Abstract
AbstractA 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 fb−1, 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 μs and 1000 s.
Highlights
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
Using a data set in which CMS recorded an integrated luminosity of 4.0 fb−1, 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
New results have been presented on long-lived particles which have stopped in the CMS detector, after being produced in 7 TeV pp collisions from the CERN Large Hadron Collider
Summary
The central feature of the CMS apparatus is a superconducting solenoid, of 6 m internal diameter, providing a magnetic field of 3.8 T. The energy deposits in ECAL and HCAL cells are summed to define the calorimeter tower energies, subsequently used to provide the energies and directions of hadronic jets. For this search, jets are reconstructed offline from the energy deposits in the calorimeter towers, clustered by an iterative cone algorithm [25] with a cone radius of 0.5 in (η, φ) space. Physics triggers are inhibited for a short time at the end of the LHC revolution period (the “LHC orbit”), while calibration triggers are taken. The integrated luminosity delivered in the control sample (3.6 pb−1) is sufficiently small that signal contamination can be neglected
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