I. Vai

Abstract Looking at the future path of high-energy physics, a muon collider offers incomparable potential for discovery in the multi-TeV energy range. However, its development must address some relevant technological challenges, which arise from the short muon lifetime, 2.2 μs, and from the difficulty of producing large numbers of muons in groups with small emittance. The first one in particular leads to the production of the so-called Beam-induced Background (BIB), which affects the design of the machine and detector. The purpose of this contribution is to describe the expected performance of the muon system of a multipurpose muon collider detector designed to reconstruct the products of multi-TeV collisions with extreme accuracy. We are proposing a design of the muon system fully based on Micropattern Gaseous Detectors (MPGD), which foresees the combination of tracking layers based on Triple-GEM detectors, with a timing layer based on a new generation MPGD called Picosec. Picosec was developed in the last few years by the RD51 collaboration, with the aim of obtaining a fast timing (sub ns) MPGD. A dedicated R&D is ongoing to optimize such a technology for the application in a muon collider experiment, both from the detector and the mechanics point of views. This contribution will present the results obtained during the R&D of the Picosec technology for the muon collider both from laboratory tests and test beams performed in 2023. Special attention will be given to the performance obtained with different gas mixtures. Moreover, we will discuss the plans for the R&D dedicated to the muon collider.

The μ-RWELL has been conceived as a compact, simple and robust Micro-Pattern-Gaseous-Detector (MPGD) for very large area HEP applications requiring the operation in harsh environment. The detector amplification stage, similar to a GEM foil, is realized with a polyimide structure micro-patterned with a blind-hole matrix, embedded through a thin Diamond Like Carbon (DLC) resistive layer in the readout PCB. The introduction of the resistive layer strongly suppressing the transition from streamer to spark gives the possibility to achieve large gains (> 104), without significantly affecting the capability to stand high particle fluxes. In this work we give an overview of the two detector layouts designed for low and high rate applications, presenting the results of a systematic study of the detector performance as a function of the surface resistivity and discussing the status of the Technology Transfer towards the industry for large area detector manufacturing.

Abstract The present generation of Micro-Pattern Gaseous Detectors (MPGDs) are radiation hard detectors, capable of detecting effciently particle rates of several MHz/cm 2 , while exhibiting good spatial resolution (≤ 50 µm) and modest time resolution of 5-10 ns, which satisfies the current generation of experiments (High Luminosity LHC upgrades of CMS and ATLAS) but it is not sufficient for bunch crossing identification of fast timing systems at FCC-hh. Thanks to the application of thin resistive films such as Diamond-Like Carbon (DLC) a new detector concept was conceived: Fast Timing MPGD (FTM). In the FTM the drift volume of the detector has been divided in several layers each with their own amplification structure. The use of resistive electrodes makes the entire structure transparent for electrical signals. After some first initial encouraging results, progress has been slowed down due to problems with the wet-etching of DLC-coated polyimide foils. To solve these problems a more in-depth knowledge of the internal stress of the DLC together with the DLC-polyimide adhesion is required. We will report on the production of DLC films produced in Italy with Ion Beam Sputtering and Pulsed Laser Deposition, where we are searching to improve the adhesion of the thin DLC films, combined with a very high uniformity of the resistivity values.

The HL-LHC phase is designed to increase by an order of magnitude the amount of data to be collected by the LHC experiments. To achieve this goal in a reasonable time scale the instantaneous luminosity would also increase by an order of magnitude up to 6 · 1034 cm−2s−1. The region of the forward muon spectrometer (|η| > 1.6) is not equipped with RPC stations. The increase of the expected particles flux up to 2 kHz/cm2 (including a safety factor 3) motivates the installation of RPC chambers to guarantee redundancy with the CSC chambers already present. The current CMS RPC technology cannot sustain the expected background level. The new technology that will be chosen should have a high rate capability and provide a good spatial and timing resolution. A new generation of Glass-RPC (GRPC) using low-resistivity glass is proposed to equip at least the two most far away of the four high η muon stations of CMS. First the design of small size prototypes and studies of their performance in high-rate particles flux are presented. Then the proposed designs for large size chambers and their fast-timing electronic readout are examined and preliminary results are provided.

We report on a systematic study of double-gap and four-gap phenolic resistive plate chambers (RPCs) for the Phase-2 upgrade of the CMS muon system at high η. In the present study, we constructed real-sized double-gap and four-gap RPCs with gap thicknesses of 1.6 and 0.8 mm, respectively, with 2-mm-thick phenolic high-pressure-laminated (HPL) plates. We examined the prototype RPCs with cosmic rays and with 100-GeV muons provided by the SPS H4 beam line at CERN. To examine the rate capability of the prototype RPCs both at Korea University and at the CERN GIF++ facility, the chambers were irradiated with 137Cs sources providing maximum gamma rates of about 1.5 kHz cm−2. For the 1.6-mm-thick double-gap RPCs, we found the relatively high threshold on the produced detector charge was conducive to effectively suppressing the rapid increase of strip cluster sizes of muon hits with high voltage, especially when measuring the narrow-pitch strips. The gamma-induced currents drawn in the four-gap RPC were about one-fourth of those drawn in the double-gap RPC. The rate capabilities of both RPC types, proven through the present testing using gamma-ray sources, far exceeded the maximum rate expected in the new high-η endcap RPCs planned for future phase-II runs of the Large Hadron Collider (LHC).

A Muon Collider represents a possible option for the next generation of high-energy machines.Among the technological challenges in the realization of such a machine, the mitigation of the beam-induced background is one of the most critical issues for the experiments.At the desired instantaneous luminosity, the decay rate of the circulating muons is very high, the decay products and subsequent particles from their interactions with the machine elements can reach the detector and compromise its performance.In this contribution, the results of a first preliminary study is presented of the beam-induced background effects on the detector response in the case of muon beams collisions at a center of mass energy of 1.5 TeV and some background mitigation strategies are illustrated.

After the Phase-2 high-luminosity upgrade to the Large Hadron Collider (LHC), the collision rate and therefore the background rate will significantly increase, particularly in the high $\eta$ region. To improve both the tracking and triggering of muons, the Compact Muon Solenoid (CMS) Collaboration plans to install triple-layer Gas Electron Multiplier (GEM) detectors in the CMS muon endcaps. Demonstrator GEM detectors were installed in CMS during 2017 to gain operational experience and perform a preliminary investigation of detector performance. We present the results of triple-GEM detector performance studies performed in situ during normal CMS and LHC operations in 2018. The distribution of cluster size and the efficiency to reconstruct high $p_T$ muons in proton--proton collisions are presented as well as the measurement of the environmental background rate to produce hits in the GEM detector.

The high pseudo-rapidity region of the CMS muon system is covered by Cathode Strip Chambers (CSC) only and lacks redundant coverage despite the fact that it is a challenging region for muons in terms of backgrounds and momentum resolution. In order to maintain good efficiency for the muon trigger in this region additional RPCs are planned to be installed in the two outermost stations at low angle named RE3/1 and RE4/1. These stations will use RPCs with finer granularity and good timing resolution to mitigate background effects and to increase the redundancy of the system.

The GEM detectors will be installed at the Compact Muon Solenoid (CMS) experiment during Long Shutdown II of the LHC in 2018. The GEM foil is a basic part of the detector which consists of a composite material, i.e. polyimide coated with copper and perforated with a high density of micro holes. In this paper the results of the GEM foil material characterization are reported, and a campaign of tensile and holes deformation tests is performed. During the tests, the complex radiation environment at CMS is taken into account and samples are prepared accordingly to see the impacts of the radiation on the GEM foil, i.e. non-irradiated samples are used as the reference and compared with neutrons- and gamma- irradiated. These studies provide the information necessary to optimize the stress level without damaging the foil and holes during the detector assembly in which the GEM foils stack is stretched simultaneously to maintain the uniform gap among the foils in order to get the designed performance of the detector. Finally, an estimate of the Young's modulus of the GEM foil is provided by using the tensile test data.

Abstract The fast timing MPGD is a micro-pattern gaseous detector conceived for achieving sub-nanosecond time resolution while maintaining the ability to instrument large areas in high-rate environments; applications of such technology are perspected in high-energy physics experiments at future colliders and medical diagnostics with time-of-flight methods. The work presented is a set of systematic studies carried on an FTM prototype on the performance of GEM foils coated with resistive DLC films, whose development is essential for the FTM operation. The resistive foil performance has been tested with several gas mixtures and compared with the results obtained on conductive foils. The results show that the performance of the FTM is presently limited by the technology of manufacturing of DLC-coated GEM foils, with high gains reachable exclusively in isobutane-based mixtures.

The muon spectrometer of the CMS (Compact Muon Solenoid) experiment at the Large Hadron Collider (LHC) is equipped with a redundant system made of Resistive Plate Chambers and Drift Tube in barrel and RPC and Cathode Strip Chamber in endcap region. In this paper, the operations and performance of the RPC system during the first three years of LHC activity will be reported. The stability of RPC performance, such as efficiency, cluster size and noise, will be reported. Finally, the radiation background levels on the RPC system have been measured as a function of the LHC luminosity. Extrapolations to the LHC and High Luminosity LHC conditions are also discussed.

A Muon Collider represents a promising possibility to combine the high energy and luminosity of hadron machines with very precise measurements of lepton colliders. The main challenges, that impact both the machine and detector design, arise from the short muon lifetime and the harsh Beam-induced Background (BIB). Therefore, a full simulation is crucial to understand the feasibility of the experiment implementation. Focusing in particular on the muon system, a preliminary simulation of sensitivity and hit rate reveals that the technology inherited from CLIC, i.e. glass Resistive Plate Chambers, is already at the limit of its rate capability. Thus, alternative MicroPattern Gaseous Detector solutions are under investigation to try to match the required performance. In parallel, studies of muon reconstruction are ongoing. Results of the muon reconstruction efficiency and BIB sensitivity are presented for multimuon final state processes at a centre-of-mass energy of 1.5 TeV. Besides, PICOSEC technology, based on a Micromegas detector coupled to a Cherenkov radiator and equipped with a photocathode, is discussed.

The muon collider offers a great discover potential for the future of high energy physics. Indeed, it combines the advantages of a lepton collider, with clean signatures and maximum available center of mass energy, with those of a hadron collider, such as low synchrotron radiation. However, it poses interesting challenges, manly related to the fact that muons decay and their product interact with the material of the machine producing the socalled Beam-induced-Background. For this reason, a careful design of the experiments running at a muon collider must be performed, starting from simulation, and moving to the R&D on dedicated technologies. This contribution will focus on the muon system of a muon collider experiment: the current design limitations will be presented, together with the alternative solutions that are being considered. In particular, we are proposing to use the Picosec Micromegas technology for a dedicated timing layer in the muon system, which will improve the muon reconstruction performance in that region. The R&D on this technology will be discussed and preliminary results will be presented.

The material characterization of the gaseous electron multiplier (GEM) detectors is presented in this article; mechanical tests were performed to examine the mechanical performance of polyimide (Kapton) and GEM foil. Bearing in mind the mechanical stresses imposed during the assembly and subsequently during operation at Compact Muon Solenoid (CMS). The detectors will run for many years in the harsh radiation and environmental conditions at the CMS. In view of this a series of the tensile tests were performed by using different samples which were prepared accordingly, i.e. a set of the samples was exposed to neutron and another exposed to gamma radiation, and then these were made dry and wet to assess the effects of radiation and humidity on their tensile properties. In this paper the experimental setup, testing procedures, sampling and detailed results are presented. In general, due to the radiation and environment variation conditions the degradation of the GEM material is not significant with respect to its toughness, but the Young's modulus was effected. POLYM. ENG. SCI., 58:1539–1547, 2018. © 2017 Society of Plastics Engineers

We present the status of the commissioning and integration of the GE1/1 slice test detectors into CMS. Ten Triple-GEM detectors were installed at the beginning of 2017 in CMS to obtain installation and commissioning expertise, as well as to demonstrate the integration into the CMS system. The paper will enlight the configuration of the slice test and then focus mainly on the integration activities and status.

Based on previous experience and attempt, a real-size mosaic Multi-gap Resistive Plate Chamber (MRPC) has been developed within the framework of the CMS muon upgrade efforts. The chamber is a 5-gap with plates made each of 6 pieces of low resistive glass. Cosmic ray test at CERN 904 shows that its efficiency can reach above 95% with a gas mixture of 90% C2H2F4, 5% i-C4H10 and 5% SF6. The chamber was also tested with CMS dry gas(95.2% C2H2F4, 4.5% i-C4H10, 0.3% SF6) at the CERN Gamma Irradiation Facility (GIF++). Efficiency results calculated by a simple tracking method show that the good performance is maintained at rates up to 10 kHz/cm2.

A muon collider has a great potential for particle physics giving the possibility to reach the high center-of-mass energy and luminosity of hadron colliders, with a greatly reduced pile up effect.However, a series of challenges arise mainly from the short muon lifetime and the Beam-induced Background.A complete simulation, based on CLIC's ILCSoft software, is ongoing to understand the performance of the full detector.Concerning the muon system, the iron yoke plates are meant to be instrumented with layers of track sensitive chamber to enhance the muon identification.At the moment, according to CLIC geometry, glass Resistive Plate Chambers with readout cells of 30x30 mm 2 have been adopted both for the barrel and the endcap region.Other possible solutions, based on MicroPattern Gaseous Detectors, will be discussed considering their characteristics and performance.The results of a preliminary study investigating the muon reconstruction efficiency, Beam-induced Background sensitivity and background mitigation are presented for muon beams collisions at a center-of-mass energy of 1.5 TeV.

A new muon reconstruction algorithm is introduced at the CMS experiment. This algorithm reconstructs muons using only the central tracker and the Resistive Plate Chamber (RPC). The aim of this work is to study how a muon reconstructed only with tracker and RPC information would perform compared to the standard muon reconstruction of the CMS detector. The efficiencies to reconstruct and identify a RPC muon with a transverse momentum greater than 20 GeV/c are measured. The probabilities to misidentify hadrons as muons at low transverse momentum are also reported. These probabilities are compared to the standard muon identification used at CMS.

The R&D on the micro-Resistive-WELL (µ-RWELL) detector technology aims in developing a new scalable, compact, spark-protected, single amplification stage Micro-Pattern Gas Detectors (MPGD) for large area HEP applications as tracking and calorimeter device as well as for industrial and medical applications as X-ray and neutron imaging gas pixel detector.The novel microstructure, exploiting several solutions and improvements achieved in the last years for MPGDs, in particular for GEMs and Micromegas, is an extremely simple detector allowing an easy engineering with consequent technological transfer toward the photolithography industry.Large area detectors (up 1×2 m 2 ) can be realized splicing µ-RWELL_PCB tiles of smaller size (about 0.5×1 m 2 -typical PCB industrial size).The detector, composed by few basic elements such as the readout-PCB embedded with the amplification stage (through the resistive layer) and the cathode defining the gas drift-conversion gap has been largely characterized on test bench with X-ray and with beam test.

Advances in the photo-lithographic techniques during the last twenty years have led to the development of micro-pattern gaseous detectors (MPGD).Their main features include high rate capability and radiation hardness, excellent spatial resolution, good time resolution, reduced radiation length and possible flexible geometries.In recent years the further development of MPGDs concentrated on using resistive materials to build compact spark-protected detectors.The use of resistive materials also opened the possibility to make electrically transparent structures with external signal pick-up electrodes.This allowed for a new idea to improve the time resolution through a multi-layered detector, consisting of alternating drift and amplification regions, where the fastest signal determines the detection time.This so-called Fast Timing MPGD (FTM) was firstly introduced by Rui de Oliveira et al. in 2015 [1] and aims to combine both the high spatial resolution and the high rate capability of a MPGD with a high time resolution of the order of 300 ps.Here, we introduce the design of a new single-layer prototype to test the gain of the amplification structure.Preliminary results on the detector characterization will be shown.

Muon collisions at multi-TeV center-of-mass energies are ideal for studying the Higgs-boson properties.The large number of produced Higgs bosons will allow to measure its couplings to fermions and bosons with an unprecedented precision.At multi-TeV centre-of-mass energies, the double (triple) Higgs-boson production rate will be sufficiently high to directly measure the parameters of trilinear (quadrilinear) self-couplings, enabling the precise determination of the Higgs boson potential.In this contribution a study of the → and → processes, where the Higgs bosons decay in two b-jets, is presented based on the full simulation of the detector with an evaluation of the beam-induced background.

An estimate of environmental background hit rate on triple-GEM chambers is performed using Monte Carlo (MC) simulation and compared to data taken by test chambers installed in the CMS experiment (GE1/1) during Run-2 at the Large Hadron Collider (LHC). The hit rate is measured using data collected with proton-proton collisions at 13 TeV and a luminosity of 1.5$\times10^{34}$ cm$^{-2}$ s$^{-1}$. The simulation framework uses a combination of the FLUKA and Geant4 packages to obtain the hit rate. FLUKA provides the radiation environment around the GE1/1 chambers, which is comprised of the particle flux with momentum direction and energy spectra ranging from $10^{-11}$ to $10^{4}$ MeV for neutrons, $10^{-3}$ to $10^{4}$ MeV for $\gamma$'s, $10^{-2}$ to $10^{4}$ MeV for $e^{\pm}$, and $10^{-1}$ to $10^{4}$ MeV for charged hadrons. Geant4 provides an estimate of detector response (sensitivity) based on an accurate description of detector geometry, material composition and interaction of particles with the various detector layers. The MC simulated hit rate is estimated as a function of the perpendicular distance from the beam line and agrees with data within the assigned uncertainties of 10-14.5%. This simulation framework can be used to obtain a reliable estimate of background rates expected at the High Luminosity LHC.

The Resistive Plate Chambers (RPC) are used in the CMS experiment at the trigger level and also in the standard offline muon reconstruction. In order to guarantee the quality of the data collected and to monitor online the detector performance, a set of tools has been developed in CMS which is heavily used in the RPC system. The Web-based monitoring (WBM) is a set of java servlets that allows users to check the performance of the hardware during data taking, providing distributions and history plots of all the parameters. The functionalities of the RPC WBM monitoring tools are presented along with studies of the detector performance as a function of growing luminosity and environmental conditions that are tracked over time.

February 1 th 2013 marked the end of the first period of running of the Large Hadron Collider (LHC) and the start of a two-year break from operation (LS1) aimed at consolidating both the accelerator as well as the detectors. By the end of LS1, the LHC is expected to provide collisions at 13 Tev. While, by 2020, the ultimate instantaneous luminosity is expected to be 1034/cm2/s. To prepare for this scenario, the Resistive Plate Chamber system at the CMS experiment is planning several detector maintainance and consolidation interventions. These include High Voltage and Low Voltage system reparations, gas leak identification and reparation, signal channel connectivity and functionality. Commissioning and upgrade plans for the existing CMS RPC system are presented here.

The CMS Collaboration is evaluating GEM detectors for the upgrade of the muon system. This contribution will focus on the R&D performed on cham design features and will discuss the performance of the upgraded detector.

The CMS experiment, located at the CERN Large Hadron Collider, has a redundant muon system composed by three different 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. During the first long shutdown (LS1) of the LHC (2013-2014) the CMS muon system has been upgraded with 144 newly installed RPCs on the forth forward stations. The new chambers ensure and enhance the muon trigger efficiency in the high luminosity conditions of the LHC Run2. The chambers have been successfully installed and commissioned. The system has been run successfully and experimental data has been collected and analyzed. The performance results of the newly installed RPCs will be presented.

The CMS experiment, located at the CERN Large Hadron Collider, has a redundant muon system composed by three different 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. During the first long shutdown (LS1) of the LHC (2013-2014) the CMS muon system has been upgraded with 144 newly installed RPCs on the forth forward stations. The new chambers ensure and enhance the muon trigger efficiency in the high luminosity conditions of the LHC Run2. The chambers have been successfully installed and commissioned. The system has been run successfully and experimental data has been collected and analyzed. The performance results of the newly installed RPCs will be presented.

In the framework of the High Luminosity LHC upgrade program, the CMS muon group built several different RPC prototypes that are now under test at the new CERN Gamma Irradiation Facility (GIF++). A dedicated Detector Control System (DCS) has been developed using the WinCC-OA tool to control and monitor these prototype detectors and to store the measured parameters data. Preliminary efficiency studies that set the base performance measurements of CMS RPC for starting aging studies are also presented.

We report on a systematic study of double-gap and four-gap phenolic resistive plate chambers (RPCs) for future high-η RPC triggers in the CMS. In the present study, we constructed real-sized double-gap and four-gap RPCs with gap thicknesses of 1.6 and 0.8 mm, respectively, with 2-mm-thick phenolic high-pressure-laminated (HPL) plates. We examined the prototype RPCs for cosmic rays and 100 GeV muons provided by the SPS H4 beam line at CERN. We applied maximum gamma rates of 1.5 kHz cm-2 provided by 137Cs sources at Korea University and the GIF++ irradiation facility installed at the SPS H4 beam line to examine the rate capabilities of the prototype RPCs. In contrast to the case of the four-gap RPCs, we found the relatively high threshold was conducive to effectively suppressing the rapid increase of strip cluster sizes of muon hits with high voltage, especially when measuring the narrow-pitch strips. The gamma-induced currents drawn in the four-gap RPC were about one-fourth of those drawn in the double-gap RPC. The rate capabilities of both RPC types, proven through the present testing using gamma-ray sources, far exceeded the maximum rate expected in the new high-η endcap RPCs planned for future phase-II LHC runs.

For the LHC High Luminosity phase (HL-LHC) the CMS GEM Collaboration is planning to install new large size triple-GEM detectors in the forward region of the muon system (1.5<|η|<2.2) of the CMS detector.The muon reconstruction with triple-GEM chambers information included have been successfully integrated in the official CMS software, allowing physics studies to be carried out.The new sub-detector will be able to cope the extreme particle rates expected in this region along with a high spatial resolution.The resulting benefit in terms of triggering and tracking capabilities has been studied: the expected improvement in the performance of the muon identification and track reconstruction as well as the expected improvement coming from the lowering of the muon p T trigger tresholds will be presented.The contribution will review the status of the CMS upgrade project with the usage of GEM detector, discussing the trigger, the muon reconstruction performance and the impact on the physics analyses.

The CMS Collaboration is developing GEM detectors for the upgrade of the CMS muon system. Their performance will be presented, analyzing the results of several test beams and an irradiation test performed in the last years.

The CMS Collaborationhas been developing large-area Triple-GEM detectors to be installed in the muon endcap regions of the CMS experiment in 2019 to maintain forward muon trigger and tracking performance at the HLLHC. Ten pre-production detectors were built at CERN to commission the first assembly line and the quality controls. These were installed in the CMS detector in early 2017 and are currently participating in the 2017 LHC run. The collaboration has prepared several additional assembly and quality control lines for distributed mass production of 160 GEM detectors at various sites worldwide. During 2017, these additional production sites have been optimizing construction techniques and quality control procedures and validating them against common specifications by constructing additional preproduction detectors. Using the specific experience from one production site as an example, we discuss how the quality controls make use of independent hardware and trained personnel to ensure fast and reliable production. Preliminary results on the construction status of CMS GEM detectors are presented.

In the context of simulation and reconstruction for the Muon Collider, muon reconstruction efficiency has been evaluated to explore the potential for the study of dark-SUSY channels.In dark-SUSY models, supersymmetric particles act as a portal between Standard Model particles and the dark sector.In this analysis, the lightest Minimal Supersymmetric Standard Model neutralino decays, on one hand, directly in a dark photon or, on the other hand, in two dark photons through a dark Higgs boson.A muon pair, with kinematics driven by the photon mass, is then expected from each dark photon.Therefore, the final state is characterized by four muons in one channel and eight muons in the other.Preliminary results of the muon reconstruction performance are shown for a possible range of neutralino and dark photon masses at a centre of mass energy of 3 TeV for the time being without the effects of the machine Beam-Induced Background.

Among the post-LHC generation of particle accelerators, the muon collider represents a unique machine with capability to provide very high energy leptonic collisions and to open the path to a vast and mostly unexplored physics programme. However, on the experimental side, such great physics potential is accompanied by unprecedented technological challenges, due to the fact that muons are unstable particles. Their decay products interact with the machine elements and produce an intense flux of background particles that eventually reach the detector and may degrade its performance. In this paper, we present technologies that have a potential to match the challenging specifications of a muon collider detector and outline a path forward for the future R&D efforts.

In this paper we report on the current status of studies on the expected performance for a detector designed to operate in a muon collider environment. Beam-induced backgrounds (BIB) represent the main challenge in the design of the detector and the event reconstruction algorithms. The current detector design aims to show that satisfactory performance can be achieved, while further optimizations are expected to significantly improve the overall performance. We present the characterization of the expected beam-induced background, describe the detector design and software used for detailed event simulations taking into account BIB effects. The expected performance of charged-particle reconstruction, jets, electrons, photons and muons is discussed, including an initial study on heavy-flavor jet tagging. A simple method to measure the delivered luminosity is also described. Overall, the proposed design and reconstruction algorithms can successfully reconstruct the high transverse-momentum objects needed to carry out a broad physics program.

The perspective of designing muon colliders with high energy and luminosity, which is being investigated by the International Muon Collider Collaboration, has triggered a growing interest in their physics reach. We present a concise summary of the muon colliders potential to explore new physics, leveraging on the unique possibility of combining high available energy with very precise measurements.

Triple-GEM detectors were selected by the CMS Collaboration for instrumenting the high η region of the muon system. This region is characterized by a huge radiation background, mainly composed by neutrons and photons. In this context, a discharge probability test was performed in 2017 at the CHARM facility at CERN, to study the operation of the detector in an environment similar to the one of the CMS muon system. A Geant4 simulation was developed in parallel to the actual test, in order to evaluate the behaviour of the detector. This paper will present this simulation, from the detector geometry implementation to the results obtained in terms of sensitivity and energy deposited into the gas gaps.

A forward muon detector (ME0) has been proposed for the installation in the CMS endcap muon system in the region 2.0 <; |η| <; 2.8, to increase the muon acceptance. This region is characterized by a very harsh radiation environment, which can reach rates up to few hundreds of kHz/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The technology proposed for the ME0 station is Triple-Gas Electron Multiplier (Triple-GEM), which has already been qualified for the operation in the CMS muon system. However an additional set of studies focused on the discharge probability is necessary for the ME0 station, due to the characteristic radiation environment mentioned above. A test was carried out in 2017 at the CERN High energy AcceleRator Mixed (CHARM) facility, with the aim of giving an estimation of the discharge probability of Triple-GEM detectors in a very intense radiation environment, similar to the one in the CMS muon system. A dedicated study with a standalone Geant4 simulation program was performed in order to evaluate the behavior of the detector exposed to the CHARM field. The geometry of the detector has been carefully reproduced, as well as the background field present in the facility. This paper will present the results obtained from the Geant4 simulation, in terms of sensitivity of the detector to the CHARM environment, together with the analysis of the energy deposited in the gas gaps.

In the next years the Large Hadron Collider (LHC) will be upgraded to significantly expand its physics program, increasing the luminosity up to 5 $\times$ 10$^{34}$cm$^{-2}$s$^{-1}$, well beyond the design value. An upgrade of the CMS detector is needed accordingly to cope with the expected growth in background rates, with the goal of keeping a high trigger efficiency. In this context, a first new station called GE1/1 will be installed in 2019-2020 in the CMS muon system. It will be composed of 144 Triple Gas Electron Multiplier (GEM) detectors to be integrated in the CMS muon endcaps in the region closest to the beam line. A fundamental operational experience has been already achieved in 2017-2018, when a demonstrator composed of ten GE1/1 Triple-GEM detectors was installed to prove the integration of the GE1/1 system into CMS itself. In parallel, a dedicated production chain has been setup in seven production sites spread around the world, for the construction and qualification of all the detectors for the complete station. This contribution presents overview of the GE1/1 project: the detectors design and performance are discussed, together with the lessons learned from the GE1/1 demonstrator installation, integration and operation. The construction and qualification processes is presented, emphasizing the results obtained with the 144 GE1/1 detectors. Finally, the plans for the installation and commissioning of the full station are outlined.

In the next years the Large Hadron Collider (LHC) will be upgraded to significantly expand its physics program, increasing the luminosity up to 5 × 1034cm−2s−1, well beyond the design value. An upgrade of the CMS detector is needed accordingly to cope with the expected growth in background rates, with the goal of keeping a high trigger efficiency. In this context, a first new station called GE1/1 will be installed in 2019-2020 in the CMS muon system. It will be composed of 144 Triple Gas Electron Multiplier (GEM) detectors to be integrated in the CMS muon endcaps in the region closest to the beam line. A fundamental operational experience has been already achieved in 2017-2018, when a demonstrator composed of ten GE1/1 Triple-GEM detectors was installed to prove the integration of the GE1/1 system into CMS itself. In parallel, a dedicated production chain has been setup in seven production sites spread around the world, for the construction and qualification of all the detectors for the complete station. This contribution presents overview of the GE1/1 project: the detectors design and performance are discussed, together with the lessons learned from the GE1/1 demonstrator installation, integration and operation. The construction and qualification processes is presented, emphasizing the results obtained with the 144 GE1/1 detectors. Finally, the plans for the installation and commissioning of the full station are outlined.

A promising proposal for the future of particle acceleration is represented by the muon collider. Indeed, it would give the possibility to probe much higher energy scales than hadrons colliding at the same energy, with a greatly reduced pile up effect. The project poses a series of technological challenges, ranging from the muon acceleration process to the design of dedicated experiments. Concerning this last point, a full simulation is vital to understand the feasibility of the experiment implementation and for its development. A complete simulation, based on CLIC’s ILCSoft software, is then ongoing to understand the performances of the full detector, for muon beams collisions at a center-of-mass energy of 1.5 TeV. Focusing on the muon system in particular, the CLIC geometry foresees the instrumentation of the iron yoke plates with layers of track sensitive chambers in order to enhance the muon identification. The selected technology currently is glass Resistive Plate Chambers both for barrel and endcap region, with readout cells of 30x30 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . However, MicroPattern Gaseous Detectors are also under investigation, with the goal of improving rate capability, space and time resolution.This contribution will present the results of the first preliminary study investigating the muon reconstruction efficiency, the sensitivity to Beam-induced Background, and background mitigation. In addition, the different technological solutions for the instrumentation of the muon system will be discussed.