Session G20: Muon Detection and Precision Timing Detectors at the HL-LHC

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The CMS muon system plays an important role in the discovery of new physics like the Higgs boson and new particles. The next phase of the LHC is planned to increase luminosity to improve the discovery power. The high luminosity LHC (HL-LHC) will be a harsh environment of pp collisions and will require high-performance muon trigger and muon track reconstruction, especially in the endcap region. In order to maintain the performance of the CMS muon system, the CMS collaboration has been developing a Gas Electron Multiplier (GEM) detector for the endcap regions of the CMS muon system. The new sub-detector system requires a new procedure of commissioning and alignment to be developed. We report the status of the GEM commissioning and alignment.   

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The ATLAS monitored drift tube (MDT) chambers are the main component of the precision tracking system in the ATLAS muon spectrometer. The MDT system is capable of measuring the sagitta of muon tracks to an accuracy of 60 $\mu$m, which corresponds to a momentum accuracy of about 10\% at $p_T=1$ TeV. ATLAS plans to use the MDT detector in the first stage of the trigger system to improve the muon transverse momentum resolution and to reduce the trigger rate expected at High-Luminosity LHC runs. A new trigger and readout system has been proposed. To test the prototypes for the frontend electronics including two ASICs and a data transmission board, a new mini-Data Acquisition (DAQ) system has been designed. We expect to use this system for integration and commissioning of new electronics on chambers on the surface and inside the ATLAS cavern. I will present the design and test of the new MiniDAQ system and its joint tests with a small-diameter MDT chamber.   

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The Endcap Timing Readout Chip (ETROC), being developed for the CMS Endcap Timing Layer (ETL) for high luminosity LHC (HL-LHC), is presented. Each endcap will be instrumented with a two-disk system of MIP-sensitive LGAD silicon devices to be read out by ETROCs for precision timing measurements with time resolution down to 30 ps level. The ETROC is designed to handle a 16×16 pixel cell matrix, each pixel cell being 1.3$\times$1.3 mm$^{2}$ to match the LGAD sensor pixel size. The design of ETROC as well as prototype testing results are presented.   

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The Large Hadron Collider (LHC) will be upgraded to increase its luminosity by a factor of 2 of its designed luminosity ($10^{34}cm^{−2}s^{−1}$). The ATLAS detector will undergo a major upgrade to fully explore the physics opportunity provided by the upgraded LHC. In order to optimize trigger efficiency at the HL-LHC(High Luminosity LHC), the Muon Spectrometer will be upgraded by replacing the MDT (Monitored Drift Tube) chambers by smaller-diameter MDT (sMDT) chambers and additional thin-gap RPC (Resistive Plate Chamber) trigger chambers in the barrel inner station. Michigan has carried out intensive R&D for sMDT construction over the past few years. Large infrastructure and tools are designed and built. The first small prototype chamber and a full-size Module-0 chamber have been built and tested at Michigan. I will report on the sMDT Module-0 chamber construction, precision measurement and test at the University of Michigan. We demonstrate that we can build the new generation muon chamber to satisfy all the stringent precision and performance requirements.   

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ATLAS plans to replace the current innermost endcap muon station with a New Small Wheel (NSW) detector. The NSW detector aims to handle the increase in data rates and harsh radiation environment expected at the High-Luminosity LHC. Both Micro-mesh gaseous structure chamber (MM) and small-strip Thin Gap Chamber (sTGC) will be used to provide complementary trigger and tracking functionality. The sTGC detector has three different detector types: pads, strips and wires. The sTGC on-detector electronics includes 768 strip frontend boards, 768 pad frontend board and 512 Level-1 Data Driver Cards (L1DDC). There are a total of 192 4-layer chambers that need to be integrated and commissioned. The total number of trigger and readout channels is about 354k. Extensive work is ongoing with the sTGC on-detector electronics integration and commissioning at CERN. Various problems have been found and solved. We expect to finish the work for 96 chambers by the end of February 2021. The integration and commissioning flow and the performance of frontend electronics and detectors will be presented.   

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The Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC) is undergoing an extensive Phase II upgrade program to prepare for the challenging conditions of the High-Luminosity LHC (HL-LHC). In particular, a new timing layer will measure minimum ionizing particles (MIPs) with a time resolution of \textasciitilde 30ps and hermetic coverage up to a pseudo-rapidity of \textbar $\eta $\textbar $=$3. The precision time information from this MIP Timing Detector (MTD) will reduce the effects of the high levels of pile-up expected at the HL-LHC and will bring new and unique capabilities to the CMS detector. The MTD will consist of a central barrel region and two end-caps. The central Barrel Timing Layer (BTL) will be based on LYSO:Ce crystals read out with silicon photomultipliers (SiPMs). The BTL will use elongated crystal bars, with double-sided read out (a SiPM on each end of the crystal), in order to maximize detector performance within the constraints of space, cost, and channel count. We will review the extensive R{\&}D studies carried out to optimize the design of the BTL sensors and the test beam results in which the goal of 30 ps timing resolution has been achieved.   

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The CMS Detector will be upgraded for the HL-LHC to include a MIP Timing Detector (MTD). The MTD will consist of barrel and endcap timing layers, BTL and ETL, respectively, providing precision timing of charged particles. The BTL sensors are based on LYSO:Ce scintillating crystals coupled to SiPMs with TOFHIR2 ASICs for the front-end readout. A resolution of 30-40 ps for MIP signals at a rate of 2.5 Mhit/s per channel is expected at the beginning of HL-LHC operation. We present an overview of the TOFHIR2 requirements and design, simulation results, and the first measurements with silicon samples.   

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The most challenging ATLAS Phase I upgrade project during Long Shutdown 2 (2019-2021) is the New Small-Wheel (NSW) for Muon Spectrometer upgrade. The main purpose of the NSW upgrade is to improve the performance of muon triggering and precision tracking for HL-LHC runs. The NSW detector system is composed of 16 layers of MicroMegas and small-strip Thin Gap Chambers (sTGC) detectors with 2.4 million readout channels and a total surface area of more than 2,500 $m^2$. This presentation focuses on the electronic integration and commissioning of sTGC detectors at CERN, including a summary of the progress achieved, the problems encountered during electronic testing and the various solutions discovered.   

Live

The Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC) is undergoing an extensive Phase II upgrade program to prepare for the challenging conditions of the High-Luminosity LHC (HL-LHC). In particular, a new timing layer will measure minimum ionizing particles (MIPs) with a time resolution of \textasciitilde 30ps and hermetic coverage up to a pseudo-rapidity of \textbar eta\textbar $=$3. This MIP Timing Detector (MTD) will include a central barrel timing layer (BTL) based on LYSO:Ce crystals read out with SiPMs. To mitigate the effects of radiation damage to the SiPMs the detector will be operated at temperatures below -35 C. The cooling system is based on evaporative CO2 cooling. To maximize the geometric detector coverage interfaces of the SiPMs to the cooling infrastructure need to be minimized. We will present detailed studies on the thermal optimization of the BTL detector layout. Detailed simulations of the thermal performance are discussed and compared to tests on prototype setups