RPC system in the CMS Level-1 Muon Trigger

International audienceThe 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

Research and development of the back-end electronics for the two-dimensional improved resistive plate chambers in CMS upgrade

International audienceTo complement and ensure redundancy in the endcap muon system of the Compact Muon Solenoid (CMS) detector and to extend the Resistive Plate Chamber (RPC) system coverage, improved RPCs (iRPCs) with either orthogonal layer strips with one-end electronics or single layer strips with two-end electronics providing more precise time measurement will be installed in the very forward pseudorapidity region of $|\eta |<2.4$. The iRPC readout system needs to support two-dimensional (2D) or two-end readout. In addition, it must combine detector data with Timing, Trigger and fast Control (TTC) and Slow Control (SC) into one data stream over a bi-directional optical link with a line rate of 4.8 Gb/s between the Front-End Electronics (FEE) and the Back-End Electronics (BEE). To fulfill these requirements, a prototype BEE for the iRPC 2D chamber has been researched and designed.A Micro-Telecommunication and Computing Architecture ($\mu$TCA)-based processing card was designed in this study to establish a prototype system together with a $\mu$TCA crate. The Giga-Bit Transceiver (GBT) protocol is integrated to provide bi-directional communication between the FEE and BEE. A server is connected with the BEE by a Gigabit Ethernet (GbE) link for SC and a 10-GbE link for Data AcQuisition (DAQ).The Bit Error Rate (BER) test of the back-end board and a joint test with the iRPC 2D prototype chamber were performed. A BER of less than $1.331\times {10^{-16}}$ was obtained. The time measurement with a resolution of 3.05 ns was successfully realized, and detector efficiencies of 97.7% for longitudinal strips and 96.0% for orthogonal strips were measured. Test results demonstrate the correctness and reliability of the prototype BEE.The BEE prototype satisfies the requirements for the iRPC 2D chamber, and it worked stably and reliably during a long-term joint test run

High voltage calibration method for the CMS RPC detector

International audienceThe 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

Search for Heavy Stable Charged Particles in the CMS Experiment using the RPC Phase II upgraded detectors

International audienceSeveral theoretical models inspired by the idea of supersymmetry (SUSY) accommodate the possibility of Heavy Stable Charged Particles (HSCPs). The Phase II upgrade of the CMS-RPC system will allow the trigger and identification of this kind of particles exploiting the Time-of-Flight Technique with the improved time resolution that a new Data Acquisition System (DAQ) system will provide (∼2 ns). Moreover, new Resistive Plate Chambers (RPC) detector chambers will be installed to extend the acceptance coverage up to |η|<2.4 with similar time resolution and better spatial resolution. We present a trigger strategy to detect HSCPs with the RPC detectors. Its performance is studied with Monte Carlo simulations and the expected results with the High Luminosity Large Hadron Collider (HL-LHC) data are shown

R&D of back-end electronics for improved resistive plate chambers for the phase 2 upgrade of the CMS end-cap muon system

International audienceThe 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

RPC radiation background simulations for the high luminosity phase in the CMS experiment

International audienceThe 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

CMS RPC efficiency measurement using the tag-and-probe method

International audienceWe measure the efficiency of CMS Resistive Plate Chamber (RPC) detectors in proton-proton collisions at the centre-of-mass energy of 13 TeV using the tag-and-probe method. A muon from a Z0 boson decay is selected as a probe of efficiency measurement, reconstructed using the CMS inner tracker and the rest of CMS muon systems. The overall efficiency of CMS RPC chambers during the 2016–2017 collision runs is measured to be more than 96% for the nominal RPC chambers

R&D of back-end electronics for improved resistive plate chambers for the phase 2 upgrade of the CMS end-cap muon system

International audienceThe 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

RE3/1 \& RE4/1 RPC chambers integration in the inner region of the forward muon spectrometer in the CMS experiment

International audienceThe high pseudorapidity (η) region of the Compact Muon Solenoid (CMS) muon system is covered by Cathode Strip Chambers only and lacks redundant coverage despite the fact that it is a challenging region for muons in terms of backgrounds and momentum resolution. During the annual Year-End Technical Stops 2022 & 2023, two new layers of improved Resistive Plate Chambers (iRPC) will be added, RE3/1 & RE4/1, which will completely cover the region of 1.8 < |η| < 2.4 in the endcap. Thus, the additional new chambers will lead to an increased 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 procedure 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 |η| region will be presented

Fast timing measurement for CMS RPC Phase-II upgrade

International audienceWith 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