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

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 19.5fb^(−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 t_2 decaying to a lighter top-squark mass eigenstate t_1 via either t_2→Ht_1 or t_2→Zt_1, followed in both cases by t_1→tχ^0_1, where ˜ χ^0_1 is an undetected, stable, lightest supersymmetric particle. The interpretation is performed in the region where the mass difference between the t_1 and χ^0_1 states is approximately equal to the top-quark mass (m_(t1)−m_χ^0_1mt), which is not probed by searches for direct t_1 squark pair production. The analysis excludes top squarks with masses m_(t2)<575GeVand m_(t1)<400GeVat a 95% confidence level.

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