Search for pair production of third-generation scalar leptoquarks and top squarks in proton-proton 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 Karancsi, János and Molnár, József and Pálinkás, József and Trócsányi, Zoltán and Ujvári, Balázs and Veres, Gábor (2014) Search for pair production of third-generation scalar leptoquarks and top squarks in proton-proton collisions at√s = 8 TeV. PHYSICS LETTERS B, 739. pp. 229-249. ISSN 0370-2693

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Abstract

A search for pair production of third-generation scalar leptoquarks and supersym- metric top quark partners, top squarks, in final states involving tau leptons and bot- tom quarks is presented. The search uses events from a data sample of proton-proton collisions corresponding to an integrated luminosity of 19.7 fb−1, collected with the CMS detector at the LHC with √s = 8 TeV. The number of observed events is found to be in agreement with the expected standard model background. Third-generation scalar leptoquarks with masses below 740 GeV are excluded at 95% confidence level, assuming a 100% branching fraction for the leptoquark decay to a tau lepton and a bottom quark. In addition, this mass limit applies directly to top squarks decaying via an R-parity violating coupling λ′ 333. The search also considers a similar signature from top squarks undergoing a chargino-mediated decay involving the R-parity vio- lating coupling λ′ 3jk. Each top squark decays to a tau lepton, a bottom quark, and two light quarks. Top squarks in this model with masses below 580 GeV are excluded at 95% confidence level. The constraint on the leptoquark mass is the most stringent to date, and this is the first search for top squarks decaying via λ′ 3jk.

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