-
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
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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
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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
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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: 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.
Physical Review Letters 12/2010; 105(26):262001. · 7.37 Impact Factor
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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: 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.
Physical Review Letters 11/2010; 105(21):211801. · 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,
G Polese,
D Reeder,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 07/2010; 105(3):032001. · 7.37 Impact Factor
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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,
G Polese,
D Reeder,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 07/2010; 105(2):022002. · 7.37 Impact Factor
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P. Achard,
O Adriani,
M. Aguilar-Benitez,
M. van den Akker,
J Alcaraz,
G. Alemanni,
J. Allaby,
A Aloisio,
M G Alviggi,
H Anderhub, [......],
J Zhao,
S J Zhou,
G Y Zhu,
R Y Zhu,
Q. Q. Zhu,
H L Zhuang,
A. Zichichi,
B. Zimmermann,
M. Zoeller,
A. N. M. Zwart
[show abstract]
[hide abstract]
ABSTRACT: Context. Primary cosmic rays experience multiple deflections in the non-uniform galactic and heliospheric magnetic fields which may generate anisotropies. Aims. A study of anisotropies in the energy range between 100 and 500 GeV is performed. This energy range is not yet well explored. Methods. The L3 detector at the CERN electron-positron collider, LEP, is used for a study of the angular distribution of atmospheric muons with energies above 20 GeV. This distribution is used to investigate the isotropy of the time-dependent intensity of the primary cosmic-ray flux with a Fourier analysis. Results. A small deviation from isotropy at energies around 200 GeV is observed for the second harmonics at the solar frequency. No sidereal anisotropy is found at a level above 10(-4). The measurements were performed in the years 1999 and 2000.
Astronomy and Astrophysics 03/2008; 488:1093-1100. · 4.59 Impact Factor
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J.J. Velthuis,
Z. Drasal,
G. Hanninger,
R. Kohrs,
M. Mathes,
L. Reuen,
D. Scheirich,
L. Andricek,
I.C. Pascual,
X. Chen, [......],
H. Kruger,
C.L. Llacer,
P. Lodomez,
H.G. Moser,
I. Peric, A. Raspereza,
R. Richter,
S. Rummel,
E. von Torne,
N. Wermes
[show abstract]
[hide abstract]
ABSTRACT: For the detection of secondary vertices of long lived particles containing bottom and charm quarks at the International Linear Collider (ILC), a DEPFET pixel detector is one of the technologically favored options. In a DEPFET sensor a MOSFET pixel detector is integrated on a sidewards depleted silicon bulk sensor, thus combining the advantages of a fully depleted silicon sensor with in-pixel amplification. DEPFET pixel matrices have been characterized in a high energy particle beam. Since the DEPFET is a very high precision device, given its large S/N (> 100) and small pixel size (36 à 22 ¿m<sup>2</sup>), a DEPFET based pixel telescope consisting of 5 DEPFETs has been developed. The uncertainty on the predicted position for a device under test (DUT) positioned inside the telescope was found to be 1.4 ¿m with the existing device, due to the limited performance of two of the five DEPFET planes. A DEPFET telescope built of 5 modules equivalent to the best plane presented here, would have a track extrapolation error as low as 0.65 ¿m at the DUT plane.
IEEE Transactions on Nuclear Science 03/2008; · 1.45 Impact Factor
