10,897 research outputs found
Triggering on hard probes in heavy ion collisions with CMS
We present a study of the CMS trigger system in heavy-ion collisions.
Concentrating on two physics channels, dimuons from decays of quarkonia and
single jets, we evaluate a possible trigger strategy for Pb+Pb running that
relies on event selection solely in the High-Level Trigger (HLT). The study is
based on measurements of the timing performance of the offline algorithms and
event-size distributions using full simulations. Using a trigger simulation
chain, we compare the physics reach for the jet and dimuon channels using
online selection in the HLT to minimum bias running. The results demonstrate
the crucial role the HLT will play for CMS heavy-ion physics.Comment: 4 pages, 4 fugures, contribution to QM'06 conferenc
CMS reconstruction improvement for the muon tracking by the RPC chambers
The contribution of Resistive Plate Chamber (RPC) to muon reconstruction in
CMS has been studied on a sample of muons collected in proton-proton collisions
at sqrt(s) = 7 TeV at the LHC in 2011. Muon reconstruction is performed using
the all-silicon inner tracker and with up to four stations of gas-ionization
muon detectors. Drift Tubes and Cathode Strip Chambers detect muons in the
barrel and endcap regions, respectively, and are complemented by the RPC
system. Measured distributions of reconstructed hits in the RPCs crossed by
muons from Z decays with a transverse momentum pT above 20 GeV/c are well
reproduced by the Monte Carlo simulation. From the samples of J/psi and Z
events, the efficiencies for muons with and without the inclusion of the RPC
hits in the muon track reconstruction are measured and compared with the
simulation. Using RPC information in track reconstruction improves up to about
3% of offline reconstruction efficiency for the muons in the region of pT above
7 GeV/c, in good agreement with simulation.Comment: Presented by Minsuk Kim at the XI workshop on Resistive Plate
Chambers and Related Detectors - RPC2012, INFN Laboratori Nazionali di
Frascati Italy, February 5-10, 201
Dihadron correlations in PbPb collisions at 2.76 TeV with CMS
Measurements of charged dihadron DeltaEta-DeltaPhi correlations from the CMS
collaboration are presented for PbPb collisions at a center-of-mass energy of
2.76 TeV per nucleon pair over a broad range of pseudorapidity and the full
range of azimuthal angle. A significant correlated yield is observed for pairs
of particles with small DeltaPhi but large longitudinal separation DeltaEta,
commonly known as the "ridge". The ridge persists up to at least |DeltaEta| = 4
and the dependence of the ridge region shape and yield on collision centrality
and transverse momentum has been measured. A Fourier analysis of the long-range
two-particle correlation is presented and discussed in the context of higher
order flow coefficients.Comment: Proceedings of presentation given at Quark Matter 201
LHC Coverage of RPV MSSM with Light Stops
We examine the sensitivity of recent LHC searches to signatures of
supersymmetry with R-parity violation (RPV). Motivated by naturalness of the
Higgs potential, which would favor light third-generation squarks, and the
stringent LHC bounds on spectra in which the gluino or first and second
generation squarks are light, we focus on scenarios dominated by the pair
production of light stops. We consider the various possible direct and cascade
decays of the stop that involve the trilinear RPV operators. We find that in
many cases, the existing searches exclude stops in the natural mass range and
beyond. However, typically there is little or no sensitivity to cases dominated
by UDD operators or LQD operators involving taus. We propose several ideas for
searches which could address the existing gaps in experimental coverage of
these signals.Comment: 41 pages, 12 figures; v2: included new searches (see footnote 10),
minor corrections and improvement
Search for a heavy Higgs boson decaying to a pair of W bosons in proton-proton collisions at 13 TeV
A search for a heavy Higgs boson in the mass range from 0.2 to 3.0 TeV,
decaying to a pair of W bosons, is presented. The analysis is based on
proton-proton collisions at 13 TeV recorded by the CMS experiment
at the LHC in 2016, corresponding to an integrated luminosity of 35.9
fb. The W boson pair decays are reconstructed in the 22 and
2q final states (with e or ). Both gluon fusion and
vector boson fusion production of the signal are considered. Interference
effects between the signal and background are also taken into account. The
observed data are consistent with the standard model (SM) expectation. Combined
upper limits at 95% confidence level on the product of the cross section and
branching fraction exclude a heavy Higgs boson with SM-like couplings and
decays up to 1870 GeV. Exclusion limits are also set in the context of a number
of two-Higgs-doublet model formulations, further reducing the allowed parameter
space for SM extensions.Comment: Replaced with the published version. Added the journal reference and
the DOI. All the figures and tables can be found at
http://cms-results.web.cern.ch/cms-results/public-results/publications/HIG-17-033
(CMS Public Pages
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