-
S. Chatrchyan,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
C. Fabjan,
M. Friedl, [......],
J. Leonard,
R. Loveless,
A. Mohapatra,
F. Palmonari,
D. Reeder,
I. Ross,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: A measurement of the t{bar{t}} production cross section in proton-proton
collisions at a centre-of-mass energy of 7 TeV has been performed at the
LHC with the CMS detector. The analysis uses a data sample corresponding
to an integrated luminosity of 36 pb-1 and is based on the
reconstruction of the final state with one isolated, high
transverse-momentum electron or muon and three or more hadronic jets.
The kinematic properties of the events are used to separate the
t{bar{t}} signal from W+jets and QCD multijet background events. The
measured cross section is 173^{+39}_{-32} (stat. + syst.) pb, consistent
with standard model expectations.
European Physical Journal C 08/2011; 71:1721. · 3.63 Impact Factor
-
S Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl, [......],
J Leonard,
R Loveless,
A Mohapatra,
F Palmonari,
D Reeder,
I Ross,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 08/2011; 107(9):091802. · 7.37 Impact Factor
-
S. Chatrchyan,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
C. Fabjan,
M. Friedl, [......],
J. Leonard,
R. Loveless,
A. Mohapatra,
F. Palmonari,
D. Reeder,
I. Ross,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: Results are reported from a search for physics beyond the standard model
in proton-proton collisions at a center-of-mass energy of 7 TeV,
focusing on the signature with a single, isolated,
high-transverse-momentum lepton (electron or muon), energetic jets, and
large missing transverse momentum. The data sample comprises an
integrated luminosity of 36 pb-1, recorded by the CMS
experiment at the LHC. The search is motivated by models of new physics,
including supersymmetry. The observed event yields are consistent with
standard model backgrounds predicted using control samples obtained from
the data. The characteristics of the event sample are consistent with
those expected for the production of {text{t}bar{text{t}}} and W + jets
events. The results are interpreted in terms of limits on the parameter
space for the constrained minimal supersymmetric extension of the
standard model.
Journal of High Energy Physics 07/2011; 8:156. · 5.83 Impact Factor
-
S. Chatrchyan,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
C. Fabjan,
M. Friedl, [......],
J. Leonard,
R. Loveless,
A. Mohapatra,
I. Ojalvo,
W. Parker,
I. Ross,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: A measurement is presented of the charged hadron multiplicity in
hadronic PbPb collisions, as a function of pseudorapidity and
centrality, at a collision energy of 2.76 TeV per nucleon pair. The data
sample is collected using the CMS detector and a minimum-bias trigger,
with the CMS solenoid off. The number of charged hadrons is measured
both by counting the number of reconstructed particle hits and by
forming hit doublets of pairs of layers in the pixel detector. The two
methods give consistent results. The charged hadron multiplicity
density, dN ch /dη| η=0, for head-on
collisions is found to be 1612 ± 55, where the uncertainty is
dominated by systematic effects. Comparisons of these results to
previous measurements and to various models are also presented.
Journal of High Energy Physics 07/2011; 8:141. · 5.83 Impact Factor
-
S. Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl, [......],
J Leonard,
R Loveless,
A Mohapatra,
F Palmonari,
D Reeder,
I Ross,
A Savin,
W.H. Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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%.
Physical Review Letters 07/2011; 107(5):052302. · 7.37 Impact Factor
-
S. Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl, [......],
J Leonard,
R Loveless,
A Mohapatra,
F Palmonari,
D Reeder,
I Ross,
A Savin,
W.H. Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 07/2011; 107(2):021802. · 7.37 Impact Factor
-
CMS Collaboration,
S. Chatrchyan,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
C. Fabjan, [......],
C. Lazaridis,
J. Leonard,
R. Loveless,
A. Mohapatra,
D. Reeder,
I. Ross,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: A new heavy gauge boson, W′, decaying to a muon and a
neutrino, is searched for in pp collisions at a centre-of-mass energy of
7 TeV. The data, collected with the CMS detector at the LHC, correspond
to an integrated luminosity of 36 pb-1. No significant excess
of events above the standard model expectation is found in the
transverse mass distribution of the muon-neutrino system. Masses below
1.40 TeV are excluded at the 95% confidence level for a sequential
standard-model-like W′. The W′ mass
lower limit increases to 1.58 TeV when the present analysis is combined
with the CMS result for the electron channel.
Physics Letters B 06/2011; 701:160-179. · 3.95 Impact Factor
-
CMS Collaboration,
S. Chatrchyan,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
C. Fabjan, [......],
C. Lazaridis,
J. Leonard,
R. Loveless,
A. Mohapatra,
D. Reeder,
I. Ross,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: A search for pair-produced bottom-like quarks in pp collisions at s=7
TeV is conducted with the CMS experiment at the LHC. The decay
b′→tW is considered in this search. The
b′b¯→tW-t¯W+
process can be identified by the distinctive signature of trileptons and
same-sign dileptons. With a data sample corresponding to an integrated
luminosity of 34 pb-1, no excess above the standard model
background predictions is observed and a b′ quark with
a mass between 255 and 361 GeV/c2 is excluded at the 95%
confidence level.
Physics Letters B 06/2011; 701:204-223. · 3.95 Impact Factor
-
CMS Collaboration,
S. Chatrchyan,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
C. Fabjan, [......],
C. Lazaridis,
J. Leonard,
R. Loveless,
A. Mohapatra,
D. Reeder,
I. Ross,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: A search for pair-produced bottom-like quarks in pp collisions at s=7
TeV is conducted with the CMS experiment at the LHC. The decay
b′→tW is considered in this search. The
b′b¯→tW-t¯W+
process can be identified by the distinctive signature of trileptons and
same-sign dileptons. With a data sample corresponding to an integrated
luminosity of 34 pb-1, no excess above the standard model
background predictions is observed and a b′ quark with
a mass between 255 and 361 GeV/c2 is excluded at the 95%
confidence level.
Physics Letters B 06/2011; 701:204-223. · 3.95 Impact Factor
-
S. Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl, [......],
J Leonard,
R Loveless,
A Mohapatra,
F Palmonari,
D Reeder,
I Ross,
A Savin,
W.H. Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 06/2011; 106(25):252001. · 7.37 Impact Factor
-
S. Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl, [......],
J Leonard,
R Loveless,
A Mohapatra,
F Palmonari,
D Reeder,
I Ross,
A Savin,
W.H. Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 06/2011; 106(23):231801. · 7.37 Impact Factor
-
S Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl, [......],
C Lazaridis,
J Leonard,
R Loveless,
A Mohapatra,
D Reeder,
I Ross,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 05/2011; 106(21):212301. · 7.37 Impact Factor
-
S Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl, [......],
J Leonard,
R Loveless,
A Mohapatra,
F Palmonari,
D Reeder,
I Ross,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 05/2011; 106(21):211802. · 7.37 Impact Factor
-
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl,
R Frühwirth, [......],
C Lazaridis,
J Leonard,
R Loveless,
A Mohapatra,
D Reeder,
I Ross,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 05/2011; 106(20):201804. · 7.37 Impact Factor
-
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl,
R Frühwirth, [......],
C Lazaridis,
J Leonard,
R Loveless,
A Mohapatra,
D Reeder,
I Ross,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 05/2011; 106(20):201803. · 7.37 Impact Factor
-
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl,
R Frühwirth, [......],
C Lazaridis,
J Leonard,
R Loveless,
A Mohapatra,
D Reeder,
I Ross,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 05/2011; 106(20):201802. · 7.37 Impact Factor
-
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl,
R Frühwirth, [......],
C Lazaridis,
J Leonard,
R Loveless,
A Mohapatra,
D Reeder,
I Ross,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 03/2011; 106(12):122003. · 7.37 Impact Factor
-
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl,
R Frühwirth, [......],
C Lazaridis,
J Leonard,
R Loveless,
A Mohapatra,
D Reeder,
I Ross,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 03/2011; 106(11):112001. · 7.37 Impact Factor
-
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl,
R Frühwirth, [......],
J Leonard,
D Lomidze,
R Loveless,
A Mohapatra,
D Reeder,
I Ross,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 02/2011; 106(8):082001. · 7.37 Impact Factor
-
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan,
M Friedl,
R Frühwirth, [......],
D Lomidze,
R Loveless,
A Mohapatra,
W Parker,
D Reeder,
I Ross,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 01/2011; 106(1):011801. · 7.37 Impact Factor
