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Search in diphoton and dielectron final states for displaced production of Higgs or Z bosons with the ATLAS detector in $\sqrt{s}$ = 13 TeV $pp$ collisions
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Search in diphoton and dielectron final states for displaced production of Higgs or Z bosons with the ATLAS detector in $\sqrt{s}$ = 13 TeV $pp$ collisions

Georges Aad, Braden Keim Abbott, Dale Abbott, Kira Abeling, Haider Abidi, Asmaa Aboulhorma, Halina Abramowicz, Henso Abreu, Yiming Abulaiti, Angel Abusleme, …
Deutsches Elektronen-Synchrotron, DESY, Hamburg
2023
DOI: https://doi.org/10.3204/pubdb-2023-05081

摘要

background calorimeter: liquid argon CERN LHC Coll channel cross section: upper limit direct detection electromagnetic electron: pair production experimental results GeV-cms Higgs particle: hadroproduction Higgs particle: radiative decay Higgsino: pair production neutral particle: decay modes neutral particle: long-lived neutralino: branching ratio neutralino: lifetime neutralino: mass p p: colliding beams p p: scattering photon: pair production signature supersymmetry: symmetry breaking trajectory transverse momentum: missing-energy two-particle two-photon Z0: leptonic decay
A search is presented for displaced production of Higgs bosons or Z bosons, originating from the decay of a neutral long-lived particle (LLP) and reconstructed in the decay modes $H → γγ$ and $Z → ee$. The analysis uses the full Run 2 dataset of proton-proton collisions delivered by the LHC at an energy of $\sqrt{s}$ = 13 TeV between 2015 and 2018 and recorded by the ATLAS detector, corresponding to an integrated luminosity of 139 fb$^{-1}$. Exploiting the capabilities of the ATLAS liquid argon calorimeter to precisely measure the arrival times and trajectories of electromagnetic objects, the analysis searches for the signature of pairs of photons or electrons which arise from a common displaced vertex and which arrive after some delay at the calorimeter. The results are interpreted in a gauge-mediated supersymmetry breaking model with pair-produced Higgsinos that decay to LLPs, and each LLP subsequently decays into either a Higgs boson or a Z boson. The final state includes at least two particles that escape direct detection, giving rise to missing transverse momentum. No significant excess is observed above the background expectation. The results are used to set upper limits on the cross section for Higgsino pair production, up to a $\widetilde{χ}$$^0_1$ mass of 369 (704) GeV for decays with 100% branching ratio of $\widetilde{χ}$$^0_1$ to Higgs (Z) bosons for a $\widetilde{χ}$$^0_1$ lifetime of 2 ns. A model-independent limit is also set on the production of pairs of photons or electrons with a significant delay in arrival at the calorimeter.

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