Y. Assran

The CMS detector team describes their experiment and observation of decay products from a standard model Higgs boson, allowing its mass to be determined.

This report summarizes some useful data on the transport characteristics of gas mixtures which are required for detection of charged particles in gas detectors. We try to replace Freon used for RPC detector in the CMS experiment with another gas while maintaining the good properties of the Freon gas mixture unchanged. We try to switch to freonless gas mixture because Freon is not a green gas, it is very expensive and its availability is decreasing. Noble gases like Ar, He, Ne and Xe (with some quenchers like carbon dioxide, methane, ethane and isobutene) are investigated. Transport parameters like drift velocity, diffusion, Townsend coefficient, attachment coefficient and Lorentz angle are computed using Garfield software for different gas mixtures and compared with experimental data.

The CMS collaboration considers upgrading the muon forward region which is particularly affected by the high-luminosity conditions at the LHC. The proposal involves Gas Electron Multiplier (GEM) chambers, which are able to handle the extreme particle rates expected in this region along with a high spatial resolution. This allows to combine tracking and triggering capabilities, which will improve the CMS muon High Level Trigger, the muon identification and the track reconstruction. Intense R&D has been going on since 2009 and it has lead to the development of several GEM prototypes and associated detector electronics. These GEM prototypes have been subjected to extensive tests in the laboratory and in test beams at the CERN Super Proton Synchrotron (SPS). This contribution will review the status of the CMS upgrade project with GEMs and its impact on the CMS performance.

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 $1.6<\left|\eta\right|<2.2$ 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 $\eta$-region where the background rates are high, and the bending of the muon trajectories due to the CMS magnetic field is small. A novel construction technique for such chambers has been developed in such a way where foils are mounted onto a single stack and then uniformly stretched mechanically, avoiding the use of spacers and glue inside the active gas volume. We describe the layout, the stretching mechanism and the overall assembly technique of such GEM chambers.

Muon radiography often referred to as muography, is an imaging technique that uses freely available cosmic-ray muons to study the interior structure of natural or man-made large-scale objects. The amount of multidisciplinary applications of this technique keeps increasing over time and a variety of basic detector types have already been used in the construction of muon telescopes. Here, we are investigating the use of advanced gaseous detectors for muography. As our basic solution, given its robustness and ease of operation in remote, outdoor environments, a scintillator-based muon telescope with silicon photomultiplier readout is being developed. To enhance the telescope performance, we are proposing the use of Multi-gap Resistive Plate Chambers (mRPCs) and Thick Gas Electron Multipliers (THGEMs). While the former offer superior time resolution which could be beneficial for detector background rejection, the latter detector type offers excellent spatial resolution, can be manufactured at low cost and operated with a simple gas mixture. Currently, prototype detector planes for each of these proposed types are being designed and constructed, and initial performance tests are in progress. In parallel, a Geant4- based muon telescope simulation is being developed, which will enable us to e.g. optimize our telescope geometry and study the use of superior time resolution for background rejection. The design and status of the three detector prototype planes and the muon telescope, along with the initial results of their performance tests and of the Geant4 simulation studies are reported.

In this work, (99 - x)CaSO4 -Dy2 O3 -xEu2 O3 , (where x = 0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5) thermoluminescence phosphors were prepared using a coprecipitation method. The thermoluminescence (TL) dosimetry (TLD) characteristics such as TL sensitivity, dose-response, minimum detectable dose, thermal fading, and the effect of sunlight on the prepared phosphors were investigated. The obtained results indicated that the most sensitive phosphor was obtained at x = 0.05. Large thermal fading of 6% after 1 h and 26% after 24 h from irradiation followed by 71% after 1 month with no additional fading was observed within a time frame exceeding 2 months throughout the remaining duration of the investigation, which also spanned over 2 months. Despite the phosphor's high fading rate, the relative sensitivity of the prepared samples was ~90% compared with TLD-100. The marked effect of day sunlight was also determined. High dose-response within the low-dose range from 0.01 to 5 Gy was observed. The obtained results suggested that the synthesized phosphor is well suited for applications involving radiation biology and radiotherapy dosimetry.

In view of the High Luminosity upgrade of the CERN LHC, the forward CMS Muon spectrometer will be extended with two new stations of improved Resistive Plate Chambers (iRPC) covering the pseudorapidity range from 1.8 to 2.4. Compared to the present RPC system, the gap thickness is reduced to lower the avalanche charge, and an innovative 2D strip readout geometry is proposed. These improvements will allow iRPC detector to cope with higher background rates. A new Front-End-Board (FEB) is designed to readout iRPC signals with a threshold as low as 30 fC and an integrated Time Digital Converter with a resolution of 30 ps. In addition, the communication bandwidth is significantly increased by using optical fibers. The history, final design, certification, and calibration of this FEB are presented.

In this work the design of a constant fraction discriminator (CFD) to be used in the VFAT3 chip for the read-out of the triple-GEM detectors of the CMS experiment, is described. A prototype chip containing 8 CFDs was implemented using 130 nm CMOS technology and test results are shown.

Resistive Plate Chambers have been chosen as dedicated trigger muon detector for the Compact Muon Solenoid experiment [1] at the Large Hadron Collider [2] at CERN. The system consists of about 3000 m2 of double gap RPC chambers placed in both the barrel and endcap muon regions.

The CMS GEM collaboration is performing a feasibility study to install triple-GEM detectors in the forward region of the muon system (1.6 < |η| < 2.4) of the CMS detector at the LHC. Such micro-pattern gas detectors are able to cope with the extreme particle rates that are expected in that region during the High Luminosity phase of the LHC. With their spatial resolution of order 100 micron GEMs would not only provide additional benefits in the CMS muon High Level Trigger, but also in the muon identification and track reconstruction, effectively combining tracking and triggering capabilities in one single device. The present status of the full project will be reviewed, highlighting all importants steps and achievements since the start of the R&amp;D in 2009. Several small and full-size prototypes were constructed with different geometries and techniques. The baseline design of the triple-GEM detector for CMS will be described, along with the results from extensive test measurements of all prototypes both in the lab and in test beams at the CERN SPS. The proposed on- and off-detector electronics for the final system will be presented.

This contribution introduces a new type of Micropattern Gaseous Detector, the Fast Timing Micropattern (FTM) detector, utilizing fully Resistive WELL structures. The structure of the prototype will be described in detail and the results of the characterization study performed with an X-ray gun will be presented, together with the first results on time resolution based on data collected with muon/pion test beams.

The Resistive Plate Chambers (RPCs) are employed in the CMS experiment at the LHC as dedicated trigger system both in the barrel and in the endcap. This note presents results of the RPC detector uniformity and stability during the 2011 data taking period, and preliminary results obtained with 2012 data. The detector uniformity has been ensured with a dedicated High Voltage scan with LHC collisions, in order to determine the optimal operating working voltage of each individual RPC chamber installed in CMS. Emphasis is given on the procedures and results of the High Voltage calibration. Moreover, an increased detector stability has been obtained by automatically taking into account temperature and atmospheric pressure variations in the CMS cavern.

The CMS GEM collaboration is considering Gas Electron Multipliers (GEMs) for upgrading the CMS forward muon system in the 1.5 <; |η| <; 2.4 endcap region. GEM detectors can provide precision tracking and fast trigger information. They would improve the CMS muon trigger and muon momentum resolution and provide missing redundancy in the high-η region. Employing a new faster construction and assembly technique, we built four full-scale Triple-GEM muon detectors for the inner ring of the first muon endcap station. We plan to install these or further improved versions in CMS during the first long LHC shutdown in 2013/14 for continued testing. These detectors are designed for the stringent rate and resolution requirements in the increasingly hostile environments expected at CMS after the second long LHC shutdown in 2018/19. The new prototypes were studied in muon/pion beams at the CERN SPS. We discuss our experience with constructing the new full-scale production prototypes and present preliminary performance results from the beam test. We also tested smaller Triple-GEM prototypes with zigzag readout strips with 2 mm pitch in these beams and measured a spatial resolution of 73 μm. This readout offers a potential reduction of channel count and consequently electronics cost for this system while maintaining high spatial resolution.

The CMS muon system includes in both the barrel and endcap region Resistive Plate Chambers (RPC). They mainly serve as trigger detectors and also improve the reconstruction of muon parameters. Over the years, the instantaneous luminosity of the Large Hadron Collider gradually increases. During the LHC Phase 1 (~first 10 years of operation) an ultimate luminosity is expected above its design value of 10^34/cm^2/s at 14 TeV. To prepare the machine and also the experiments for this, two long shutdown periods are scheduled for 2013-2014 and 2018-2019. The CMS Collaboration is planning several detector upgrades during these long shutdowns. In particular, the muon detection system should be able to maintain a low-pT threshold for an efficient Level-1 Muon Trigger at high particle rates. One of the measures to ensure this, is to extend the present RPC system with the addition of a 4th layer in both endcap regions. During the first long shutdown, these two new stations will be equipped in the region |eta|<1.6 with 144 High Pressure Laminate (HPL) double-gap RPCs operating in avalanche mode, with a similar design as the existing CMS endcap chambers. Here, we present the upgrade plans for the CMS RPC system for the fist long shutdown, including trigger simulation studies for the extended system, and details on the new HPL production, the chamber assembly and the quality control procedures.

Gas Electron Multipliers (GEM) are a proven position sensitive gas detector technology which nowadays is becoming more widely used in High Energy Physics. GEMs offer an excellent spatial resolution and a high particle rate capability, with a close to 100% detection efficiency. In view of the high luminosity phase of the CERN Large Hadron Collider, these aforementioned features make GEMs suitable candidates for the future upgrades of the Compact Muon Solenoid (CMS) detector. In particular, the CMS GEM Collaboration proposes to cover the high-eta region of the muon system with large-area triple-GEM detectors, which have the ability to provide robust and redundant tracking and triggering functions. In this contribution, after a general introduction and overview of the project, the construction of full-size trapezoidal triple-GEM prototypes will be described in more detail. The procedures for the quality control of the GEM foils, including gain uniformity measurements with an x-ray source will be presented. In the past few years, several CMS triple-GEM prototype detectors were operated with test beams at the CERN SPS. The results of these test beam campaigns will be summarised.

The dedicated CMS R&D program was intended to study the feasibility of using micropattern detectors for the instrumentation of the vacant |η|>1.6 region in the present Resistive Plate Chambers (RPCs) endcap system. The proposed detector for CMS is a Triple-Gas Electron Multiplier (GEM) trapezoidal chamber, equipped with 1D readout. While during 2010–2011 the Collaboration worked on the prototyping of the detector, during the first part of 2012 a newly developed assembly technique to be used for the mass production was adopted. GEMs can provide precision tracking and fast trigger information, contributing on one hand to the improvement of the CMS muon Trigger and on the other hand to provide the missing redundancy in the high η region. In the view of the next LHC long shutdown (LS1) the CMS GEM Collaboration designed and built four full-size Triple GEM-based muon detectors.

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 all muon track finders and thus contributing to both muon trigger and reconstruction. The summary of the detector performance results obtained with proton-proton collision at √s = 13 TeV during 2016 and 2017 data taking have been presented. The stability of the system is presented in terms of efficiency and cluster size vs time and increasing instantaneous luminosity. Data-driven predictions about the expected performance during High Luminosity LHC (HL-LHC) stage have been reported.

Abstract A new generation of resistive plate chambers, capable of withstanding high particle fluxes (up to 2000 Hz · cm -2 ) and instrumented with precise timing readout electronics is proposed to equip two of the four high pseudorapidity stations of the CMS muon system. Double-gap RPC detectors, with each gap made of two 1.4 mm High Pressure Laminate electrodes and separated by a gas gap of the same thickness, are proposed. The new layout reduces the amount of the avalanche charge produced by the passage of a charged particle through the detector. This improves the RPC rate capability by reducing the needed time to collect this charge. To keep the RPC efficiency high, a sensitive, low-noise and high time resolution front-end electronics is needed to cope with the lower charge signal of the new RPC. An ASIC called PETIROC that has all these characteristics has been selected to read out the strips of new chambers. Thin (0.6 mm) printed circuit board, 160 cm long, equipped with pickup strips of 0.75 cm average pitch, will be inserted between the two new RPC's gaps. The strips will be read out from both ends, and the arrival time difference of the two ends will be used to determine the hit position along the strip. Results from the improved RPC equipped with the new readout system and exposed to cosmic muons in the high irradiation environment at CERN GIF++ facility are presented in this work.

The Resistive Plate Chambers (RPCs) are employed in the CMS Experiment at the LHC as dedicated trigger system both in the barrel and in the endcap. This article presents results of the radiation background measurements performed with the 2011 and 2012 proton-proton collision data collected by CMS. Emphasis is given to the measurements of the background distribution inside the RPCs. The expected background rates during the future running of the LHC are estimated both from extrapolated measurements and from simulation.

Cosmic-ray muons which impinge upon the Earth's surface can be used to image the density of geological and man-made materials located above a muon detector. The detectors used for these measurements must be capable of determining the muon rate as a function of the angle of incidence. Applications of this capability include geological carbon storage, natural gas storage, enhanced oil recovery, compressed air storage, oil and gas production, tunnel detection, and detection of hidden rooms in man-made structures such as the pyramids. For these applications the detector must be small, rugged, and have operational characteristics which enable its use in remote locations, such as low power requirements. A new muon detector design is now being constructed to make measurements on the Khafre pyramid, in Egypt, to look for unknown voids that might exist in the structure. The new detector design uses monolithic plates of scintillator with wavelength shifting fiber optic readout to obtain location information. This design will meet the operational requirements, while also providing a geometry which can be modified for different measurement conditions.

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).

The CMS GEM collaboration is considering Gas Electron Multipliers (GEMs) for upgrading the CMS forward muon system in the 1.5<|eta|<2.4 endcap region. GEM detectors can provide precision tracking and fast trigger information. They would improve the CMS muon trigger and muon momentum resolution and provide missing redundancy in the high-eta region. Employing a new faster construction and assembly technique, we built four full-scale Triple-GEM muon detectors for the inner ring of the first muon endcap station. We plan to install these or further improved versions in CMS during the first long LHC shutdown in 2013/14 for continued testing. These detectors are designed for the stringent rate and resolution requirements in the increasingly hostile environments expected at CMS after the second long LHC shutdown in 2018/19. The new prototypes were studied in muon/pion beams at the CERN SPS. We discuss our experience with constructing the new full-scale production prototypes and present preliminary performance results from the beam test. We also tested smaller Triple-GEM prototypes with zigzag readout strips with 2 mm pitch in these beams and measured a spatial resolution of 73 microns. This readout offers a potential reduction of channel count and consequently electronics cost for this system while maintaining high spatial resolution.

During the next shutdown of the LHC at CERN, the CMS experiment plans to start installing GEM detectors in the endcap (high pseudorapidity) region. These muon detectors have excellent spatial and temporal resolution as well as a high chemical stability and radiation hardness. A report is given on preliminary results of materials studies that aimed to fully characterize the GEM detector components before and after the exposure to a high-radiation environment.

The LHC data-taking will resume in 2015 with energy of 13–14 TeV and luminosity of 2÷5 × 1034 cm−2 s−1. At those energies, a considerable fraction of the particles produced propagate in the high pseudo-rapidity regions. The proposal for the upgrade of the CMS muon forward system involves Gas Electron Multiplier (GEM) chambers to be installed during the second LHC Long Shutdown (LS2) covering the pseudorapidity range 1.5 < |η| < 2.2. This detector is able to handle the extreme particle rates expected in this region when the LHC will be running at higher luminosity. The GEM is an excellent choice, as its high spatial resolution (order of 100 μm) allows to combine tracking and triggering capabilities, which will improve the CMS muon High Level Trigger, the muon identification and the track reconstruction. Intense R&D has been going on since 2009 and it has lead to the development of several GEM prototypes and associated detector electronics. These GEM prototypes have been subjected to extensive tests in the laboratory and in test beams at the CERN Super Proton Synchrotron (SPS). This contribution will review the status of the CMS upgrade project with GEMs, discussing also the trigger performance.

The international CMS GEM collaboration is studying the feasibility of upgrading the CMS forward muon system by adding layers of triple GEM based detectors. After successful tests of small size tripe-GEM chambers in the period of 2010-2011, the collaboration has designed, built and tested full-size GEM chambers for the upgrade purpose. We report on results from test beam and simulation that were conducted to study the performance of the GEM chambers.

In order to cope with the harsh environment expected from the high luminosity LHC, the CMS forward muon system requires an upgrade. The two main challenges expected in this environment are an increase in the trigger rate and increased background radiation leading to a potential degradation of the particle ID performance. Additionally, upgrades to other subdetectors of CMS allow for extended coverage for particle tracking, and adding muon system coverage to this region will further enhance the performance of CMS. Following an extensive R&D program, CMS has identified triple-foil gas electron multiplier (GEM) detectors as a solution for the first muon station in the region 1.6<|η|<2.2, while continuing R&D is ongoing for additional regions.

Four double-gap CMS resistive plate chambers are being tested at the CERN Gamma Irradiation Facility to determine the performance and aging effects at the expected conditions of the High Luminosity-Large Hadron Collider. Results up to an integrated charge of 290 millicoulomb/cm2 are reported.

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.

Abstract During the upcoming High Luminosity phase of the Large Hadron Collider (HL-LHC), the integrated luminosity of the accelerator will increase to 3000 fb −1 . The expected experimental conditions in that period in terms of background rates, event pileup, and the probable aging of the current detectors present a challenge for all the existing experiments at the LHC, including the Compact Muon Solenoid (CMS) experiment. To ensure a highly performing muon system for this period, several upgrades of the Resistive Plate Chamber (RPC) system of the CMS are currently being implemented. These include the replacement of the readout system for the present system, and the installation of two new RPC stations with improved chamber and front-end electronics designs. The current overall status of this CMS RPC upgrade project is presented.

Cosmic-ray muons which impinge upon the Earth's surface can be used to image the density of geological and man-made materials located above a muon detector.The detectors used for these measurements must be capable of determining the muon rate as a function of the angle of incidence.Applications of this capability include geological carbon storage, natural gas storage, enhanced oil recovery, compressed air storage, oil and gas production, tunnel detection, and detection of hidden rooms in man-made structures such as the pyramids.For these applications, the detector must be small and rugged and have operational characteristics which enable its use in remote locations, such as low power requirements.A new muon detector design is now being constructed to make measurements on the Khafre pyramid, in Egypt, to look for unknown voids that might exist in the structure.The new detector design uses monolithic plates of scintillator with wavelength-shifting fiber optic readout to obtain location information.This design will meet the operational requirements, while also providing a geometry that can be modified for different measurement conditions.

This report summarizes some useful data on the transport characteristics of gas mixtures which are required for detection of charged particles in gas detectors. We try to replace Freon used for RPC detector in the CMS experiment with another gas while maintaining the good properties of the Freon gas mixture unchanged. We try to switch to freonless gas mixture because Freon is not a green gas, it is very expensive and its availability is decreasing. Noble gases like Ar, He, Ne and Xe (with some quenchers like carbon dioxide, methane, ethane and isobutene) are investigated. Transport parameters like drift velocity, diffusion, Townsend coefficient, attachment coefficient and Lorentz angle are computed using Garfield software for different gas mixtures and compared with experimental data.

In this contribution we will report on the progress of the design of the readout and data acquisition system being developed for triple-GEM detectors which will be installed in the forward region (1.5 < |η| < 2.2) of the CMS muon spectrometer during the 2nd long shutdown of the LHC, expected in the period 2017–2018. The system will be designed to take full advantage of current generic developments introduced for the LHC upgrades. The current design is based on the use of CERN GLIB boards hosted in micro-TCA crates for the off-detector electronics and the Versatile Link with the GBT chipset to link the front-end electronics to the GLIB boards. In this contribution we will describe the physics goals, the hardware architectures and report on the expected performance of the CMS GEM readout system, including preliminary timing resolution simulations.

The CMS Collaboration has been developing large-area triple-gas electron multiplier (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 High-Luminosity upgrade of the Large Hadron Collider (LHC); 10 preproduction detectors were built at CERN to commission the first assembly line and the quality controls (QCs). These were installed in the CMS detector in early 2017 and participated in the 2017 LHC run. The collaboration has prepared several additional assembly and QC lines for distributed mass production of 160 GEM detectors at various sites worldwide. In 2017, these additional production sites have optimized construction techniques and QC procedures and validated them against common specifications by constructing additional preproduction detectors. Using the specific experience from one production site as an example, we discuss how the QCs 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 with details of the assembly sites involvement.

With the increase of the LHC luminosity foreseen in the coming years, many detectors currently used in the different LHC experiments will be dramatically impacted and some need to be replaced or upgraded. The new ones should be capable to provide time information to reduce the data ambiguity due to the expected high pileup. We propose to equip CMS high |η| muon chambers with pairs of single gap RPC detectors read out by long pickup strips PCB. The precise time measurement (0<15 ps) of the signal induced by particles crossing the detector on both ends of each strip will give an accurate measurement of the position of the incoming particle along the strip. The absolute time measurement, determined by RPC signal (around 1.5 ns) will also reduce the data ambiguity due to the highly expected pileup and help to identify Heavy Stable Charged Particles (HSCP). The development of a specific electronic chain (analog front-end ASIC, time-to-digital converter stage and printed circuit board design) and the corresponding first results on prototype chambers are presented.

The high luminosity expected from the HL-LHC will be a challenge for the CMS detector. The increased rate of particles coming from the collisions and the radioactivity induced in the detector material could cause significant damage and result in a progressive degradation of its performance. Simulation studies are very useful in these scenarios as they allow one to study the radiation environment and the impact on detector performance. Results are presented for CMS RPC stations considering the operating conditions expected at the HL-LHC.

The CMS experiment recorded 177.75 /fb of proton-proton collision data during the RUN-1 and RUN-2 data taking period. Successful data taking at increasing instantaneous luminosities with the evolving detector configuration was a big achievement of the collaboration. The CMS RPC system provided redundant information for the robust muon triggering, reconstruction, and identification. To ensure stable data taking, the CMS RPC collaboration has performed detector operation, calibration, and performance studies. Various software and related tools are developed and maintained accordingly. In this paper, the overall performance of the CMS RPC system and experiences of the data taking during the RUN-2 period are summarised.

A novel approach which uses Fiber Bragg Grating (FBG) sensors has been utilized to assess and monitor the flatness of Gaseous Electron Multipliers (GEM) foils. The setup layout and preliminary results are presented.

The Compact Muon Solenoid (CMS) detector is one of the two general-purpose detectors at the CERN LHC. LHC will provide exceptional high instantaneous and integrated luminosity after second long shutdown. The forward region |η| ≥ 1:5 of CMS detector will face extremely high particle rates in tens of kHz/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and hence it will affect the momentum resolution, efficiency and longevity of the muon detectors. Here, η is pseudorapidity defined as η = −ln(tan(θ/2)), where θ is the polar angle measured from z-axis. To overcome these issues the CMSGEM collaboration has proposed to install new large size rate capable Triple Gas Electron Multiplier (GEM) detectors in the forward region of CMS muon system. The first set of Triple GEM detectors will be installed in the GE1/1 region (1:6 < |η| < 2.2) of the muon endcap during the long shutdown 2 (LS2) of the LHC. Towards this goal, full size CMS Triple GEM detectors have been fabricated and tested at the CERN SPS, H2 and H4 test beam facility. The GEM detectors were operated with two gas mixtures: Ar/CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (70/30) and Ar/CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> /CF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> (45/15/40). In 2014, good quality data was collected during test beam campaigns. In this paper, the performance of the detectors is summarized based on their tracking efficiency and time resolution.

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.

During Run-3, the LHC is preparing to deliver instantaneous luminosity in the range from 5 × 1034 cm−2 s−1 to 7.5 × 1034 cm−2 s−1. To ensure stable data taking, providing redundant information for robust muon triggering, reconstruction and identification, the CMS RPC collaboration has used the opportunity given by the LHC long shutdown 2 (LS2), to perform a series of maintenance and preparation activities for the new data taking period. The overall performance of the RPC system after the LS2 commissioning period and the activities in preparation for future data taking will be presented.

During Run2 the high instantaneous luminosity, up to 2.21034cm−2s−1, lead to a substantial hit rate in the Compact Muon Solenoid experiment’s muon chambers due to multiple background sources to physics processes sought for at LHC. In this article we will describe the analysis method devised to measure and identify the contributions to such background in the Resistive Plate Chambers. Thorough understanding of the background rates provides the base for the upgrade of the muon detectors for the High-Luminosity LHC.

The ScIDEP (Scintillator Imaging Detector for the Egyptian Pyramids) Collaboration is constructing a scintillator-based muon telescope to investigate the internal structure of the Egyptian Pyramid of Khafre. This pyramid is only slightly smaller than the Great Pyramid, however its known internal structure seems much simpler compared to the latter and hence raises the question if there are any hidden rooms or structures that have yet to be discovered. The previous and very first muography campaign at this pyramid conducted by Alvarez et al. in the 1970s yielded no indications of any hidden structures.The current project aims to install a new muon telescope inside the king’s burial chamber which is located at the very bottom of the pyramid, slightly off-center from the central axis. The base detector that has been developed consists of two 61x61x2cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> plastic scintillator planes with wavelength shifting fibers embedded in orthogonal orientations in both faces of each scintillator, to retrieve 2D hit information from each plane for muon tracking. The scintillation light is read out by SiPMs connected to each individual fiber. The data-acquisition system is based on commercial CAEN Petiroc2A-ASIC based digitizer modules. The detector construction has recently been completed and commissioning of the setup in the lab is currently ongoing.In parallel to the detector commissioning, a detailed simulation package for the full setup is being developed. The cosmic ray spectrum is taken from the CRY generator, while the particle transport through the pyramid and the detector is modelled both in the Geant4 and MCNP packages.An overview of this project will be given, including the detector description and initial results, plus results from the simulation studies.

The CMS experiment at LHC will upgrade its forward muon spectrometer by incorporating Triple-GEM detectors. This upgrade referred to as GEM Endcap (GE1/1), consists of adding two back-to-back Triple-GEM detectors in front of the existing Cathode Strip Chambers (CSC) in the innermost ring of the endcap muon spectrometer. Before the full installation of 144 detectors in 2019–2020, CMS will first install ten single chamber prototypes during the early 2017. This pre-installation is referred as the slice test. These ten detectors will be read-out by VFAT2 chips [1]. On-detector there is also a FPGA mezzanine card which sends VFAT2 data optically to the μTCA back-end electronics. The correct and safe operation of the GEM system requires a sophisticated and powerful online Detector Control System, able to monitor and control many heterogeneous hardware devices. The DCS system developed for the slice test has been tested with CMS Triple-GEM detectors in the laboratory. In this paper we describe the newly developed DCS system and present the first results obtained in the GEM assembly and quality assurance laboratory.

We present a novel application of Fiber Bragg Grating (FBG) sensors in the construction and characterisation of Micro Pattern Gaseous Detector (MPGD), with particular attention to the realisation of the largest triple (Gas electron Multiplier) GEM chambers so far operated, the GE1/1 chambers of the CMS experiment at LHC. The GE1/1 CMS project consists of 144 GEM chambers of about 0.5 m 2 active area each, employing three GEM foils per chamber, to be installed in the forward region of the CMS endcap during the long shutdown of LHC in 2108-2019. The large active area of each GE1/1 chamber consists of GEM foils that are mechanically stretched in order to secure their flatness and the consequent uniform performance of the GE1/1 chamber across its whole active surface. So far FBGs have been used in high energy physics mainly as high precision positioning and re-positioning sensors and as low cost, easy to mount, low space consuming temperature sensors. FBGs are also commonly used for very precise strain measurements in material studies. In this work we present a novel use of FBGs as flatness and mechanical tensioning sensors applied to the wide GEM foils of the GE1/1 chambers. A network of FBG sensors have been used to determine the optimal mechanical tension applied and to characterise the mechanical tension that should be applied to the foils. We discuss the results of the test done on a full-sized GE1/1 final prototype, the studies done to fully characterise the GEM material, how this information was used to define a standard assembly procedure and possible future developments.

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.

Abstract The expected radiation background in the CMS RPC system has been studied using the MC prediction with the CMS FLUKA simulation of the detector and the cavern. The MC geometry used in the analysis describes very accurately the present RPC system but still does not include the complete description of the RPC upgrade region with pseudorapidity 1.9 &lt; |η| &lt; 2.4. Present results will be updated with the final geometry description, once it is available. The radiation background has been studied in terms of expected particle rates, absorbed dose and fluence. Two High Luminosity LHC (HL-LHC) scenarios have been investigated — after collecting 3000 and 4000 fb -1 . Estimations with safety factor of 3 have been considered, as well.

The CMS experiment implements a two-level triggering system composed of Level-1, instrumented by custom-design hardware boards, and a software High Level Trigger. To cope with the more challenging luminosity conditions, a new Level-1 architecture has been deployed during run II. This new architecture exploits in a better way the redundancy and complementarity of the three muon subsystems: Cathode Strip Chambers (CSC), Drift Tubes (DT) and Resistive Plate Chambers (RPC). The role of each subsystem in the Level-1 Muon Trigger is described here, highlighting the contribution from the RPC system. Challenges brought by the HL-LHC environment and new possibilities coming from detector and trigger upgrades are also discussed.

The high pseudorapidity ($\eta$) 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 $1.8 < |\eta| < 2.4$ in the endcap. Thus, the additional new chambers will lead to increase efficiency for both trigger and offline reconstruction in the difficult region where the background is the highest and the magnetic field is the lowest within the muon system. The extended RPC system will improve the performance and the robustness of the muon trigger. The final design of iRPC chambers and the concept to integrate and install them in the CMS muon system have been finalized. In this report, the main results demonstrating the implementation and installation of the new iRPC detectors in the CMS muon system at high $|\eta|$ region will be presented.

Abstract The present RPC Link System has been servicing as one of the CMS subsystems since installation in 2008. Although the current Link System has been functioning well for the past 13 years, the aging of its electronic components and lack of radiation hard ASICs could present problems for future operations. Additionally, the needs to have a more robust control interface against electromagnetic interference, to improve the trigger performance with finer time granularity and to incorporate a higher bandwidth transmission lines led the idea of upgrading the Link System for the HL-LHC. This paper reviews the features of the recently developed prototype of the new Link System.

For the High Luminosity LHC CMS is planning to install new large size Triple-GEM detectors, equipped with a new readout system in the forward region of its muon system (1.5<|η|<2.2). In this note we report on the status of the project, the main achievements regarding the detectors as well as the electronics and readout system.

The Large Hadron Collider (LHC) at European Organization for Nuclear Research is planned to be upgraded to the high luminosity LHC. Increasing the luminosity makes muon triggering reliable and offline reconstruction very challenging. To enhance the redundancy of the Compact Muon Solenoid (CMS) Muon system and resolve the ambiguity of track reconstruction in the forward region, an improved Resistive Plate Chamber (iRPC) with excellent time resolution will be installed in the Phase-2 CMS upgrade. The iRPC will be equipped with Front-End Electronics (FEE), which can perform high-precision time measurements of signals from both ends of the strip. New Back-End Electronics (BEE) need to be researched and developed to provide sophisticated functionalities such as interacting with FEE with shared links for fast, slow control (SC) and data, in addition to trigger primitives (TPs) generation and data acquisition (DAQ). The BEE prototype uses a homemade hardware board compatible with the MTCA standard, the back-end board (BEB). BEE interacts with FEE via a bidirectional 4.8 Gbps optical paired-link that integrates clock, data, and control information. The clock and fast/slow control commands are distributed from BEB to the FEE via the downlink. The uplink is used for BEB to receive the time information of the iRPC’s fired strips and the responses to the fast/slow control commands. To have a pipelined detector data for cluster finding operation, recover (DeMux) the time relationship of which is changed due to the transmission protocol for the continuous incoming MUXed data from FEE. Then at each bunch crossing (BX), clustering fired strips that satisfy time and spatial constraints to generate TPs. Both incoming raw MUXed detector data and TPs in a time window and latency based on the trigger signal are read out to the DAQ system. Gigabit Ethernet (GbE) of SiTCP and commercial 10-GbE are used as link standards for SC and DAQ, respectively, for the BEB to interact with the server. The joint test results of the BEB with iRPC and Front-End Board (FEB) show a Bit Error Rate of the transmission links less than $$1\times {10^{-16}}$$ , a time resolution of the FEB Time-to-Digital Converter of 16 ps, and the resolution of the time difference between both ends of 160 ps which corresponding a spatial resolution of the iRPC of approximately 1.5 cm. Test results showed the correctness and stable running of the BEB prototype, of which the functionalities fulfill the iRPC requirements.

The Compact Muon Solenoid (CMS) experiment at the LHC is planning an upgrade of its muon detection system aiming to extend the muon detection capabilities in the forward region with the installation of new muon stations based on Gas Electron Multiplier (GEM) and Resistive Plate Chambers (RPC) technologies during the so-called Phase-2 upgrade scenario. With the imminent increase on luminosity to 5 × 1034cm-2s-1 and center of mass collision energy of 14 TeV an unprecedented and hostile radiation environment will be created, the most affected detectors will be the ones located in the forward region where the intense flux of neutrons and photons could potentially degrade the detector performance. Using FLUKA simulation the expected radiation environment is estimated for the regions of interest, possible shielding scenarios are proposed and the effect on the detector performance is discussed.

Gas Electron Multiplier (GEM) technology is being considered for the forward muon upgrade of the CMS experiment in Phase 2 of the CERN LHC. Its first implementation is planned for the GE1/1 system in the $1.5 < \mid\eta\mid < 2.2$ region of the muon endcap mainly to control muon level-1 trigger rates after the second long LHC shutdown. A GE1/1 triple-GEM detector is read out by 3,072 radial strips with 455 $\mu$rad pitch arranged in eight $\eta$-sectors. We assembled a full-size GE1/1 prototype of 1m length at Florida Tech and tested it in 20-120 GeV hadron beams at Fermilab using Ar/CO$_{2}$ 70:30 and the RD51 scalable readout system. Four small GEM detectors with 2-D readout and an average measured azimuthal resolution of 36 $\mu$rad provided precise reference tracks. Construction of this largest GEM detector built to-date is described. Strip cluster parameters, detection efficiency, and spatial resolution are studied with position and high voltage scans. The plateau detection efficiency is [97.1 $\pm$ 0.2 (stat)]\%. The azimuthal resolution is found to be [123.5 $\pm$ 1.6 (stat)] $\mu$rad when operating in the center of the efficiency plateau and using full pulse height information. The resolution can be slightly improved by $\sim$ 10 $\mu$rad when correcting for the bias due to discrete readout strips. The CMS upgrade design calls for readout electronics with binary hit output. When strip clusters are formed correspondingly without charge-weighting and with fixed hit thresholds, a position resolution of [136.8 $\pm$ 2.5 stat] $\mu$rad is measured, consistent with the expected resolution of strip-pitch/$\sqrt{12}$ = 131.3 $\mu$rad. Other $\eta$-sectors of the detector show similar response and performance.

The CMS Collaboration plans to equip the very forward muon system with triple-GEM detectors that can withstand the environment of the High-Luminosity LHC. This project is at the final stages of R&amp;D and moving to production. An unprecedented large area of several 100 m 2 are to be instrumented with GEM detectors which will be produced in six different sites around the world. A common construction and quality control procedure is required to ensure the performance of each detector. The quality control steps will include optical inspection, cleaning and baking of all materials and parts used to build the detector, leakage current tests of the GEM foils, high voltage tests, gas leak tests of the chambers and monitoring pressure drop vs. time, gain calibration to know the optimal operation region of the detector, gain uniformity tests, and studying the efficiency, noise and tracking performance of the detectors in a cosmic stand using scintillators.

In the next decades, the Large Hadron Collider (LHC) will run at very high luminosity (HL-LHC) 5×1034 cm−2s−1, factor five more than the nominal LHC luminosity. During this period the CMS RPC system will be subjected to high background rates which could affect the performance by inducing aging effects. A dedicated longevity program to qualify the present RPC system for the HL-LHC running period is ongoing. At the CERN Gamma Irradiation Facility (GIF++) four RPC detectors, from the spare production, are exposed to an intense gamma radiation for a dose equivalent to the one expected at the HL-LHC . The main detector parameters are under monitoring as a function of the integrated charge and the performance is studied with a muon beam. Preliminary results of the study after having collected ≈ 34% of the expected integrated charge will be presented.

The Resistive Plate Chambers (RPC) are used for muon triggers in the CMS experiment. To calibrate the high voltage working-points (WP) and identify degraded detectors due to radiation or chemical damage, a high voltage scan has been performed using 2017 data from pp collisions at a center-of-mass energy of 13 TeV. In this paper, we present the calibration method and the latest results obtained for the 2017 data. A comparison with all scans taken since 2011 is considered to investigate the stability of the detector performance in time.

The second LHC long shutdown period (LS2) is an important opportunity for the CMS Resistive Plate Chambers (RPC) to complete their consolidation and upgrade projects. The consolidation includes detector maintenance for gas tightness, HV (high voltage), LV (low voltage) and slow control operation. All services for the RPC Phase-2 upgrade: improved RPC in stations RE3/1 and RE4/1, were anticipated for installation to LS2. This paper summarises the RPC system maintenance and upgrade activities.

The CMS experiment has 1054 RPCs in its muon system. Monitoring their currents is the first essential step towards maintaining the stability of the CMS RPC detector performance. The current depends on several parameters such as applied voltage, luminosity, environmental conditions, etc. Knowing the influence of these parameters on the RPC current is essential for the correct interpretation of its instabilities as they can be caused either by changes in external conditions or by malfunctioning of the detector in the ideal case. We propose a Machine Learning(ML) based approach to be used for monitoring the CMS RPC currents. The approach is crucial for the development of an automated monitoring system capable of warning for possible hardware problems at a very early stage, which will contribute further to the stable operation of the CMS RPC detector.

The Muon Upgrade Phase II of the Compact Muon Solenoid (CMS) aims to guarantee the optimal conditions of the present system and extend the η coverage to ensure a reliable system for the High Luminosity Large Hadron Collider (HL-LHC) period. The Resistive Plate Chambers (RPCs) system will upgrade the off-detector electronics (called link system) of the chambers currently installed chambers and place improved RPCs (iRPCs) to cover the high pseudo−rapidity region, a challenging region for muon reconstruction in terms of background and momentum resolution. In order to find the best option for the iRPCs, an R&D program for new detectors was performed and real size prototypes have been tested in the Gamma Irradiation Facility (GIF++) at CERN. The results indicated that the technology suitable for the high background conditions is based on High Pressure Laminate (HPL) double-gap RPC. The RPC Upgrade Phase II program is planned to be ready after the Long Shutdown 3 (LS3).

Abstract As part of the Compact Muon Solenoid experiment Phase-II upgrade program, new resistive plate chambers will be installed in the region at low angle with respect to the beam collision axis, in order to improve the detection of muons with a low transverse momentum. High background conditions are expected in this region during the high-luminosity phase of the Large Hadron Collider, therefore an improved-RPC design has been proposed with a new front-end electronics to sustain a higher particle rate capability and better time resolution. A new technology is used in the front-end electronics resulting in low achievable signal detection of 1–20 fC. Crucial in the design of the improved-RPC is the capability of a two-dimensional readout in order to improve the spatial resolution, mainly motivated by trigger requirements. In this work, the first performance results towards this two-dimensional readout are presented, based on data taken on a real-size prototype chamber with two embedded readout planes with orthogonal strips.

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.

During the future LHC upgrade planned in 2018, the forward endcap region of the CMS muon spectrometer will be upgraded with GEM chambers. GEM technology is able to withstand the radiation environment expected in the forward region. The GE1/1 station will be included in the muon L1 trigger, allowing to keep low p(T) threshold even at high luminosity. Moreover, it will bring detection redundancy in the most critical part of the CMS muon system, along with benefits to muon reconstruction performance.

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 Compact Muon Solenoid (CMS) detector installed at the CERN Large Hadron Collider (LHC) has an extensive muon system which provides information simultaneously for identification, track reconstruction and triggering of muons. As a consequence of the extreme particle rate and high integrated charge, the essentiality to upgrade the LHC has given rise to the High Luminosity phase of the LHC (HL-LHC) project so that the CMS muon system will be upgraded with superior technological challenges. The CMS GEM collaboration offers a solution to equip the high-eta region of the muon system for Phase 2 (after the year 2017) with large-area triple-layer Gas Electron Multiplier (GEM) detectors, since GEMs have the ability to provide robust and redundant tracking and triggering functions with an excellent spatial resolution of order 100 micron and a high particle rate capability, with a close to 100% detection efficiency. In this contribution, the present status of the triple-GEM project will be reviewed, and the significant achievements from the start of the R&D in 2009 will be emphasized.

For the High-Luminosity LHC (HL-LHC) phase the CMS GEM Collaboration is planning to install new large-size (990×220–455mm2) triple-GEM detectors, equipped with a new readout system, in the forward region of the muon system (1.5< |η| <2.2) of the CMS detector. Combining triggering and tracking functionalities the new triple-foil Gas Electron Multiplier (GEM) chambers will improve both the performance of the CMS muon trigger and the muon reconstruction/identification in CMS experiment. The addition of triple-GEM chambers to the forward region of the CMS muon system will add a necessary layer of redundancy. Starting from 2009 the CMS GEM Collaboration has built several small and full-size prototypes with different geometries, keeping improving the assembly techniques. All these prototypes have been tested in laboratories as well as with beam tests at the CERN Super Proton Synchrotron (SPS) and at Fermi National Accelerator Laboratory. In this contribution we will report on the status of the CMS upgrade project with triple-GEM chambers and its impact on the CMS performance as well as the hardware architectures and expected capability of the CMS GEM readout system.

In view of the high-luminosity phase of the LHC, the CMS Collaboration is considering the use of Gas Electron Multiplier (GEM) detector technology for the upgrade of its muon system in the forward region. With their ability to handle the extreme particle rates expected in that area, such micro-pattern gas detectors can sustain a high performance and redundant muon trigger system. At the same time, with their excellent spatial resolution, they can improve the muon track reconstruction and identification capabilities of the forward detector, effectively combining tracking and triggering functions in one single device. The present status of the CMS GEM project will be reviewed, highlighting importants steps and achievements since the start of the R&D activities in 2009. The baseline design of the triple-GEM detectors proposed for installation in different stations of the CMS muon endcap system will be described, along with the associated frontend electronics and data-acquisition system. The expected impact on the performance of the CMS muon system will be discussed, and results from detector tests, both in the lab and in test beams 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.

We present a novel application of Fiber Bragg Grating (FBG) sensors in the construction and characterisation of Micro Pattern Gaseous Detector (MPGD), with particular attention to the realisation of the largest triple (Gas electron Multiplier) GEM chambers so far operated, the GE1/1 chambers of the CMS experiment at LHC. The GE1/1 CMS project consists of 144 GEM chambers of about 0.5 m2 active area each, employing three GEM foils per chamber, to be installed in the forward region of the CMS endcap during the long shutdown of LHC in 2108-2019. The large active area of each GE1/1 chamber consists of GEM foils that are mechanically stretched in order to secure their flatness and the consequent uniform performance of the GE1/1 chamber across its whole active surface. So far FBGs have been used in high energy physics mainly as high precision positioning and re-positioning sensors and as low cost, easy to mount, low space consuming temperature sensors. FBGs are also commonly used for very precise strain measurements in material studies. In this work we present a novel use of FBGs as flatness and mechanical tensioning sensors applied to the wide GEM foils of the GE1/1 chambers. A network of FBG sensors have been used to determine the optimal mechanical tension applied and to characterise the mechanical tension that should be applied to the foils. We discuss the results of the test done on a full-sized GE1/1 final prototype, the studies done to fully characterise the GEM material, how this information was used to define a standard assembly procedure and possible future developments.

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.

The RPC muon detector of the CMS experiment at the LHC (CERN, Geneva, Switzerland) is equipped with a Gas Gain Monitoring (GGM) system. A report on the stability of the system during the 2011-2012 data taking run is given, as well as the observation of an effect which suggests a novel method for the monitoring of gas mixture composition.

In this paper an analysis is presented on performance of RPC chambers installed in the cosmic ray test stand at ISR, CERN. The currents of RPC chambers are studied as a function of environmental parameters such as temperature, humidity and pressure, which are important for the operation of the RPC detector system at CMS. A neural network approach has been used to analyze the data and to build a model using experimental measurements and combining the results of the simulations.

The Resistive Plate Chamber (RPC) muon subsystem contributes significantly to the formation of the trigger decision and reconstruction of the muon trajectory parameters. Simulation of the RPC response is a crucial part of the entire CMS Monte Carlo software and directly influences the final physical results. An algorithm based on the parametrization of RPC efficiency, noise, cluster size and timing for every strip has been developed. Experimental data obtained from cosmic and proton-proton collisions at √s = 7 TeV have been used for determination of the parameters. A dedicated validation procedure has been developed. A good agreement between the simulated and experimental data has been achieved.

Charge-dependent anisotropy Fourier coefficients ($v_n$) of particle azimuthal distributions are measured in pPb and PbPb collisions at $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = $ 5.02 TeV with the CMS detector at the LHC. The normalized difference in the second-order anisotropy coefficients ($v_2$) between positively and negatively charged particles is found to depend linearly on the observed event charge asymmetry with comparable slopes for both pPb and PbPb collisions over a wide range of charged particle multiplicity. In PbPb, the third-order anisotropy coefficient, $v_3$, shows a similar linear dependence with the same slope as seen for $v_2$. The observed similarities between the $v_2$ slopes for pPb and PbPb, as well as the similar slopes for $v_2$ and $v_3$ in PbPb, are compatible with expectations based on local charge conservation in the decay of clusters or resonances, and constitute a challenge to the hypothesis that the observed charge asymmetry dependence of $v_2$ in heavy ion collisions arises from a chiral magnetic wave.

Muography is an imaging technique that can be used to examine the interior structure of large-size objects.The technique is based on measurements of the absorption of cosmic-ray muons passing through the object under study.Muographic imaging was already successfully applied to the discovery of a new void inside the Great Pyramid of Khufu at Giza, Egypt.With the aim of studying the Pyramid of Khafre, the second largest pyramid at Giza, a new muography detector is currently being constructed.In this paper, we report on the development of a corresponding new simulation framework of the Great Pyramids and the detector setup.This simulation will serve as a basis to develop the data and image reconstruction algorithms to be used during our future muography campaign in the Pyramid of Khafre, and will allow us to study the relevant experimental conditions at the site.

Muon radiography often referred to as muography, is an imaging technique that uses freely available cosmic-ray muons to study the interior structure of natural or man-made large-scale objects. The amount of multidisciplinary applications of this technique keeps increasing over time and a variety of basic detector types have already been used in the construction of muon telescopes. Here, we are investigating the use of advanced gaseous detectors for muography. As our basic solution, given its robustness and ease of operation in remote, outdoor environments, a scintillator-based muon telescope with silicon photomultiplier readout is being developed. To enhance the telescope performance, we are proposing the use of Multi-gap Resistive Plate Chambers (mRPCs) and Thick Gas Electron Multipliers (THGEMs). While the former offer superior time resolution which could be beneficial for detector background rejection, the latter detector type offers excellent spatial resolution, can be manufactured at low cost and operated with a simple gas mixture. Currently, prototype detector planes for each of these proposed types are being designed and constructed, and initial performance tests are in progress. In parallel, a Geant4- based muon telescope simulation is being developed, which will enable us to e.g. optimize our telescope geometry and study the use of superior time resolution for background rejection. The design and status of the three detector prototype planes and the muon telescope, along with the initial results of their performance tests and of the Geant4 simulation studies are reported.