Search for direct top squark pair production in events with a Z boson, b-jets and missing transverse momentum in √s = 8 TeV pp collisions with the ATLAS detector

Aad, G. and Abbott, B. and Abdallah, J. and Khalek, S. Abdel and Abdinov, O. and Aben, R. and Abi, B. and Abolins, M. and AbouZeid, O. S. and Abramowicz, H. and Abreu, H. and Abreu, R. and Abulaiti, Y. and Acharya, B. S. and Adamczyk, L. and Adams, D. L. and Adelman, J. and Adomeit, S. and Adye, T. and Agatonovic-Jovin, T. and Aguilar-Saavedra, J. A. and Agustoni, M. and Ahlen, S. P. and Ahmad, A. and Ahmadov, F. and Aielli, G. and Åkesson, T. P. A. and Akimoto, G. and Akimov, A. V. and Alberghi, G. L. and Krasznahorkay, Attila and Nagai, Yoshikazu and Pásztor, Gabriella and Tóth, József (2014) Search for direct top squark pair production in events with a Z boson, b-jets and missing transverse momentum in √s = 8 TeV pp collisions with the ATLAS detector. EUROPEAN PHYSICAL JOURNAL C, 74. ISSN 1434-6044

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Abstract

A search is presented for direct top squark pair production using events with at least two leptons including a same-flavour opposite-sign pair with invariant mass consistent with the Z boson mass, jets tagged as originating from b-quarks and missing transverse momentum. The analysis is performed with proton-proton collision data at √s = 8 TeV collected with the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of 20.3 fb−1. No excess beyond the Standard Model expectation is observed. Interpretations of the results are provided in models based on the direct pair production of the heavier top squark state (˜t2) followed by the decay to the lighter top squark state (˜t1) via ˜t2 → Z˜t1, and for ˜t1 pair production in natural gauge-mediated supersymmetry breaking scenarios where the neutralino ( ˜χ0 1) is the next-to-lightest supersymmetric particle and decays producing a Z boson and a gravitino ( ˜G) via the ˜χ0 1 → Z ˜G process.

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