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2023 LHC DM WG Winter Meeting
LHC DM WG workshop
Zoom Meeting ID
68024266716
Host
Oleg Brandt
Alternative hosts
Spyros Argyropoulos, James Frost
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Zoom URL
t-channel
White paper call for contributions
M. Strassler: p4 includes all YY contributions?
=> No only Y-anti-Y is included in this plot
Z. Wang: p7: difference between middle and left plot?
-> the middle plot corresponds to the sum of the individual signal channels
D. Tucker: is there any motivation to extend the couplings of the mediators to other flavours other than the up?
-> In principle all possibilities would be there. Charm coupling has started being explored as well
A. Grohsjean: what is the goal for the white paper?
-> main goal was to define benchmarks
Is there a potential for unexplored signatures?
In non-minimal models with more particles and couplings
J. Frost: are the YY contributions high enough for dijet angular analyses to be relevant, i.e. beyond jet+MET?
-> the goal was to study this in the context of the white paper
B.Maier: Overleaf of t-channel WP skeleton can be found at https://www.overleaf.com/1532482451chsczyfhmrjx
SVJ ATLAS
A. de Cosa: how is Rinv defined here?
-> Rinv corresponds to the fraction of dark hadrons that decay to stable dark hadrons
Does it include the off-diagonal mesons?
-> It includes all the dark mesons that are produced
Is Rinv determined in Pythia 8? If you change parton shower do you get different results?
-> It is treated as an “event parameter” in pythia, e.g. like a branching ratio for the decay of hadrons into invisible hadrons
M. Strassler: it is true that different showers will give different predictions but the issue lies in the fact that we don’t know exactly what theory to use an a dark extension of QCD
SVJ CMS
- M. Strassler: p21 there is an assumption here about the z’ couplings. If the couplings decrease the exclusion will also decrease (the model is not excluded).
If instead of using softdrop and the BDT, and instead take all events with mT > mTcut and fit the softdrop mass would you do better?
-> p13 the softdrop mass is not dropping as steeply as the transverse masses so presumably it is going to be worse
SVJ workshop
- Z. Wang: p8 are there cases where a variation of different fundamental parameters gives the same Rinv and in that case is the signature exactly the same?
-> they would look the same in the current implementation that only includes Rinv
K. Pedro: we also wrote a paper about signal-agnostic tagging using autoencoders: https://arxiv.org/abs/2112.02864
SVJ with leptons
- J. Frost: would an SVJl analysis be only sensitive to the A’ mixing or also to other parameters?
-> The BR are independent of the mixing, the mixing affects the lifetime. Mixing affects the number of leptons present in the jet
Snowmass
- S. Argyropoulos: how do you handle the issue that there are many uncertainties in the underlying theory?
-> The main point is to make sure that we do not miss a discovery
- C. Cazzaniga: does it make sense to have a confinement scale for dark QCD that is lower than Lambda_QCD?
-> Theoretically yes. If this is the case the lifetimes of the dark hadrons would be long.
J. Frost: should the neext step be to set some benchmarks?
-> Annapaola’s talk and the snowmass paper presented some benchmarks which should be the first ones to study. It is important to come up with intermediate simplified models with fewer parameters
M. Bona: in ATLAS there was some conversation in this direction
Frustrated dark matter
- S. Argyropoulos: is tttt cross-section always higher than ttuu?
-> not necessarily. There are parameter spaces where ttuu could provide complementary sensitivity.
Suggestions for run 3 samples
A. Grohsjean: if we specify couplings orders for the 4top final state then we cannot use MadSpin for the top decays. It should be checked if this is a limitation that would affect the analyses (e.g. compare Pythia vs MadSpin).
A, Grohsjean: for tW/tt+MET how is the double counting removed?
-> there is a modified UFO that one can get from Uli
T. Robens: for tt+MET one can get the same final states from 2HDMa, however it is not always clear how the parameters of one map to the other and if the cross-sections are reproducible. One should check this.
-> Clarification: s-channel and 2hdma interpretations are published separately by the collaborations and the respective samples are generated with different UFOs.
Btw, Uli checked the cross-sections later and they seem to be in agreement:
for M_mediator = 200 GeV I get 0.8074 pb and 0.2008 pb in DMsimp and 2HDM+a
for 300 GeV MG spits 0.5996 pb and 0.1496 pb
i have set all relevant couplings equal and fixed the width of the pseudoscalar to 1 GeV
m_DM is also 1 GeV
sin(theta) = 1/sqrt(2)
one would expect a factor 4 between the numbers
for 300 GeV MG spits 0.5996 pb and 0.1496 pb
0.8074/0.2008/4 = 1.00523
0.5996/0.1496/4 = 1.00201
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