1,952 research outputs found
GEM Detectors for the CMS Endcap Muon System: status of three new detector stations
The High-Luminosity LHC (HL-LHC, or Phase 2 LHC) will deliver proton-proton
collisions at 5-7.5 times the nominal LHC luminosity, with an expected number
of 140-200 pp-interactions per bunch crossing (Pile-up or PU). To maintain the
performance of muon triggering and reconstruction under high background
radiation, the forward part of the Muon spectrometer of the CMS experiment will
be upgraded with Gas Electron Multipliers (GEM) and improved Resistive Plate
Chambers (iRPC) detectors. A first GEM station (GE1/1) was installed during
long-shutdown 2 (LS2, 2019-2021), a 2 station (GE2/1) of
Triple-GEM detectors will be installed in winter 2023-24 and 2024-25, while a
new 6-layer station (ME0) will be installed in the third long shutdown (LS3,
2026-2028). GE11 is considered an early Phase 2 upgrade as it will reduce the
threshold by combining GEM and Cathode Strip Chamber (CSC) hits in the
forward muon system at twice the LHC design luminosity ( cms, 50 PU). After a successful start of Run 3 in 2022,
with almost 40 fb collected, the commissioning of the GE1/1 detector is
nearly complete. Most chambers are operated stabily with an efficiency in
excess of 95%, next being the demonstration of the combined CSC-GEM trigger in
2023. The lessons learnt with the first large-area GEM station have lead to
improvements in detector and electronics design for the Phase 2 detectors GE2/1
and ME0. This proceeding will discuss the progress made since last MPGD
Conference (MPGD 2019), discussing the commissioning and early performance of
GE1/1; the design improvements and start of construction of GE2/1; and the R&D
currently ongoing for ME0.Comment: The 7th International Conference on Micro Pattern Gaseous Detectors,
MPGD202
Data-driven determination of Z(νν) background to new-physics searches with jets and missing transverse momentum at CMS
Production and characterization of random electrode sectorization in GEM foils
In triple-GEM detectors, the segmentation of GEM foils in electrically
independent sectors allows reducing the probability of discharge damage to the
detector and improving the detector rate capability; however, a segmented foil
presents thin dead regions in the separation between two sectors and the
segmentation pattern has to be manually aligned with the GEM hole pattern
during the foil manufacturing, a procedure potentially sensitive to errors.
We describe the production and characterization of triple-GEM detectors
produced with an innovative GEM foil segmentation technique, the ``random hole
segmentation'', that allows an easier manufacturing of segmented GEM foils. The
electrical stability to high voltage and the gain uniformity of a random-hole
segmented triple-GEM prototype are measured. The results of a test beam on a
prototype assembled for the Phase-2 GEM upgrade of the CMS experiment are also
presented; a high-statistics efficiency measurement shows that the random hole
segmentation can limit the efficiency loss of the detector in the areas between
two sectors, making it a viable alternative to blank segmentation for the GEM
foil manufacturing of large-area detector systems
Tests of multigap RPCs for high-eta triggers in CMS
In this paper, we report a systematic study of multigap Resistive Plate Chambers (RPCs) for high-eta triggers in CMS. Prototype RPC modules with four- and six-gap structures have been constructed with phenolic high-pressure-laminated (HPL) plates and tested with cosmic muons and gamma rays irradiated from a 200-mCi Cs-137 source. The detector characteristics of the prototype multigap RPCs were compared with those of the double-gap RPCs currently used in the CMS experiment at LHC. The mean values for detector charges of cosmic-muon signals drawn in the four- and six-gap RPCs for the efficiency values in the middle of the plateau were about 1.5 and 0.9 pC, respectively, when digitized with charge thresholds of 150 and 100 fC, respectively. They were respectively about one third and one fifth of that drawn in the current CMS double-gap RPC with a charge threshold of 200 fC. We concluded from the current R&D that use of the current phenolic-HPL multigap RPCs is advantageous to the high-eta triggers in CMS in virtue of the smaller detector pulses
Towards a muon collider
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
Towards a Muon Collider
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.Comment: 118 pages, 103 figure
Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV
Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio
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