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# Search results

954 records were found.

## Measurement of the muon charge asymmetry in inclusive pp to WX production at sqrt(s)=7 TeV and an improved determination of light parton distribution functions

Measurements of the muon charge asymmetry in inclusive pp to WX production at sqrt(s)=7 TeV are presented. The data sample corresponds to an integrated luminosity of 4.7 inverse femtobarns recorded with the CMS detector at the LHC. With a sample of more than twenty million W to mu nu events, the statistical precision is greatly improved in comparison to previous measurements. These new results provide additional constraints on the parton distribution functions of the proton in the range of the Bjorken scaling variable x from 10E-3 to 10E-1. These measurements and the recent CMS measurement of associated W + charm production are used together with the cross sections for inclusive deep inelastic ep scattering at HERA in a next-to-leading-order QCD analysis. The determination of the valence quark distributions is improved, and the strange...

## Observation of Long-Range Near-Side Angular Correlations in Proton-Proton Collisions at the LHC

Results on two-particle angular correlations for charged particles emitted in proton-proton collisions at center-of-mass energies of 0.9, 2.36, and 7 TeV are presented, using data collected with the CMS detector over a broad range of pseudorapidity (eta) and azimuthal angle (phi). Short-range correlations in Delta(eta), which are studied in minimum bias events, are characterized using a simple "independent cluster" parametrization in order to quantify their strength (cluster size) and their extent in eta (cluster decay width). Long-range azimuthal correlations are studied differentially as a function of charged particle multiplicity and particle transverse momentum using a 980 inverse nb data set at 7 TeV. In high multiplicity events, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with int...

## Measurement of the underlying event in the Drell-Yan process in proton-proton collisions at sqrt(s) = 7 TeV

A measurement of the underlying event (UE) activity in proton-proton collisions at a centre-of-mass energy of 7 TeV is performed using Drell--Yan events in a data sample corresponding to an integrated luminosity of 2.2 inverse femtobarns, collected by the CMS experiment at the LHC. The activity measured in the muonic final state (q q-bar to opposite sign muons) is corrected to the particle level and compared with the predictions of various Monte Carlo generators and hadronization models. The dependence of the UE activity on the dimuon invariant mass is well described by PYTHIA and HERWIG++ tunes derived from the leading jet/track approach, illustrating the universality of the UE activity. The UE activity is observed to be independent of the dimuon invariant mass in the region above 40 GeV, while a slow increase is observed with increas...

## Search for pair production of first- and second-generation scalar leptoquarks in pp collisions at sqrt(s)= 7 TeV

Results are presented from a search for the pair production of first- and second-generation scalar leptoquarks in proton-proton collisions at sqrt(s)= 7 TeV. The data sample corresponds to an integrated luminosity of 5.0 inverse femtobarns, collected by the CMS detector at the LHC. The search signatures involve either two charged leptons of the same-flavour (electrons or muons) and at least two jets, or a single charged lepton (electron or muon), missing transverse energy, and at least two jets. If the branching fraction of the leptoquark decay into a charged lepton and a quark is assumed to be beta=1, leptoquark pair production is excluded at the 95% confidence level for masses below 830 GeV and 840 GeV for the first and second generations, respectively. For beta = 0.5, masses below 640 GeV and 650 GeV are excluded. These limits are t...

## Search for a light pseudoscalar Higgs boson in the dimuon decay channel in pp collisions at sqrt(s) = 7 TeV

The dimuon invariant mass spectrum is searched in the range between 5.5 and 14 GeV for a light pseudoscalar Higgs boson "a", predicted in a number of new physics models, including the next-to-minimal supersymmetric standard model. The data sample used in the search corresponds to an integrated luminosity of 1.3 inverse femtobarns collected in pp collisions at sqrt(s) = 7 TeV with the CMS detector at the LHC. No excess is observed above the background predictions and upper limits are set on the cross section times branching fraction sigma times B(pp to "a" to an oppositely charged muon pair) in the range of 1.5-7.5 pb. These results improve on existing bounds on the "a" b-bbar coupling for m("a") < m(Upsilon(1S)) and are the first significant limits for m("a") > m(Upsilon(1S)). Constraints on the supersymmetric parameter space are prese...

## Search for a narrow spin-2 resonance decaying to a pair of Z vector bosons in the semileptonic final state

Results are presented from a search for a narrow, spin-2 resonance decaying into a pair of Z bosons, with one Z-boson decaying into leptons (e+e- or mu+mu-) and the other into jets. An example of such a resonance is the Kaluza--Klein graviton, G[KK], predicted in Randall--Sundrum models. The analysis is based on a 4.9 inverse femtobarn sample of proton-proton collisions at a center-of-mass energy of 7 TeV, collected with the CMS detector at the LHC. Kinematic and topological properties, including decay angular distributions as a novel feature of the analysis, are used to discriminate between signal and background. No evidence for a resonance is observed, and upper limits on the production cross sections times branching fractions are set. In two models that predict Z-boson spin correlations in graviton decays, graviton masses are exclud...

## Search for the standard model Higgs boson produced in association with W and Z bosons in pp collisions at sqrt(s)=7 TeV

A search for the Higgs boson produced in association with a W or Z boson in proton-proton collisions at a center-of-mass energy of 7 TeV is performed with the CMS detector at the LHC using the full 2011 data sample, from an integrated luminosity of 5 inverse femtobarns. Higgs boson decay modes to tau tau and WW are explored by selecting events with three or four leptons in the final state. No excess above the standard model expectation is observed, resulting in exclusion limits on the product of Higgs associated production cross section and decay branching fraction for Higgs boson masses between 110 and 200 GeV in these channels. Combining these results with other CMS associated production searches using the same dataset in the H to gamma gamma and H to b b-bar decay modes, the cross section for associated Higgs boson production 3.3 ti...