5,824 research outputs found
Measurement of the inelastic proton-proton cross section at = 13 TeV
A measurement of the inelastic proton-proton cross section at a
centre-of-mass energy of = 13 TeV is presented. The analysis is
performed using the CMS detector, in particular with information from forward
calorimetry at pseudorapidities of 3.0 < {\eta} < 5.2 and -6.6 < {\eta} < -3.0.
A visible cross section is measured in two different detector acceptances and
finally extrapolated to the full inelastic phase space domain. The results are
compared with those of other experiments, and with models used to describe
high-energy hadronic interactions.Comment: 5 pages, 2 figures, proceedings of the XXIV International Workshop on
Deep-Inelastic Scattering and Related Subjects, 11-15 April 2016, DESY
Hamburg, German
Treating jet correlations in high pile-up at hadron colliders
Experiments in the high-luminosity runs at the Large Hadron Collider face the
challenges of very large pile-up. Primary techniques to deal with this are
based on precise vertex and track reconstruction. Outside tracker acceptances,
however, lie regions of interest for many aspects of the LHC physics program.
We explore complementary approaches to pile-up treatment and propose a
data-driven jet-mixing method which can be used outside tracker acceptances
without depending on Monte Carlo generators. The method can be applied to treat
correlation observables and take into account, besides the jet transverse
momentum pedestal, effects of hard jets from pile-up.Comment: Latex. 8 pages, 5 figure
Measurements of the forward energy flow and forward jet production with CMS
We present measurements of the forward (3 < |eta| < 5) energy flow in minimum
bias events and in events with either hard jets or W and Z bosons produced at
central rapidities together with first measurements of the inclusive forward
jet cross section and central forward jet correlations. Results are compared to
MC models with different parameter tunes for the description of the underlying
event.Comment: 8 pages, DPF 2011 conference proceeding
Single inclusive jet production and the nuclear modification ratio at very forward rapidity in proton-lead collisions with = 5.02 TeV
We present calculations of single inclusive jet transverse momentum and
energy spectra at forward rapidity () in proton-lead
collisions with = 5.02 TeV. The predictions are obtained with
the KaTie Monte Carlo event generator, which allows to calculate interactions
within the High Energy Factorisation framework. The tree-level matrix element
results are subsequently interfaced with the CASCADE Monte Carlo event
generator to account for hadronisation. The effects of the saturation of the
gluon density, leading to suppression of the cross section, are investigated.Comment: 10 page
Higgs boson as a gluon trigger: the study of QCD in high pile-up environments
In the forthcoming high-luminosity phase of the LHC many of the most
interesting measurements for precision QCD studies are hampered by large
pile-up conditions, especially at not very high transverse momenta. However,
with the recently discovered Higgs boson, which couples in the heavy top limit
directly to gluons, we have access to a novel production process to probe QCD
by a colour-singlet current. In this study we compare observables in Higgs
boson and Drell-Yan production and investigate whether measuring ratios or
subtractions can yield results that are stable in high pile-up environments,
and yet sensitive to (small-) QCD physics in gluon fusion
processes. We present results of Monte Carlo event generator calculations for a
few specific examples.Comment: 7 pages, 10 figures, DIS2014 conference proceeding
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Measurement of double-differential cross sections for top quark pair production in pp collisions at [Formula: see text][Formula: see text] and impact on parton distribution functions.
Normalized double-differential cross sections for top quark pair ([Formula: see text]) production are measured in pp collisions at a centre-of-mass energy of 8[Formula: see text] with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 19.7[Formula: see text]. The measurement is performed in the dilepton [Formula: see text] final state. The [Formula: see text] cross section is determined as a function of various pairs of observables characterizing the kinematics of the top quark and [Formula: see text] system. The data are compared to calculations using perturbative quantum chromodynamics at next-to-leading and approximate next-to-next-to-leading orders. They are also compared to predictions of Monte Carlo event generators that complement fixed-order computations with parton showers, hadronization, and multiple-parton interactions. Overall agreement is observed with the predictions, which is improved when the latest global sets of proton parton distribution functions are used. The inclusion of the measured [Formula: see text] cross sections in a fit of parametrized parton distribution functions is shown to have significant impact on the gluon distribution
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Performance of photon reconstruction and identification with the CMS detector in proton-proton collisions at √s = 8 TeV
A description is provided of the performance of the CMS detector for photon reconstruction and identification in proton-proton collisions at a centre-of-mass energy of 8 TeV at the CERN LHC. Details are given on the reconstruction of photons from energy deposits in the electromagnetic calorimeter (ECAL) and the extraction of photon energy estimates. The reconstruction of electron tracks from photons that convert to electrons in the CMS tracker is also described, as is the optimization of the photon energy reconstruction and its accurate modelling in simulation, in the analysis of the Higgs boson decay into two photons. In the barrel section of the ECAL, an energy resolution of about 1% is achieved for unconverted or late-converting photons from Hγγ decays. Different photon identification methods are discussed and their corresponding selection efficiencies in data are compared with those found in simulated events
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