Search for stopped long-lived particles produced in pp collisions at sqrt(s) = 7 TeV

TL;DR

This study searches for long-lived particles that stop in the CMS detector and decay during quiet periods, setting limits on gluino and stop masses over a wide range of lifetimes based on 7 TeV LHC data.

Contribution

It provides the first limits on long-lived gluino and stop particles over a broad lifetime range using stopped particle searches at the LHC.

Findings

No significant excess observed over background.

Excluded gluino masses below 640 GeV for certain lifetimes.

Excluded stop masses below 340 GeV for certain lifetimes.

Abstract

A search has been performed for long-lived particles that have stopped in the CMS detector, during 7 TeV proton-proton operations of the CERN LHC. The existence of such particles could be inferred from observation of their decays when there were no proton-proton collisions in the CMS detector, namely during gaps between LHC beam crossings. Using a data set in which CMS recorded an integrated luminosity of 4.0 inverse femtobarns, and a search interval corresponding to 246 hours of trigger live time, 12 events are observed, with a mean background prediction of 8.6 +/- 2.4 events. Limits are presented at 95% confidence level on long-lived gluino and stop production, over 13 orders of magnitude of particle lifetime. Assuming the "cloud model" of R-hadron interactions, a gluino with mass below 640 GeV and a stop with mass below 340 GeV are excluded, for lifetimes between 10 microseconds and 1000 seconds.