Abstract
Confining dark sectors with pseudo-conformal dynamics produce SUEPs, or Soft Unclustered Energy Patterns, at colliders: isotropic dark hadrons with soft and democratic energies. We target the experimental nightmare scenario, SUEPs in exotic Higgs decays, where all dark hadrons decay promptly to SM hadrons. First, we identify three promising observables: the charged particle multiplicity, the event ring isotropy, and the matrix of geometric distances between charged tracks. Their patterns can be exploited through a cut-and-count search, supervised machine learning, or an unsupervised autoencoder. We find that the HL-LHC will probe exotic Higgs branching ratios at the per-cent level, even without a detailed knowledge of the signal features. Our techniques can be applied to other SUEP searches, especially the unsupervised strategy, which is independent of overly specific model assumptions and the corresponding precision simulations.
Highlights
The dominant background to our signal is production of one or two leptons in association with any number of QCD jets
To ensure that all types of SUEP signals can be discovered at the LHC, we focus on a well-motivated SUEP nightmare scenario, where SUEP is produced in exotic Higgs decays and the dark hadrons decay promptly and exclusively to SM hadrons
SUEPs represent a highly plausible but extremely challenging experimental signature of confining hidden sectors, which typically results in a high multiplicity of soft SM final states
Summary
The dominant background to our signal is production of one or two leptons in association with any number of QCD jets. For the purpose of developing our analysis techniques, we simulate QCD+leptons background samples using MadGraph5_aMC@NLO 2.6.6 and Pythia 8.243. One should simulate fully matched multi-jet + / ν samples to capture the background distribution as closely as possible. We simulate nj + / ν, where n = 2, 3, 4 without jet matching and pT > 15 GeV at generator level, to determine the effect of jet multiplicity at the hard event level on our analysis. We find that n > 2 leads to lower cross section while being more distinguishable from the SUEP signal using the analysis techniques we develop here. To be conservative, we simulate 2j + / ν as our background samples for Zh and W h production and decay into SUEP, respectively. We use 108 background events to represent the σ(QCD + / ν) ≈ 3.7 × 103 pb (3.2)
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