model particles, these are called visible decays, which is what we're 21 00:01:42,839 --> 00:01:48,959 going to be concentrating on in this talk. So the dark photon couples to standard 22 00:01:48,959 --> 00:01:54,209 model particles via the electromagnetic current is suppressed relative to that of 23 00:01:54,209 --> 00:01:58,949 the ordinary photon by a factor of epsilon, which is one of the two free 24 00:01:58,949 --> 00:02:03,359 parameters and the minimum dock photo model, the other one is the mass of the 25 00:02:03,359 --> 00:02:10,349 dock proton. So here you can see the existing limits for the most promising 26 00:02:10,349 --> 00:02:16,529 visible parameter space. The naively interesting region is parameterised in 27 00:02:16,529 --> 00:02:22,859 this white rectangle. However, any of the parameter space here is interesting, even 28 00:02:22,889 --> 00:02:29,939 a slightly different model. So, if we use a collider of high energy, we can also 29 00:02:29,939 --> 00:02:34,409 cover the region that's all the way in the top right here. And in order to cover some 30 00:02:34,409 --> 00:02:39,719 of this box in space, we need a lot of data because the parameter epsilon is 31 00:02:39,719 --> 00:02:44,129 small. And in order to use the state efficiently, we also need good background 32 00:02:44,129 --> 00:02:50,009 projection, and that needs to be very efficient. And the hcb detector can help 33 00:02:50,039 --> 00:02:57,479 handle all of these challenges. So lm DB is a single arm forward spectrometer with 34 00:02:57,479 --> 00:03:02,099 excellent lifetime and mass resolution. These are needed for background 35 00:03:02,099 --> 00:03:08,009 projection. And we have collected data on the scratch surface of 13 Db from 36 00:03:08,009 --> 00:03:14,849 2016 2017 and 2018. For this, in order to capture visible doctorate on the case, we 37 00:03:14,849 --> 00:03:20,369 can't just trigger on some high PT Mian hits or colorimetric clusters. So we need 38 00:03:20,399 --> 00:03:28,199 a flexible triggering scheme. So our strategy is as follows. We look for both 39 00:03:28,199 --> 00:03:36,719 prompt and displaced, inclusive, dark photons going to damiana case. And as the 40 00:03:36,719 --> 00:03:40,949 dark photon behaves just like an offshore photon, the kinematics of its production 41 00:03:40,949 --> 00:03:45,809 and decay are exactly the same as for offshore photons of the same mass. So 42 00:03:45,809 --> 00:03:50,219 therefore, after making stringent particle identification, geometric and other 43 00:03:50,219 --> 00:03:55,559 requirements, we reject backgrounds and get a number of single catalysts, your 44 00:03:55,559 --> 00:03:59,879 competitors this number to predictions from the off shelf photon yield and claim 45 00:03:59,879 --> 00:04:04,499 it Discovery I'll set limits. So as beautiful about this scenario here is that 46 00:04:04,769 --> 00:04:10,679 we get a fully data driven search, which simplifies the search significantly. 47 00:04:12,570 --> 00:04:13,890 So let's look at background. 48 00:04:15,210 --> 00:04:20,550 The first one is an off shell photon to demyan production. This is irreducible and 49 00:04:20,550 --> 00:04:28,140 is exactly what is needed to normalize the doctoral candidate. So, we also know and 50 00:04:28,140 --> 00:04:32,280 love our center model resonances, that peaks in the dummy on spectrum and so, 51 00:04:33,390 --> 00:04:37,080 they make a search for doctoral Tom's hottest we veto these regions in this 52 00:04:37,080 --> 00:04:44,070 specific search. There are several types of Mr constructions and these can be 53 00:04:44,070 --> 00:04:49,950 mitigated by by a fit and by a dedicated same sign demyan sample which is 54 00:04:49,950 --> 00:04:56,760 subtracted. And overall, these backgrounds are still highly suppressed by the 55 00:04:56,790 --> 00:05:02,010 stringent mewn identification and prompt library. quirements applied in the trigger 56 00:05:02,010 --> 00:05:09,810 and offline. But above a mass of the dark photon of 1.1 gV, misconstruction still 57 00:05:09,810 --> 00:05:14,100 dominates, so we still need to do something. So here we apply an isolation 58 00:05:14,100 --> 00:05:21,180 requirement. And that we can do because of the way the minimum dock photo model 59 00:05:21,210 --> 00:05:27,390 produces it. And so here you kind of get an idea of what we're dealing with. So 60 00:05:27,390 --> 00:05:31,980 this blows shot shows the demyan spectrum from the threshold all the way up to those 61 00:05:31,980 --> 00:05:37,890 that mass. And if you look at the eater here, the yield is 300,000, which is 62 00:05:37,890 --> 00:05:44,250 roughly 2000 times that combined previous false data. And this plate plot was made 63 00:05:44,760 --> 00:05:50,550 only with 2016 running. So we have more than three times the amount of data in 64 00:05:50,550 --> 00:05:55,020 this plot. That kind of gives you a clue of what we're dealing with. And you see 65 00:05:55,020 --> 00:06:01,020 the isolation requirement here that we've set. So the The strategy we use is the 66 00:06:01,020 --> 00:06:06,390 following. So we want to set limits on epsilon squared for every value of mass. 67 00:06:06,960 --> 00:06:10,920 And remember that epsilon is this parameter that tells us how suppressed the 68 00:06:10,920 --> 00:06:17,790 coupling is in comparison to the standard model. So first we find the off shell 69 00:06:17,790 --> 00:06:25,650 photon yield to fit and for prompt like doc photons, to came to them yawns so the 70 00:06:25,650 --> 00:06:31,950 case experimental indistinguishable from the off show photon decays. And this means 71 00:06:31,950 --> 00:06:38,010 that there's efficiency between the sufficiency ratio between doctors dark 72 00:06:38,010 --> 00:06:42,090 photons and offshore photons is exactly one. 73 00:06:43,350 --> 00:06:45,150 And then, we 74 00:06:46,470 --> 00:06:51,540 either discover or set limits on the dark photon yield, which we get from the pump 75 00:06:51,540 --> 00:06:55,860 pump. And this pump on itself is pretty special and requires thousands of 76 00:06:55,860 --> 00:07:01,290 automatic automatic automatic fits, and so dedicated people has been written on this 77 00:07:02,310 --> 00:07:07,470 and this has been studied specifically. And now that we have all of the terms in 78 00:07:07,470 --> 00:07:14,700 this equation, we can set limits on this problem to epsilon. Alright, and here you 79 00:07:14,700 --> 00:07:23,250 see the results from the problem such and we LCB sets word leading limits from 80 00:07:23,250 --> 00:07:30,330 threshold which is twice the last of the way all the way up to 740 maybe and from 81 00:07:30,330 --> 00:07:38,340 10.6 to 30, Gd and T obviously, no significant access was found. And we have 82 00:07:38,340 --> 00:07:46,290 statistics limited so, we look forward to run through quite a bit. All right. So, 83 00:07:46,500 --> 00:07:52,620 shifting gears a bit. Now, we are looking at the displaced search. So, here we have 84 00:07:53,280 --> 00:07:57,180 a couple of different backgrounds. So, firstly we have some behead on Mickie 85 00:07:57,180 --> 00:08:06,840 James, which are mitigated by requiring a strict decay decay topology. Secondly, we 86 00:08:06,840 --> 00:08:12,930 have a key short to pi pi tail with whether to pions miss a deed as nuance. 87 00:08:13,470 --> 00:08:18,480 And this is subtracted by extrapolation, but so limits on master age for the 88 00:08:18,480 --> 00:08:25,350 display search because this is quite a big peak. And lastly, we have photon 89 00:08:25,350 --> 00:08:31,320 conversions to Danya ons in the silicon strip vertex detector, or called also 90 00:08:31,320 --> 00:08:36,840 called the bellow. So here they've developed a specific tool, just switch 91 00:08:36,840 --> 00:08:44,430 recall the material veto tool which uses an ACB velo to image itself and therefore, 92 00:08:45,450 --> 00:08:50,460 be able to reject the hypothesis of our dumb yawns just coming from material 93 00:08:50,460 --> 00:08:56,100 interactions. comparison to the prom strategy, we have to make a couple of 94 00:08:56,100 --> 00:09:03,780 changes. We keep just we still set limits on this parameter epsilon. And we keep the 95 00:09:03,780 --> 00:09:11,430 same normalization. However, now the sufficiency is no longer one because our 96 00:09:12,060 --> 00:09:17,850 duck proton flies, and so the efficiency depends on the kid decay time. And we now 97 00:09:17,850 --> 00:09:23,880 also have a looser trigger for this. So we implement a data driven resampling to 98 00:09:23,880 --> 00:09:30,060 estimate it and validate it with the dedicated sample. So in order to set 99 00:09:30,060 --> 00:09:36,420 limits on the doc photon ELT, we can now perform a 3d fit in a dummy on mass, decay 100 00:09:36,420 --> 00:09:43,350 time, and decay topology consistency. And here are the results for the displaced 101 00:09:43,350 --> 00:09:48,570 case. Everything that is in blue or simplify everything that's in blue is 102 00:09:48,570 --> 00:09:53,670 rolled out and everything that's in pretty dark gray is very close to being rolled 103 00:09:53,670 --> 00:10:01,500 out. So this means that the upgrades of the nhc and just donated CB and just 104 00:10:01,500 --> 00:10:06,150 running for a little bit longer will greatly increase our dark photon discovery 105 00:10:06,180 --> 00:10:14,220 potential. And this plot puts the prompt and displays such as into context. This is 106 00:10:14,220 --> 00:10:19,440 like our previous plot with our new constraints put in. And you can see that 107 00:10:19,440 --> 00:10:27,180 LCB covers new prompt regions near demyan mass, and also high masses. And it's the 108 00:10:27,180 --> 00:10:31,320 first experiment to set limits in this intermediate space by its display search. 109 00:10:33,810 --> 00:10:39,360 However, this minimal Dakota model as short as talked about the last speaker is 110 00:10:39,360 --> 00:10:45,330 not the only viable Dark Sector scenario. So firstly, we can say that the searches 111 00:10:45,330 --> 00:10:50,310 presented can provide serendipitous discovery potential for other types of 112 00:10:51,090 --> 00:10:55,740 particles. However, still, there's many motivated models that can avoid detection 113 00:10:55,740 --> 00:11:00,750 or previous experiments and such as and some of these models can be be constrained 114 00:11:00,990 --> 00:11:06,450 by slightly altering the session. And for example, removing the kinetic mixing 115 00:11:06,450 --> 00:11:11,430 assumption, which makes it more general and at the other, on the other hand, also 116 00:11:11,430 --> 00:11:15,810 playing some extra extra cuts in order to have some dedicated searches. 117 00:11:18,750 --> 00:11:23,310 However, when performing the searches, we now can no longer beautifully normalize to 118 00:11:23,310 --> 00:11:28,230 that offshore photon. And so we need to calculate absolute efficiencies and 119 00:11:28,230 --> 00:11:33,810 luminosity and to provide results and bins of mass and PT. This makes this more 120 00:11:33,810 --> 00:11:39,240 difficult but it means that now we have I'm going to show you some very new 121 00:11:39,240 --> 00:11:45,600 results that are luminary and have not been shown before. And so for these non 122 00:11:45,600 --> 00:11:51,510 minimum models, we have two types of probe searches, both with our isolation 123 00:11:51,510 --> 00:11:58,260 requirement and inclusive search. Where a B jet is required in the event and an 124 00:11:58,260 --> 00:12:05,190 inclusive one on The displaced side of things, we also have two sections. The 125 00:12:05,190 --> 00:12:09,720 first one is where the doc photon is produced at the primary vertex. And the 126 00:12:09,720 --> 00:12:17,190 second one does not make this requirement, and no signal has been found here. So here 127 00:12:17,220 --> 00:12:24,090 are the results for the prompt, non minimal searches. So the top here is the 128 00:12:24,090 --> 00:12:31,740 inclusive and the bottom is the ones with a beach at any event. And so the gray 129 00:12:31,740 --> 00:12:38,490 regions here show that limits could not be set because, for example of resonances. 130 00:12:42,540 --> 00:12:50,370 And here you see the prompts no minimal results for high analysis. And the pity 131 00:12:50,370 --> 00:12:55,140 bins are no longer necessary here, since both the resolution and efficiency I'm 132 00:12:55,140 --> 00:13:00,360 nearly independent of the PT in this regime, however, now, we can Consider 133 00:13:00,360 --> 00:13:06,750 nonzero width, just on turn on the y axis. And these are upper limits on 134 00:13:08,280 --> 00:13:09,120 the cross section. 135 00:13:11,610 --> 00:13:19,410 We've gone now, these are the displaced non minimal results. And here, the gray 136 00:13:19,410 --> 00:13:27,690 region is from the case shortcode to pi pi, which is V tilde. So, theorists can 137 00:13:27,690 --> 00:13:31,680 use these models in order to set limits on their own models and so we have provided 138 00:13:31,680 --> 00:13:37,650 them in a format that they can be recast. For example, their models were a complex 139 00:13:37,980 --> 00:13:43,620 scalar sigma that's added to the to Hicks doublet. And these models. They often 140 00:13:43,620 --> 00:13:48,330 feature a light pseudo scalar pause on that can decay into the down yawns that we 141 00:13:48,330 --> 00:13:57,030 can observe here LCB and wildling limits are set from the prompt search and 142 00:13:57,330 --> 00:14:04,440 assuming a extra BB bar to follow For such a model lacp is limits are 20 times lower 143 00:14:04,620 --> 00:14:14,820 than the access that was seen by CMS in the extra BB bar such okay also there are 144 00:14:14,820 --> 00:14:22,710 some such as use of displaced searches. So here for example, we can look at Hidden 145 00:14:22,710 --> 00:14:27,420 Valley theories that produce high multiplicity of light, hidden hydrants 146 00:14:27,930 --> 00:14:33,120 from showering and these particles have low PTO displays from the TV and therefore 147 00:14:33,120 --> 00:14:39,960 fail they have inflator veto we we require in the minimal such. So here we have 148 00:14:39,960 --> 00:14:43,560 limits that are set on the kinetic mixing strength between the photon and a heavy 149 00:14:43,860 --> 00:14:51,300 Hidden Valley boson with photon like couplings. So overall, dark sectors are 150 00:14:51,300 --> 00:14:55,230 documented scenarios that are worth exploring. And lacp has world leading 151 00:14:55,230 --> 00:15:01,200 sensitivity to different models. There's also a document I'm going to die. Electron 152 00:15:01,200 --> 00:15:05,670 search has been performed with 2018 data now. So stay tuned. 153 00:15:09,750 --> 00:15:14,070 Excellent concentrated. These were some very interesting results. Do we have any 154 00:15:14,070 --> 00:15:17,340 questions for Constantine? Just raise your hand in zoom. 155 00:15:25,710 --> 00:15:31,560 Maybe I can ask one. Then. On slide 23, similar to one of the earlier summaries 156 00:15:31,560 --> 00:15:38,130 you showed, I noticed that the gaps where you can't set limits right now with HCP, 157 00:15:38,130 --> 00:15:41,940 which is you mentioned that because there's some resonance there, it seems 158 00:15:41,940 --> 00:15:46,170 that some of the older results are able to get a little bit more into those polls. 159 00:15:46,170 --> 00:15:50,010 Like for example, the bar has a limit that goes across the first graph and then this 160 00:15:50,010 --> 00:15:55,050 relates to be run one results around 10 G, what's the difference or what makes that 161 00:15:55,050 --> 00:15:56,280 easier for them to access? 162 00:15:56,879 --> 00:16:01,799 So number one here is that this is we have the form to search all the way through all 163 00:16:01,799 --> 00:16:06,029 the way from very low masses to high masses. And looking at this epsilon region 164 00:16:06,029 --> 00:16:11,789 here is we need a dedicated search. And so this has been performed in run one, but 165 00:16:11,789 --> 00:16:20,069 it's not something we tackled with this first search with lacp. This is a search 166 00:16:20,069 --> 00:16:24,509 that hopefully will be performed with round two. So we will see a significantly 167 00:16:25,319 --> 00:16:30,929 better coverage there in the future. So this is just something that requires extra 168 00:16:30,929 --> 00:16:32,729 attention has not been performed yet. 169 00:16:35,400 --> 00:16:36,780 Does this answer the question? 170 00:16:37,590 --> 00:16:38,850 Yes. Thanks a lot. 171 00:16:47,070 --> 00:16:47,610 ahead, Brian. 172 00:16:48,900 --> 00:16:52,290 Yeah, hi. This is really interesting. And these new results are great. I'm curious 173 00:16:52,290 --> 00:16:57,960 in this plot. When you show for instance, the bar and CMS results, which is a bar 174 00:16:57,960 --> 00:17:01,680 because I was involved in all of these which serve Are you using for constraining 175 00:17:01,680 --> 00:17:02,400 this model? 176 00:17:04,259 --> 00:17:08,189 Um, I have to say, I don't know right now, but I can get back to you if you want. 177 00:17:09,809 --> 00:17:16,109 This is a recasting that I was not involved in, so I can get back to you on 178 00:17:16,109 --> 00:17:16,439 that one. 179 00:17:17,279 --> 00:17:21,209 Okay, because we just, I mean, that was one of the things, the results that I 180 00:17:21,209 --> 00:17:26,039 showed was something that came out in the past few weeks. So it might might change 181 00:17:26,039 --> 00:17:27,089 some of this, but yeah, this 182 00:17:27,089 --> 00:17:28,709 might change. Yeah, if you if you 183 00:17:29,790 --> 00:17:34,410 let me know that then we can include this in. But I mean, this is really incredible 184 00:17:34,410 --> 00:17:37,590 sensitivity, I guess a related question. I mean, maybe this this falls the same 185 00:17:37,590 --> 00:17:41,850 category. But yeah, we were able to cover the row region because it's quite a broad 186 00:17:41,850 --> 00:17:45,750 resonance. And presumably, you could do the same but I guess you just need a 187 00:17:45,750 --> 00:17:47,730 dedicated search. Exactly. Yeah.