-
G. Aad,
B Abbott,
J Abdallah,
A.A. Abdelalim,
A. Abdesselam,
O. Abdinov,
B. Abi,
M Abolins,
H Abramowicz,
H. Abreu, [......],
R Zitoun,
L Zivković,
V.V. Zmouchko,
G Zobernig,
A. Zoccoli,
Y Zolnierowski,
A Zsenei,
M zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: This Letter presents a measurement of the W+ W- production cross section in sqrt(s) = 7 TeV pp collisions by the ATLAS experiment, using 34 pb(-1) of integrated luminosity produced by the Large Hadron Collider at CERN. Selecting events with two isolated leptons, each either an electron or a muon, 8 candidate events are observed with an expected background of 1.7 ± 0.6 events. The measured cross section is 41(-16)(+20)(stat) ± 5(syst)±1(lumi) pb, which is consistent with the standard model prediction of 44 ± 3 pb calculated at next-to-leading order in QCD.
Physical Review Letters 07/2011; 107(4):041802. · 7.37 Impact Factor
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ATLAS Collaboration,
G. Aad,
B. Abbott,
J. Abdallah,
A. A. Abdelalim,
A. Abdesselam,
O. Abdinov,
B. Abi,
M. Abolins,
H. Abramowicz, [......],
R. Zitoun,
L. Živković,
V. V. Zmouchko,
G. Zobernig,
A. Zoccoli,
Y. Zolnierowski,
A. Zsenei,
M. Zur Nedden,
V. Zutshi,
L. Zwalinski
Physics Letters B 06/2011; 701:186-203. · 3.95 Impact Factor
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G. Aad,
B Abbott,
J Abdallah,
A.A. Abdelalim,
A. Abdesselam,
O. Abdinov,
B. Abi,
M Abolins,
H Abramowicz,
H. Abreu, [......],
R Zitoun,
L Zivković,
V.V. Zmouchko,
G Zobernig,
A. Zoccoli,
Y Zolnierowski,
A Zsenei,
M zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: This Letter presents the first search for a heavy particle decaying into an e ± μ(-/+) final state in sqrt[s] = 7 TeV pp collisions at the LHC. The data were recorded by the ATLAS detector during 2010 and correspond to a total integrated luminosity of 35 pb(-1). No excess above the standard model background expectation is observed. Exclusions at 95% confidence level are placed on two representative models. In an R-parity violating supersymmetric model, tau sneutrinos with a mass below 0.75 TeV are excluded, assuming all R-parity violating couplings are zero except λ(311)' = 0.11 and λ312 = 0.07. In a lepton flavor violating model, a Z'-like vector boson with masses of 0.70-1.00 TeV and corresponding cross sections times branching ratios of 0.175-0.183 pb is excluded. These results extend to higher mass R-parity violating sneutrinos and lepton flavor violating Z's than previous constraints from the Tevatron.
Physical Review Letters 06/2011; 106(25):251801. · 7.37 Impact Factor
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ATLAS Collaboration,
G. Aad,
B. Abbott,
J. Abdallah,
A. A. Abdelalim,
A. Abdesselam,
O. Abdinov,
B. Abi,
M. Abolins,
H. Abramowicz, [......],
R. Zitoun,
L. Živković,
V. V. Zmouchko,
G. Zobernig,
A. Zoccoli,
Y. Zolnierowski,
A. Zsenei,
M. Zur Nedden,
V. Zutshi,
L. Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: This Letter presents a search for high mass e+e-
or μ+μ- resonances in pp collisions at s=7
TeV at the LHC. The data were recorded by the ATLAS experiment during
2010 and correspond to a total integrated luminosity of ˜40
pb-1. No statistically significant excess above the Standard
Model expectation is observed in the search region of dilepton invariant
mass above 110 GeV. Upper limits at the 95% confidence level are set on
the cross section times branching ratio of Z′
resonances decaying to dielectrons and dimuons as a function of the
resonance mass. A lower mass limit of 1.048 TeV on the Sequential
Standard Model Z′ boson is derived, as well as mass
limits on Z* and E-motivated Z′
models.
Physics Letters B 05/2011; 700:163-180. · 3.95 Impact Factor
-
G Aad,
B Abbott,
J Abdallah,
A A Abdelalim,
A Abdesselam,
O Abdinov,
B Abi,
M Abolins,
H Abramowicz,
H Abreu, [......],
R Zitoun,
L Živković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
Y Zolnierowski,
A Zsenei,
M zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: A search for new interactions and resonances produced in LHC proton–proton (pp) collisions at a centre-of-mass energy was performed with the ATLAS detector. Using a dataset with an integrated luminosity of 36 pb− 1, dijet mass and angular distributions were measured up to dijet masses of ~3.5 TeV and were found to be in good agreement with Standard Model predictions. This analysis sets limits at 95% CL on various models for new physics: an excited quark is excluded for mass between 0.60 and 2.64 TeV, an axigluon hypothesis is excluded for axigluon masses between 0.60 and 2.10 TeV and quantum black holes are excluded in models with six extra space–time dimensions for quantum gravity scales between 0.75 and 3.67 TeV. Production cross section limits as a function of dijet mass are set using a simplified Gaussian signal model to facilitate comparisons with other hypotheses. Analysis of the dijet angular distribution using a novel technique simultaneously employing the dijet mass excludes quark contact interactions with a compositeness scale Λ below 9.5 TeV.
New Journal of Physics 05/2011; 13(5):053044. · 4.18 Impact Factor
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G Aad,
B Abbott,
J Abdallah,
A A Abdelalim,
A Abdesselam,
O Abdinov,
B Abi,
M Abolins,
H Abramowicz,
H Abreu, [......],
R Zitoun,
L Živković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
Y Zolnierowski,
A Zsenei,
M zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: Measurements are presented from proton–proton collisions at centre-of-mass energies of , 2.36 and 7 TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum-bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. Measurements in different regions of phase space are shown, providing diffraction-reduced measurements as well as more inclusive ones. The observed distributions are corrected to well-defined phase-space regions, using model-independent corrections. The results are compared to each other and to various Monte Carlo (MC) models, including a new AMBT1 pythia6 tune. In all the kinematic regions considered, the particle multiplicities are higher than predicted by the MC models. The central charged-particle multiplicity per event and unit of pseudorapidity, for tracks with pT>100 MeV, is measured to be 3.483±0.009 (stat)±0.106 (syst) at and 5.630±0.003 (stat)±0.169 (syst) at .
New Journal of Physics 05/2011; 13(5):053033. · 4.18 Impact Factor
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G Aad,
B Abbott,
J Abdallah,
A A Abdelalim,
A Abdesselam,
O Abdinov,
B Abi,
M Abolins,
H Abramowicz,
H Abreu, [......],
R Zitoun,
L Zivković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
Y Zolnierowski,
A Zsenei,
M zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: Azimuthal decorrelations between the two central jets with the largest transverse momenta are sensitive to the dynamics of events with multiple jets. We present a measurement of the normalized differential cross section based on the full data set (∫Ldt=36 pb(-1)) acquired by the ATLAS detector during the 2010 sqrt(s)=7 TeV proton-proton run of the LHC. The measured distributions include jets with transverse momenta up to 1.3 TeV, probing perturbative QCD in a high-energy regime.
Physical Review Letters 04/2011; 106(17):172002. · 7.37 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We have reconsidered the Higgs boson search via the "golden mode" for
Tevatron. It is shown that this mode will give opportunity to observe the Higgs
boson with mass up to 300 GeV before Tevatron shutdown.
04/2011;
-
G Aad,
B Abbott,
J Abdallah,
A A Abdelalim,
A Abdesselam,
O Abdinov,
B Abi,
M Abolins,
H Abramowicz,
H Abreu, [......],
R Zitoun,
L Živković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
Y Zolnierowski,
A Zsenei,
M zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: This Letter presents the first search for supersymmetry in final states containing one isolated electron or muon, jets, and missing transverse momentum from √s=7 TeV proton-proton collisions at the LHC. The data were recorded by the ATLAS experiment during 2010 and correspond to a total integrated luminosity of 35 pb(-1). No excess above the standard model background expectation is observed. Limits are set on the parameters of the minimal supergravity framework, extending previous limits. Within this framework, for A(0)=0 GeV, tanβ=3, and μ>0 and for equal squark and gluino masses, gluino masses below 700 GeV are excluded at 95% confidence level.
Physical Review Letters 04/2011; 106(13):131802. · 7.37 Impact Factor
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G Aad,
B Abbott,
J Abdallah,
A A Abdelalim,
A Abdesselam,
O Abdinov,
B Abi,
M Abolins,
H Abramowicz,
H Abreu, [......],
R Zitoun,
L Živković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
Y Zolnierowski,
A Zsenei,
M zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: A search for diphoton events with large missing transverse energy is presented. The data were collected with the ATLAS detector in proton-proton collisions at √s=7 TeV at the CERN Large Hadron Collider and correspond to an integrated luminosity of 3.1 pb⁻¹. No excess of such events is observed above the standard model background prediction. In the context of a specific model with one universal extra dimension with compactification radius R and gravity-induced decays, values of 1/R<729 GeV are excluded at 95% C. L., providing the most sensitive limit on this model to date.
Physical Review Letters 03/2011; 106(12):121803. · 7.37 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The resonant production of the fourth family slepton ~l_4 via R-parity
violating interactions of supersymmetry at the Large Hadron Collider has been
investigated. We study the decay mode of ~l_4 into the fourth family neutrino
nu_4 and W boson. The signal will be a like-sign dimuon and dijet if the fourth
family neutrino has Majorana nature. We discuss the constraints on the R-parity
violating couplings lambda and lambda' of the fourth family charged slepton at
the LHC with the center of mass energies of 7, 10 and 14 TeV.
03/2011;
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[show abstract]
[hide abstract]
ABSTRACT: Existence of the fourth family follows from the basics of the standard model (SM) and the actual mass spectrum of the third family fermions. We discuss possible manifestations of the fourth SM family at existing and future colliders. The LHC and Tevatron potentials to discover the fourth SM family have been compared. The scenario with dominance of the anomalous decay modes of the fourth-family quarks has been considered in detail.
Phys. Rev. D. 03/2011; 83(5).
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[show abstract]
[hide abstract]
ABSTRACT: We study the possible dynamics associated with leptonic charge in future
linear colliders. Leptophilic massive vector boson, Z_(l), have been
investigated through the process e^(+)e^(-) -> mu^(+)mu^(-). We have shown that
ILC and CLIC will give opportunity to observe Z_(l) with masses up to the
center of mass energy if the corresponding coupling constant g_(l) exceeds
10^(-3).
03/2011;
-
G Aad,
B Abbott,
J Abdallah,
A A Abdelalim,
A Abdesselam,
O Abdinov,
B Abi,
M Abolins,
H Abramowicz,
H Abreu, [......],
R Zitoun,
L Zivković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
Y Zolnierowski,
A Zsenei,
M zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: By using the ATLAS detector, observations have been made of a centrality-dependent dijet asymmetry in the collisions of lead ions at the Large Hadron Collider. In a sample of lead-lead events with a per-nucleon center of mass energy of 2.76 TeV, selected with a minimum bias trigger, jets are reconstructed in fine-grained, longitudinally segmented electromagnetic and hadronic calorimeters. The transverse energies of dijets in opposite hemispheres are observed to become systematically more unbalanced with increasing event centrality leading to a large number of events which contain highly asymmetric dijets. This is the first observation of an enhancement of events with such large dijet asymmetries, not observed in proton-proton collisions, which may point to an interpretation in terms of strong jet energy loss in a hot, dense medium.
Physical Review Letters 12/2010; 105(25):252303. · 7.37 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: In this study we investigated indirect manifestations of color octet electron
at the next generation linear colliders: International Linear Collider (ILC)
and Compact Linear Collider (CLIC). Namely, production of two gluons via color
octet electron exchange is considered. Signal and background analysis have been
performed taking into account initial state radiation and beamstrahlung. We
show that color octet electron (e_(8)) manifestation will be seen upto
M(e_(8))=1.75 TeV and 1.70 TeV at ILC and CLIC with sqrt(s)=0.5 TeV,
respectively. CLIC with sqrt(s)=3 TeV will be sensitive upto M(e_(8))=6.88 TeV.
12/2010;
-
[show abstract]
[hide abstract]
ABSTRACT: Comment on "Event Excess in the MiniBooNE Search for $\bar \nu_{\mu}\rightarrow \bar \nu_e$ Oscillations" Comment: 2 pages
11/2010;
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G Aad,
B Abbott,
J Abdallah,
A A Abdelalim,
A Abdesselam,
O Abdinov,
B Abi,
M Abolins,
H Abramowicz,
H Abreu, [......],
M Ziolkowski,
R Zitoun,
L Zivković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
Y Zolnierowski,
A Zsenei,
M Zur Nedden,
V Zutshi
[show abstract]
[hide abstract]
ABSTRACT: A search for new heavy particles manifested as resonances in two-jet final states is presented. The data were produced in 7 TeV proton-proton collisions by the LHC and correspond to an integrated luminosity of 315 nb⁻¹ collected by the ATLAS detector. No resonances were observed. Upper limits were set on the product of cross section and signal acceptance for excited-quark (q*) production as a function of q* mass. These exclude at the 95% C.L. the q* mass interval 0.30<m(q*)<1.26 TeV, extending the reach of previous experiments.
Physical Review Letters 10/2010; 105(16):161801. · 7.37 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Existence of the fourth family follows from the basics of the Standard Model and the actual mass spectrum of the third family fermions. We discuss possible manifestations of the fourth SM family at existing and future colliders. The LHC and Tevatron potentials to discover the fourth SM family have been compared. The scenario with dominance of the anomalous decay modes of the fourth family quarks has been considered in details. Comment: 31 pages, 24 figures and 12 tables
09/2010;
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[show abstract]
[hide abstract]
ABSTRACT: We study the pair production of $\tilde{l}_{4}$, which is the supersymmetric
partner of the fourth family charged lepton, at the $e^{+}e^{-}$ colliders. It
is shown that the investigation of this process at ILC/CLIC will give
opportunity to differentiate the MSSM with three and four families.
06/2010;
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[show abstract]
[hide abstract]
ABSTRACT: The existence of fourth family follows from the basics of the Standard Model. Because of the high masses of the fourth family quarks, their anomalous decays could be dominant, if certain criteria are met. This will drastically change the search strategy at hadron colliders. We show that the fourth SM family down quarks with masses up to 400-450 GeV can be observed (or excluded) via anomalous decays by Tevatron before the LHC. Comment: 8 pages, 2 figures
05/2010;
