论文标题
proton-proton碰撞中CMS级别1触发的性能在$ \ sqrt {s} = $ 13 TEV
Performance of the CMS Level-1 trigger in proton-proton collisions at $\sqrt{s} =$ 13 TeV
论文作者
论文摘要
在2015年第2次运行开始时，LHC在13 TEV的质量中心能量中交付了质子 - 普罗顿碰撞。在运行2（2015-2018年）期间，LHC最终达到2.1 $ \ times $ 10 $^{34} $ cm $ $^{ - 2} $ s $ s $^{ - 1} $，几乎是运行1（2009-2013）期间达到的两倍（2009-2013）和两倍的代理价值，指导50的事件，均为50次的事件。每束杂交碰撞（堆积）。在2016年之前升级了CMS Level-1触发器，以改善LHC第二次运行的具有挑战性条件下的物理事件的选择。本文描述了在2016 - 2018年数据期间，CMS Level-1触发升级的性能。升级后的触发器实现模式识别和提高amuon重建的决策树回归技术，包括用于喷气机和能量总和的堆积减法，并包含了电子和tau leptons的堆积依赖性隔离要求。此外，新的触发器计算高级量，例如成对的重建粒子对不变质量。升级从背景过程中降低了触发率，并提高了各种物理信号的触发效率。
At the start of Run 2 in 2015, the LHC delivered proton-proton collisions at a center-of-mass energy of 13 TeV. During Run 2 (years 2015-2018) the LHC eventually reached a luminosity of 2.1 $\times$ 10$^{34}$ cm$^{-2}$ s$^{-1}$, almost three times that reached during Run 1 (2009-2013) and a factor of two larger than the LHC design value, leading to events with up to a mean of about 50 simultaneous inelastic proton-proton collisions per bunch crossing (pileup). The CMS Level-1 trigger was upgraded prior to 2016 to improve the selection of physics events in the challenging conditions posed by the second run of the LHC. This paper describes the performance of the CMS Level-1 trigger upgrade during the data taking period of 2016-2018. The upgraded trigger implements pattern recognition and boosted decision tree regression techniques for muon reconstruction, includes pileup subtraction for jets and energy sums, and incorporates pileup-dependent isolation requirements for electrons and tau leptons. In addition, the new trigger calculates high-level quantities such as the invariant mass of pairs of reconstructed particles. The upgrade reduces the trigger rate from background processes and improves the trigger efficiency for a wide variety of physics signals.
