Abstract
A search for long-lived particles decaying to photons and weakly interacting particles, using proton-proton collision data at $\sqrt{s} =$ 13 TeV collected by the CMS experiment in 2016-2017 is presented. The data set corresponds to an integrated luminosity of 77.4 fb$^{-1}$. Results are interpreted in the context of supersymmetry with gauge-mediated supersymmetry breaking, where the neutralino is long-lived and decays to a photon and a gravitino. Limits are presented as a function of the neutralino proper decay length and mass. For neutralino proper decay lengths of 0.1, 1, 10, and 100 m, masses up to 320, 525, 360, and 215 GeV are excluded at 95% confidence level, respectively. We extend the previous best limits in the neutralino proper decay length by up to one order of magnitude, and in the neutralino mass by up to 100 GeV.
Highlights
The results of a search for long-lived particles (LLP) decaying to a photon and a weakly interacting particle are presented
Pair-produced squarks and gluinos undergo cascade decays as shown in Fig. 1, and eventually produce the lightest SUSY particle (LSP), the gravitino (G ), which is stable and weakly interacting. The phenomenology of such decay chains is primarily determined by the nature of the next-to-lightest SUSY particle (NLSP)
If the NLSP has a proper decay length that is a significant fraction of the radius of the CMS tracking volume, the photons produced at the secondary vertex tend to exhibit distinctive features
Summary
The results of a search for long-lived particles (LLP) decaying to a photon and a weakly interacting particle are presented. If the NLSP has a proper decay length that is a significant fraction of the radius of the CMS tracking volume (about 1.2 m), the photons produced at the secondary vertex tend to exhibit distinctive features Because of their production at displaced vertices and their resulting trajectories, the photons have significantly delayed arrival times (order of ns) at the CMS electromagnetic calorimeter (ECAL) compared to particles produced at the primary vertex and traveling at the speed of light. Past LHC searches for invisible Higgs boson decays in association with photons [28] have sensitivity to such models
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