Progress in the development of Fast Timing Micro-pattern Gaseous Detectors

Advances in the photo-lithographic techniques during the last twenty years have led to the development of micro-pattern gaseous detectors (MPGD). Their main features include high rate capability and radiation hardness, excellent spatial resolution, good time resolution, reduced radiation length and possible flexible geometries. In recent years the further development of MPGDs concentrated on using resistive materials to build compact spark-protected detectors. The use of resistive materials also opened the possibility to make electrically transparent structures with external signal pick-up electrodes. This allowed for a new idea to improve the time resolution through a multi-layered detector, consisting of alternating drift and amplification regions, where the fastest signal determines the detection time. This so-called Fast Timing MPGD (FTM) was firstly introduced by Rui de Oliveira et al. in 2015 [1] and aims to combine both the high spatial resolution and the high rate capability of a MPGD with a high time resolution of the order of 300 ps. Here, we introduce the design of a new single-layer prototype to test the gain of the amplification structure. Preliminary results on the detector characterization will be shown

Dark-SUSY channels to study muon reconstruction performance at the Muon Collider

In the context of simulation and reconstruction for the Muon Collider, muon reconstruction efficiency has been evaluated to explore the potential for the study of dark-SUSY channels. In dark-SUSY models, supersymmetric particles act as a portal between Standard Model particles and the dark sector. In this analysis, the lightest Minimal Supersymmetric Standard Model neutralino decays, on one hand, directly in a dark photon or, on the other hand, in two dark photons through a dark Higgs boson. A muon pair, with kinematics driven by the photon mass, is then expected from each dark photon. Therefore, the final state is characterized by four muons in one channel and eight muons in the other. Preliminary results of the muon reconstruction performance are shown for a possible range of neutralino and dark photon masses at a centre of mass energy of 3 TeV for the time being without the effects of the machine Beam-Induced Background

Muon reconstruction performance and detector-design considerations for a Muon Collider

A muon collider has a great potential for particle physics giving the possibility to reach the high center-of-mass energy and luminosity of hadron colliders, with a greatly reduced pile up effect. However, a series of challenges arise mainly from the short muon lifetime and the Beam-induced Background. A complete simulation, based on CLIC’s ILCSoft software, is ongoing to understand the performance of the full detector. Concerning the muon system, the iron yoke plates are meant to be instrumented with layers of track sensitive chamber to enhance the muon identification. At the moment, according to CLIC geometry, glass Resistive Plate Chambers with readout cells of 30x30 mm2 have been adopted both for the barrel and the endcap region. Other possible solutions, based on MicroPattern Gaseous Detectors, will be discussed considering their characteristics and performance. The results of a preliminary study investigating the muon reconstruction efficiency, Beam-induced Background sensitivity and background mitigation are presented for muon beams collisions at a center-of-mass energy of 1.5 TeV

Higgs physics possibilities at a Muon Collider

Muon collisions at multi-TeV center-of-mass energies are ideal for studying the Higgs-boson properties. The large number of produced Higgs bosons will allow to measure its couplings to fermions and bosons with an unprecedented precision. At multi-TeV centre-of-mass energies, the double (triple) Higgs-boson production rate will be sufficiently high to directly measure the parameters of trilinear (quadrilinear) self-couplings, enabling the precise determination of the Higgs boson potential. In this contribution a study of the μμ→Hνν and μμ→HHνν processes, where the Higgs bosons decay in two b-jets, is presented based on the full simulation of the detector with an evaluation of the beam-induced background

Detector Performance Studies at a Muon Collider

A Muon Collider represents a possible option for the next generation of high-energy machines. Among the technological challenges in the realization of such a machine, the mitigation of the beam-induced background is one of the most critical issues for the experiments. At the desired instantaneous luminosity, the decay rate of the circulating muons is very high, the decay products and subsequent particles from their interactions with the machine elements can reach the detector and compromise its performance. In this contribution, the results of a first preliminary study is presented of the beam-induced background effects on the detector response in the case of muon beams collisions at a center of mass energy of 1.5 TeV and some background mitigation strategies are illustrated

Measurements of properties of the Higgs boson decaying to a W boson pair in pp collisions at s=13TeV

Measurements of the production of the standard model Higgs boson decaying to a W boson pair are reported. The W + W − candidates are selected in events with an oppositely charged lepton pair, large missing transverse momentum, and various numbers of jets. To select Higgs bosons produced via vector boson fusion and associated production with a W or Z boson, events with two jets or three or four leptons are also selected. The event sample corresponds to an integrated luminosity of 35.9fb −1 , collected in pp collisions at s=13TeV by the CMS detector at the LHC during 2016. Combining all channels, the observed cross section times branching fraction is 1.28 −0.17+0.18 times the standard model prediction for the Higgs boson with a mass of 125.09GeV. This is the first observation of the Higgs boson decay to W boson pairs by the CMS experiment

A new calibration method for charm jet identification validated with proton-proton collision events at √s = 13 TeV

Many measurements at the LHC require efficient identification of heavy-flavour jets, i.e. jets originating from bottom (b) or charm (c) quarks. An overview of the algorithms used to identify c jets is described and a novel method to calibrate them is presented. This new method adjusts the entire distributions of the outputs obtained when the algorithms are applied to jets of different flavours. It is based on an iterative approach exploiting three distinct control regions that are enriched with either b jets, c jets, or light-flavour and gluon jets. Results are presented in the form of correction factors evaluated using proton-proton collision data with an integrated luminosity of 41.5 fb-1 at √s = 13 TeV, collected by the CMS experiment in 2017. The closure of the method is tested by applying the measured correction factors on simulated data sets and checking the agreement between the adjusted simulation and collision data. Furthermore, a validation is performed by testing the method on pseudodata, which emulate various mismodelling conditions. The calibrated results enable the use of the full distributions of heavy-flavour identification algorithm outputs, e.g. as inputs to machine-learning models. Thus, they are expected to increase the sensitivity of future physics analyses

Triple-GEM discharge probability studies at CHARM: Simulations and experimental results

The CMS muon system in the region with 2.03<|η|<2.82 is characterized by a very harsh radiation environment which can generate hit rates up to 144 kHz/cm$^{2}$ and an integrated charge of 8 C/cm$^{2}$ over ten years of operation. In order to increase the detector performance and acceptance for physics events including muons, a new muon station (ME0) has been proposed for installation in that region. The technology proposed is Triple—Gas Electron Multiplier (Triple-GEM), which has already been qualified for the operation in the CMS muon system. However, an additional set of studies focused on the discharge probability is necessary for the ME0 station, because of the large radiation environment mentioned above. A test was carried out in 2017 at the Cern High energy AcceleRator Mixed (CHARM) facility, with the aim of giving an estimation of the discharge probability of Triple-GEM detectors in a very intense radiation field environment, similar to the one of the CMS muon system. A dedicated standalone Geant4 simulation was performed simultaneously, to evaluate the behavior expected in the detector exposed to the CHARM field. The geometry of the detector has been carefully reproduced, as well as the background field present in the facility. This paper presents the results obtained from the Geant4 simulation, in terms of sensitivity of the detector to the CHARM environment, together with the analysis of the energy deposited in the gaps and of the processes developed inside the detector. The discharge probability test performed at CHARM will be presented, with a complete discussion of the results obtained, which turn out to be consistent with measurements performed by other groups