-
S Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
E Aguilo,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan, [......],
R Loveless,
A Mohapatra,
M U Mozer,
I Ojalvo,
F Palmonari,
G A Pierro,
I Ross,
A Savin,
W H Smith,
J Swanson
[show abstract]
[hide abstract]
ABSTRACT: A study is presented of the mass and spin-parity of the new boson recently observed at the LHC at a mass near 125 GeV. An integrated luminosity of 17.3 fb^{-1}, collected by the CMS experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, is used. The measured mass in the ZZ channel, where both Z bosons decay to e or μ pairs, is 126.2±0.6(stat)±0.2(syst) GeV. The angular distributions of the lepton pairs in this channel are sensitive to the spin-parity of the boson. Under the assumption of spin 0, the present data are consistent with the pure scalar hypothesis, while disfavoring the pure pseudoscalar hypothesis.
Physical Review Letters 02/2013; 110(8):081803. · 7.37 Impact Factor
-
S Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
E Aguilo,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan, [......],
J Leonard,
R Loveless,
A Mohapatra,
I Ojalvo,
F Palmonari,
G A Pierro,
I Ross,
A Savin,
W H Smith,
J Swanson
[show abstract]
[hide abstract]
ABSTRACT: Results are presented from a search for the pair production of third-generation scalar and vector leptoquarks, as well as for top squarks in R-parity-violating supersymmetric models. In either scenario, the new, heavy particle decays into a τ lepton and a b quark. The search is based on a data sample of pp collisions at sqrt[s]=7 TeV, which is collected by the CMS detector at the LHC and corresponds to an integrated luminosity of 4.8 fb^{-1}. The number of observed events is found to be in agreement with the standard model prediction, and exclusion limits on mass parameters are obtained at the 95% confidence level. Vector leptoquarks with masses below 760 GeV are excluded and, if the branching fraction of the scalar leptoquark decay to a τ lepton and a b quark is assumed to be unity, third-generation scalar leptoquarks with masses below 525 GeV are ruled out. Top squarks with masses below 453 GeV are excluded for a typical benchmark scenario, and limits on the coupling between the top squark, τ lepton, and b quark, λ_{333}^{'} are obtained. These results are the most stringent for these scenarios to date.
Physical Review Letters 02/2013; 110(8):081801. · 7.37 Impact Factor
-
S Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
E Aguilo,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan, [......],
C Lazaridis,
R Loveless,
A Mohapatra,
I Ojalvo,
F Palmonari,
G A Pierro,
I Ross,
A Savin,
W H Smith,
J Swanson
[show abstract]
[hide abstract]
ABSTRACT: The polarizations of the Υ(1S), Υ(2S), and Υ(3S) mesons are measured in proton-proton collisions at sqrt[s]=7 TeV, using a data sample of Υ(nS)→μ^{+}μ^{-} decays collected by the CMS experiment, corresponding to an integrated luminosity of 4.9 fb^{-1}. The dimuon decay angular distributions are analyzed in three different polarization frames. The polarization parameters λ_{ϑ}, λ_{φ}, and λ_{ϑφ}, as well as the frame-invariant quantity λ[over ˜], are presented as a function of the Υ(nS) transverse momentum between 10 and 50 GeV, in the rapidity ranges |y|<0.6 and 0.6<|y|<1.2. No evidence of large transverse or longitudinal polarizations is seen in the explored kinematic region.
Physical Review Letters 02/2013; 110(8):081802. · 7.37 Impact Factor
-
S Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
E Aguilo,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan, [......],
J Leonard,
R Loveless,
A Mohapatra,
I Ojalvo,
F Palmonari,
G A Pierro,
I Ross,
A Savin,
W H Smith,
J Swanson
[show abstract]
[hide abstract]
ABSTRACT: Evidence is presented for the associated production of a single top quark and W boson in pp collisions at sqrt[s]=7 TeV with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 4.9 fb^{-1}. The measurement is performed using events with two leptons and a jet originated from a b quark. A multivariate analysis based on kinematic properties is utilized to separate the tt[over ¯] background from the signal. The observed signal has a significance of 4.0σ and corresponds to a cross section of 16_{-4}^{+5} pb, in agreement with the standard model expectation of 15.6±0.4_{-1.2}^{+1.0} pb.
Physical Review Letters 01/2013; 110(2):022003. · 7.37 Impact Factor
-
S Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
E Aguilo,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan, [......],
C Lazaridis,
R Loveless,
A Mohapatra,
I Ojalvo,
F Palmonari,
G A Pierro,
I Ross,
A Savin,
W H Smith,
J Swanson
[show abstract]
[hide abstract]
ABSTRACT: Results are presented from a search for heavy, right-handed muon neutrinos, N_{μ}, and right-handed W_{R} bosons, which arise in the left-right symmetric extensions of the standard model. The analysis is based on a 5.0 fb^{-1} sample of proton-proton collisions at a center-of-mass energy of 7 TeV, collected by the CMS detector at the Large Hadron Collider. No evidence is observed for an excess of events over the standard model expectation. For models with exact left-right symmetry, heavy right-handed neutrinos are excluded at 95% confidence level for a range of neutrino masses below the W_{R} mass, dependent on the value of M_{W_{R}}. The excluded region in the two-dimensional (M_{W_{R}}, M_{N_{μ}}) mass plane extends to M_{W_{R}}=2.5 TeV.
Physical Review Letters 12/2012; 109(26):261802. · 7.37 Impact Factor
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S Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
E Aguilo,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan, [......],
J Leonard,
R Loveless,
A Mohapatra,
I Ojalvo,
F Palmonari,
G A Pierro,
I Ross,
A Savin,
W H Smith,
J Swanson
[show abstract]
[hide abstract]
ABSTRACT: We report an investigation of the invariant mass spectrum of the two jets with highest transverse momentum in pp→W+2-jet and W+3-jet events to look for resonant enhancement. The data sample corresponds to an integrated luminosity of 5.0 fb^{-1} collected with the CMS detector at sqrt[s]=7 TeV. We find no evidence for the anomalous structure reported by the CDF Collaboration, and establish an upper limit of 5.0 pb at 95% confidence level on the production cross section for a generic Gaussian signal with mass near 150 GeV. Additionally, we exclude two theoretical models that predict a CDF-like dijet resonance near 150 GeV.
Physical Review Letters 12/2012; 109(25):251801. · 7.37 Impact Factor
-
S Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
E Aguilo,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan, [......],
J Leonard,
R Loveless,
A Mohapatra,
I Ojalvo,
F Palmonari,
G A Pierro,
I Ross,
A Savin,
W H Smith,
J Swanson
[show abstract]
[hide abstract]
ABSTRACT: The suppression of the individual Υ(nS) states in PbPb collisions with respect to their yields in pp data has been measured. The PbPb and pp data sets used in the analysis correspond to integrated luminosities of 150 μb^{-1} and 230 nb^{-1}, respectively, collected in 2011 by the CMS experiment at the LHC, at a center-of-mass energy per nucleon pair of 2.76 TeV. The Υ(nS) yields are measured from the dimuon invariant mass spectra. The suppression of the Υ(nS) yields in PbPb relative to the yields in pp, scaled by the number of nucleon-nucleon collisions, R_{AA}, is measured as a function of the collision centrality. Integrated over centrality, the R_{AA} values are 0.56±0.08(stat)±0.07(syst), 0.12±0.04(stat)±0.02(syst), and lower than 0.10 (at 95% confidence level), for the Υ(1S), Υ(2S), and Υ(3S) states, respectively. The results demonstrate the sequential suppression of the Υ(nS) states in PbPb collisions at LHC energies.
Physical Review Letters 11/2012; 109(22):222301. · 7.37 Impact Factor
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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,
F Palmonari,
G A Pierro,
I Ross,
A Savin,
W H Smith,
J Swanson
[show abstract]
[hide abstract]
ABSTRACT: A search for physics beyond the standard model is performed in events with at least three jets and large missing transverse momentum produced in proton-proton collisions at a center-of-mass energy of sqrt[s]=7 TeV. No significant excess of events above the expected backgrounds is observed in 4.98 fb^{-1} of data collected with the CMS detector at the Large Hadron Collider. The results are presented in the context of the constrained minimal supersymmetric extension of the standard model and more generically for simplified models. For the simplified models of gluino-gluino and squark-squark production, gluino masses below 1.0 TeV and squark masses below 0.76 TeV are excluded in case the lightest supersymmetric particle mass is below 200 GeV. These results significantly extend previous searches.
Physical Review Letters 10/2012; 109(17):171803. · 7.37 Impact Factor
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T. Aaltonen,
B. Alvarez Gonzalez,
S. Amerio,
D. Amidei,
A. Anastassov,
A. Annovi,
J. Antos,
G. Apollinari,
J. A. Appel,
A. Apresyan, [......],
J. Yoh,
K. Yorita,
T. Yoshida,
G. B. Yu,
I. Yu,
S. S. Yu,
J. C. Yun,
A. Zanetti,
Y. Zeng,
S. Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of the mass difference between top ($t$) and
anti-top ($\bar{t}$) quarks using $t\bar{t}$ candidate events reconstructed in
the final state with one lepton and multiple jets. We use the full data set of
Tevatron $\sqrt{s} = 1.96$ TeV proton-antiproton collisions recorded by the CDF
II detector, corresponding to an integrated luminosity of 8.7 fb$^{-1}$. We
estimate event-by-event the mass difference to construct templates for
top-quark signal events and background events. The resulting mass difference
distribution of data compared to signal and background templates using a
likelihood fit yields $\Delta M_{top} = {M}_{t} - {M}_{\bar{t}} = -1.95 $pm$
1.11 (stat) $pm$ 0.59 (syst)$ and is in agreement with the standard model
prediction of no mass difference.
10/2012;
-
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,
F Palmonari,
G A Pierro,
I Ross,
A Savin,
W H Smith,
J Swanson
[show abstract]
[hide abstract]
ABSTRACT: The transverse energy (E_{T}) in Pb-Pb collisions at 2.76 TeV nucleon-nucleon center-of-mass energy (sqrt[s_{NN}]) has been measured over a broad range of pseudorapidity (η) and collision centrality by using the CMS detector at the LHC. The transverse energy density per unit pseudorapidity (dE_{T}/dη) increases faster with collision energy than the charged particle multiplicity. This implies that the mean energy per particle is increasing with collision energy. At all pseudorapidities, the transverse energy per participating nucleon increases with the centrality of the collision. The ratio of transverse energy per unit pseudorapidity in peripheral to central collisions varies significantly as the pseudorapidity increases from η=0 to |η|=5.0. For the 5% most central collisions, the energy density per unit volume is estimated to be about 14 GeV/fm^{3} at a time of 1 fm/c after the collision. This is about 100 times larger than normal nuclear matter density and a factor of 2.6 times higher than the energy density reported at sqrt[s_{NN}]=200 GeV at the Relativistic Heavy Ion Collider.
Physical Review Letters 10/2012; 109(15):152303. · 7.37 Impact Factor
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S Chatrchyan,
V Khachatryan,
A M Sirunyan,
A Tumasyan,
W Adam,
E Aguilo,
T Bergauer,
M Dragicevic,
J Erö,
C Fabjan, [......],
J Leonard,
R Loveless,
A Mohapatra,
I Ojalvo,
F Palmonari,
G A Pierro,
I Ross,
A Savin,
W H Smith,
J Swanson
[show abstract]
[hide abstract]
ABSTRACT: A search is performed in pp collisions at sqrt[s]=7 TeV for exotic particles decaying via WZ to final states with electrons and muons. The data sample corresponds to an integrated luminosity of approximately 5 fb^{-1}. No significant excess is observed in the data above the expected standard model background. Upper bounds at 95% confidence level are set on the production cross section of the W^{'} boson described by the sequential standard model and on the W^{'} WZ coupling. W^{'} bosons with masses below 1143 GeV are excluded. Limits are also set in the context of low-scale technicolor models, under a range of assumptions concerning the model parameters.
Physical Review Letters 10/2012; 109(14):141801. · 7.37 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The pumping intensity (I) dependence of the photoluminescence (PL) spectra of
perfectly laterally two-dimensionally ordered SiGe quantum dots on Si(001)
substrates was studied. The PL results from recombinations of holes localized
in the SiGe quantum dots and electrons localized due to the strain field in the
surrounding Si matrix. The analysis of the spectra revealed several distinct
bands, attributed to phonon-assisted recombination and no-phonon recombination
of the excitonic ground state and of the excited excitonic states, which all
exhibit a linear I dependence of the PL intensity. At approximately I>3W/cm^2,
additional bands with a nearly quadratic I dependence appear in the PL spectra,
resulting from biexcitonic transitions. These emerging PL contributions shift
the composite no-phonon PL band of the SiGe quantum dots to higher energies.
The experimentally obtained energies of the no-phonon transitions are in good
agreement with the exciton and biexciton energies calculated using the envelope
function approximation and the configuration interaction method.
09/2012;
-
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,
F Palmonari,
G A Pierro,
I Ross,
A Savin,
W H Smith,
J Swanson
[show abstract]
[hide abstract]
ABSTRACT: 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 fb^{-1} 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 σ×B(pp→a→μ^{+}μ^{-}) in the range of 1.5-7.5 pb. These results improve on existing bounds on the abb[over ¯] coupling for m_{a}<m_{Υ(1S)} and are the first significant limits for m_{a}>m_{Υ(3S)}. Constraints on the supersymmetric parameter space are presented in the context of the next-to-minimal model.
Physical Review Letters 09/2012; 109(12):121801. · 7.37 Impact Factor
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CDF Collaboration,
T. Aaltonen,
B. Alvarez Gonzalez,
S. Amerio,
D. Amidei,
A. Anastassov,
A. Annovi,
J. Antos,
G. Apollinari,
J. A. Appel, [......],
J. Yoh,
K. Yorita,
T. Yoshida,
G. B. Yu,
I. Yu,
S. S. Yu,
J. C. Yun,
A. Zanetti,
Y. Zeng,
S. Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: This paper reports the result of a search for the standard model Higgs boson
in events containing four reconstructed jets associated with quarks. For masses
below 135GeV/c2, Higgs boson decays to bottom-antibottom quark pairs are
dominant and result primarily in two hadronic jets. An additional two jets can
be produced in the hadronic decay of a W or Z boson produced in association
with the Higgs boson, or from the incoming quarks that produced the Higgs boson
through the vector-boson fusion process. The search is performed using a sample
of \sqrt{s} = 1.96 TeV proton-antiproton collisions corresponding to an
integrated luminosity of 9.45 fb-1 recorded by the CDF II detector. The data
are in agreement with the background model and 95% credibility level upper
limits on Higgs boson production are set as a function of the Higgs boson mass.
The median expected (observed) limit for a 125GeV/c2 Higgs boson is 11.0 (9.0)
times the predicted standard model rate.
08/2012;
-
T. Aaltonen,
B. Alvarez Gonzalez,
S. Amerio,
D. Amidei,
A. Anastassov,
A. Annovi,
J. Antos,
G. Apollinari,
J. A. Appel,
A. Apresyan, [......],
J. Yoh,
K. Yorita,
T. Yoshida,
G. B. Yu,
I. Yu,
S. S. Yu,
J. C. Yun,
A. Zanetti,
Y. Zeng,
S. Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We present a precision measurement of the top-quark mass using the full
sample of Tevatron $\sqrt{s}=1.96$ TeV proton-antiproton collisions collected
by the CDF II detector, corresponding to an integrated luminosity of 8.7
$fb^{-1}$. Using a sample of $t\bar{t}$ candidate events decaying into the
lepton+jets channel, we obtain distributions of the top-quark masses and the
invariant mass of two jets from the $W$ boson decays from data. We then compare
these distributions to templates derived from signal and background samples to
extract the top-quark mass and the energy scale of the calorimeter jets with
{\it in situ} calibration. The likelihood fit of the templates from signal and
background events to the data yields the single most-precise measurement of the
top-quark mass, $\mtop = 172.85 $\pm$ 0.71 (stat) $\pm$ 0.85 (syst) GeV/c^{2}.$
07/2012;
-
T. Aaltonen,
B. Alvarez Gonzalez,
S. Amerio,
D. Amidei,
A. Anastassov,
A. Annovi,
J. Antos,
G. Apollinari,
J. A. Appel,
A. Apresyan, [......],
J. Yoh,
K. Yorita,
T. Yoshida,
G. B. Yu,
I. Yu,
S. S. Yu,
J. C. Yun,
A. Zanetti,
Y. Zeng,
S. Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: An inclusive search for the standard model Higgs boson using the four-lepton
final state in proton-antiproton collisions produced by the Tevatron at sqrt(s)
= 1.96 TeV is conducted. The data are recorded by the CDF II detector and
correspond to an integrated luminosity of 9.7 /fb. Three distinct Higgs decay
modes, namely ZZ, WW, and tau-tau, are simultaneously probed. Nine potential
signal events are selected and found to be consistent with the background
expectation. We set a 95% credibility limit on the production cross section
times the branching ratio and subsequent decay to the four lepton final state
for hypothetical Higgs boson masses between 120 GeV/c^2 and 300 GeV/c^2.
07/2012;
-
T. Aaltonen,
B. Álvarez González,
S. Amerio,
D. Amidei,
A. Anastassov,
A. Annovi,
J. Antos,
G. Apollinari,
J. A. Appel,
A. Apresyan, [......],
J. Yoh,
K. Yorita,
T. Yoshida,
G. B. Yu,
I. Yu,
S. S. Yu,
J. C. Yun,
A. Zanetti,
Y. Zeng,
S. Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We report a set of measurements of inclusive invariant pT differential cross sections of Λ0, Λ̅ 0, Ξ±, and Ω± hyperons reconstructed in the central region with pseudorapidity |η|<1 and pT up to 10 GeV/c. Events are collected with a minimum-bias trigger in pp̅ collisions at a center-of-mass energy of 1.96 TeV using the CDF II detector at the Tevatron Collider. As pT increases, the slopes of the differential cross sections of the three particles are similar, which could indicate a universality of the particle production in pT. The invariant differential cross sections are also presented for different charged-particle multiplicity intervals.
Phys. Rev. D. 07/2012; 86(1).
-
T Aaltonen,
B Álvarez González,
S Amerio,
D Amidei,
A Anastassov,
A Annovi,
J Antos,
G Apollinari,
J A Appel,
A Apresyan, [......],
J Yoh,
K Yorita,
T Yoshida,
G B Yu,
I Yu,
S S Yu,
J C Yun,
A Zanetti,
Y Zeng,
S Zucchelli
Phys. Rev. D. 07/2012; 86(1):012002.
-
S. CMS Collaboration 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,
I. Ojalvo,
G. A. Pierro,
I. Ross,
A. Savin,
W. H. Smith,
J. Swanson
[show abstract]
[hide abstract]
ABSTRACT: A search for neutral Higgs bosons decaying to tau pairs at a
center-of-mass energy of 7 TeV is performed using a dataset
corresponding to an integrated luminosity of 4.6 fb-1
recorded by the CMS experiment at the LHC. The search is sensitive to
both the standard model Higgs boson and to the neutral Higgs bosons
predicted by the minimal supersymmetric extension of the standard model
(MSSM). No excess of events is observed in the tau-pair invariant-mass
spectrum. For a standard model Higgs boson in the mass range of
110-145 GeV upper limits at 95% confidence level (CL) on the
production cross section are determined. We exclude a Higgs boson with
mH=115 GeV with a production cross section 3.2 times of
that predicted by the standard model. In the MSSM, upper limits on the
neutral Higgs boson production cross section times branching fraction to
tau pairs, as a function of the pseudoscalar Higgs boson mass,
mA, sets stringent new bounds in the parameter space,
excluding at 95% CL values of tan β as low as 7.1 at
mA=160 GeV in the mhmax benchmark scenario.
Physics Letters B 05/2012; 713:68-90. · 3.95 Impact Factor
-
The CMS Collaboration,
S. Chatrchyan,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
C. Fabjan, [......],
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[`(t)]\mathrm{t{\bar{t}}} production cross section in proton-proton collisions at a centre-of-mass energy of 7TeV has been performed at the LHC with
the CMS detector. The analysis uses a data sample corresponding to an integrated luminosity of 36pb−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[`(t)]\mathrm{t{\bar{t}}} signal from W+jets and QCD multijet background events. The measured cross section is 173+39-32(stat. + syst.)173^{+39}_{-32}~(\mathrm{stat}. + \mathrm{syst}.)pb, consistent with standard model expectations.
European Physical Journal C 05/2012; 71(9):1-27. · 3.63 Impact Factor
