Abstract
A search for long-lived particles (LLPs) produced in decays of standard model (SM) Higgs bosons is presented. The data sample consists of 137 fb^{-1} of proton-proton collisions at sqrt[s]=13 TeV, recorded at the LHC in 2016-2018. A novel technique is employed to reconstruct decays of LLPs in the end cap muon detectors. The search is sensitive to a broad range of LLP decay modes and to masses as low as a few GeV. No excess of events above the SM background is observed. The most stringent limits to date on the branching fraction of the Higgs boson to LLPs subsequently decaying to quarks and τ^{+}τ^{-} are found for proper decay lengths greater than 6, 20, and 40m, for LLP masses of 7, 15, and 40GeV, respectively.
Highlights
Data number of hits in the cluster (Nhits)102 Nhits ≥ 130 required mS = 7 GeV mmmBaSSSc===kg145r505oGGGuneeeVVVd Data S → dd cτ = 1 mB(H → SS) = 1% 10Δφ(p, miss cluster) [radians] T corresponding to an integrated luminosity of 137 fb−1, have been used to conduct the first search for beyond the standard model (SM) long-lived particles (LLPs) using the CMS end cap muon detectors as a calorimeter
In this Letter, we describe the first search at the Large Hadron Collider (LHC) that uses a muon detector as a sampling calorimeter to identify showers produced by decays of LLPs
The CMS end cap muon detectors (EMD) are composed of detector planes interleaved with the steel layers of the magnet flux-return yoke
Summary
(Received 10 July 2021; revised 18 September 2021; accepted 26 October 2021; published 23 December 2021). In this Letter, we describe the first search at the LHC that uses a muon detector as a sampling calorimeter to identify showers produced by decays of LLPs. The CMS end cap muon detectors (EMD) are composed of detector planes interleaved with the steel layers of the magnet flux-return yoke. The hadron calorimeter, solenoid magnet, and steel flux-return yoke together provide 20–27 nuclear interaction lengths of shielding, which is sufficiently large to suppress particle showers that are not fully contained (punch through) to negligible levels. This search has sensitivity to singly or multiply produced LLPs decaying to final states including hadrons, taus, electrons, or photons. For cτ > 0.3 m, displaced vertices in the ATLAS muon spectrometer [30,31] set the most stringent previous limit
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