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

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 (t ˜ 2) followed by the decay to the lighter top squark state (t ˜ 1) via t ˜ 2 → Zt ˜ 1, and for t ˜ 1 pair production in natural gaugemediated supersymmetry breaking scenarios where the neutralino (χ˜ 0 1 ) is the next-to-lightest supersymmetric particle and decays producing a Z boson and a gravitino (G˜ ) via the χ˜ 0 1 → ZG˜ process.