LHCP2014海报的流程：用ATLAS探测器在$\sqrt{s}=8$ TeV上寻找质子-质子碰撞中全强子末态顶夸克的直接产生
Proceeding for LHCP2014 Poster: Search for direct pair production of the top squark in all-hadronic final states in proton-proton collisions at $\sqrt{s}=8$ TeV with the ATLAS detector
摘要：
本文报道了利用ATLAS探测器在LHC上记录的质子-质子碰撞数据的积分光度$20.1 \rm{fb}^{-1}$寻找顶夸克标量伙伴的直接对产生的结果。顶夸克被假定通过$\tilde{t} \rightarrow t \tildeχ_{1}^{0}$或$\tilde{t}\rightarrow b\tildeχ_{1}^{\pm} \rightarrow b W^{\left(\ast\right)} \tildeχ_{1}^{0}$衰变，其中$\tildeχ_{1}^{0}$（$\tildeχ_{1}^{\pm}$）表示超对称模型中最轻的中性伴子（电荷伴子）。搜索的目标是一个完全强子的最终状态的事件与四个或更多的喷流和大失踪的横向动量。没有显着超过标准模型的背景预测观察到，和排斥限制的顶部夸克和中性伴子的质量，并作为一个功能的分支分数的$\tilde{t} \rightarrow t \tildeχ_{1}^{0}$。对于100%的分支分数，对于低于30 GeV的$\tildeχ_{1}^{0}$质量，排除了270-645 GeV范围内的顶夸克质量。对于$\tilde{t} \rightarrow t \tildeχ_{1}^{0}$或$\tilde{t}\rightarrow b\tildeχ_{1}^{\pm}$的50%的支化分数，并且假设$\tildeχ_{1}^{\pm}$质量是$\tildeχ_{1}^{0}$质量的两倍，对于低于60 GeV的$\tildeχ_{1}^{0}$，排除250-550 GeV范围内的顶夸克质量。
英文摘要：
The results of a search for direct pair production of the scalar partner to the top quark using an integrated luminosity of $20.1 \rm{fb}^{-1}$ of proton-proton collision data at $\sqrt{s}=8$ TeV recorded with the ATLAS detector at the LHC are reported. The top squark is assumed to decay via $\tilde{t} \rightarrow t \tildeχ_{1}^{0}$ or $\tilde{t}\rightarrow b\tildeχ_{1}^{\pm} \rightarrow b W^{\left(\ast\right)} \tildeχ_{1}^{0}$, where $\tildeχ_{1}^{0}$ ($\tildeχ_{1}^{\pm}$) denotes the lightest neutralino (chargino) in supersymmetric models. The search targets a fully-hadronic final state in events with four or more jets and large missing transverse momentum. No significant excess over the Standard Model background prediction is observed, and exclusion limits are reported in terms of the top squark and neutralino masses and as a function of the branching fraction of $\tilde{t} \rightarrow t \tildeχ_{1}^{0}$. For a branching fraction of 100%, top squark masses in the range 270-645 GeV are excluded for $\tildeχ_{1}^{0}$ masses below 30 GeV. For a branching fraction of 50% to either $\tilde{t} \rightarrow t \tildeχ_{1}^{0}$ or $\tilde{t}\rightarrow b\tildeχ_{1}^{\pm}$, and assuming the $\tildeχ_{1}^{\pm}$ mass to be twice the $\tildeχ_{1}^{0}$ mass, top squark masses in the range 250-550 GeV are excluded for $\tildeχ_{1}^{0}$ masses below 60 GeV.
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