Search for non-pointing photons in the diphoton and E_T^miss final state in sqrt(s) = 7 TeV proton-proton collisions using the ATLAS detector

TL;DR

This paper reports a search for non-pointing photons from long-lived particle decays in proton-proton collisions, using ATLAS detector data, setting limits on supersymmetric models with long-lived neutralinos.

Contribution

It introduces a novel method to identify non-pointing photons using precise calorimeter measurements and sets new exclusion limits on long-lived neutralino decays in supersymmetry.

Findings

No excess observed above Standard Model background.

Limits set on neutralino lifetime and mass in GMSB models.

Demonstrates the ATLAS calorimeter's capability to detect non-pointing photons.

Abstract

A search has been performed for photons originating in the decay of a neutral long-lived particle, exploiting the capabilities of the ATLAS electromagnetic calorimeter to make precise measurements of the flight direction of photons, as well as the calorimeter's excellent time resolution. The search has been made in the diphoton plus missing transverse energy final state, using the full data sample of 4.8/fb of 7 TeV proton-proton collisions collected in 2011 with the ATLAS detector at the LHC. No excess is observed above the background expected from Standard Model processes. The results are used to set exclusion limits in the context of Gauge Mediated Supersymmetry Breaking models, with the lightest neutralino being the next-to-lightest supersymmetric particle and decaying with a lifetime in excess of 0.25 ns into a photon and a gravitino.