Search for metastable heavy charged particles with large ionisation energy loss in pp collisions at sqrt (s) = 8 TeV using the ATLAS experiment

Many extensions of the Standard Model predict the existence of charged and heavy long-lived particles, such as R-hadrons or charginos. These particles, if produced at the Large Hadron Collider, should be moving non-relativistically and are therefore identifiable through the measurement of an anomalously large specific energy loss in the ATLAS pixel detector. Measuring heavy long-lived particles through their track parameters in the vicinity of the interaction vertex allows sensitivity to metastable particles with lifetimes in the nanosecond range. A search for such particles with the ATLAS detector at the LHC is presented, based on a data sample corresponding to an integrated luminosity of 18.4 fb−1 of pp collisions at $\sqrt (s)$ = 8 TeV. No significant deviation from Standard Model background expectations is observed, and lifetime dependent upper limits on R-hadrons and chargino production cross sections and masses are set. Gluino R-hadrons with 10 ns lifetime and masses up to 1183 GeV are excluded at 95% confidence level as well as charginos with 4 ns lifetime and masses up to 496 GeV.