1,655 research outputs found
CMS endcap RPC gas gap production for upgrade
The CMS experiment will install a RE4 layer of 144 new Resistive Plate Chambers (RPCs) on the existing york YE3 at both endcap regions to trigger high momentum muons from the proton-proton interaction. In this paper, we present the detailed procedures used in the production of new RPC gas gaps adopted in the CMS upgrade. Quality assurance is enforced as ways to maintain the same quality of RPC gas gaps as the existing 432 endcap RPC chambers that have been operational since the beginning of the LHC operation
Performance of the Gas Gain Monitoring system of the CMS RPC muon detector and effective working point fine tuning
The Gas Gain Monitoring (GGM) system of the Resistive Plate Chamber (RPC)
muon detector in the Compact Muon Solenoid (CMS) experiment provides fast and
accurate determination of the stability in the working point conditions due to
gas mixture changes in the closed loop recirculation system. In 2011 the GGM
began to operate using a feedback algorithm to control the applied voltage, in
order to keep the GGM response insensitive to environmental temperature and
atmospheric pressure variations. Recent results are presented on the feedback
method used and on alternative algorithms
The Upgrade of the CMS RPC System during the First LHC Long Shutdown
The CMS muon system includes in both the barrel and endcap region Resistive
Plate Chambers (RPC). They mainly serve as trigger detectors and also improve
the reconstruction of muon parameters. Over the years, the instantaneous
luminosity of the Large Hadron Collider gradually increases. During the LHC
Phase 1 (~first 10 years of operation) an ultimate luminosity is expected above
its design value of 10^34/cm^2/s at 14 TeV. To prepare the machine and also the
experiments for this, two long shutdown periods are scheduled for 2013-2014 and
2018-2019. The CMS Collaboration is planning several detector upgrades during
these long shutdowns. In particular, the muon detection system should be able
to maintain a low-pT threshold for an efficient Level-1 Muon Trigger at high
particle rates. One of the measures to ensure this, is to extend the present
RPC system with the addition of a 4th layer in both endcap regions. During the
first long shutdown, these two new stations will be equipped in the region
|eta|<1.6 with 144 High Pressure Laminate (HPL) double-gap RPCs operating in
avalanche mode, with a similar design as the existing CMS endcap chambers.
Here, we present the upgrade plans for the CMS RPC system for the fist long
shutdown, including trigger simulation studies for the extended system, and
details on the new HPL production, the chamber assembly and the quality control
procedures.Comment: 9 pages, 6 figures, presented by M.Tytgat at the XI workshop on
Resistive Plate Chambers and Related Detectors (RPC2012), INFN - Laboratori
Nazionali di Frascati, February 5-10, 201
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
An overview of the design, construction and performance of large area triple-GEM prototypes for future upgrades of the CMS forward muon system
GEM detectors are used in high energy physics experiments given their good spatial resolution, high rate capability and radiation hardness. An international collaboration is investigating the possibility of covering the 1.6 < vertical bar eta vertical bar < 2.4 region of the CMS muon endcaps with large-area triple-GEM detectors. The CMS high-eta area is actually not fully instrumented, only Cathode Strip Chamber (CSC) are installed. The vacant area presents an opportunity for a detector technology able to to cope with the harsh radiation environment; these micropattern gas detectors are an appealing option to simultaneously enhance muon tracking and triggering capabilities in a future upgrade of the CMS detector. A general overview of this feasibility study is presented. Design and construction of small (10cm x 10cm) and full-size trapezoidal (1m x 0.5m) triple-GEM prototypes is described. Results from measurements with x-rays and from test beam campaigns at the CERN SPS is shown for the small and large prototypes. Preliminary simulation studies on the expected muon reconstruction and trigger performances of this proposed upgraded muon system are reported
Construction and Performance of Large-Area Triple-GEM Prototypes for Future Upgrades of the CMS Forward Muon System
At present, part of the forward RPC muon system of the CMS detector at the
CERN LHC remains uninstrumented in the high-\eta region. An international
collaboration is investigating the possibility of covering the 1.6 < |\eta| <
2.4 region of the muon endcaps with large-area triple-GEM detectors. Given
their good spatial resolution, high rate capability, and radiation hardness,
these micro-pattern gas detectors are an appealing option for simultaneously
enhancing muon tracking and triggering capabilities in a future upgrade of the
CMS detector. A general overview of this feasibility study will be presented.
The design and construction of small (10\times10 cm2) and full-size trapezoidal
(1\times0.5 m2) triple-GEM prototypes will be described. During detector
assembly, different techniques for stretching the GEM foils were tested.
Results from measurements with x-rays and from test beam campaigns at the CERN
SPS will be shown for the small and large prototypes. Preliminary simulation
studies on the expected muon reconstruction and trigger performances of this
proposed upgraded muon system will be reported.Comment: 7 pages, 25 figures, submitted for publication in conference record
of the 2011 IEEE Nuclear Science Symposium, Valencia, Spai
Simulation of the CMS Resistive Plate Chambers
The Resistive Plate Chamber (RPC) muon subsystem contributes significantly to
the formation of the trigger decision and reconstruction of the muon trajectory
parameters. Simulation of the RPC response is a crucial part of the entire CMS
Monte Carlo software and directly influences the final physical results. An
algorithm based on the parametrization of RPC efficiency, noise, cluster size
and timing for every strip has been developed. Experimental data obtained from
cosmic and proton-proton collisions at TeV have been used for
determination of the parameters. A dedicated validation procedure has been
developed. A good agreement between the simulated and experimental data has
been achieved.Comment: to be published in JINS
Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at = 5.02 TeV
Two-particle angular correlations between unidentified charged trigger and
associated particles are measured by the ALICE detector in p-Pb collisions at a
nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum
range 0.7 5.0 GeV/ is examined,
to include correlations induced by jets originating from low
momen\-tum-transfer scatterings (minijets). The correlations expressed as
associated yield per trigger particle are obtained in the pseudorapidity range
. The near-side long-range pseudorapidity correlations observed in
high-multiplicity p-Pb collisions are subtracted from both near-side
short-range and away-side correlations in order to remove the non-jet-like
components. The yields in the jet-like peaks are found to be invariant with
event multiplicity with the exception of events with low multiplicity. This
invariance is consistent with the particles being produced via the incoherent
fragmentation of multiple parton--parton scatterings, while the yield related
to the previously observed ridge structures is not jet-related. The number of
uncorrelated sources of particle production is found to increase linearly with
multiplicity, suggesting no saturation of the number of multi-parton
interactions even in the highest multiplicity p-Pb collisions. Further, the
number scales in the intermediate multiplicity region with the number of binary
nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/161
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
Multi-particle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider
Measurements of multi-particle azimuthal correlations (cumulants) for charged
particles in p-Pb and Pb-Pb collisions are presented. They help address the
question of whether there is evidence for global, flow-like, azimuthal
correlations in the p-Pb system. Comparisons are made to measurements from the
larger Pb-Pb system, where such evidence is established. In particular, the
second harmonic two-particle cumulants are found to decrease with multiplicity,
characteristic of a dominance of few-particle correlations in p-Pb collisions.
However, when a gap is placed to suppress such correlations,
the two-particle cumulants begin to rise at high-multiplicity, indicating the
presence of global azimuthal correlations. The Pb-Pb values are higher than the
p-Pb values at similar multiplicities. In both systems, the second harmonic
four-particle cumulants exhibit a transition from positive to negative values
when the multiplicity increases. The negative values allow for a measurement of
to be made, which is found to be higher in Pb-Pb collisions at
similar multiplicities. The second harmonic six-particle cumulants are also
found to be higher in Pb-Pb collisions. In Pb-Pb collisions, we generally find
which is indicative of a Bessel-Gaussian
function for the distribution. For very high-multiplicity Pb-Pb
collisions, we observe that the four- and six-particle cumulants become
consistent with 0. Finally, third harmonic two-particle cumulants in p-Pb and
Pb-Pb are measured. These are found to be similar for overlapping
multiplicities, when a gap is placed.Comment: 25 pages, 11 captioned figures, 3 tables, authors from page 20,
published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/87
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