Search for light long-lived neutral particles that decay to collimated pairs of leptons or light hadrons in pp collisions at √s = 13 TeV with the ATLAS detector

ATLAS Publications, T.M. Carter, R.Y. Gonzalez Andana, A. Hasib, M.P. Heath, S. Palazzo, V.A. Parrish, E.P. Takeva, N. Themistokleous, E.M. Villhauer, E. Zaid

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

A search for light long-lived neutral particles with masses in the O(MeV–GeV)
range is presented. The analysis targets the production of long-lived dark photons in the decay of a Higgs boson produced via gluon–gluon fusion or in association with a W boson. Events that contain displaced collimated Standard Model fermions reconstructed in the calorimeter or muon spectrometer are selected in 139 fb−1 of √s = 13 TeV pp collision data collected by the ATLAS detector at the LHC. Background estimates for contributions from Standard Model processes and instrumental effects are extracted from data. The
observed event yields are consistent with the expected background. Exclusion limits are reported on the production cross-section times branching fraction as a function of the mean proper decay length cτ of the dark photon, or as a function of the dark-photon mass and kinetic mixing parameter that quantifies the coupling between the Standard Model and potential hidden (dark) sectors. A Higgs boson branching fraction above 1% is excluded at 95% CL for a Higgs boson decaying into two dark photons for dark-photon mean proper
decay lengths between 10 mm and 250 mm and dark photons with masses between 0.4 GeV and 2 GeV.
Original languageEnglish
Article number153
Pages (from-to)1-54
Number of pages54
Journal Journal of High Energy Physics
Volume2023
Issue number6
DOIs
Publication statusPublished - 23 Jun 2023

Keywords / Materials (for Non-textual outputs)

  • Exotics
  • Hadron-Hadron Scattering

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