Abstract
A search is presented for long-lived charged particles that decay within the CMS detector and produce the signature of a disappearing track. Disappearing tracks are identified as those with little or no associated calorimeter energy deposits and with missing hits in the outer layers of the tracker. The search uses proton-proton collision data recorded at sqrt(s) = 8 TeV that corresponds to an integrated luminosity of 19.5 inverse femtobarns. The results of the search are interpreted in the context of the anomaly-mediated supersymmetry breaking (AMSB) model. The number of observed events is in agreement with the background expectation, and limits are set on the cross section of direct electroweak chargino production in terms of the chargino mass and mean proper lifetime. At 95% confidence level, AMSB models with a chargino mass less than 260 GeV, corresponding to a mean proper lifetime of 0.2 ns, are excluded.
Highlights
Background characterization we examine the sources of both physics and instrumental backgrounds to this search
A search is presented for long-lived charged particles that decay within the CMS detector and produce the signature of a disappearing track
Two data events are observed in the search sample, which is consistent with the expected background
Summary
At 95% confidence level, AMSB models with a chargino mass less than 260 GeV, corresponding to a mean proper lifetime of 0.2 ns, are excluded. One example is anomaly-mediated supersymmetry breaking (AMSB) [6, 7], which predicts a particle mass spectrum that has a small mass splitting between the lightest chargino (χ±1 ) and the lightest neutralino (χ01). We benchmark our search in terms of its sensitivity to the chargino mass and chargino-neutralino mass splitting (or equivalently, the chargino mean proper lifetime, τ ) in AMSB. A search for disappearing tracks conducted by the ATLAS Collaboration excludes at 95% confidence level (CL) a chargino in AMSB scenarios with mass less than 270 GeV and mean proper lifetime of approximately 0.2 ns [11]
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