Abstract
New metastable massive particles with electric and colour charge are features of many theories beyond the Standard Model. A search is performed for long-lived gluino-based R-hadrons with the ATLAS detector at the LHC using a data sample corresponding to an integrated luminosity of 31 pb^-1. We search for evidence of particles that have come to rest in the ATLAS detector and decay at some later time during the periods in the LHC bunch structure without proton-proton collisions. No significant deviations from the expected backgrounds are observed, and a cross-section limit is set. It can be interpreted as excluding gluino-based R-hadrons with masses less than 341 GeV at the 95% C.L., for lifetimes from 10^-5 to 10^3 seconds and a neutralino mass of 100 GeV.
Highlights
The search for exotic massive long-lived particles (LLPs) is an important component of the early data exploration program of the Large Hadron Collider (LHC) experiments
Lower energy R-hadron decays tend to be reconstructed as a single jet, but very energetic ones may be reconstructed as multiple jets due to their larger spatial extent
To quantify the expected number of background events in the search sample we investigate three different sources: cosmic ray muons, beam-halo muons, and calorimeter noise
Summary
The search for exotic massive long-lived particles (LLPs) is an important component of the early data exploration program of the Large Hadron Collider (LHC) experiments. At LHC energies, some fraction (typically several per cent) of R-hadrons, produced with low kinetic energy, would lose sufficient energy to come to rest inside the dense detector materials of the ATLAS calorimeter. These stopped R-hadrons may have lifetimes spanning many orders of magnitude, and may decay with significant delay after the collision that created them. The search is sensitive to any potential new physics scenario producing large out-of-time energy deposits in the calorimeter with minimal additional detector activity. The data analysed in this Letter were recorded by the ATLAS experiment between April and November 2010, exploiting proton–proton collisions at a centre-of-mass energy of 7 TeV
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