Search for disappearing tracks in proton-proton collisions at sqrt(s) = 8 TeV

TL;DR

This paper reports a search for long-lived charged particles with disappearing tracks in 8 TeV proton-proton collisions, setting limits on supersymmetric models and excluding certain chargino masses and lifetimes.

Contribution

It introduces a novel search method for disappearing tracks and constrains AMSB supersymmetry models using 8 TeV collision data.

Findings

No excess events observed beyond background expectations.

Excluded chargino masses below 260 GeV for specific lifetimes.

Set new limits on electroweak chargino production cross sections.

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.