"Table 56" of "Search for direct top squark pair production in events with a Z boson, b-jets and missing transverse momentum in sqrt(s)=8 TeV pp collisions with the ATLAS detector"

CERN-LHC. 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 sqrt(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 (chi1^0) is the next-to-lightest supersymmetric particle and decays producing a Z boson and a gravitino (G) via the chi1^0 --> Z G process.

欧洲核子研究中心大型强子对撞机（CERN-LHC）。本研究报告了一项针对顶夸克超伴子（top squark）直接成对产生过程的搜寻分析，分析采用的事件样本需至少包含两个轻子，其中需存在一对同味异号轻子，其不变质量与Z玻色子（Z boson）质量相符；事件同时需包含标记为b夸克起源的喷注以及横向缺失动量。本分析使用2012年大型强子对撞机上ATLAS探测器（ATLAS detector）采集的质心系能量√s=8 TeV的质子-质子对撞数据，对应积分亮度为20.3 fb⁻¹。本研究未观测到任何超出标准模型（Standard Model）预期的信号异常。针对两类模型给出了本结果的诠释：一类基于重顶夸克超伴子态（t2）的直接成对产生，随后通过t2→Z t1的衰变过程衰变至轻顶夸克超伴子态（t1）；另一类针对自然规范媒介超对称破缺情景下的t1成对产生过程，此类情景中中性微子（neutralino，χ₁⁰）为次轻超对称粒子，并通过χ₁⁰→Z G的衰变过程产生Z玻色子与引力微子（gravitino，G）。