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- Aad, G., et al.
(author)
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The ATLAS Simulation Infrastructure
- 2010
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:3, s. 823-874
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Journal article (peer-reviewed)abstract
- The simulation software for the ATLAS Experiment at the Large Hadron Collider is being used for large-scale production of events on the LHC Computing Grid. This simulation requires many components, from the generators that simulate particle collisions, through packages simulating the response of the various detectors and triggers. All of these components come together under the ATLAS simulation infrastructure. In this paper, that infrastructure is discussed, including that supporting the detector description, interfacing the event generation, and combining the GEANT4 simulation of the response of the individual detectors. Also described are the tools allowing the software validation, performance testing, and the validation of the simulated output against known physics processes.
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| 15. |
- Aad, G., et al.
(author)
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Readiness of the ATLAS Tile Calorimeter for LHC collisions
- 2010
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:4, s. 1193-1236
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Journal article (peer-reviewed)abstract
- The Tile hadronic calorimeter of the ATLAS detector has undergone extensive testing in the experimental hall since its installation in late 2005. The readout, control and calibration systems have been fully operational since 2007 and the detector has successfully collected data from the LHC single beams in 2008 and first collisions in 2009. This paper gives an overview of the Tile Calorimeter performance as measured using random triggers, calibration data, data from cosmic ray muons and single beam data. The detector operation status, noise characteristics and performance of the calibration systems are presented, as well as the validation of the timing and energy calibration carried out with minimum ionising cosmic ray muons data. The calibration systems' precision is well below the design value of 1%. The determination of the global energy scale was performed with an uncertainty of 4%.
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| 16. |
- Aad, G., et al.
(author)
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The ATLAS Inner Detector commissioning and calibration
- 2010
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:3, s. 787-821
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Journal article (peer-reviewed)abstract
- The ATLAS Inner Detector is a composite tracking system consisting of silicon pixels, silicon strips and straw tubes in a 2 T magnetic field. Its installation was completed in August 2008 and the detector took part in data-taking with single LHC beams and cosmic rays. The initial detector operation, hardware commissioning and in-situ calibrations are described. Tracking performance has been measured with 7.6 million cosmic-ray events, collected using a tracking trigger and reconstructed with modular pattern-recognition and fitting software. The intrinsic hit efficiency and tracking trigger efficiencies are close to 100%. Lorentz angle measurements for both electrons and holes, specific energy-loss calibration and transition radiation turn-on measurements have been performed. Different alignment techniques have been used to reconstruct the detector geometry. After the initial alignment, a transverse impact parameter resolution of 22.1 +/- 0.9 mu m and a relative momentum resolution sigma (p) /p=(4.83 +/- 0.16)x10(-4) GeV(-1)xp (T) have been measured for high momentum tracks.
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| 17. |
- Aad, G., et al.
(author)
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Studies of the performance of the ATLAS detector using cosmic-ray muons
- 2011
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 71:3
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Journal article (peer-reviewed)abstract
- Muons from cosmic-ray interactions in the atmosphere provide a high-statistics source of particles that can be used to study the performance and calibration of the ATLAS detector. Cosmic-ray muons can penetrate to the cavern and deposit energy in all detector subsystems. Such events have played an important role in the commissioning of the detector since the start of the installation phase in 2005 and were particularly important for understanding the detector performance in the time prior to the arrival of the first LHC beams. Global cosmic-ray runs were undertaken in both 2008 and 2009 and these data have been used through to the early phases of collision data-taking as a tool for calibration, alignment and detector monitoring. These large datasets have also been used for detector performance studies, including investigations that rely on the combined performance of different subsystems. This paper presents the results of performance studies related to combined tracking, lepton identification and the reconstruction of jets and missing transverse energy. Results are compared to expectations based on a cosmic-ray event generator and a full simulation of the detector response.
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| 18. |
- Abazov, V. M., et al.
(author)
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Direct observation of the strange b baryon Xi(-)(b)
- 2007
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:5, s. 052001-
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Journal article (peer-reviewed)abstract
- We report the first direct observation of the strange b baryon Xi(-)(b)(Xi) over bar (+)(b)). We reconstruct the decay Xi(-)(b)-->J/psi Xi(-), with J/psi-->mu(+)mu(-), and Xi(-)-->Lambda pi(-)-->p pi(-)pi(-) in p (p) over bar collisions at root s = 1.96 TeV. Using 1.3 fb(-1) of data collected by the D0 detector, we observe 15.2 +/- 4.4(stat)(-0.4)(+1.9)(syst) Xi(-)(b) candidates at a mass of 5.774 +/- 0.011(stat) +/- 0.015(syst) GeV. The significance of the observed signal is 5.5 sigma, equivalent to a probability of 3.3 x 10(-8) of it arising from a background fluctuation. Normalizing to the decay Lambda(b)-->J/psi Lambda, we measure the relative rate sigma(Xi(-)(b))xB(Xi(-)(b)-->J/psi Xi)/ sigma(Lambda(b))xB(Lambda(b)-->J/psi Lambda) = 0.28 +/- 0.09(stat)(-0.08)(+0.09)(syst).
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| 19. |
- Abazov, V. M., et al.
(author)
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Measurement of the Lambda(0)(b) lifetime using semileptonic decays
- 2007
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:18, s. 182001-
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Journal article (peer-reviewed)abstract
- We report a measurement of the Lambda(0)(b) lifetime using a sample corresponding to 1.3 fb(-1) of data collected by the D0 experiment in 2002-2006 during run II of the Fermilab Tevatron collider. The Lambda(0)(b) baryon is reconstructed via the decay Lambda(0)(b)->mu(nu) over bar Lambda X-+(c). Using 4437 +/- 329 signal candidates, we measure the Lambda(0)(b) lifetime to be tau(Lambda(0)(b))=1.290(-0.110)(+0.119)(stat)(-0.091)(+0.087)(syst) ps, which is among the most precise measurements in semileptonic Lambda(0)(b) decays. This result is in good agreement with the world average value.
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| 20. |
- Abazov, V. M., et al.
(author)
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Measurement of the Lambda(b) lifetime in the exclusive decay Lambda(b)-> J/psi Lambda
- 2007
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:14, s. 142001-
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Journal article (peer-reviewed)abstract
- We have measured the Lambda(b) lifetime using the exclusive decay Lambda(b)-> J/psi Lambda, based on 1.2 fb(-1) of data collected with the D0 detector during 2002-2006. From 171 reconstructed Lambda(b) decays, where the J/psi and Lambda are identified via the decays J/psi ->mu(+)mu(-) and Lambda -> p pi, we measured the Lambda(b) lifetime to be tau(Lambda(b))=1.218(-0.115)(+0.130)(stat)+/- 0.042(syst) ps. We also measured the B-0 lifetime in the decay B-0 -> J/psi(mu(+)mu(-))K-S(0)(pi(+)pi(-)) to be tau(B-0)=1.501(-0.074)(+0.078)(stat)+/- 0.050(syst) ps, yielding a lifetime ratio of tau(Lambda(b))/tau(B-0)=0.811(-0.087)(+0.096)(stat)+/- 0.034(syst).
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| 21. |
- Abazov, V. M., et al.
(author)
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Measurement of the t(t)over-bar production cross section in p(p)over-bar collisions at root s=1.96 TeV using kinematic characteristics of lepton plus jets events
- 2007
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In: Physical Review D. - 1550-7998 .- 1550-2368. ; 76:9
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Journal article (peer-reviewed)abstract
- We present a measurement of the top quark pair production cross section in p (p) over bar collisions at root s=1.96 TeV utilizing 425 pb(-1) of data collected with the D0 detector at the Fermilab Tevatron Collider. We consider the final state of the top quark pair containing one high-p(T) electron or muon and at least four jets. We exploit specific kinematic features of t (t) over bar events to extract the cross section. For a top quark mass of 175 GeV, we measure sigma(t (t) over bar)=6.4(-1.2)(+1.3)(stat)+/- 0.7(syst)+/- 0.4(lum) pb, in good agreement with the standard model prediction.
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| 22. |
- Abazov, V. M., et al.
(author)
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Measurement of the t(t)over-bar production cross section in p(p)over-bar collisions using dilepton events
- 2007
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In: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 76:5, s. 052006-
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Journal article (peer-reviewed)abstract
- We present a measurement of the t (t) over bar pair production cross section in p (p) over bar collisions at root s=1.96 TeV utilizing approximately 425 pb(-1) of data collected with the D0 detector. We consider decay channels containing two high p(T) charged leptons (either e or mu) from leptonic decays of both top-daughter W bosons. These were gathered using four sets of selection criteria, three of which required that a pair of fully identified leptons (i.e., e mu, ee, or mu mu) be found. The fourth approach imposed less restrictive criteria on one of the lepton candidates and required that at least one hadronic jet in each event be tagged as containing a b quark. For a top quark mass of 175 GeV, the measured cross section is 7.4 +/- 1.4(stat)+/- 1.0(syst) pb and for the current Tevatron average top quark mass of 170.9 GeV, the resulting value of the cross section is 7.8 +/- 1.8(stat+syst) pb.
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| 23. |
- Abazov, V. M., et al.
(author)
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Properties of l=1 B-1 and B*(2) Mesons
- 2007
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:17, s. 172001-
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Journal article (peer-reviewed)abstract
- This Letter presents the first strong evidence for the resolution of the excited B mesons B-1 and B-2(*) as two separate states in fully reconstructed decays to B+(*())pi(-). The mass of B-1 is measured to be 5720.6 +/- 2.4 +/- 1.4 MeV/c(2) and the mass difference Delta M between B-2* and B-1 is 26.2 +/- 3.1 +/- 0: 9 MeV/c(2), giving the mass of the B-2* as 5746.8 +/- 2.4 +/- 1.7 MeV/c(2). The production rate for B-1 and B-2* mesons is determined to be a fraction (13.9 +/- 1.9 +/- 3.2)% of the production rate of the B+ meson.
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| 24. |
- Abazov, V. M., et al.
(author)
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Search for a Higgs boson produced in association with a Z boson in p(p)over-bar collisions
- 2007
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In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 655:5-6, s. 209-216
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Journal article (peer-reviewed)abstract
- We describe a search for the Standard Model Higgs boson with a mass of 105 GeV/c(2) to 145 GeV/c(2) in data corresponding to an integrated luminosity of approximately 450 pb(-1) collected with the D phi detector at the Fermilab Tevatron p (p) over bar collider at a center-of-mass energy of 1.96 TeV. The Higgs boson is required to be produced in association with a Z boson, and the Z boson is required to decay to either electrons or muons with the Higgs boson decaying to a b (b) over bar pair. The data are well described by the expected background, leading to 95% confidence level cross section upper limits sigma (p (p) over bar -> ZH) x B(H -> b (b) over bar) in the range of 3.1 pb to 4.4 pb.
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| 25. |
- Abazov, V. M., et al.
(author)
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Search for stopped gluinos from p(p)over-bar collisions at root s=1.96 TeV
- 2007
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:13, s. 131801-
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Journal article (peer-reviewed)abstract
- Long-lived, heavy particles are predicted in a number of models beyond the standard model of particle physics. We present the first direct search for such particles' decays, occurring up to 100 h after their production and not synchronized with an accelerator bunch crossing. We apply the analysis to the gluino (g), predicted in split supersymmetry, which after hadronization can become charged and lose enough momentum through ionization to come to rest in dense particle detectors. Approximately 410 pb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected with the D0 detector during Run II of the Fermilab Tevatron collider are analyzed in search of such "stopped gluinos" decaying into a gluon and a neutralino ((chi) over tilde (0)(1)). Limits are placed on the (gluino cross section) x (probability to stop) x [BR((g) over tilde -> g (chi) over tilde (0)(1))] as a function of the gluino and (chi) over tilde (0)(1) masses, for gluino lifetimes from 30 mu s-100 h.
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