-
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 a heavy standard model Higgs boson decaying via H→ZZ→→ℓ(+)ℓ(-)νν, where ℓ=e, μ, is presented. It is based on proton-proton collision data at √s=7 TeV, collected by the ATLAS experiment at the LHC in the first half of 2011 and corresponding to an integrated luminosity of 1.04 fb(-1). The data are compared to the expected standard model backgrounds. The data and the background expectations are found to be in agreement and upper limits are placed on the Higgs boson production cross section over the entire mass window considered; in particular, the production of a standard model Higgs boson is excluded in the region 340<m(H)<450 GeV at the 95% confidence level.
Physical Review Letters 11/2011; 107(22):221802. · 7.37 Impact Factor
-
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: A measurement of the cross-section for
ϒ(1S)→μμ production in
proton-proton collisions at centre of mass energy of 7 TeV is presented.
The cross-section is measured as a function of the ϒ(1S)
transverse momentum in two bins of rapidity, |y|<1.2 and
1.2<|y|<2.4. The measurement requires that both muons
have transverse momentum pTμ>4 GeV and pseudorapidity
|η|<2.5 in order to reduce theoretical uncertainties
on the acceptance, which depend on the poorly known polarisation. The
results are based on an integrated luminosity of 1.13 pb-1,
collected with the ATLAS detector at the Large Hadron Collider. The
cross-section measurement is compared to theoretical predictions: it
agrees to within a factor of two with a prediction based on the NRQCD
model including colour-singlet and colour-octet matrix elements as
implemented in PYTHIA while it disagrees by up to a factor of ten with
the next-to-leading order prediction based on the colour-singlet model.
Physics Letters B 10/2011; 705:9-27. · 3.95 Impact Factor
-
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: A search for new phenomena in events featuring a high energy jet and
large missing transverse momentum in proton-proton collisions at s = 7
TeV is presented using a dataset corresponding to an integrated
luminosity of 33 pb -1 recorded with the ATLAS detector at
the Large Hadron Collider. The number of observed events is consistent
with the Standard Model prediction. This result is interpreted in terms
of limits on a model of Large Extra Dimensions.
Physics Letters B 10/2011; 705:294-312. · 3.95 Impact Factor
-
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: A search for long-lived charged particles reaching the muon spectrometer
is performed using a data sample of 37 pb - 1 from pp
collisions at s = 7 TeV collected by the ATLAS detector at the LHC in
2010. No excess is observed above the estimated background. Stable τ
˜ sleptons are excluded at 95% CL up to a mass of 136 GeV , in
GMSB models with N = 3 , m = 250 TeV , sign (
μ ) = 1 and tan β = 5 . Electroweak production of sleptons is
excluded up to a mass of 110 GeV . Gluino R -hadrons in a generic
interaction model are excluded up to masses of 530 GeV to 544 GeV
depending on the fraction of R -hadrons produced as g ˜ -balls.
Physics Letters B 08/2011; 703:428-446. · 3.95 Impact Factor
-
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: The inclusive J/ψ production cross-section and fraction of J/ψ
mesons produced in B-hadron decays are measured in proton-proton
collisions at s=7 TeV with the ATLAS detector at the LHC, as a function
of the transverse momentum and rapidity of the J/ψ, using 2.3
pb-1 of integrated luminosity. The cross-section is measured
from a minimum p of 1 GeV to a maximum of 70 GeV and for
rapidities within |y|<2.4 giving the widest reach of any measurement
of J/ψ production to date. The differential production
cross-sections of prompt and non-prompt J/ψ are separately
determined and are compared to Colour Singlet NNLO⋆,
Colour Evaporation Model, and FONLL predictions.
Nuclear Physics B 08/2011; 850:387-444. · 4.66 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 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
-
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
-
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
-
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
-
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
-
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
-
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
-
E Abat,
J M Abdallah,
T N Addy,
P Adragna,
M Aharrouche,
A Ahmad,
T P A Akesson,
M Aleksa,
C Alexa,
K Anderson, [......],
H H Williams,
I Wingerter-Seez,
Y Yasu,
A Zaitsev,
A Zenin,
T Zenis,
Z Zenonos,
H Zhang,
A Zhelezko,
N Zhou
[show abstract]
[hide abstract]
ABSTRACT: The reconstruction of photons in the ATLAS detector is studied with data taken during the 2004 Combined Test Beam, where a full slice of the ATLAS detector was exposed to beams of particles of known energy at the CERN SPS. The results presented show significant differences in the longitudinal development of the electromagnetic shower between converted and unconverted photons as well as in the total measured energy. The potential to use the reconstructed converted photons as a means to precisely map the material of the tracker in front of the electromagnetic calorimeter is also considered. All results obtained are compared with a detailed Monte-Carlo simulation of the test-beam setup which is based on the same simulation and reconstruction tools as those used for the ATLAS detector itself.
Journal of Instrumentation 03/2011; 6(04):P04001. · 1.87 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 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
-
E. Abat,
J.M. Abdallah,
T.N. Addy,
P. Adragna,
M. Aharrouche,
A Ahmad,
T.P.A. Akesson,
M. Aleksa,
C. Alexa,
K Anderson, [......],
H. H. Williams,
I Wingerter-Seez,
Y. Yasu,
A Zaitsev,
A. Zenin,
T. Zenis,
Z. Zenonos,
H Zhang,
A. Zhelezko,
N Zhou
[show abstract]
[hide abstract]
ABSTRACT: A new method for calibrating the hadron response of a segmented calorimeter
is developed and successfully applied to beam test data. It is based on a
principal component analysis of energy deposits in the calorimeter layers,
exploiting longitudinal shower development information to improve the measured
energy resolution. Corrections for invisible hadronic energy and energy lost in
dead material in front of and between the calorimeters of the ATLAS experiment
were calculated with simulated Geant4 Monte Carlo events and used to
reconstruct the energy of pions impinging on the calorimeters during the 2004
Barrel Combined Beam Test at the CERN H8 area. For pion beams with energies
between 20 GeV and 180 GeV, the particle energy is reconstructed within 3% and
the energy resolution is improved by between 11% and 25% compared to the
resolution at the electromagnetic scale.
12/2010;
-
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
-
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
-
[show abstract]
[hide abstract]
ABSTRACT: The electronic-nose instrumentation has advanced rapidly during the past decade, as the need for highly sensitive, fast and accurate analytical measurements have considerably stimulated the interest in developing these sensors as diagnostic tools. Given that the pathogen-induced plant responses also include changes in emission of volatiles, the electronic-nose may represent a powerful and operator-friendly alternative for rapid and reliable screening of asymptomatic plant material. In the present study, the electronic nose EOS835 (Sacmi, Imola, Italy), based on metal oxide semiconductors, was used. EOS835 was able to detect asymptomatic apple and pear plants experimentally infected with Erwinia amylovora (fire blight). The electronic nose was also successfully tested for discriminating Botrytis and Sclerotinia rots on both green and yellow kiwifruits. Even if the electronic-nose can be successfully used in experimental conditions for early diagnosis of both pre- and post-harvest diseases, its practical application in open fields, nurseries and packing houses still requires further studies.
Bulletin OEPP/EPPO Bulletin 03/2010; 40(1):59 - 67.
-
[show abstract]
[hide abstract]
ABSTRACT: In our previous studies, we reported that neonatally handled rats have an increased ingestion of sweet food but are resistant to the damaging effects of a chronic exposure to a highly palatable diet. Accumbal serotonin (5-HT) is important for feeding behavior and plays a role in the vulnerability to diet-induced obesity. Therefore, our hypotheses were (1) 5-HT turnover in the nucleus accumbens is altered in neonatally handled animals and plays a role in their differential feeding behavior and (2) if this is so, a chronic pharmacological treatment affecting 5-HT reuptake (chronic imipramine) would be able to revert the behavioral findings. Litters were divided into nonhandled and handled (10 min/day, Days 1–10 after birth). In Experiment 1, we demonstrated that a decreased 5-HT metabolism in the nucleus accumbens was observed in adult handled animals. In Experiment 2, the two previous groups were subdivided and assigned to receive imipramine diluted in water or water alone. After 30 days of treatment, we evaluated their weight gain and feeding behavior. Handled rats weighed less than nonhandled rats, and all imipramine-treated rats showed a reduction in weight gain after 60 days of treatment. Imipramine reverted the increased sweet food consumption seen in neonatally handled rats. We conclude that serotonin is involved in the altered feeding behavior of neonatally handled rats, and this protocol is an important tool for studying the mechanisms by which early life events have a long-term impact on feeding preferences. © 2010 Wiley Periodicals, Inc. Dev Psychobiol 52:190–196, 2010
Developmental Psychobiology 01/2010; 52(2):190 - 196. · 2.98 Impact Factor
