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

Khachatryan, V. and Sirunyan, A. M. and Tumasyan, A. and Adam, W. and Bergauer, T. and Dragicevic, M. and Ero, J. and Fabjan, C. and Friedl, M. and Fruhwirth, R. and Ghete, V. M. and Hartl, C. and Hormann, N. and Hrubec, J. and Jeitler, M. and Kiesenhofer, W. and Knunz, V. and Krammer, M. and Kratschmer, I. and Liko, D. and Mikulec, I. and Rabady, D. and Rahbaran, B. and Rohringer, H. and Schofbeck, R. and Strauss, J. and Taurok, A. and Treberer-Treberspurg, W. and Waltenberger, W. and Wulz, C. E. and Filipovic, Nicolas and Bencze, György and Hajdu, Csaba and Hidas, Pál and Horváth, Dezső and Siklér, Ferenc and Veszprémi, Viktor and Vesztergombi, György and Zsigmond, Anna Júlia and Béni, Noémi Tekla and Karancsi, János and Molnár, József and Pálinkás, József and Szillási, Zoltán and Raics, Péter and Trócsányi, Zoltán and Ujvári, Balázs and Veres, Gábor (2014) Search for top-squark pairs decaying into Higgs or Z bosons in pp collisions at √s = 8 TeV. PHYSICS LETTERS B, 736. pp. 371-397. ISSN 0370-2693

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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 = 8 TeV 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 per- formed using a selection of events containing leptons and bottom-quark jets. No evidence for a significant excess of events over the standard model background pre- diction is observed. The results are interpreted in the context of simplified super- symmetric 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˜t1 or ˜t2 → Z˜t1, followed in both cases by ˜t1 → t ˜χ0 1, where ˜χ0 1 is an undetected, stable, lightest su- persymmetric particle. The interpretation is performed in the region where the mass difference between the ˜t1 and ˜χ0 1 states is approximately equal to the top-quark mass (m˜t1 − m˜χ0 1 ' mt), which is not probed by searches for direct˜t1 squark pair production. The analysis excludes top squarks with masses m˜t2 < 575 GeV and m˜t1 < 400 GeV at a 95% confidence level.

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