Search for long-lived particles using delayed photons in proton-proton collisions at $\sqrt{s} =$ 13 TeV

TL;DR

This paper reports a search for long-lived particles decaying into photons using CMS data at 13 TeV, setting new limits on neutralino properties in supersymmetry models with gauge-mediated breaking.

Contribution

It introduces a novel search method for long-lived neutralinos decaying to photons, extending previous limits on their decay length and mass.

Findings

Excluded neutralino masses up to 320 GeV for 0.1 m decay length

Extended the decay length limits by up to ten times

Improved neutralino mass limits by up to 100 GeV

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.