Search for low-mass hidden-valley dark showers with non-prompt muon pairs in proton-proton collisions at $\sqrt{s}$ = 13 TeV

Abstract

A search for signatures of a dark analog to quantum chromodynamics is performed. The analysis targets long-lived dark mesons that decay into standard-model particles, with a high branching fraction of the dark mesons decaying into muons. The dark mesons are formed by the hadronisation of dark partons, which are produced by a decay of the Higgs boson. The search is performed using a data set corresponding to an integrated luminosity of 41.6 fb${}^{-1}$, which was collected in proton-proton collisions at $\sqrt{s}$ = 13 TeV by the CMS experiment at the CERN LHC in 2018 using non-prompt muon triggers. The search is based on resonant muon pair signatures. Machine-learning techniques are employed in the analysis, utilising boosted decision trees to discriminate between signal and background. No significant excess is observed above the standard model expectation. Upper limits on the branching fraction of the Higgs boson decaying to dark partons are determined to be as low as 10${}^{-4}$ at 95% confidence level, surpassing and extending the existing limits on models with dark $\tilde{\omega }$ mesons for mean proper decay lengths of less than 500 mm and for $\tilde{\omega }$ masses down to 0.3 GeV. First limits are set for extended dark-shower models with two dark flavours that contain dark photons, probing their masses down to 0.33 GeV.

arXiv commentReplaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/EXO-24-008 (CMS Public Pages)

References in corpus (23)

• XGBoost: A Scalable Tree Boosting System
• An Introduction to PYTHIA 8.2
• Asymptotic formulae for likelihood-based tests of new physics
• Confidence Level Computation for Combining Searches with Small Statistics
• Parton distributions from high-precision collider data
• Direct constraints on the dark matter self-interaction cross-section from the merging galaxy cluster 1E0657-56
• Echoes of a Hidden Valley at Hadron Colliders
• Description and performance of track and primary-vertex reconstruction with the CMS tracker
• Illuminating Dark Photons with High-Energy Colliders
• Exotic Decays of the 125 GeV Higgs Boson
• Dark matter and the early Universe: a review
• Emerging Jets
• Quirky Composite Dark Matter
• Handling uncertainties in background shapes: the discrete profiling method
• Discerning Secluded Sector gauge structures
• Electroweak symmetry breaking and cold dark matter from strongly interacting hidden sector
• Perturbative benchmark models for a dark shower search program
• Strongly interacting dark sectors in the early Universe and at the LHC through a simplified portal
• A flavoured dark sector
• Dark Matter from Strong Dynamics: The Minimal Theory of Dark Baryons
• Dark matter in Hidden Valley models with stable and unstable light dark mesons
• Enriching the physics program of the CMS experiment via data scouting and data parking
• Dark showers from Z-dark Z' mixing