183 research outputs found

    Search for supersymmetry in pp collisions at 7 TeV in events with jets and missing transverse energy

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    A search for supersymmetry with R-parity conservation in proton-proton collisions at a centre-of-mass energy of 7 TeV is presented. The data correspond to an integrated luminosity of 35 pb(-1) collected by the CMS experiment at the LHC. The search is performed in events with jets and significant missing transverse energy, characteristic of the decays of heavy, pair-produced squarks and gluinos. The primary background, from standard model multijet production, is reduced by several orders of magnitude to a negligible level by the application of a set of robust kinematic requirements. With this selection, the data are consistent with the standard model backgrounds, namely t (t) over bar, W + jet and Z + jet production, which are estimated from data control samples. Limits are set on the parameters of the constrained minimal supersymmetric extension of the standard model. These limits extend those set previously by experiments at the Tevatron and LEP colliders. (C) 2011 CMS Collaboration

    Erratum: Measurement of the t(t)over-bar production cross section in the dilepton channel in pp collisions at root s = 8 TeV (vol 2, 024, 2014)

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    Search for pair production of second-generation scalar leptoquarks in pp collisions at √s=7 TeV

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    This is the pre-print version of the Published Article which can be accessed from the link below.A search for pair production of second-generation scalar leptoquarks in the final state with two muons and two jets is performed using proton-proton collision data at √s=7  TeV collected by the CMS detector at the LHC. The data sample used corresponds to an integrated luminosity of 34  pb-1. The number of observed events is in good agreement with the predictions from the standard model processes. An upper limit is set on the second-generation leptoquark cross section times β2 as a function of the leptoquark mass, and leptoquarks with masses below 394 GeV are excluded at a 95% confidence level for β=1, where β is the leptoquark branching fraction into a muon and a quark. These limits are the most stringent to date

    First measurement of Bose-Einstein correlations in proton-proton collisions at √s=0.9 and 2.36 TeV at the LHC

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    Bose-Einstein correlations have been measured using samples of proton-proton collisions at 0.9 and 2.36 TeV center-of-mass energies, recorded by the CMS experiment at the CERN Large Hadron Collider. The signal is observed in the form of an enhancement of pairs of same-sign charged particles with small relative four-momentum. The size of the correlated particle emission region is seen to increase significantly with the particle multiplicity of the event

    Transverse-momentum and pseudorapidity distributions of charged hadrons in pp collisions at √s=7 TeV

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    This is the pre-print version of the Published Article which can be accessed from the link below.Charged-hadron transverse-momentum and pseudorapidity distributions in proton-proton collisions at √s=7  TeV are measured with the inner tracking system of the CMS detector at the LHC. The charged-hadron yield is obtained by counting the number of reconstructed hits, hit pairs, and fully reconstructed charged-particle tracks. The combination of the three methods gives a charged-particle multiplicity per unit of pseudorapidity dNch/dη||η|<0.5=5.78±0.01(stat)±0.23(syst) for non-single-diffractive events, higher than predicted by commonly used models. The relative increase in charged-particle multiplicity from √s=0.9 to 7 TeV is [66.1±1.0(stat)±4.2(syst)]%. The mean transverse momentum is measured to be 0.545±0.005(stat)±0.015(syst)  GeV/c. The results are compared with similar measurements at lower energies

    Observation of long-range, near-side angular correlations in proton-proton collisions at the LHC

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    This is the pre-print version of the Published Article, which can be accessed from the link below - Copyright @ 2010 Springer VerlagResults 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 intermediate transverse momentum of 1-3 GeV/c, 2.0< |Delta(eta)| <4.8 and Delta(phi) near 0. This is the first observation of such a long-range, near-side feature in two-particle correlation functions in pp or p p-bar collisions

    Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC

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    Measurement of the B+ Production Cross Section in pp Collisions at root s=7 TeV

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    Measurements of the total and differential cross sections d sigma/dp(T)(B) and d sigma/dy(B) for B+ mesons produced in pp collisions at root s = 7 TeV are presented. The data correspond to an integrated luminosity of 5.8 pb(-1) collected by the CMS experiment operating at the LHC. The exclusive decay B+ -> J/psi K+, with J/psi -> mu(+)mu(-), is used to detect B+ mesons and to measure the production cross section as a function of p(T)(B) and y(B). The total cross section for p(T)(B) > 5 GeV and vertical bar y(B)vertical bar < 2.4 is measured to be 28.1 +/- 2.4 +/- 2.0 +/- 3.1 mu b, where the first uncertainty is statistical, the second is systematic, and the last is from the luminosity measurement

    Erratum: Search for dijet resonances in 7 TeV pp collisions at CMS (Physical Review Letters (2010) 105 (211801))

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    Search for Dijet Resonances in 7 TeV pp Collisions at CMS (vol 105, 211801, 2010)

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    Publisher’s Note: Search for Dijet Resonances in 7 TeV pp Collisions at CMS [Phys. Rev. Lett. 105, 211801 (2010)
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