-
The ATLAS Collaboration,
G. Aad,
B. Abbott,
J. Abdallah,
A. A. Abdelalim,
A. Abdesselam,
O. Abdinov,
B. Abi,
M. Abolins,
H. Abramowicz, [......],
M. Ziolkowski,
R. Zitoun,
L. Živković,
V. V. Zmouchko,
G. Zobernig,
A. Zoccoli,
Y. Zolnierowski,
A. Zsenei,
M. zur Nedden,
V. Zutshi
[show abstract]
[hide abstract]
ABSTRACT: First measurements of the W → ℓν and Z/γ
*
→ ℓℓ (ℓ = e, μ) production cross sections in proton-proton collisions at
Ös = 7\textTeV \sqrt {s} = 7\;{\text{TeV}} are presented using data recorded by the ATLAS experiment at the LHC. The results are based on 2250 W → ℓν and 179 Z/γ
* → ℓℓ candidate events selected from a data set corresponding to an integrated luminosity of approximately 320 nb. The measured
total W and Z/γ
∗-boson production cross sections times the respective leptonic branching ratios for the combined electron and muon channels
are
sW\texttot \sigma_W^{\text{tot}} . BR(W → ℓν) = 9.96 ± 0.23(stat) ± 0.50(syst) ± 1.10(lumi) nb and
sZ /
g \texttot \sigma_{{{Z} \left/ {\gamma } \right.}}^{\text{tot}} BR(Z/γ
∗ → ℓℓ) = 0.82 ± 0.06 (stat) ± 0.05 (syst) ± 0.09(lumi) nb (within the invariant mass window 66 < m
ℓℓ
< 116GeV). The W/Z cross-section ratio is measured to be 11.7 ± 0.9(stat) ± 0.4(syst). In addition, measurements of the W
+ and W
− production cross sections and of the lepton charge asymmetry are reported. Theoretical predictions based on NNLO QCD calculations
are found to agree with the measurements.
KeywordsHadron-Hadron Scattering
Journal of High Energy Physics 04/2012; 2010(12):1-65. · 5.83 Impact Factor
-
The 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 production cross-section for top quark pairs (t[`(t)]t\bar{t}) in pp collisions at Ös=7TeV\sqrt{s}=7\ \ \mbox{TeV} is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two different
topologies: single lepton (electron e or muon μ) with large missing transverse energy and at least four jets, and dilepton (ee, μμ or eμ) with large missing transverse energy and at least two jets. In a data sample of 2.9pb−1, 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding
expected backgrounds from non-t[`(t)]t\bar{t} Standard Model processes are estimated using data-driven methods and determined to be 12.2±3.9 events and 2.5±0.6 events,
respectively. The kinematic properties of the selected events are consistent with SM t[`(t)]t\bar{t} production. The inclusive top quark pair production cross-section is measured to be
st[`(t)]=145±31(stat.) +42-27(syst.)pb.\sigma_{t\bar{t}}=145\pm31(\mathrm{stat.}) {}^{+42}_{-27}(\mathrm {syst.})\ \mbox{pb}.
The measurement agrees with perturbative QCD calculations.
European Physical Journal C 04/2012; 71(3):1-36. · 3.63 Impact Factor
-
The ATLAS Collaboration,
G. Aad,
B. Abbott,
J. Abdallah,
A. A. Abdelalim,
A. Abdesselam,
O. Abdinov,
B. Abi,
M. Abolins,
H. Abramowicz, [......],
M. Ziolkowski,
R. Zitoun,
L. Živković,
V. V. Zmouchko,
G. Zobernig,
A. Zoccoli,
Y. Zolnierowski,
A. Zsenei,
M. zur Nedden,
V. Zutshi
[show abstract]
[hide abstract]
ABSTRACT: Jet cross sections have been measured for the first time in proton-proton collisions at a centre-of-mass energy of 7TeV using
the ATLAS detector. The measurement uses an integrated luminosity of 17nb−1 recorded at the Large Hadron Collider. The anti-k
t
algorithm is used to identify jets, with two jet resolution parameters, R=0.4 and 0.6. The dominant uncertainty comes from the jet energy scale, which is determined to within 7% for central jets
above 60GeV transverse momentum. Inclusive single-jet differential cross sections are presented as functions of jet transverse
momentum and rapidity. Dijet cross sections are presented as functions of dijet mass and the angular variableχ. The results are compared to expectations based on next-to-leading-order QCD, which agree with the data, providing a validation
of the theory in a new kinematic regime.
European Physical Journal C 04/2012; 71(2):1-59. · 3.63 Impact Factor
-
The ATLAS collaboration,
G. Aad,
E. Abat,
B. Abbott,
J. Abdallah,
A. A. Abdelalim,
A. Abdesselam,
O. Abdinov,
B. Abi,
M. Abolins, [......],
M. Ziolkowski,
R. Zitoun,
L. Živković,
V. V. Zmouchko,
G. Zobernig,
A. Zoccoli,
Y. Zolnierowski,
A. Zsenei,
M. zur Nedden,
V. Zutshi
[show abstract]
[hide abstract]
ABSTRACT: More than half a million minimum-bias events of LHC collision data were collected by the ATLAS experiment in December 2009
at centre-of-mass energies of 0.9 TeV and 2.36 TeV. This paper reports on studies of the initial performance of the ATLAS
detector from these data. Comparisons between data and Monte Carlo predictions are shown for distributions of several track-and
calorimeter-based quantities. The good performance of the ATLAS detector in these first data gives confidence for successful
running at higher energies.
KeywordsHadron-Hadron Scattering
Journal of High Energy Physics 04/2012; 2010(9):1-66. · 5.83 Impact Factor
-
The 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: Measurements of luminosity obtained using the ATLAS detector during early running of the Large Hadron Collider (LHC) at Ös = 7\sqrt{s} = 7TeV are presented. The luminosity is independently determined using several detectors and multiple algorithms, each having
different acceptances, systematic uncertainties and sensitivity to background. The ratios of the luminosities obtained from
these methods are monitored as a function of time and of μ, the average number of inelastic interactions per bunch crossing. Residual time- and μ-dependence between the methods is less than 2% for 0<μ<2.5. Absolute luminosity calibrations, performed using beam separation scans, have a common systematic uncertainty of ±11%,
dominated by the measurement of the LHC beam currents. After calibration, the luminosities obtained from the different methods
differ by at most ±2%. The visible cross sections measured using the beam scans are compared to predictions obtained with
the PYTHIA and PHOJET event generators and the ATLAS detector simulation.
European Physical Journal C 04/2012; 71(4):1-37. · 3.63 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 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
-
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
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Progress in Photovoltaics Research and Applications 10/2008; 17(1):11 - 33. · 5.79 Impact Factor
-
E Abat,
A Abdesselam,
T N Addy,
T P A Åkesson,
P P Allport,
L Andricek,
F Anghinolfi,
R Apsimon,
E Arik,
M Arik, [......],
D Whittington,
A Wildauer,
I Wilhelm,
H H Williams,
J A Wilson,
M W Wolter,
S L Wu,
A Zhelezko,
H Z Zhu,
A Zsenei
[show abstract]
[hide abstract]
ABSTRACT: The ATLAS (A Toroidal LHC ApparatuS) Inner Detector provides charged particle tracking in the centre of the ATLAS experiment at the Large Hadron Collider (LHC). The Inner Detector consists of three subdetectors: the Pixel Detector, the Semiconductor Tracker (SCT), and the Transition Radiation Tracker (TRT). This paper summarizes the tests that were carried out at the final stage of SCT+TRT integration prior to their installation in ATLAS. The combined operation and performance of the SCT and TRT barrel and endcap detectors was investigated through a series of noise tests, and by recording the tracks of cosmic rays. This was a crucial test of hardware and software of the combined tracker detector systems. The results of noise and cross-talk tests on the SCT and TRT in their final assembled configuration, using final readout and supply hardware and software, are reported. The reconstruction and analysis of the recorded cosmic tracks allowed testing of the offline analysis chain and verification of basic tracker performance parameters, such as efficiency and spatial resolution, in combined operation before installation.
Journal of Instrumentation 08/2008; 3(08):P08003. · 1.87 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We have developed an apparatus that allows the measurement of applied torque as a function of angle of twist during shear removal of cored specimens. This allows us to characterize the strength and durability of various interfaces within many types of photovoltaic (PV) modules. We have used this device to evaluate several parameters in terms of their ability to quantify degradation of interfacial adhesion in weathered PV modules. The usefulness of shear modulus in this regard is marginal. However, peak torque, angle at peak torque, and toughness are very sensitive parameters. Published in 2008 by John Wiley & Sons, Ltd.
Progress in Photovoltaics Research and Applications 03/2008; 16(6):519 - 527. · 5.79 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Among the infrequently measured but essential properties for thin-film (T-F) module reliability are the interlayer adhesion and cohesion within a layer. These can be cell contact layers to glass, contact layers to the semiconductor, encapsulant to cell, glass, or backsheet, etc. We use an Instron mechanical testing unit to measure peel strengths at 90deg or 180deg and, in some cases, a scratch and tape pull test to evaluate inter-cell layer adhesion strengths. We present peel strength data for test specimens laminated from the three T-F technologies, before and after damp heat, and in one instance at elevated temperatures. On laminated T-F cell samples, failure can occur uniformly at any one of the many interfaces, or non-uniformly across the peel area at more than one interface. Some peel strengths are Lt1 N/mm. This is far below the normal ethylene vinyl acetate/glass interface values of >10 N/mm. We measure a wide range of adhesion strengths and suggest that adhesion measured under higher temperature and relative humidity conditions is more relevant for module reliability
Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on; 06/2006
-
G. Abbiendi,
C. Ainsley,
P. F. Åkesson,
G. Alexander,
J. Allison,
P. Amaral,
G. Anagnostou,
K. J. Anderson,
S. Arcelli,
S. Asai, [......],
T. Wengler,
N. Wermes,
D. Wetterling,
G. W. Wilson,
J. A. Wilson,
G. Wolf,
T. R. Wyatt,
S. Yamashita,
D. Zer-Zion,
L. Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: A search for stable and long-lived massive particles of electric charge
Q/e=1 or fractional charges of 2/3, 4/3, and 5/3 is reported using data
collected by the OPAL detector at LEP, at centre-of-mass energies from
130 to 209 GeV. These particles are assumed to be pair-produced in
e+e- collisions and not to interact strongly. No
evidence for the production of these particles was observed.
Model-independent upper limits on the production cross-section between
0.005 and 0.028 pb have been derived for scalar and spin-1/2 particles
with charge +/-1. Within the framework of the Constrained Minimal
Supersymmetric Standard Model (CMSSM), this implies a lower limit of
98.0 (98.5) GeV on the mass of long-lived right- (left-)handed scalar
muons and scalar taus. Long-lived charged heavy leptons and charginos
are excluded for masses below 102.0 GeV. For particles with fractional
charge +/-2/3, +/-4/3 and +/-5/3, the upper limit on the production
cross-section varies between 0.005 and 0.020 pb. All mass and
cross-section limits are derived at the 95% confidence level and are
valid for particles with lifetimes longer than 10-6 s.
Physics Letters B 09/2003; 572:8-20. · 3.95 Impact Factor
-
OPAL Collaboration,
G. Abbiendi,
C. Ainsley,
P. F. Åkesson,
G. Alexander,
J. Allison,
P. Amaral,
G. Anagnostou,
K. J. Anderson,
S. Arcelli, [......],
T. Wengler,
N. Wermes,
D. Wetterling,
G. W. Wilson,
J. A. Wilson,
G. Wolf,
T. R. Wyatt,
S. Yamashita,
D. Zer-Zion,
L. Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: The τ--->μ-
ν¯μντ branching ratio has
been measured using data collected from 1990 to 1995 by the OPAL
detector at the LEP collider. The resulting value of
B(τ--->μ-
ν¯μντ)=0.1734+/-
0.0009(stat)+/-0.0006(syst) has been used in conjunction with other OPAL
measurements to test lepton universality, yielding the coupling constant
ratios gμ/ge=1.0005+/-0.0044 and
gτ/ge=1.0031+/-0.0048, in good agreement with
the Standard Model prediction of unity. A value for the Michel parameter
/η=0.004+/-0.037 has also been determined and used to find a limit
for the mass of the charged Higgs boson,
mH+/->1.28tanβ, in the Minimal
Supersymmetric Standard Model.
Physics Letters B 12/2002; 551:35-48. · 3.95 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: High moisture barrier high resistivity coatings on polyethylene terepthalate (PET) have been fabricated and characterized for use in PV module back sheet applications. These thin film barriers exhibit water vapor transmission rates (WVTR) as low as 0.1 g/m<sup>2</sup>-day at 37.8°C and have shown excellent adhesion (> 10 N/mm) to both ethylene vinyl acetate (EVA) and PET even after filtered xenon arc lamp UV exposure. The WVTR and adhesion values for this construction are compared to and shown to be superior to candidate polymeric backsheet materials.
Photovoltaic Specialists Conference, 2002. Conference Record of the Twenty-Ninth IEEE; 06/2002
-
[show abstract]
[hide abstract]
ABSTRACT: Degradation leading to failure in photovoltaic modules follows a progression that is dependent on multiple factors, some of which interact causing degradation that is difficult to simulate in the lab. This paper defines observed degradation in field-aged modules, including degradation of packaging materials, adhesional loss, degradation of interconnects, degradation due to moisture intrusion, and semiconductor device degradation. Additionally, this paper suggests that the onset and progression of degradation need to be studied to gain a more comprehensive understanding of module degradation rates and module failures.
Photovoltaic Specialists Conference, 2002. Conference Record of the Twenty-Ninth IEEE; 06/2002
-
[show abstract]
[hide abstract]
ABSTRACT: As photovoltaic modules become more widely disseminated in high-power or utility-power applications, their ability to withstand high voltage relative to ground becomes a reliability issue. Long-term effects of exposure to high-voltage stress in the field are investigated. Starting in early 1998, four commercially available PV modules inaugurated the high-voltage stress test at the Outdoor Test Facility at NREL. Modules representing both crystalline and amorphous silicon technologies were deployed on the high-voltage stress testbed located outdoors in order to simulate and assess operation in high-voltage array configurations. They were biased at positive and negative polarity 600 V at all times—except for 1 min at noon each day, when they were subjected to 2200 V bias—and their leakage currents to ground were monitored continuously. The ubiquitous effects of moisture on leakage conductance are analyzed. Module leakage conductance is found to be thermally activated with a characteristic energy that depends on relative humidity. Separate current paths likely responsible for leakage conductance are analyzed and identified at opposite ends of the relative humidity range. Leakage current data are integrated against time to arrive at accumulated charge due to long-term, high-voltage exposure. Published in 2002 by John Wiley & Sons, Ltd.
Progress in Photovoltaics Research and Applications 01/2002; 10(1):15 - 28. · 5.79 Impact Factor
-
G. Abbiendi,
K. Ackerstaff,
P. F. Akesson,
G. Alexander,
J. Allison,
K. J. Anderson,
S. Arcelli,
S. Asai,
S. F. Ashby,
D. Axen, [......],
T. Wengler,
N. Wermes,
D. Wetterling,
J. S. White,
G. W. Wilson,
J. A. Wilson,
T. R. Wyatt,
S. Yamashita,
V. Zacek,
D. Zer-Zion
[show abstract]
[hide abstract]
ABSTRACT: The magnitude of the Cabibbo-Kobayashi-Maskawa matrix element
Vcb has been measured using
B¯0-->D*+l-ν¯ decays
recorded on the Z0 peak using the OPAL detector at LEP. The
D*+-->D0π+ decays were
reconstructed both in the particular decay modes
D0-->K-π+ and
D0-->K-π+π0 and via
an inclusive technique. The product of Vcb and the decay form
factor of the
B¯0-->D*+l-ν¯
transition at zero recoil /F(1) was measured to be
F(1)Vcb=(37.1+/-1.0+/-2.0)×10- 3, where the
uncertainties are statistical and systematic respectively. By using
Heavy Quark Effective Theory calculations for /F(1), a value
ofVcb=(40.7+/-1.1+/-2.2+/-1.6)×10- 3was
obtained, where the third error is due to theoretical uncertainties in
the value of /F(1). The branching ratio
Br(B¯0-->D*+l-ν¯) was
also measured to be /(5.26+/-0.20+/-0.46)%.
Physics Letters B 05/2000; 482:15-30. · 3.95 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: In this paper, we review the progress made by the CdTe Thin Film Partnership Reliability Team in developing an accelerated environmental test (AET) methodology that will indicate the expected life of CdTe cells incorporated in a module operated in the field. The primary focus is on test design, cell reliability, and the correlation of indoor accelerated testing with outdoor exposure. The team has emphasized cell-stability issues, and is not examining failure modes such as those involving module packaging, junction boxes, and mounting. The goal is to develop a CdTe cell technology with a 30 yr life, and verify that reliability through AETs. © 1999 American Institute of Physics.
AIP Conference Proceedings. 03/1999; 462(1):54-61.
