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Measurement of the rapidity and transverse momentum distributions ofZbosons inppcollisions at(s)=7 TeV. Int J Clin Exp Med 2012. [DOI: 10.1103/physrevd.85.032002] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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2
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Search for a vectorlike quark with charge 2/3 in t+Z events from pp collisions at √s=7 TeV. PHYSICAL REVIEW LETTERS 2011; 107:271802. [PMID: 22243304 DOI: 10.1103/physrevlett.107.271802] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Indexed: 05/31/2023]
Abstract
A search for pair-produced heavy vectorlike charge-2/3 quarks, T, in pp collisions at a center-of-mass energy of 7 TeV, is performed with the CMS detector at the LHC. Events consistent with the flavor-changing-neutral-current decay of a T quark to a top quark and a Z boson are selected by requiring two leptons from the Z-boson decay, as well as an additional isolated charged lepton. In a data sample corresponding to an integrated luminosity of 1.14 fb(-1), the number of observed events is found to be consistent with the standard model background prediction. Assuming a branching fraction of 100% for the decay T→tZ, a T quark with a mass less than 475 GeV/c(2) is excluded at the 95% confidence level.
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3
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Search for supersymmetry at the LHC in events with jets and missing transverse energy. PHYSICAL REVIEW LETTERS 2011; 107:221804. [PMID: 22182023 DOI: 10.1103/physrevlett.107.221804] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Indexed: 05/31/2023]
Abstract
A search for events with jets and missing transverse energy is performed in a data sample of pp collisions collected at √s=7 TeV by the CMS experiment at the LHC. The analyzed data sample corresponds to an integrated luminosity of 1.14 fb(-1). In this search, a kinematic variable α(T) is used as the main discriminator between events with genuine and misreconstructed missing transverse energy. No excess of events over the standard model expectation is found. Exclusion limits in the parameter space of the constrained minimal supersymmetric extension of the standard model are set. In this model, squark masses below 1.1 TeV are excluded at 95% C.L. Gluino masses below 1.1 TeV are also ruled out at 95% C.L. for values of the universal scalar mass parameter below 500 GeV.
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Search for new physics with a monojet and missing transverse energy in pp collisions at √s = 7 TeV. PHYSICAL REVIEW LETTERS 2011; 107:201804. [PMID: 22181725 DOI: 10.1103/physrevlett.107.201804] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Indexed: 05/31/2023]
Abstract
A study of events with missing transverse energy and an energetic jet is performed using pp collision data at a center-of-mass energy of 7 TeV. The data were collected by the CMS detector at the LHC, and correspond to an integrated luminosity of 36 pb(-1). An excess of these events over standard model contributions is a signature of new physics such as large extra dimensions and unparticles. The number of observed events is in good agreement with the prediction of the standard model, and significant extension of the current limits on parameters of new physics benchmark models is achieved.
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5
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Search for B(s)(0) → μ+ μ- and B(0) → μ+ μ- decays in pp collisions at sqrt[s] = 7 TeV. PHYSICAL REVIEW LETTERS 2011; 107:191802. [PMID: 22181597 DOI: 10.1103/physrevlett.107.191802] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Indexed: 05/31/2023]
Abstract
A search for the rare decays B(s)(0) → μ+ μ- and B(0) → μ+ μ- is performed in pp collisions at sqrt[s] = 7 TeV, with a data sample corresponding to an integrated luminosity of 1.14 fb(-1), collected by the CMS experiment at the LHC. In both cases, the number of events observed after all selection requirements is consistent with expectations from background and standard-model signal predictions. The resulting upper limits on the branching fractions are B(B(s)(0) → μ+ μ-) < 1.9 × 10(-8) and B(B(0) → μ+ μ-)<4.6 × 10(-9), at 95% confidence level.
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6
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Measurement of the inclusive jet cross section in pp collisions at √s = 7 TeV. PHYSICAL REVIEW LETTERS 2011; 107:132001. [PMID: 22026843 DOI: 10.1103/physrevlett.107.132001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Indexed: 05/31/2023]
Abstract
The inclusive jet cross section is measured in pp collisions with a center-of-mass energy of 7 TeV at the Large Hadron Collider using the CMS experiment. The data sample corresponds to an integrated luminosity of 34 pb(-1). The measurement is made for jet transverse momenta in the range 18-1100 GeV and for absolute values of rapidity less than 3. The measured cross section extends to the highest values of jet p(T) ever observed and, within the experimental and theoretical uncertainties, is generally in agreement with next-to-leading-order perturbative QCD predictions.
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7
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Search for three-jet resonances in pp collisions at square root(s)=7 TeV. PHYSICAL REVIEW LETTERS 2011; 107:101801. [PMID: 21981492 DOI: 10.1103/physrevlett.107.101801] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2011] [Indexed: 05/31/2023]
Abstract
A search for three-jet hadronic resonance production in pp collisions at a center-of-mass energy of 7 TeV has been conducted by the CMS Collaboration at the LHC, using a data sample corresponding to an integrated luminosity of 35 pb(-1). Events with high jet multiplicity and a large scalar sum of jet transverse momenta are analyzed using a signature-based approach. The number of expected standard model background events is found to be in good agreement with the observed events. Limits on the cross section times branching ratio are set in a model of gluino pair production with an R-parity-violating decay to three quarks, and the data rule out such particles within the mass range of 200 to 280 GeV/c2.
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8
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Measurement of the t-channel single top quark production cross section in pp collisions at √s=7 TeV. PHYSICAL REVIEW LETTERS 2011; 107:091802. [PMID: 21929225 DOI: 10.1103/physrevlett.107.091802] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Indexed: 05/31/2023]
Abstract
Electroweak production of the top quark is measured for the first time in pp collisions at √=7 TeV, using a data set collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 36 pb⁻¹. With an event selection optimized for t-channel production, two complementary analyses are performed. The first one exploits the special angular properties of the signal, together with background estimates from the data. The second approach uses a multivariate analysis technique to probe the compatibility with signal topology expected from electroweak top-quark production. The combined measurement of the cross section is 83.6±29.8(stat+syst)±3.3(lumi) pb, consistent with the standard model expectation.
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9
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Indications of suppression of excited Υ states in Pb-Pb collisions at √(s(NN))=2.76 TeV. PHYSICAL REVIEW LETTERS 2011; 107:052302. [PMID: 21867063 DOI: 10.1103/physrevlett.107.052302] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Indexed: 05/31/2023]
Abstract
A comparison of the relative yields of Υ resonances in the μ(+)μ(-) decay channel in Pb-Pb and pp collisions at a center-of-mass energy per nucleon pair of 2.76 TeV is performed with data collected with the CMS detector at the LHC. Using muons of transverse momentum above 4 GeV/c and pseudorapidity below 2.4, the double ratio of the Υ(2S) and Υ(3S) excited states to the Υ(1S) ground state in Pb-Pb and pp collisions, [Υ(2S+3S)/Υ(1S)](Pb-Pb)/[Υ(2S+3S)/Υ(1S)](pp), is found to be 0.31(-0.15)(+0.19)(stat)±0.03(syst). The probability to obtain the measured value, or lower, if the true double ratio is unity, is calculated to be less than 1%.
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10
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Measurement of the polarization of W bosons with large transverse momenta in W + jets events at the LHC. PHYSICAL REVIEW LETTERS 2011; 107:021802. [PMID: 21797595 DOI: 10.1103/physrevlett.107.021802] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Indexed: 05/31/2023]
Abstract
A first measurement of the polarization of W bosons with large transverse momenta in pp collisions is presented. The measurement is based on 36 pb⁻¹ of data recorded at √s = 7 TeV by the CMS detector at the LHC. The left-handed, right-handed, and longitudinal polarization fractions (f(L), f(R), and f₀, respectively) of W bosons with transverse momenta larger than 50 GeV are determined by using decays to both electrons and muons. The muon final state yields the most precise measurement: (f(L) - f(R))⁻ = 0.240 ± 0.036(stat) ± 0.031(syst) and f₀⁻ = 0.183 ± 0.087(stat) ± 0.123(syst) for negatively charged W bosons and (f(L) - f(R))⁺ = 0.310 ± 0.036(stat) ± 0.017(syst) and f₀⁺ = 0.171 ± 0.085(stat) ± 0.099(syst) for positively charged W bosons. This establishes, for the first time, that W bosons produced in pp collisions with large transverse momenta are predominantly left-handed, as expected in the standard model.
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11
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Measurement of the B0 production cross section in pp collisions at sqrt[s] = 7 TeV. PHYSICAL REVIEW LETTERS 2011; 106:252001. [PMID: 21770632 DOI: 10.1103/physrevlett.106.252001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Indexed: 05/31/2023]
Abstract
Measurements of the differential production cross sections dσ/dpTB and dσ/dyB for B0 mesons produced in pp collisions at sqrt[s] = 7 TeV are presented. The data set used was collected by the CMS experiment at the LHC and corresponds to an integrated luminosity of 40 pb-1. The production cross section is measured from B0 meson decays reconstructed in the exclusive final state J/ψKS0, with the subsequent decays J/ψ → μ + μ - and KS0 → π+}π-. The total cross section for pTB>5 GeV and |yB|<2.2 is measured to be 33.2 ± 2.5 ± 3.5 μb, where the first uncertainty is statistical and the second is systematic.
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12
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Search for neutral minimal supersymmetric standard model Higgs bosons decaying to tau pairs in pp collisions at √s=7 TeV. PHYSICAL REVIEW LETTERS 2011; 106:231801. [PMID: 21770497 DOI: 10.1103/physrevlett.106.231801] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2011] [Indexed: 05/31/2023]
Abstract
A search for neutral minimal supersymmetric standard model (MSSM) Higgs bosons in pp collisions at the LHC at a center-of-mass energy of 7 TeV is presented. The results are based on a data sample corresponding to an integrated luminosity of 36 pb(-1) recorded by the CMS experiment. The search uses decays of the Higgs bosons to tau pairs. No excess is observed in the tau-pair invariant-mass spectrum. The resulting upper limits on the Higgs boson production cross section times branching fraction to tau pairs, as a function of the pseudoscalar Higgs boson mass, yield stringent new bounds in the MSSM parameter space.
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13
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Search for supersymmetry in pp collisions at √7 TeV in events with two photons and missing transverse energy. PHYSICAL REVIEW LETTERS 2011; 106:211802. [PMID: 21699288 DOI: 10.1103/physrevlett.106.211802] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Indexed: 05/31/2023]
Abstract
A search for supersymmetry in the context of general gauge-mediated breaking with the lightest neutralino as the next-to-lightest supersymmetric particle and the gravitino as the lightest is presented. The data sample corresponds to an integrated luminosity of 36 pb(-1) recorded by the CMS experiment at the LHC. The search is performed by using events containing two or more isolated photons, at least one hadronic jet, and significant missing transverse energy. No excess of events at high missing transverse energy is observed. Upper limits on the signal cross section for general gauge-mediated supersymmetry between 0.3 and 1.1 pb at the 95% confidence level are determined for a range of squark, gluino, and neutralino masses, excluding supersymmetry parameter space that was inaccessible to previous experiments.
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14
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Study of Z Boson Production in PbPb Collisions at √S(NN)=2.76 TeV. PHYSICAL REVIEW LETTERS 2011; 106:212301. [PMID: 21699291 DOI: 10.1103/physrevlett.106.212301] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Indexed: 05/31/2023]
Abstract
A search for Z bosons in the μ(+)μ(-) decay channel has been performed in PbPb collisions at √S(NN)=2.76 TeV with the CMS detector at the LHC, in a 7.2 μb(-1) data sample. The number of opposite-sign muon pairs observed in the 60-120 GeV/c(2) invariant mass range is 39, corresponding to a yield per unit of rapidity (y) and per minimum bias event of [33.8±5.5(stat)±4.4(syst)]×10(-8), in the |y|<2.0 range. Rapidity, transverse momentum, and centrality dependencies are also measured. The results agree with next-to-leading order QCD calculations, scaled by the number of incoherent nucleon-nucleon collisions.
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15
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Measurement of dijet angular distributions and search for quark compositeness in pp collisions at √s = 7 TeV. PHYSICAL REVIEW LETTERS 2011; 106:201804. [PMID: 21668222 DOI: 10.1103/physrevlett.106.201804] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Indexed: 05/30/2023]
Abstract
Dijet angular distributions are measured over a wide range of dijet invariant masses in pp collisions at √s = 7 TeV, at the CERN LHC. The event sample, recorded with the CMS detector, corresponds to an integrated luminosity of 36 pb⁻¹. The data are found to be in good agreement with the predictions of perturbative QCD, and yield no evidence of quark compositeness. With a modified frequentist approach, a lower limit on the contact interaction scale for left-handed quarks of Λ⁺ = 5.6 TeV (Λ⁻ = 6.7 TeV) for destructive (constructive) interference is obtained at the 95% confidence level.
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16
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Search for pair production of second-generation scalar leptoquarks in pp collisions at √s = 7 TeV. PHYSICAL REVIEW LETTERS 2011; 106:201803. [PMID: 21668221 DOI: 10.1103/physrevlett.106.201803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Indexed: 05/30/2023]
Abstract
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.
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17
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Search for pair production of first-generation scalar leptoquarks in pp collisions at √s = 7 TeV. PHYSICAL REVIEW LETTERS 2011; 106:201802. [PMID: 21668220 DOI: 10.1103/physrevlett.106.201802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Indexed: 05/30/2023]
Abstract
A search for pair production of first-generation scalar leptoquarks is performed in the final state containing two electrons and two jets using proton-proton collision data at √s = 7 TeV. The data sample used corresponds to an integrated luminosity of 33 pb⁻¹ collected with the CMS detector at the CERN LHC. The number of observed events is in good agreement with the predictions for the standard model background processes, and an upper limit is set on the leptoquark pair production cross section times β² as a function of the leptoquark mass, where β is the branching fraction of the leptoquark decay to an electron and a quark. A 95% confidence level lower limit is set on the mass of a first-generation scalar leptoquark at 384 GeV for β = 1, which is the most stringent direct limit to date.
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18
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Dijet azimuthal decorrelations in pp collisions at √s=7 TeV. PHYSICAL REVIEW LETTERS 2011; 106:122003. [PMID: 21517306 DOI: 10.1103/physrevlett.106.122003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Indexed: 05/30/2023]
Abstract
Measurements of dijet azimuthal decorrelations in pp collisions at √s=7 TeV using the CMS detector at the CERN LHC are presented. The analysis is based on an inclusive dijet event sample corresponding to an integrated luminosity of 2.9 pb⁻¹. The results are compared to predictions from perturbative QCD calculations and various Monte Carlo event generators. The dijet azimuthal distributions are found to be sensitive to initial-state gluon radiation.
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19
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Measurement of the B(+) production cross section in pp collisions at sqrt[s]=7 TeV. PHYSICAL REVIEW LETTERS 2011; 106:112001. [PMID: 21469857 DOI: 10.1103/physrevlett.106.112001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2010] [Indexed: 05/30/2023]
Abstract
Measurements of the total and differential cross sections dσ/dp(T)(B) and dσ/dy(B) for B(+) mesons produced in pp collisions at sqrt[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/ψK(+), with J/ψ→μ(+)μ(-), 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 |y(B)|<2.4 is measured to be 28.1±2.4±2.0±3.1 μb, where the first uncertainty is statistical, the second is systematic, and the last is from the luminosity measurement.
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20
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Measurement of the isolated prompt photon production cross section in pp collisions at √s=7 TeV. PHYSICAL REVIEW LETTERS 2011; 106:082001. [PMID: 21405566 DOI: 10.1103/physrevlett.106.082001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Revised: 01/15/2011] [Indexed: 05/30/2023]
Abstract
The differential cross section for the inclusive production of isolated prompt photons has been measured as a function of the photon transverse energy E(T)(γ) in pp collisions at √s=7 TeV using data recorded by the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 2.9 pb(-1). Photons are required to have a pseudorapidity |η(γ)|<1.45 and E(T)(γ)>21 GeV, covering the kinematic region 0.006<x(T)<0.086. The measured cross section is found to be in agreement with next-to-leading-order perturbative QCD calculations.
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21
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Search for stopped Gluinos in pp collisions at square root s=7 TeV. PHYSICAL REVIEW LETTERS 2011; 106:011801. [PMID: 21231732 DOI: 10.1103/physrevlett.106.011801] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Indexed: 05/30/2023]
Abstract
The results of the first search for long-lived gluinos produced in 7 TeV pp collisions at the CERN Large Hadron Collider are presented. The search looks for evidence of long-lived particles that stop in the CMS detector and decay in the quiescent periods between beam crossings. In a dataset with a peak instantaneous luminosity of 1×10(32) cm-2 s-1, an integrated luminosity of 10 pb-1, and a search interval corresponding to 62 hours of LHC operation, no significant excess above background was observed. Limits at the 95% confidence level on gluino pair production over 13 orders of magnitude of gluino lifetime are set. For a mass difference mg - mχ1(0) >100 GeV/c2, and assuming BR(g→gχ1(0))=100%, mg < 370 GeV/c2 are excluded for lifetimes from 10 μs to 1000 s.
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Search for quark compositeness with the dijet centrality ratio in pp collisions at √s=7 TeV. PHYSICAL REVIEW LETTERS 2010; 105:262001. [PMID: 21231646 DOI: 10.1103/physrevlett.105.262001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Indexed: 05/30/2023]
Abstract
A search for quark compositeness in the form of quark contact interactions, based on hadronic jet pairs (dijets) produced in proton-proton collisions at √s=7 TeV, is described. The data sample of the study corresponds to an integrated luminosity of 2.9 pb(-1) collected with the CMS detector at the LHC. The dijet centrality ratio, which quantifies the angular distribution of the dijets, is measured as a function of the invariant mass of the dijet system and is found to agree with the predictions of the standard model. A statistical analysis of the data provides a lower limit on the energy scale of quark contact interactions. The sensitivity of the analysis is such that the expected limit is 2.9 TeV; because the observed value of the centrality ratio at high invariant mass is below the expectation, the observed limit is 4.0 TeV at the 95% confidence level.
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Search for dijet resonances in 7 TeV pp collisions at CMS. PHYSICAL REVIEW LETTERS 2010; 105:211801. [PMID: 21231289 DOI: 10.1103/physrevlett.105.211801] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Indexed: 05/30/2023]
Abstract
A search for narrow resonances in the dijet mass spectrum is performed using data corresponding to an integrated luminosity of 2.9 pb⁻¹ collected by the CMS experiment at the Large Hadron Collider. Upper limits at the 95% confidence level are presented on the product of the resonance cross section, branching fraction into dijets, and acceptance, separately for decays into quark-quark, quark-gluon, or gluon-gluon pairs. The data exclude new particles predicted in the following models at the 95% confidence level: string resonances, with mass less than 2.50 TeV, excited quarks, with mass less than 1.58 TeV, and axigluons, colorons, and E6 diquarks, in specific mass intervals. This extends previously published limits on these models.
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First measurement of Bose-Einstein correlations in proton-proton collisions at √s=0.9 and 2.36 TeV at the LHC. PHYSICAL REVIEW LETTERS 2010; 105:032001. [PMID: 20867758 DOI: 10.1103/physrevlett.105.032001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Indexed: 05/29/2023]
Abstract
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.
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25
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Transverse-momentum and pseudorapidity distributions of charged hadrons in pp collisions at square root of s = 7 TeV. PHYSICAL REVIEW LETTERS 2010; 105:022002. [PMID: 20867699 DOI: 10.1103/physrevlett.105.022002] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Indexed: 05/29/2023]
Abstract
Charged-hadron transverse-momentum and pseudorapidity distributions in proton-proton collisions at square root of 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 dN(ch)/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 square root of 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.
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26
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The basic requirements for psychotherapists. AUSTRALIAN JOURNAL OF PSYCHOLOGY 2007. [DOI: 10.1080/00049536008255056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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