Can you see the full screen?
Yes, go ahead.
Alright, so, once again, thanks to the organizers, and thanks for having me here.
So I'm going to be talking about dark photons at elite cb. And so there are many
theoretical attempts of tackling this problem of the nature of dark matter,
right? A lack of discoveries both at the IHC direct detection experiments suggest
that we should explore other scenarios beyond a simple extension of the standard
model. So what if there's a Dark Sector that can be rich in quarks and leptons,
but there's no connection between the standard model and the Dark Sector, not
case dogmatic could easily evade detection and particle physics experiments at the
energy frontier? Even if there is a Dark Sector particles are relatively light. So
what do we do here? A simple possibility is that die Matter interacts with itself
by a new force. This force is similar in structure to the non forces. A loop can
create a so called Portland direction that allows us to probe this dark matter. This
loop can be due to particles of that charged under both the standard model and
Dark Sector forces, but it can have arbitrary monsters all the way up to the
point scale. And also you can have an exchange to get those on in there. So the
vector portal with the dark photon portal is the most valuable of the four portals
for thermal models of light dark matter. And when the dark photon is light decays
to standard model particles, these are called visible decays, which is what we're
going to be concentrating on in this talk. So the dark photon couples to standard
model particles via the electromagnetic current is suppressed relative to that of
the ordinary photon by a factor of epsilon, which is one of the two free
parameters and the minimum dock photo model, the other one is the mass of the
dock proton. So here you can see the existing limits for the most promising
visible parameter space. The naively interesting region is parameterised in
this white rectangle. However, any of the parameter space here is interesting, even
a slightly different model. So, if we use a collider of high energy, we can also
cover the region that's all the way in the top right here. And in order to cover some
of this box in space, we need a lot of data because the parameter epsilon is
small. And in order to use the state efficiently, we also need good background
projection, and that needs to be very efficient. And the hcb detector can help
handle all of these challenges. So lm DB is a single arm forward spectrometer with
excellent lifetime and mass resolution. These are needed for background
projection. And we have collected data on the scratch surface of 13 Db from
2016 2017 and 2018. For this, in order to capture visible doctorate on the case, we
can't just trigger on some high PT Mian hits or colorimetric clusters. So we need
a flexible triggering scheme. So our strategy is as follows. We look for both
prompt and displaced, inclusive, dark photons going to damiana case. And as the
dark photon behaves just like an offshore photon, the kinematics of its production
and decay are exactly the same as for offshore photons of the same mass. So
therefore, after making stringent particle identification, geometric and other
requirements, we reject backgrounds and get a number of single catalysts, your
competitors this number to predictions from the off shelf photon yield and claim
it Discovery I'll set limits. So as beautiful about this scenario here is that
we get a fully data driven search, which simplifies the search significantly.
So let's look at background.
The first one is an off shell photon to demyan production. This is irreducible and
is exactly what is needed to normalize the doctoral candidate. So, we also know and
love our center model resonances, that peaks in the dummy on spectrum and so,
they make a search for doctoral Tom's hottest we veto these regions in this
specific search. There are several types of Mr constructions and these can be
mitigated by by a fit and by a dedicated same sign demyan sample which is
subtracted. And overall, these backgrounds are still highly suppressed by the
stringent mewn identification and prompt library. quirements applied in the trigger
and offline. But above a mass of the dark photon of 1.1 gV, misconstruction still
dominates, so we still need to do something. So here we apply an isolation
requirement. And that we can do because of the way the minimum dock photo model
produces it. And so here you kind of get an idea of what we're dealing with. So
this blows shot shows the demyan spectrum from the threshold all the way up to those
that mass. And if you look at the eater here, the yield is 300,000, which is
roughly 2000 times that combined previous false data. And this plate plot was made
only with 2016 running. So we have more than three times the amount of data in
this plot. That kind of gives you a clue of what we're dealing with. And you see
the isolation requirement here that we've set. So the The strategy we use is the
following. So we want to set limits on epsilon squared for every value of mass.
And remember that epsilon is this parameter that tells us how suppressed the
coupling is in comparison to the standard model. So first we find the off shell
photon yield to fit and for prompt like doc photons, to came to them yawns so the
case experimental indistinguishable from the off show photon decays. And this means
that there's efficiency between the sufficiency ratio between doctors dark
photons and offshore photons is exactly one.
And then, we
either discover or set limits on the dark photon yield, which we get from the pump
pump. And this pump on itself is pretty special and requires thousands of
automatic automatic automatic fits, and so dedicated people has been written on this
and this has been studied specifically. And now that we have all of the terms in
this equation, we can set limits on this problem to epsilon. Alright, and here you
see the results from the problem such and we LCB sets word leading limits from
threshold which is twice the last of the way all the way up to 740 maybe and from
10.6 to 30, Gd and T obviously, no significant access was found. And we have
statistics limited so, we look forward to run through quite a bit. All right. So,
shifting gears a bit. Now, we are looking at the displaced search. So, here we have
a couple of different backgrounds. So, firstly we have some behead on Mickie
James, which are mitigated by requiring a strict decay decay topology. Secondly, we
have a key short to pi pi tail with whether to pions miss a deed as nuance.
And this is subtracted by extrapolation, but so limits on master age for the
display search because this is quite a big peak. And lastly, we have photon
conversions to Danya ons in the silicon strip vertex detector, or called also
called the bellow. So here they've developed a specific tool, just switch
recall the material veto tool which uses an ACB velo to image itself and therefore,
be able to reject the hypothesis of our dumb yawns just coming from material
interactions. comparison to the prom strategy, we have to make a couple of
changes. We keep just we still set limits on this parameter epsilon. And we keep the
same normalization. However, now the sufficiency is no longer one because our
duck proton flies, and so the efficiency depends on the kid decay time. And we now
also have a looser trigger for this. So we implement a data driven resampling to
estimate it and validate it with the dedicated sample. So in order to set
limits on the doc photon ELT, we can now perform a 3d fit in a dummy on mass, decay
time, and decay topology consistency. And here are the results for the displaced
case. Everything that is in blue or simplify everything that's in blue is
rolled out and everything that's in pretty dark gray is very close to being rolled
out. So this means that the upgrades of the nhc and just donated CB and just
running for a little bit longer will greatly increase our dark photon discovery
potential. And this plot puts the prompt and displays such as into context. This is
like our previous plot with our new constraints put in. And you can see that
LCB covers new prompt regions near demyan mass, and also high masses. And it's the
first experiment to set limits in this intermediate space by its display search.
However, this minimal Dakota model as short as talked about the last speaker is
not the only viable Dark Sector scenario. So firstly, we can say that the searches
presented can provide serendipitous discovery potential for other types of
particles. However, still, there's many motivated models that can avoid detection
or previous experiments and such as and some of these models can be be constrained
by slightly altering the session. And for example, removing the kinetic mixing
assumption, which makes it more general and at the other, on the other hand, also
playing some extra extra cuts in order to have some dedicated searches.
However, when performing the searches, we now can no longer beautifully normalize to
that offshore photon. And so we need to calculate absolute efficiencies and
luminosity and to provide results and bins of mass and PT. This makes this more
difficult but it means that now we have I'm going to show you some very new
results that are luminary and have not been shown before. And so for these non
minimum models, we have two types of probe searches, both with our isolation
requirement and inclusive search. Where a B jet is required in the event and an
inclusive one on The displaced side of things, we also have two sections. The
first one is where the doc photon is produced at the primary vertex. And the
second one does not make this requirement, and no signal has been found here. So here
are the results for the prompt, non minimal searches. So the top here is the
inclusive and the bottom is the ones with a beach at any event. And so the gray
regions here show that limits could not be set because, for example of resonances.
And here you see the prompts no minimal results for high analysis. And the pity
bins are no longer necessary here, since both the resolution and efficiency I'm
nearly independent of the PT in this regime, however, now, we can Consider
nonzero width, just on turn on the y axis. And these are upper limits on
the cross section.
We've gone now, these are the displaced non minimal results. And here, the gray
region is from the case shortcode to pi pi, which is V tilde. So, theorists can
use these models in order to set limits on their own models and so we have provided
them in a format that they can be recast. For example, their models were a complex
scalar sigma that's added to the to Hicks doublet. And these models. They often
feature a light pseudo scalar pause on that can decay into the down yawns that we
can observe here LCB and wildling limits are set from the prompt search and
assuming a extra BB bar to follow For such a model lacp is limits are 20 times lower
than the access that was seen by CMS in the extra BB bar such okay also there are
some such as use of displaced searches. So here for example, we can look at Hidden
Valley theories that produce high multiplicity of light, hidden hydrants
from showering and these particles have low PTO displays from the TV and therefore
fail they have inflator veto we we require in the minimal such. So here we have
limits that are set on the kinetic mixing strength between the photon and a heavy
Hidden Valley boson with photon like couplings. So overall, dark sectors are
documented scenarios that are worth exploring. And lacp has world leading
sensitivity to different models. There's also a document I'm going to die. Electron
search has been performed with 2018 data now. So stay tuned.
Excellent concentrated. These were some very interesting results. Do we have any
questions for Constantine? Just raise your hand in zoom.
Maybe I can ask one. Then. On slide 23, similar to one of the earlier summaries
you showed, I noticed that the gaps where you can't set limits right now with HCP,
which is you mentioned that because there's some resonance there, it seems
that some of the older results are able to get a little bit more into those polls.
Like for example, the bar has a limit that goes across the first graph and then this
relates to be run one results around 10 G, what's the difference or what makes that
easier for them to access?
So number one here is that this is we have the form to search all the way through all
the way from very low masses to high masses. And looking at this epsilon region
here is we need a dedicated search. And so this has been performed in run one, but
it's not something we tackled with this first search with lacp. This is a search
that hopefully will be performed with round two. So we will see a significantly
better coverage there in the future. So this is just something that requires extra
attention has not been performed yet.
Does this answer the question?
Yes. Thanks a lot.
ahead, Brian.
Yeah, hi. This is really interesting. And these new results are great. I'm curious
in this plot. When you show for instance, the bar and CMS results, which is a bar
because I was involved in all of these which serve Are you using for constraining
this model?
Um, I have to say, I don't know right now, but I can get back to you if you want.
This is a recasting that I was not involved in, so I can get back to you on
that one.
Okay, because we just, I mean, that was one of the things, the results that I
showed was something that came out in the past few weeks. So it might might change
some of this, but yeah, this
might change. Yeah, if you if you
let me know that then we can include this in. But I mean, this is really incredible
sensitivity, I guess a related question. I mean, maybe this this falls the same
category. But yeah, we were able to cover the row region because it's quite a broad
resonance. And presumably, you could do the same but I guess you just need a
dedicated search. Exactly. Yeah.