-
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 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.
Physical Review Letters 12/2011; 107(27):271802. · 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,
I Ojalvo,
W Parker,
I Ross,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 11/2011; 107(22):221804. · 7.37 Impact Factor
-
ZEUS Collaboration,
H Abramowicz,
I Abt,
L Adamczyk,
M Adamus,
R. Aggarwal,
S. Antonelli,
P. Antonioli,
A. Antonov,
M Arneodo, [......],
L Zawiejski,
O. Zenaiev,
W Zeuner,
B.O. Zhautykov,
N. Zhmak,
C Zhou,
A. Zichichi,
Z. Zolkapli,
M. Zolko,
D.S. Zotkin
[show abstract]
[hide abstract]
ABSTRACT: The exclusive electroproduction of two pions in the mass range 0.4 <
M{\pi}{\pi} < 2.5 GeV has been studied with the ZEUS detector at HERA using an
integrated luminosity of 82 pb-1. The analysis was carried out in the kinematic
range of 2 < Q2 < 80 GeV2, 32 < W < 180 GeV and |t| < 0.6 GeV2, where Q2 is the
photon virtuality, W is the photon-proton centre-of-mass energy and t is the
squared four-momentum transfer at the proton vertex. The two-pion
invariant-mass distribution is interpreted in terms of the pion electromagnetic
form factor, |F(M{\pi}{\pi})|, assuming that the studied mass range includes
the contributions of the {\rho}, {\rho}' and {\rho}" vector-meson states. The
masses and widths of the resonances were obtained and the Q2 dependence of the
cross-section ratios {\sigma}({\rho}' \rightarrow {\pi}{\pi})/{\sigma}({\rho})
and {\sigma}({\rho}" \rightarrow {\pi}{\pi})/{\sigma}({\rho}) was extracted.
The pion form factor obtained in the present analysis is compared to that
obtained in e+e- \rightarrow {\pi}+{\pi}-.
11/2011;
-
ZEUS Collaboration,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
R. Aggarwal,
S. Antonelli,
P. Antonioli,
A. Antonov,
M. Arneodo, [......],
L. Zawiejski,
O. Zenaiev,
W. Zeuner,
B. O. Zhautykov,
N. Zhmak,
C. Zhou,
A. Zichichi,
Z. Zolkapli,
M. Zolko,
D. S. Zotkin
[show abstract]
[hide abstract]
ABSTRACT: A search for single-top production, $ep \rightarrow etX$, has been performed
with the ZEUS detector at HERA using data corresponding to an integrated
luminosity of $0.37\fbi$. No evidence for top production was found, consistent
with the expectation from the Standard Model. Limits were computed for
single-top production via flavour changing neutral current transitions. The
result was combined with a previous ZEUS result yielding a total luminosity of
0.50fb-1. A 95% credibility level upper limit of 0.13 pb was obtained for the
cross section at the centre-of-mass energy of $\sqrt{s}=315\gev$.
11/2011;
-
ZEUS Collaboration,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
R. Aggarwal,
S. Antonelli,
P. Antonioli,
A. Antonov,
M. Arneodo, [......],
L. Zawiejski,
O. Zenaiev,
W. Zeuner,
B. O. Zhautykov,
N. Zhmak,
C. Zhou,
A. Zichichi,
Z. Zolkapli,
M. Zolko,
D. S. Zotkin
[show abstract]
[hide abstract]
ABSTRACT: Scaled momentum distributions for the strange hadrons K0s and Lambda/bar
Lambda were measured in deep inelastic ep scattering with the ZEUS detector at
HERA using an integrated luminosity of 330 pb-1. The evolution of these
distributions with the photon virtuality, Q2, was studied in the kinematic
region 10<Q2<40000 GeV2 and 0.001<x<0.75, where x is the Bjorken scaling
variable. Clear scaling violations are observed. Predictions based on different
approaches to fragmentation were compared to the measurements.
Leading-logarithm parton-shower Monte Carlo calculations interfaced to the Lund
string fragmentation model describe the data reasonably well in the whole range
measured. Next-to-leading-order QCD calculations based on fragmentation
functions, FFs, extracted from e+e- data alone, fail to describe the
measurements. The calculations based on FFs extracted from a global analysis
including e+e-, ep and pp data give an improved description. The measurements
presented in this paper have the potential to further constrain the FFs of
quarks, anti-quarks and gluons yielding K0s and Lambda/bar Lambda strange
hadrons.
11/2011;
-
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 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.
Physical Review Letters 11/2011; 107(20):201804. · 7.37 Impact Factor
-
ZEUS collaboration,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
R. Aggarwal,
S. Antonelli,
P. Antonioli,
A. Antonov,
M. Arneodo, [......],
L. Zawiejski,
O. Zenaiev,
W. Zeuner,
B. O. Zhautykov,
N. Zhmak,
C. Zhou,
A. Zichichi,
Z. Zolkapli,
M. Zolko,
D. S. Zotkin
[show abstract]
[hide abstract]
ABSTRACT: The exclusive photoproduction reaction gamma p -> Upsilon(1S) p has been
studied with the ZEUS detector in ep collisions at HERA using an integrated
luminosity of 468 pb^-1. The measurement covers the kinematic range 60<W<220
GeV and Q^2<1 GeV^2, where W is the photon-proton centre-of-mass energy and Q^2
is the photon virtuality. The exponential slope, b, of the t dependence of the
cross section, where t is the squared four-momentum transfer at the proton
vertex, has been measured, yielding b = 4.3 +2.0 -1.3 (stat.) +0.5 -0.6 (syst.)
GeV^-2. This constitutes the first measurement of the t dependence of the gamma
p -> Upsilon(1S) p cross section.
11/2011;
-
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 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.
Physical Review Letters 11/2011; 107(19):191802. · 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,
I. Ojalvo,
W. Parker,
I. Ross,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: The Drell-Yan differential cross section is measured in pp collisions at
sqrt {s} = 7 TeV, from a data sample collected with the CMS detector at
the LHC, corresponding to an integrated luminosity of 36
pb-1. The cross section measurement, normalized to the
measured cross section in the Z region, is reported for both the dimuon
and dielectron channels in the dilepton invariant mass range 15-600 GeV.
The normalized cross section values are quoted both in the full phase
space and within the detector acceptance. The effect of final state
radiation is also identified. The results are found to agree with
theoretical predictions.
Journal of High Energy Physics 09/2011; 10:007. · 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: 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.
Physical Review Letters 09/2011; 107(13):132001. · 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,
I Ojalvo,
D Reeder,
I Ross,
A Savin,
W H Smith,
J Swanson,
M Weinberg
[show abstract]
[hide abstract]
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.
Physical Review Letters 09/2011; 107(10):101801. · 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 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
