"Figure 28 aux" of "Search for long-lived particles using out-of-time trackless jets in proton-proton collisions at $\sqrt{s}$ = 13 TeV"

A search for long-lived particles decaying in the outer regions of the CMS silicon tracker or in the calorimeters is presented. The search is based on a data sample of proton-proton collisions at $\sqrt{s} = 13$ TeV recorded with the CMS detector at the LHC in 2016-2018, corresponding to an integrated luminosity of 138 $\text{fb}^{-1}$. A novel technique, using trackless and out-of-time jet information combined in a deep neural network discriminator, is employed to identify decays of long-lived particles. The results are interpreted in a simplified model of chargino-neutralino production, where the neutralino is the next-to-lightest supersymmetric particle, is long-lived, and decays to a gravitino and either a Higgs or $Z$ boson.This search is most sensitive to neutralino proper decay lengths of approximately 0.5 m, for which masses up to 1.18 TeV are excluded at 95% confidence level. The current search is the best result to date in the mass range from the kinematic limit imposed by the Higgs mass up to 1.8 TeV.

本文报道了一项针对在CMS硅径迹仪（silicon tracker）外围区域或量能器（calorimeters）内发生衰变的长寿命粒子的搜寻分析。本分析基于大型强子对撞机（Large Hadron Collider, LHC）上CMS探测器在2016至2018年间采集的质心系能量$sqrt{s}=13$ TeV的质子-质子碰撞数据样本，对应的积分亮度为138 fb⁻¹。本分析采用一项新颖的分析方法：将无径迹粒子与脱时喷注信息整合至深度神经网络（deep neural network）判别器中，以识别长寿命粒子的衰变信号。分析结果在一个简化的chargino-中性微子（neutralino）产生模型中展开诠释：该模型中中性微子为次轻超对称粒子，具有长寿命属性，其衰变产物为引力微子（gravitino）与希格斯（Higgs）玻色子或Z玻色子。本搜寻对固有衰变长度约为0.5米的中性微子具有最高灵敏度，在此参数区间内，质量不超过1.18 TeV的中性微子在95%置信水平（confidence level）下被排除。在由希格斯质量所限定的运动学极限至1.8 TeV的质量区间内，本次分析是迄今为止该领域灵敏度最优的搜寻结果。