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arXiv 1407.0583hep-ex
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用ATLAS探测器在$\sqrt{s}=$ 8 TeV pp碰撞中寻找具有一个孤立轻子、喷流和丢失横向动量的末态顶夸克对的产生

Search for top squark pair production in final states with one isolated lepton, jets, and missing transverse momentum in $\sqrt{s}=$ 8 TeV pp collisions with the ATLAS detector

ATLAS Collaboration

摘要:

搜索的结果顶部夸克(停止)对生产的最终状态与一个孤立的轻子,喷流,和失踪的横向动量的报告。分析是用2012年在LHC用ATLAS探测器收集的$\sqrt{s} = 8$ TeV的质子-质子碰撞数据进行的,对应于$20$ fb $^{-1}$的积分光度。最轻的超对称粒子(LSP)被认为是最轻的中性伴子,它们之间的相互作用很弱,并且被认为是稳定的。所考虑的终止衰变模式是顶夸克和LSP以及底夸克和最轻的电荷子,其中电荷子通过发射$W$玻色子衰变到LSP。一个广泛的场景与不同的质量分裂之间的停止,最轻的中性伴子和最轻的电荷子被认为是,包括$W$玻色子或顶夸克的情况下,离壳。衰变模式涉及较重的电荷和neutralinos解决使用一套唯象模型的超对称性。没有观察到超过标准模型预测的显著过量。质量在$210$和$640$ GeV之间直接衰变为顶夸克和无质量LSP的停止在$95$ %置信水平下被排除,并且在最轻电荷子质量是LSP质量的两倍的模型中,对于质量在$100$和$150$ GeV范围内的LSP,停止在$95$ %置信水平下被排除,直到质量为$500$ GeV。严格的排斥限制也来自所有其他停止衰减模式考虑,和模型无关的上限设置在可见的横截面上的过程超出标准模型。

英文摘要:

The results of a search for top squark (stop) pair production in final states with one isolated lepton, jets, and missing transverse momentum are reported. 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 $20$ fb$^{-1}$. The lightest supersymmetric particle (LSP) is taken to be the lightest neutralino which only interacts weakly and is assumed to be stable. The stop decay modes considered are those to a top quark and the LSP as well as to a bottom quark and the lightest chargino, where the chargino decays to the LSP by emitting a $W$ boson. A wide range of scenarios with different mass splittings between the stop, the lightest neutralino and the lightest chargino are considered, including cases where the $W$ bosons or the top quarks are off-shell. Decay modes involving the heavier charginos and neutralinos are addressed using a set of phenomenological models of supersymmetry. No significant excess over the Standard Model prediction is observed. A stop with a mass between $210$ and $640$ GeV decaying directly to a top quark and a massless LSP is excluded at $95$ % confidence level, and in models where the mass of the lightest chargino is twice that of the LSP, stops are excluded at $95$ % confidence level up to a mass of $500$ GeV for an LSP mass in the range of $100$ to $150$ GeV. Stringent exclusion limits are also derived for all other stop decay modes considered, and model-independent upper limits are set on the visible cross-section for processes beyond the Standard Model.

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