Search for a scalar partner of the top quark in the all-hadronic t(t)over-bar plus missing transverse momentum final state at √s=13 TeV with the ATLAS detector
Search for a scalar partner of the top quark in the all-hadronic t(t)over-bar plus missing transverse momentum final state at √s=13 TeV with the ATLAS detector
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DOI：
10.1140/epjc/s10052-020-8102-8
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发表时间：
2020-08-13
影响因子：
4.4
通讯作者：
Zwalinski, L.
中科院分区：
文献类型：
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作者：
Aad, G.;Abbott, B.;Zwalinski, L.
在全强子t(T)+横动量丢失的末态中，寻找顶夸克(顶夸克或标量第三代上型轻夸克)标量对的直接产生。在大型强子对撞机上使用ATLAS探测器收集的139Fb(-1)根S=13TeV质子-质子碰撞数据的分析没有得到明显超出标准模型背景预期的结果。为了解释结果，使用了一个超对称模型，其中顶夸克通过(T)在tilde-t；t((*))(Chi)在tilde(0)(1)上衰变，t((*))表示壳层上(离壳层)顶夸克，(Chi)在tilde(0)(1)上是最轻的中性微子。针对以下情况优化了三个特定的事件选择。在m((T)over tilde)>；m(T)+m((Chi)over tilde 10)的情况下，在95%的置信度水平下，对于(Chi)over tilde(0)(1)低于200GeV的质量，顶夸克质量被排除在400-1250GeV的范围内。在类似于m(T)+m((Chi)on tilde 10)的情况下，300-630GeV范围内的顶方夸克质量被排除，而当m((T)over tilde)<；m(W)+m(B)+m(10)(其中m(T)over tilde)-m((Chi)on tilde 10)>；=5GeV时，300-660GeV范围内的顶方夸克质量被排除在外。当只考虑轻夸克衰变为顶夸克和中微子时，也为标量第三代上型轻夸克设定了限制，不包括质量在1240GeV以下的轻夸克。
A search for direct pair production of scalar partners of the top quark (top squarks or scalar third-generation up-type leptoquarks) in the all-hadronic t (t) over bar plus missing transverse momentum final state is presented. The analysis of 139 fb(-1) of root s = 13 TeV proton-proton collision data collected using the ATLAS detector at the LHC yields no significant excess over the Standard Model background expectation. To interpret the results, a supersymmetric model is used where the top squark decays via (t) over tilde -> t((*))(chi) over tilde (0)(1), with t((*)) denoting an on-shell (off-shell) top quark and (chi) over tilde (0)(1) the lightest neutralino. Three specific event selections are optimised for the following scenarios. In the scenario where m((t) over tilde) > m(t) + m((chi) over tilde 10), top squark masses are excluded in the range 400-1250 GeV for (chi) over tilde (0)(1) masses below 200 GeV at 95% confidence level. In the situation where m((t) over tilde) similar to m(t) + m((chi) over tilde 10), top squark masses in the range 300-630 GeV are excluded, while in the case where m((t) over tilde) < m(W) + m(b) + m(10) (with m((t) over tilde) - m((chi) over tilde 10) >= 5 GeV), considered for the first time in an ATLAS all-hadronic search, top squark masses in the range 300-660 GeV are excluded. Limits are also set for scalar third-generation up-type leptoquarks, excluding leptoquarks with masses below 1240 GeV when considering only leptoquark decays into a top quark and a neutrino.