Search for Light Gravitinos in Events with Photons and Missing Transverse Momentum at HERA

TL;DR

This paper reports a search for light gravitinos at HERA through events with photons and missing energy, setting new exclusion limits on supersymmetric particles and couplings.

Contribution

First analysis of photon plus missing energy events at HERA to search for light gravitinos in R-parity-violating supersymmetry models.

Findings

No deviation from the Standard Model observed.

Excluded neutralino masses up to 112 GeV at 95% CL.

Excluded supersymmetric partner masses up to 164 GeV at 95% CL.

Abstract

A search for gravitinos produced in ep collisions is performed using the H1 detector at HERA. The data were taken at a centre-of-mass energy of 319 GeV and correspond to an integrated luminosity of 64.3 pb^{-1} for e^+p collisions and 13.5 pb^{-1} for e^-p collisions. If R-parity is not conserved, the t-channel exchange of a selectron can produce a neutralino, which, in models where the gravitino is the lightest supersymmetric particle, subsequently decays into a photon and a light gravitino. The resulting event signature, which involves an isolated photon, a jet and missing transverse energy, is analysed for the first time at HERA. No deviation from the Standard Model is found. Exclusion limits on the cross section and on R-parity-violating Yukawa couplings are derived in a Gauge Mediated Supersymmetry Breaking scenario. The results are independent of the squark sector. Neutralinos and supersymmetric partners of the left-handed electron with masses up to 112 GeV and 164 GeV, respectively, can be ruled out at the 95% confidence level for R-parity-violating couplings lambda' equal to 1.