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

A search for new physics with long-lived particles decaying to photons is presented using proton-proton collisions data at $\sqrt{s}=13~\mathrm{TeV}$ collected by the CMS experiment in 2016 and 2017 corresponding to $35.9~\mathrm{fb}^{-1}$ and $41.5~\mathrm{fb}^{-1}$ of integrated luminosity, respectively. Results are interpreted in the context of supersymmetry with gauge-mediated supersymmetry breaking, where long-lived neutralinos are produced as secondaries and decay 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 $10^1$, $10^2$, $10^3$, and $10^4~\mathrm{cm}$, masses up to $320$, $525$, $360$, and $215~\mathrm{GeV}$ are excluded at $95\%$ CL, respectively. We extend the previous best limits in the neutralino proper decay length by up to about one order of magnitude, and in neutralino mass by up to about $100~\mathrm{GeV}$.