The powerful muon and tracker systems of the CMS detector together with dedicated reconstruction software allow precise and efficient measurement of muon tracks originating from proton-proton collisions. The standard muon reconstruction algorithms, however, are inadequate to deal with muons that do not originate from collisions. We present the design, implementation, and performance of a dedicated cosmic muon track reconstruction algorithm, which features pattern recognition optimized for muons that are not coming from the interaction point, i.e. cosmic muons and beam-halo muons. To evaluate the performance of the new algorithm, data taken during Cosmic Challenge phases I and II as well as beam-halo muons recorded during the first LHC beam operation were studied. In addition, a variety of more general topologies of cosmic muons and beam-halo muons were studied using simulated data to demonstrate some key features of the new algorithm.
The CMS muon detector system, muon reconstruction software, and high-level trigger underwent significant changes in 2013-2014 in preparation for running at higher LHC collision energy and instantaneous luminosity. The performance of the modified system is studied using proton-proton collision data at center-of-mass energy $\sqrt{s}=$ 13 TeV, collected at the LHC in 2015 and 2016. The measured performance parameters, including spatial resolution, efficiency, and timing, are found to meet all design specifications and are well reproduced by simulation. Despite the more challenging running condit…
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…
The electronics of the CMS Drift Tube (DT) chambers need to be replaced during Long Shutdown 3 to tolerate the High Luminosity LHC (HL-LHC) data taking conditions. The first DT prototypes of the HL-LHC electronics, the on-detector board (OBDT), have been installed in the DT chambers of one sector, out of 60 sectors, and integrated into the central data acquisition and trigger systems. The signals from the chambers are split and reach both the legacy and Phase-2 demonstrator chains, which will allow them to operate in parallel during LHC collisions.
The high-luminosity phase of the Large Hadron Collider (HL-LHC) will result in ten times higher particle background than measured during the first phase of LHC operation. In order to fully exploit the highly-demanding operating conditions during HL-LHC, the Compact Muon Solenoid (CMS) Collaboration will use Gas Electron Multiplier (GEM) detector technology. The technology will be integrated into the innermost region of the forward muon spectrometer of CMS as an additional muon station called GE11. The primary purpose of this auxiliary station is to help in muon reconstruction and to control le…
The CMS muon system at the LHC is built of different detector technologies. The measurement of the background hit rates in the different muon detectors during the LHC Run-2 is of prime importance for an assessment of the longevity of the chambers and their on-board electronics, and therefore for the expected performance of the system at HL-LHC. Moreover, an accurate modelling of the backgrounds using simulations is also critical, as an estimation of the expected radiation background for the Phase-2 upgrade can only rely on Montecarlo-based predictions in the regions where new detectors are bei…
The CMS experiment, located at the Large Hadron Collider (LHC) in CERN, has a redundant muon system composed by three different gaseous detector technologies: Cathode Strip Chambers (in the forward regions), Drift Tubes (in the central region), and Resistive Plate Chambers (both its central and forward regions). All three are used for muon reconstruction and triggering. The CMS RPC system confers robustness and redundancy to the muon trigger. The RPC system operation in the challenging background and pileup conditions of the LHC environment is presented. The RPC system provides information to …
The high pseudorapidity ($η$) region of the Compact Muon Solenoid (CMS) muon system is covered by Cathode Strip Chambers only and lacks redundant coverage despite the fact that it is a challenging region for muons in terms of backgrounds and momentum resolution. During the annual Year-End Technical Stops 2022 & 2023, two new layers of improved Resistive Plate Chambers (iRPC) will be added, RE3/1 & RE4/1, which will completely cover the region of $1.8 < |η| < 2.4$ in the endcap. Thus, the additional new chambers will lead to increase efficiency for both trigger and offline reconstruction in the…
Triple-GEM detector technology was recently selected by CMS for a part of the upgrade of its forward muon detector system as GEM detectors provide a stable operation in the high radiation environment expected during the future High-Luminosity phase of the Large Hadron Collider (HL-LHC). In a first step, GEM chambers (detectors) will be installed in the innermost muon endcap station in the $1.6<\left|η\right|<2.2$ pseudo-rapidity region, mainly to control level-1 muon trigger rates after the second LHC Long Shutdown. These new chambers will add redundancy to the muon system in the $η$-region wh…
The Large Hadron Collider is currently undergoing its High Luminosity upgrade, which is set to increase the instantaneous luminosity by about a factor of five. Consequently, the Compact Muon Solenoid experiment is upgrading its muon spectrometer to cope with the increased muon flux in the forward region. The GE2/1 triple-Gas Electron Multiplier detector, which has recently entered the mass production phase, and the ME0 triple-GEM detector system, which is in the late prototyping phase, are undergoing electronics integration. These proceedings briefly discuss the frontend electronics for the GE…
A full replacement of the existing muon trigger system in the CMS (Compact Muon Solenoid) detector is planned for operating at the maximum instantaneous luminosities of about $5-7.5\times10^{34}$ cm$^{-2}$ s$^{-1}$ expected in HL-LHC (High Luminosity Large Hadron Collider). In this plan, the new on-detector electronics that is being designed for the DT (Drift Tubes) detector will read out all the chamber information at its maximum time resolution. A new trigger system, based on the highest performing FPGAs, is being designed and will be capable of providing precise muon reconstruction and bunc…
We report on the design and test results of a prototype processor for the CMS Level-1 trigger that performs 3-D track reconstruction and measurement from data recorded by the cathode strip chambers of the endcap muon system. The tracking algorithms are written in C++ using a class library we developed that facilitates automatic conversion to Verilog. The code is synthesized into firmware for field-programmable gate-arrays from the Xilinx Virtex-II series. A second-generation prototype has been developed and is currently under test. It performs regional track-finding in a 60 degree azimuthal se…
The LHC is undergoing a high luminosity upgrade, which is set to increase the instantaneous luminosity by at least a factor of five, resulting in a higher muon flux rate in the forward region, which will overwhelm the current trigger system of the CMS experiment. The ME0, a gas electron multiplier detector, is proposed for the Phase-2 Muon System Upgrade to help increase the muon acceptance and to control the Level 1 muon trigger rate. To lower the probability of HV discharges, the ME0 was designed with GEM foils that are segmented on both sides. Initial testing of the ME0 showed substantial c…
The CMS muon system operates gas-based detectors. Upgrades of the detectors and trigger components are needed to cope with increasingly challenging conditions of the HL-LHC. New irradiation tests are performed to ensure that the muon detectors will survive the harsher conditions and operate reliably. The new CERN GIF++ (Gamma Irradiation Facility) allowed to perform aging tests. We present results in terms of system performance under large backgrounds and after accelerated aging tests. New detectors will be added to improve the performance in the critical forward region: gas electron multiplie…
The Compact Muon Solenoid (CMS) detector is a general-purpose experimental setup at the Large Hadron Collider (LHC) at CERN to investigate the production of new particles in the proton-proton collisions at a centre of mass energy 13 TeV. The third run of the data taken is started in April 2022 and will continue till the end of 2025. Then, during a long shutdown time, the existing CMS hadron endcap calorimeter will be replaced with a new high granularity calorimeter (HGCal) designed for the higher LHC luminosity. The HGCal contains the stainless-steel absorber plates with a relative permeabilit…
