R. Venditti

The project of a Multi-TeV Muon Collider represents a unique opportunity to explore the high energy physics frontier and to measure with high precision the Higgs coupling with the other particles of the Standard Model as well as the trilinear and quadrilinear Higgs self-coupling, leading to a precise determination of the Higgs potential, in order to confirm the theoretical predictions of the SM and possibly to find evidences for new physics. One of the major challenges for the design and optimization of the technologies suitable for a Muon Collider experiment is represented by the high background induced by the decay of the muons coming from the beam. This contribution present the design of an innovative MPGD-based hadronic calorimeter (HCAL). The detector consists of a sampling calorimeter exploiting the Micro Pattern Gas Detectors (MPGDs) as active layers: MPGDs offer a fast and robust technology for high radiation environments and a high granularity for precise spatial measurements. Moreover, the detector is designed to optimize the jet reconstruction and for background suppression. The calorimeter is simulated using the Geant4 toolkit to support the detector R&D. The detector design and layout optimization supported by the simulation is described.

Motivated by the success of the flavour physics programme carried out over the last decade at the Large Hadron Collider (LHC), we characterize in detail the physics potential of its High-Luminosity and High-Energy upgrades in this domain of physics. We document the extraordinary breadth of the HL/HE-LHC programme enabled by a putative Upgrade II of the dedicated flavour physics experiment LHCb and the evolution of the established flavour physics role of the ATLAS and CMS general purpose experiments. We connect the dedicated flavour physics programme to studies of the top quark, Higgs boson, and direct high-$p_T$ searches for new particles and force carriers. We discuss the complementarity of their discovery potential for physics beyond the Standard Model, affirming the necessity to fully exploit the LHC's flavour physics potential throughout its upgrade eras.

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

The 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.

In 2019 during the second long shutdown (LS2) of the CERN Large Hadron Collider, the injector chain will be upgraded, allowing the instantaneous luminosity of the colliding beams to reach 2⋅1034 cm−2s−1 during the next run (Run 3). The physics program of the LHC experiments will benefit from the augmented luminosity; the sensitivity CMS experiment to the new physics and to Standard Model will be fully exploited, providing that a suitable upgrade will enable the CMS detector to cope the Run 3 data-taking conditions. Among the upgrades, the installation of a new station based on GEM technology (GE1/1), in the endcap of the Muon System will start in early 2019. The CMS GEM Collaboration is working on the production of the 144 GEM detectors to be installed, sharing the assembly and testing of the detectors among several production sites spread all over the world. A detailed common assembly protocol and quality control procedure (QC) has been deployed, with the ambitious goal to ensure standardization of the performance of the detectors produced by the different sites. In this contribution the results of the QC tests performed on the GEM chambers, assembled by the production sites following the common specification parameters, will be presented.

Abstract The Large Hadron Collider (LHC) will be upgraded in several phases that will allow significant expansion of its physics program. After the long shutdown in 2019 (LS2) the accelerator luminosity will be increased to 2-3 ×10 34 cm −2 s −1 for Run 3 and later up to 5×10 34 cm −2 s −1 for Phase 2 (HL-LHC). The physics program of the LHC experiments will benefit from the augmented luminosity; the sensitivity of the CMS experiment to new physics and to the Standard Model will be fully exploited, providing that a suitable upgrade will enable the CMS detector to cope with future data-taking conditions. Among the upgrades, the installation of new muon stations based on Gas Electron Multiplier (GEM) technology in the endcap will start in early 2019 (GE1/1 station), followed by the installation of two additional stations (GE2/1 and ME0) in 2023. The CMS Muon Collaboration produced the 144 GEM detectors to be installed in the GE1/1 station, sharing the assembly and testing of the detectors among several production sites spread all over the world. A detailed common assembly protocol and quality control procedure (QC) has been deployed, with the ambitious goal to ensure standardization of the performance of the detectors produced by the different sites. The same procedure has been successfully adopted to test the first prototypes of the GE2/1 detectors. In this contribution, we present the final results of the QC tests performed on the GE1/1 chambers, assembled by all the production sites following the common specification parameters.

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

A Multi-TeV muon collider is one of the best candidates for the future development of High Energy Particle physics in the post High Luminosity LHC era. Such a machine will allow to reach high center-of mass energy in leptonic collisions, thus opening the path to a vast and mostly unexplored physics program. However, the design of a suitable detection apparatus represents a technological challenge, mainly because of the unstable nature of the muons. The interaction of the muon decay products with the machine elements, can produce an intense flux of background particles that eventually reach the detector and may degrade its performance. In this contribution, the latest simulation studies performed to optimize the detector design will be presented, together with an overview of the detector technologies that have a potential to match the challenging specifications of a muon collider, with a focus on the ongoing R&D efforts.

The proposal to create a Muon Collider with Multi-TeV energy levels presents an unprecedented opportunity for advancing high energy physics research. With this collider, it will be possible to accurately measure the Higgs coupling with other Standard Model particles, as well as the trilinear and quadrilinear Higgs self-coupling. By doing so, researchers hope to gain a more precise understanding of the Higgs potential and potentially discover evidence of new physics beyond the Standard Model. However, one of the primary challenges for this project is dealing with the high background radiation caused by decaying muons in the beam. To address this, an innovative hadronic calorimeter has been designed that utilizes Micro Pattern Gas Detectors (MPGDs) as active layers. MPGDs are ideal for high radiation environments and offer high granularity for precise spatial measurements. The calorimeter has been optimized for jet reconstruction and background suppression, and its design and layout have been simulated using the Geant4 toolkit to support detector R&D. This article details the design and optimization of the MPGD-based hadronic calorimeter.

The compact muon solenoid (CMS) experiment is a general-purpose detector for high-energy collision at the large hadron collider (LHC) at CERN. It employs an online data quality monitoring (DQM) system to promptly spot and diagnose particle data acquisition problems to avoid data quality loss. In this study, we present semi-supervised spatio-temporal anomaly detection (AD) monitoring for the physics particle reading channels of the hadronic calorimeter (HCAL) of the CMS using three-dimensional digi-occupancy map data of the DQM. We propose the GraphSTAD system, which employs convolutional and graph neural networks to learn local spatial characteristics induced by particles traversing the detector, and global behavior owing to shared backend circuit connections and housing boxes of the channels, respectively. Recurrent neural networks capture the temporal evolution of the extracted spatial features. We have validated the accuracy of the proposed AD system in capturing diverse channel fault types using the LHC Run-2 collision data sets. The GraphSTAD system has achieved production-level accuracy and is being integrated into the CMS core production system--for real-time monitoring of the HCAL. We have also provided a quantitative performance comparison with alternative benchmark models to demonstrate the promising leverage of the presented system.

The Compact Muon Solenoid (CMS) experiment is a general-purpose detector for high-energy collision at the Large Hadron Collider (LHC) at CERN. It employs an online data quality monitoring (DQM) system to promptly spot and diagnose particle data acquisition problems to avoid data quality loss. In this study, we present a semi-supervised spatio-temporal anomaly detection (AD) monitoring system for the physics particle reading channels of the Hadron Calorimeter (HCAL) of the CMS using three-dimensional digi-occupancy map data of the DQM. We propose the GraphSTAD system, which employs convolutional and graph neural networks to learn local spatial characteristics induced by particles traversing the detector and the global behavior owing to shared backend circuit connections and housing boxes of the channels, respectively. Recurrent neural networks capture the temporal evolution of the extracted spatial features. We validate the accuracy of the proposed AD system in capturing diverse channel fault types using the LHC collision data sets. The GraphSTAD system achieves production-level accuracy and is being integrated into the CMS core production system for real-time monitoring of the HCAL. We provide a quantitative performance comparison with alternative benchmark models to demonstrate the promising leverage of the presented system.

All contributions to this work have been refereed as abstracts and subsequently a second time as full papers.

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

The High-Luminosity Large Hadron Collider (HL-LHC) is a major upgrade of the LHC, expected to deliver an integrated luminosity of up to 3000/fb over one decade. The very high instantaneous luminosity will lead to about 200 proton-proton collisions per bunch crossing (pileup) superimposed to each event of interest, therefore providing extremely challenging experimental conditions. The scientific goals of the HL-LHC physics program include precise measurement of the properties of the recently discovered standard model Higgs boson and searches for beyond the standard model physics (heavy vector bosons, SUSY, dark matter and exotic long-lived signatures, to name a few). In this contribution we will present the strategy of the CMS experiment to investigate the feasibility of such search and quantify the increase of sensitivity in the HL-LHC scenario.

During Run-2 the Large Hadron Collider (LHC) has delivered instantaneous luminosities up to 2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">34</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , being twice the design Luminosity. During the second Long Shutdown (LS2) the accelerator complex will be upgraded for the next Run-3 and anticipating the future High Luminosity LHC (HL- LHC) which will start taking data in 2025 with an instantaneous luminosity of 5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">34</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> or even 7.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">34</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> in the ultimate performance scenario. To cope with the corresponding increase in background rates in the forward muon system of CMS and to improve the trigger capabilities to keep the trigger rate at an acceptable level while not compromising the physics potential, the forward muon system of the CMS experiment will be upgraded with Gas Electron Multiplier (GEM) and Resistive Plate Chamber (RPC) detectors. In 2019 triple-GEM detectors will be installed in the first station of the muon detector, while a second station will be installed in 2022. Furthermore to enlarge the acceptance of the muon spectrometer a new station is considered to be installed directly behind the new High-Granularity Calorimeter during LS3 (2023-2024). We will present an overview of the CMS muon detector upgrade with Triple-GEM detectors: operational experience obtained from a test-slice installation in 2017, the production and quality control of the 144 Triple-GEM chambers for the first station, together with the design and prototyping of the Triple-GEM upgrades envisioned until 2024 along with the schedule for their production and quality control.

A muon collider represents the ideal machine to reach very high center-of-mass energies ($\sqrt{s}=1.5-10$ TeV) and luminosities $O$($0.5-10$/ab). A large number of Higgs bosons will be produced mainly through the Vector Boson Fusion ($VBF$) processes. The $VBF$ through Z bosons ($ZZH$) production process could be difficult to disentangle from the dominant $WWZ$, since the final state $VBF$ muons, produced in the very forward region, could escape the detector. As a consequence, at a multi-TeV muon collider, the $H \rightarrow ZZ$ decay process turns out to be favoured to probe exclusively the Higgs boson coupling to Z bosons. In this paper, for the first time, a feasibility study of the search for $H \rightarrow ZZ^{*} \rightarrow 4\mu$ at a 1.5 and 3 TeV muon collider is presented. The study of the four muons final state, performed on fully simulated Monte Carlo samples, allows to optimize the muon reconstruction, thus providing feedback for the detector design. Irreducible backgrounds from Standard Model are studied. A first estimate of the senistivity of the Higgs boson coupling to Z bosons in the $4 \mu$ channel is provided, along with a preliminary evaluation of the impact of the machine background in the 1.5-TeV scenario.

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.

A search for the standard model Higgs boson decaying to τ pair has been performed in proton-proton collision data recorded by CMS detector at LHC at centre of mass energy 8 TeV (7 TeV) corresponding to an integrated luminosity 20 fb−1 (5 fb−1). The production modes considered are gluon-gluon fusion, VBF and associated production with a vector boson. The analysis strategy and the resulting evidence for the Higgs boson in tau pair channel are reported.

The algorithm used for reconstruction and identification of hadronic tau decays by the CMS experiment at the LHC is presented. The tau reconstruction in CMS takes advantage of the particle-flow algorithm which allows to reconstruct individual hadronic decay modes. The performance of the algorithm in terms of tau identification efficiency and rates for jets to be misidentified as hadronic tau decays is measured in pp collision data recorded in 2012 at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb−1

The algorithm used for reconstruction and identification of hadronic tau decays by the CMS experiment at the LHC will be presented. The tau reconstruction in CMS takes advantage of the particle-flow algorithm which allows to reconstruct individual hadronic decay modes. The performance of the algorithm in terms of tau identification efficiency and in terms of the rates with which jets, electrons and muons are misidentified as hadronic tau decays, is measured in pp collision data recorded in 2012 at a center–of–mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb−1.

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

The algorithm used for reconstruction and identification of hadronic tau decays by the CMS experiment at the LHC is presented. The tau reconstruction in CMS takes advantage of the particle-flow algorithm which allows to reconstruct individual hadronic decay modes. The performance of the algorithm in terms of tau identification efficiency and rates for jets to be misidentified as hadronic tau decays is measured in pp collision data recorded in 2012 at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb−1

Nowadays detectors based on Gas Electron Multipliers (GEM) technology are widely used in High Energy Physics. Thanks to their excellent spatial and time resolution, high particle rate capability and a close to 100% detection efficiency, GEM detectors meet all requirements for the upgrade of the CMS end cap. 144 large area trapezoidal triple-GEM detectors will be installed in 2019 in the first station of the end cap of CMS (Compact Muon Solenoid) experiment at the LHC. The features of the new GEM detectors will bring higher resolution of the muon transverse momentum to the first trigger level, lowering the rates in end cap region. This will allow to keep the same performance, both at trigger level and offline, as in the previous LHC runs despite the increased instantaneous luminosity of the colliding beams. In this contribution, after a general introduction and overview of the project, the design of full-size trapezoidal triple-GEM detectors wiU be described, followed by a detailed description of the quality control procedure. Six sites spread all over the world will participate to the assembly and quality control process. The INFN Bari section is one of those site since it successfully completed the commissioning of the labs and the validation of the test procedure.

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

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

A Multi-TeV ($\sqrt{s}$ = 1.5 - 10 TeV) Muon Collider providing $\mathcal{O}(ab^{-1})$ integrated luminosity will be a great opportunity to probe the most intimate nature of the Standard Model (SM) and the Electroweak Symmetry Breaking mechanism, allowing the precise measurement of the Higgs couplings to several SM particles. The study of the Higgs boson couplings to the second generations of fermions is of particular interest due to sensitivity to a whole class of new physics models. It is also true that this measurement is extremely challenging, because of the small branching ratio. Indeed, it is currently not accessible at LHC, where the quantum chromodynamics processes are overwhelming. In this paper it is explored, for the first time, the search for $H \rightarrow c\bar{c}$ at a Multi-TeV Muon Collider. The $\mu^{+} \mu^{-} \rightarrow H \nu\bar{\nu} \rightarrow c\bar{c} \nu\bar{\nu} $ signal process has been fully simulated and reconstructed at $\sqrt{s}=1.5\; TeV$ with a preliminary detector design, along with the main physics backgrounds. The machine background originated from the decay of beam muons, the so-called Beam Induced Background (BIB), is not included in this preliminary study. A c quark-tagging algorithm has been developed, combining several observables in a single discriminator using Machine Learning techniques, with the goal to improve the rejection of jets coming from b-quark and u-d-s-g hadronization. A first estimate of the precision on the Higgs coupling with c-quark reachable with a Muon Collider machine is presented. The relative uncertainty on the coupling at $\sqrt{s}=1.5\; TeV$ is estimated to be 5.5 $\%$. A projection to $\sqrt{s} = 3 \; TeV$ shows that the precision improves with increasing energy, reaching the value of $2.6\%$.

During Run 3 the LHC will deliver instantaneous luminosities in the range 5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">34</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> to 7×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">34</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> . To cope with the high background rates and to improve the trigger capabilities in the forward region, the muon system of the CMS experiment has been upgraded with two new stations of detectors (GE1/1), one in each endcap, based on triple-GEM technology. The system was installed in 2020 and consists of 72 ten-degree chambers, each made up of two layers of triple-GEM detectors. GE1/1 provides two additional muon hit measurements which will improve muon tracking and triggering performance. We report on the status of the ongoing commissioning phase of the detector and present preliminary results obtained from cosmic-ray events. We discuss detector and readout electronics operation, stability and performance, and preparation for Run 3 of the LHC.