Performance of electron reconstruction and selection with the CMS detector in proton-proton collisions at sqrt(s) = 8 TeV

Pileup mitigation at CMS in 13 TeV data

With increasing instantaneous luminosity at the LHC come additional reconstruction challenges. At high luminosity, many collisions occur simultaneously within one proton-proton bunch crossing. The isolation of an interesting collision from the additional "pileup" collisions is needed for effective physics performance. In the CMS Collaboration, several techniques capable of mitigating the impact of these pileup collisions have been developed. Such methods include charged-hadron subtraction, pileup jet identification, isospin-based neutral particle "$δβ$" correction, and, most recently, pileup p…

Performance of the CMS muon trigger system in proton-proton collisions at $\sqrt{s} =$ 13 TeV

The muon trigger system of the CMS experiment uses a combination of hardware and software to identify events containing a muon. During Run 2 (covering 2015-2018) the LHC achieved instantaneous luminosities as high as 2 $\times$ 10$^{34}$cm$^{-2}$s$^{-1}$ while delivering proton-proton collisions at $\sqrt{s} =$ 13 TeV. The challenge for the trigger system of the CMS experiment is to reduce the registered event rate from about 40 MHz to about 1 kHz. Significant improvements important for the success of the CMS physics program have been made to the muon trigger system via improved muon reconstru…

Performance of missing transverse momentum reconstruction in proton-proton collisions at $\sqrt{s} =$ 13 TeV using the CMS detector

The performance of missing transverse momentum (${\vec p}_{\mathrm{T}}^\mathrm{miss}$) reconstruction algorithms for the CMS experiment is presented, using proton-proton collisions at a center-of-mass energy of 13 TeV, collected at the CERN LHC in 2016. The data sample corresponds to an integrated luminosity of 35.9 fb$^{-1}$. The results include measurements of the scale and resolution of ${\vec p}_{\mathrm{T}}^\mathrm{miss}$, and detailed studies of events identified with anomalous ${\vec p}_{\mathrm{T}}^\mathrm{miss}$. The performance is presented of a ${\vec p}_{\mathrm{T}}^\mathrm{miss}$ …

CMS实验在13.6 TeV质子-质子碰撞中高层级 hadronic tau lepton 触发器研究

High-level hadronic tau lepton triggers of the CMS experiment in proton-proton collisions at $\sqrt{s}$ = 13.6 TeV

本文介绍了CMS实验在13.6 TeV碰撞中采用机器学习算法提升hadronic tau lepton识别效率，以应对高亮度下的触发挑战。

The performance of the CMS muon detector in proton-proton collisions at sqrt(s) = 7 TeV at the LHC

The performance of all subsystems of the CMS muon detector has been studied by using a sample of proton--proton collision data at sqrt(s) = 7 TeV collected at the LHC in 2010 that corresponds to an integrated luminosity of approximately 40 inverse picobarns. The measured distributions of the major operational parameters of the drift tube (DT), cathode strip chamber (CSC), and resistive plate chamber (RPC) systems met the design specifications. The spatial resolution per chamber was 80-120 micrometers in the DTs, 40-150 micrometers in the CSCs, and 0.8-1.2 centimeters in the RPCs. The time reso…

在√s = 13 TeV质子-质子碰撞中利用CMS实验中的多变量技术进行μ子鉴别

Muon identification using multivariate techniques in the CMS experiment in proton-proton collisions at $\sqrt{s}$ = 13 TeV

本研究基于CMS实验2018年13 TeV、59.7 fb⁻¹数据，开发两种多变量μ子鉴别算法，以提升横动量大于10 GeV的瞬发孤立μ子鉴别并抑制重味衰变污染。

Comparison of CMS Resistive Plate Chambers performance during LHC RUN-1 and RUN-2

The Resistive Plate Chambers detector system at the CMS experiment at the LHC provides robustness and redundancy to the muon trigger. A total of 1056 double-gap chambers cover the pseudo-rapidity region < 1.6. The main detector parameters and environmental conditions are constantly and closely monitored to achieve operational stability and high quality data in the harsh conditions of the second run period of the LHC with center-of-mass energy of 13 TeV. First results of overall detector stability with 2015 data and comparisons with data from the LHC RUN-1 period at 8 TeV are presented.

Identification of heavy-flavour jets with the CMS detector in pp collisions at 13 TeV

Many measurements and searches for physics beyond the standard model at the LHC rely on the efficient identification of heavy-flavour jets, i.e. jets originating from bottom or charm quarks. In this paper, the discriminating variables and the algorithms used for heavy-flavour jet identification during the first years of operation of the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, are presented. Heavy-flavour jet identification algorithms have been improved compared to those used previously at centre-of-mass energies of 7 and 8 TeV. For jets with transverse …

Performance of the CMS Level-1 trigger in proton-proton collisions at $\sqrt{s} =$ 13 TeV

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 th…

Calibration of the CMS hadron calorimeters using proton-proton collision data at $\sqrt{s} =$ 13 TeV

Methods are presented for calibrating the hadron calorimeter system of the CMS detector at the LHC. The hadron calorimeters of the CMS experiment are sampling calorimeters of brass and scintillator, and are in the form of one central detector and two endcaps. These calorimeters cover pseudorapidities $|η| <$ 3 and are positioned inside a solenoidal magnet. An outer calorimeter, outside the magnet coil, covers $|η| <$ 1.26, and a steel and quartz-fiber Cherenkov forward calorimeter extends the coverage to $|η| <$ 5.19. The initial calibration of the calorimeters was based on results from test b…

Run 2及早期Run 3中的CMS径迹重建性能

CMS tracking performance in Run 2 and early Run 3

本文介绍CMS探测器为适配LHC Run 3更高亮度与堆积条件所做的探测器升级及径迹寻找、筛选算法改进，并利用Run 2与早期Run 3对撞数据及模拟数据测量径迹重建性能。