Search for top-squark pairs decaying into Higgs or Z bosons in pp collisions at vs=8 TeV

Abstract

A search for supersymmetry through the direct pair production of top squarks, with Higgs (H) or Z bosons in the decay chain, is performed using a data sample of proton–proton collisions at vs=8 TeV collected in 2012 with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 19.5fb-1. The search is performed using a selection of events containing leptons and bottom-quark jets. No evidence for a significant excess of events over the standard model background prediction is observed. The results are interpreted in the context of simplified supersymmetric models with pair production of a heavier top-squark mass eigenstate ˜t2 decaying to a lighter top-squark mass eigenstate ˜t1 via either ˜t2?H˜t1or ˜t2?Z˜t1, followed in both cases by ˜t1?t˜?01, where ˜?01 is an undetected, stable, lightest supersymmetric particle. The interpretation is performed in the region where the mass difference between the ˜t1and ˜?01 states is approximately equal to the top-quark mass (m˜t1-m˜?01 mt), which is not probed by searches for direct ˜t1 squark pair production. The analysis excludes top squarks with masses m˜t2<575GeVand m˜t1<400GeVat a 95% confidence level.