Filippo Errico

Abstract A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10 TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work.

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.

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.

The Higgs boson mass and its decay width are fundamental properties of this particle. Here we summarise the latest measurements of these properties performed analysing Run 2 data at a centre of mass energy of 13 TeV, with the CMS experiment, in the four-lepton and di-photon final states. The most precise Higgs boson mass measurement is $m_{H}$ = 125.38 $\pm$ 0.14 GeV, while for the width is $\Gamma_{H} = 3.2^{+2.4}_{-1.7}$ MeV, excluding the scenario with $\Gamma_{H}$ = 0 with 3.6 standard deviation.

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.

Although it is well known that chronic ethanol abuse produces sexual dysfunction and impaired spermatogenesis, the mechanisms of ethanol-induced testicular alterations are not fully explained. Therefore, the aim of this study was to investigate the mechanisms of testicular oxidative damage in rats given drinking water containing 3% ethanol for 8 weeks. Control rats were pair-fed with saccharose. The mean daily ethanol intake was 4.05 g kg−1, corresponding to the consumption of 4 l of wine (10% alcohol) or 0.7 l of whiskey (40% alcohol) by a man of 70 kg body wt. Exposure to ethanol caused a significant depletion in the testicular levels of glutathione (GSH), protein containing sulfhydryl groups, tocopherol and ascorbic acid, and an increase in the concentrations of malondialdehyde (index of lipid peroxidation) and carbonyl proteins (index of protein oxidation). Other effects were decreases in the concentration of adenosine 5′-triphosphate and in the activity of glutathione peroxidase, and an increase in the activity of alcohol dehydrogenase. In summary, this study shows that in the rat, daily consumption of ethanol in the drinking water increases lipid and protein oxidation. In addition to impaired antioxidant defence, an imbalance in energy production may also play a role in the toxic reaction to alcohol. © 1997 John Wiley & Sons, Ltd.

A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10 TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work.

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.

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.

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.

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 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.

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.

Oxidative modification of proteins is of great importance because of their biological role in transport, enzyme activity, immune response and membrane fluidity. This study investigated the redox status of proteins in plasma, erythrocyte and erythrocyte ghosts of chronic alcoholics; a comparison with subjects affected by chronic viral hepatitis and healthy controls was also performed. Compared to the other groups, chronic active alcoholics showed significant increase of plasma, erythrocyte and erythrocyte ghost concentrations of carbonyl proteins, marker of protein oxidative damage. Also, a significant correlation was noted between daily alcohol intake and plasma levels of carbonyl proteins. The incubation of fresh human plasma with acetaldehyde, but not with ethanol, led to a significant increase of the carbonyl protein production. In conclusion, plasma, erythrocyte and membrane proteins are oxidatively modified in active chronic alcoholics; these changes seem to be related to acetaldehyde rather than ethanol toxicity.

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.

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.

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 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.

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.

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.

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.

Positron emission tomography (PET) is an effective functional imaging technique especially for cancer diagnosis. Its performance is strictly connected to the ability to detect and reconstruct photons emitted by the positron–electron annihilation. Its sensitivity is enhanced when time information is included (time-of-flight (ToF) PET). The measure of the detection time difference between the annihilation of the two photons leads to a higher contrast image and more accurate diagnoses. We describe the studies for a possible development of a ToF-PET based on Micro Pattern Gas Detector (MPGD). This kind of detector has a very good spatial and time resolution (order of 100 μ m and few ns, respectively) and very low price, making it suitable for a full-body scanner. Further improvement in the time precision (suitable goal is to achieve values of the order of 100 ps) could be reached thanks to the Fast Timing MPGD (FTM) design, where multiple layers of MPGD compete in better measuring time information.

A search for new massive resonances in the dielectron and dimuon decay channels has been performed combining 2015 data collected by the CMS experiment in proton -proton collisions at a center of mass energy of 13 TeV (corresponding to an integrated luminosity of 2.9 fb -1 ) with a previous analysed set of data obtained at 8 TeV (corresponding to 20 fb -1 ).The analysis has been updated with data collected during Run II in 2016 at 13 TeV (13 fb -1 ).In the absence of a significant deviation from the standard model predictions, 95% confidence level limits are set on the ratio of the production cross section times branching fraction for possible new high-mass resonances to that for the Z boson.Limits are set on the masses of hypothetical particles that could appear in new-physics scenarios.

Latest results on Higgs boson property measurements in final states with photons, W and Z bosons are presented, using data collected by the CMS experiment in proton - proton collisions at a center of mass energy $\sqrt{s}$ = 13 $\mathrm{TeV}$ during Run 2, and combining them with data collected during Run 1 at 7-8 $\mathrm{TeV}$.

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 $2.6\%$.