Search for top-squark pairs decaying into Higgs or Z bosons in pp collisions at √s=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 √s = 8TeV collected in 2012 with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 19.5 fb−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 decaying to a lighter top-squark mass eigenstate t1 via either t2 -> Ht1 or t2 -> Zt1 , followed in both cases by t1 -> tx1 0, where x1 0 is an undetected, stable, lightest supersymmetric particle. The interpretation is performed in the region where the mass difference between the t1 and t1 0 states is approximately equal to the top-quark mass (mt1 - mx1 0 ≈ mt), which is not probed by searches for direct t1 squark pair production. The analysis excludes top squarks with masses mt2 < 575GeV and mt1 < 400GeVat a 95% confidence level.