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Showing papers by "Prafulla Kumar Behera published in 2010"


Journal ArticleDOI
Georges Aad1, Brad Abbott1, Jalal Abdallah1, A. A. Abdelalim1  +2582 moreInstitutions (23)
TL;DR: 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, including supporting the detector description, interfacing the event generation, and combining the GEANT4 simulation of the response of the individual detectors.
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.

1,514 citations


Journal ArticleDOI
Georges Aad1, Brad Abbott2, Jalal Abdallah3, A. A. Abdelalim4  +3098 moreInstitutions (192)
TL;DR: In this article, the authors used the ATLAS detector to detect dijet asymmetry in the collisions of lead ions at the Large Hadron Collider and found that the transverse energies of dijets in opposite hemispheres become systematically more unbalanced with increasing event centrality, leading to a large number of events which contain highly asymmetric di jets.
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.

630 citations


Journal ArticleDOI
Bernard Aubert1, Y. Karyotakis1, J. P. Lees1, V. Poireau1  +488 moreInstitutions (78)
TL;DR: In this article, the authors performed searches for lepton-flavor-violating decays of a tau lepton to a lighter mass lepton and a photon with the entire data set of (963 +/- 7) x 10(6) tau decays collected by the BABAR detector near the Y(4S), Y(3S) and Y(2S) resonances.
Abstract: Searches for lepton-flavor-violating decays of a tau lepton to a lighter mass lepton and a photon have been performed with the entire data set of (963 +/- 7) x 10(6) tau decays collected by the BABAR detector near the Y(4S), Y(3S) and Y(2S) resonances. The searches yield no evidence of signals and we set upper limits on the branching fractions of B(tau(+/-) -> e(+/-)gamma) mu(+/-)gamma) < 4.4 X 10(-8) at 90% confidence level.

502 citations


Journal ArticleDOI
Georges Aad1, Brad Abbott2, Jalal Abdallah3, A. A. Abdelalim4  +2565 moreInstitutions (176)
TL;DR: An overview of the Tile Calorimeter performance as measured using random triggers, calibration data, data from cosmic ray muons and single beam data and the determination of the global energy scale was performed with an uncertainty of 4%.
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%.

203 citations


Journal ArticleDOI
Georges Aad1, Brad Abbott2, Jalal Abdallah3, A. A. Abdelalim4  +2627 moreInstitutions (185)
TL;DR: The ATLAS Inner Detector as mentioned in this paper is a composite tracking system consisting of silicon pixels, silicon strips and straw tubes in a 2 T magnetic field, which was completed in 2008 and the detector took part in data-taking with single LHC beams and cosmic rays.
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.

181 citations


Journal ArticleDOI
P. Del Amo Sanchez1, J. P. Lees1, V. Poireau1, E. Prencipe1  +442 moreInstitutions (77)
TL;DR: In this paper, a study of the decay mode X(3872)→J/ψω, with product branching fractions B(B^+→X( 3872)K^+π^-π^0K^(0,+), using 467×10^6 BB[overbar] pairs recorded with the BABAR detector.
Abstract: We present a study of the decays B^(0,+)→J/ψπ^+π^-π^0K^(0,+), using 467×10^6 BB[overbar] pairs recorded with the BABAR detector. We present evidence for the decay mode X(3872)→J/ψω, with product branching fractions B(B^+→X(3872)K^+)×B(X(3872)→J/ψω)=[0.6±0.2(stat)±0.1(syst)]×10^(-5), and B(B^0→X(3872)K^0)×B(X(3872)→J/ψω)=[0.6±0.3(stat)±0.1(syst)]×10^(-5). A detailed study of the π^+π^-π^0 mass distribution from X(3872) decay favors a negative-parity assignment.

157 citations


Journal ArticleDOI
Georges Aad1, Brad Abbott2, Jalal Abdallah3, A. A. Abdelalim4  +3232 moreInstitutions (192)
TL;DR: A search for new heavy particles manifested as resonances in two-jet final states in 7 TeV proton-proton collisions by the LHC is presented, extending the reach of previous experiments.
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.

137 citations


Journal ArticleDOI
Georges Aad1, Brad Abbott2, Jalal Abdallah3, A. A. Abdelalim4  +3240 moreInstitutions (194)
TL;DR: In this paper, the first measurements of the W and Z/gamma*-boson production cross sections in proton-proton collisions at 7 TeV are presented using data recorded by the ATLAS experiment at the LHC.
Abstract: First measurements of the W -> lnu and Z/gamma* -> ll (l = e, mu) production cross sections in proton-proton collisions at sqrt(s) = 7 TeV are presented using data recorded by the ATLAS experiment at the LHC. The results are based on 2250 W -> lnu and 179 Z/gamma* -> ll candidate events selected from a data set corresponding to an integrated luminosity of approximately 320 nb-1. The measured total W and Z/gamma*-boson production cross sections times the respective leptonic branching ratios for the combined electron and muon channels are $\stotW$ * BR(W -> lnu) = 9.96 +- 0.23(stat) +- 0.50(syst) +- 1.10(lumi) nb and $\stotZg$ * BR(Z/gamma* -> ll) = 0.82 +- 0.06(stat) +- 0.05(syst) +- 0.09(lumi) nb (within the invariant mass window 66 < m_ll < 116 GeV). 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.

131 citations


Journal ArticleDOI
Georges Aad1, Brad Abbott2, Jalal Abdallah3, A. A. Abdelalim4  +2923 moreInstitutions (184)
TL;DR: In this article, an overview of the ATLAS liquid argon calorimeter performance measured in situ with random triggers, calibration data, cosmic muons, and LHC beam splash events is presented.
Abstract: The ATLAS liquid argon calorimeter has been operating continuously since August 2006. At this time, only part of the calorimeter was readout, but since the beginning of 2008, all calorimeter cells have been connected to the ATLAS readout system in preparation for LHC collisions. This paper gives an overview of the liquid argon calorimeter performance measured in situ with random triggers, calibration data, cosmic muons, and LHC beam splash events. Results on the detector operation, timing performance, electronics noise, and gain stability are presented. High energy deposits from radiative cosmic muons and beam splash events allow to check the intrinsic constant term of the energy resolution. The uniformity of the electromagnetic barrel calorimeter response along eta (averaged over phi) is measured at the percent level using minimum ionizing cosmic muons. Finally, studies of electromagnetic showers from radiative muons have been used to cross-check the Monte Carlo simulation. The performance results obtained using the ATLAS readout, data acquisition, and reconstruction software indicate that the liquid argon calorimeter is well-prepared for collisions at the dawn of the LHC era.

123 citations


Journal ArticleDOI
P. Del Amo Sanchez1, J. P. Lees1, V. Poireau1, E. Prencipe1  +447 moreInstitutions (77)
TL;DR: A direct measurement of D0-D0 mixing parameters through a time-dependent amplitude analysis of the Dalitz plots and, for the first time, D0 → K(S)(0)K+ K- decays is reported, which identifies the flavor of the neutral D meson at its production.
Abstract: We report a direct measurement of D^0-D(overbar)^0 mixing parameters through a time-dependent amplitude analysis of the Dalitz plots of D^0 → K_(S)^(0)π^(+)π^(-) and, for the first time, D^0 → K_(S)^(0)K^(+)K^(-) decays. The low-momentum pion π^(+)_s in the decay D^(*+)→D^(0)π^(+)_s identifies the flavor of the neutral D meson at its production. Using 468.5 fb^(-1) of e^(+)e^(-) colliding-beam data recorded near √s=10.6 GeV by the BABAR detector at the PEP-II asymmetric-energy collider at SLAC, we measure the mixing parameters x=[1.6±2.3(stat)±1.2(syst)±0.8(model)]×10^(-3), and y=[5.7±2.0(stat)±1.3(syst)±0.7(model)]×10^(-3). These results provide the best measurement to date of x and y. The knowledge of the value of x, in particular, is crucial for understanding the origin of mixing.

86 citations


Journal ArticleDOI
J. P. Lees1, V. Poireau1, E. Prencipe1, V. Tisserand1  +459 moreInstitutions (77)
TL;DR: A search for neutrinoless, lepton-flavor violating decay of the tau lepton into three charged leptons has been performed using an integrated luminosity of 468 fb{sup -1} collected with the BABAR detector at the PEP-II collider as mentioned in this paper.
Abstract: A search for the neutrinoless, lepton-flavor violating decay of the {tau} lepton into three charged leptons has been performed using an integrated luminosity of 468 fb{sup -1} collected with the BABAR detector at the PEP-II collider. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (1.8-3.3) x 10{sup -8} at 90% confidence level.

Journal ArticleDOI
Bernard Aubert1, Y. Karyotakis1, J. P. Lees1, V. Poireau1  +490 moreInstitutions (78)
TL;DR: In this article, a measurement of the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V-cb vertical bar and the form-factor slope rho(2) in (B) over bar -> Dl(-) (nu) over b (l) decays based on 460 X 10(6) B (B)-over bar events recorded at the Gamma(4S) resonance with the BABAR detector is presented.
Abstract: We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V-cb vertical bar and the form-factor slope rho(2) in (B) over bar -> Dl(-) (nu) over bar (l) decays based on 460 X 10(6) B (B) over bar events recorded at the Gamma(4S) resonance with the BABAR detector. (B) over bar -> Dl(-) (nu) over bar (l) decays are selected in events in which a hadronic decay of the second B meson is fully reconstructed. We measure B(B- -> D(0)l(-) (nu) over bar (l))/B(B- -> Xl(-) (nu) over bar (l)) = (0.255 +/- 0.009 +/- 0.009) and B((B) over bar (0) -> D(+)l(-) (nu) over bar (l))/B((B) over bar (0) -> Xl(-) (nu) over bar (l)) = (0.230 +/- 0.011 +/- 0.011), along with the differential decay distribution in (B) over bar -> Dl(-) (nu) over bar (l) decays. We then determine G(1)vertical bar V-cb vertical bar = 42.3 +/- 1.9 +/- 1.4) X 10(-3) and rho(2) = 1.20 +/- 0.09 +/- 0.04, where G(1) is the hadronic form factor at the point of zero recoil.

Journal ArticleDOI
Georges Aad1, Georges Aad2, E. Abat3, Brad Abbott4  +3253 moreInstitutions (185)
TL;DR: In this paper, the performance of the ATLAS detector in the first half a million minimum bias events of the LHC collision data was investigated at center-of-mass energies of 0.9 TeV and 2.36 TeV.
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.

Journal ArticleDOI
Bernard Aubert1, Y. Karyotakis1, J. P. Lees1, V. Poireau1  +481 moreInstitutions (78)
TL;DR: In this paper, a search for the Z(3930) resonance in gamma gamma production of the DDbar system has been performed using a data sample corresponding to an integrated luminosity of 384 fb^-1 recorded by the BABAR experiment at the PEP-II asymmetric-energy electron-positron collider.
Abstract: A search for the Z(3930) resonance in gamma gamma production of the DDbar system has been performed using a data sample corresponding to an integrated luminosity of 384 fb^-1 recorded by the BABAR experiment at the PEP-II asymmetric-energy electron-positron collider. The DDbar invariant mass distribution shows clear evidence of the Z(3930) state with a significance of 5.8 sigma. We determine mass and width values of (3926.7 +- 2.7 +- 1.1) MeV/c^2 and (21.3 +- 6.8 +- 3.6) MeV, respectively. A decay angular analysis provides evidence that the Z(3930) is a tensor state with positive parity and C-parity (J^PC = 2^++); therefore we identify the Z(3930) state as the chi_c2(2P) meson. The value of the partial width Gamma_(gamma gamma)xB(Z(3930)-> DDbar) is found to be (0.24 +- 0.05 +- 0.04) keV.

Journal ArticleDOI
P. Del Amo Sanchez1, J. P. Lees1, V. Poireau1, E. Prencipe1  +437 moreInstitutions (74)
TL;DR: In this article, a study of the D+π-, D0π+, and D*+π- systems in inclusive e+e-→cc interactions in a search for new excited D meson states is presented.
Abstract: We present a study of the D+π-, D0π+, and D*+π- systems in inclusive e+e-→cc interactions in a search for new excited D meson states. We use a data set, consisting of ∼454 fb-1, collected at center-of-mass energies near 10.58 GeV by the BABAR detector at the SLAC PEP-II asymmetric-energy collider. We observe, for the first time, candidates for the radial excitations of the D0, D*0, and D*+, as well as the L=2 excited states of the D0 and D+, where L is the orbital angular momentum of the quarks.

Journal ArticleDOI
Georges Aad1, Brad Abbott2, Jalal Abdallah3, A. A. Abdelalim4  +2658 moreInstitutions (165)
TL;DR: In this paper, the performance of the trigger and tracking chambers, their alignment, the detector control system, the data acquisition and the analysis programs are discussed. And the results show that the detector is close to the design performance and that the Muon Spectrometer is ready to detect muons produced in high energy protonproton collisions.
Abstract: The ATLAS detector at the Large Hadron Collider has collected several hundred million cosmic ray events during 2008 and 2009. These data were used to commission the Muon Spectrometer and to study the performance of the trigger and tracking chambers, their alignment, the detector control system, the data acquisition and the analysis programs. We present the performance in the relevant parameters that determine the quality of the muon measurement. We discuss the single element efficiency, resolution and noise rates, the calibration method of the detector response and of the alignment system, the track reconstruction efficiency and the momentum measurement. The results show that the detector is close to the design performance and that the Muon Spectrometer is ready to detect muons produced in high energy proton-proton collisions.

Journal ArticleDOI
P. Del Amo Sanchez1, J. P. Lees1, V. Poireau1, E. Prencipe1  +443 moreInstitutions (78)
TL;DR: In this article, the authors reported the measurement of the Cabibbo-Kobayashi-Maskawa CP-violating angle {gamma} through a Dalitz plot analysis of neutral D meson.
Abstract: We report the measurement of the Cabibbo-Kobayashi-Maskawa CP-violating angle {gamma} through a Dalitz plot analysis of neutral D meson decays to K{sub S}{sup 0}{pi}{sup +}{pi}{sup -} and K{sub S}{sup 0} K{sup +}K{sup -} produced in the processes B{sup {-+}} {yields} DK{sup {-+}}, B{sup {-+}} {yields} D* K{sup {-+}} with D* {yields} D{pi}{sup 0}, D{gamma}, and B{sup {-+}} {yields} DK*{sup {-+}} with K*{sup {-+}} {yields} K{sub S}{sup 0}{pi}{sup {-+}}, using 468 million B{bar B} pairs collected by the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at SLAC. We measure {gamma} = (68 {+-} 14 {+-} 4 {+-} 3){sup o} (modulo 180{sup o}), where the first error is statistical, the second is the experimental systematic uncertainty and the third reflects the uncertainty in the description of the neutral D decay amplitudes. This result is inconsistent with {gamma} = 0 (no direct CP violation) with a significance of 3.5 standard deviations.


Journal ArticleDOI
Bernard Aubert1, Y. Karyotakis1, J. P. Lees1, V. Poireau1  +488 moreInstitutions (76)
TL;DR: In this paper, the BABAR detector was used to measure (B(τ- → π- ν(τ)))/(Bτ − → e-ν(e) ν (τ))) = (0.9796±0.0016±0 0.0036), (Bτ - → K-ξ(τ)), where the uncertainties are statistical and systematic, respectively.
Abstract: Using 467 fb(-1) of e+e- annihilation data collected with the BABAR detector, we measure (B(τ- → μ- ν(μ) ν(τ)))/(B(τ- → e- ν(e) ν(τ))) =(0.9796±0.0016±0.0036), (B(τ- → π- ν(τ)))/(B(τ- → e- ν(e) ν(τ))) = (0.5945±0.0014±0.0061), and (B(τ- → K- ν(τ)))/(B(τ- → e- ν(e) ν(τ))) = (0.03882±0.00032±0.00057), where the uncertainties are statistical and systematic, respectively. From these precision τ measurements, we test the standard model assumption of μ-e and τ-μ charge current lepton universality and provide determinations of |Vus| experimentally independent of the decay of a kaon.

Journal ArticleDOI
P. Del Amo Sanchez1, J. P. Lees1, V. Poireau1, E. Prencipe1  +445 moreInstitutions (75)
TL;DR: In this article, a sample of 471 million B{bar B} events collected with the BABAR detector was used to study the sum of seven exclusive final states B {yields} X{sub s(d){gamma}, where X is a strange (nonstrange) hadronic system with a mass of up to 2.0 GeV/c{sup 2}.
Abstract: Using a sample of 471 million B{bar B} events collected with the BABAR detector, we study the sum of seven exclusive final states B {yields} X{sub s(d){gamma}}, where X{sub s(d)} is a strange (non-strange) hadronic system with a mass of up to 2.0 GeV/c{sup 2}. After correcting for unobserved decay modes, we obtain a branching fraction for b {yields} d{gamma} of (9.2 {+-} 2.0(stat.) {+-} 2.3(syst.)) x 10{sup -6} in this mass range, and a branching fraction for b {yields} s{gamma} of (23.0 {+-} 0.8(stat.) {+-} 3.0(syst.)) x 10{sup -5} in the same mass range. We find {Beta}(b{yields}d{gamma})/{Beta}(b{yields}s{gamma}) = 0.040 {+-} 0.009(stat.) {+-} 0.010(syst.), from which we determine |V{sub td}/V{sub ts}| = 0.199 {+-} 0.022(stat.) {+-} 0.024(syst.) {+-} 0.002(th.).

Journal ArticleDOI
P. Del Amo Sanchez1, J. P. Lees1, V. Poireau1, E. Prencipe1  +441 moreInstitutions (74)
TL;DR: In this article, the authors performed an analysis of B^± → DK^± decays, using decay modes in which the neutral D meson decays to either CP-eigenstates or non-CP eigenstates.
Abstract: Using the entire sample of 467×10^6 Υ(4S)→BB[overbar] decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the SLAC National Accelerator Laboratory, we perform an analysis of B^± → DK^± decays, using decay modes in which the neutral D meson decays to either CP-eigenstates or non-CP-eigenstates. We measure the partial decay rate charge asymmetries for CP-even and CP-odd D final states to be A_(CP+) = 0.25±0.06±0.02 and A_(CP-) = -0.09±0.07±0.02, respectively, where the first error is the statistical and the second is the systematic uncertainty. The parameter A_(CP+) is different from zero with a significance of 3.6 standard deviations, constituting evidence for direct CP violation. We also measure the ratios of the charged-averaged B partial decay rates in CP and non-CP decays, R_(CP+) = 1.18±0.09±0.05 and R_(CP-) = 1.07±0.08±0.04. We infer frequentist confidence intervals for the angle γ of the unitarity triangle, for the strong phase difference δ_B, and for the amplitude ratio r_B, which are related to the B^- → DK^- decay amplitude by r_(B)e^(i(δB-γ)) = A(B^- → D[overbar]^(0)K^-)/A(B^- → D^(0)K^-). Including statistical and systematic uncertainties, we obtain 0.24 < r_B < 0.45 (0.06 < r_B <0.51) and, modulo 180°, 11.3° < γ < 22.7° or 80.8° < γ <99.2° or 157.3° <γ < 168.7° (7.0°<γ<173.0°) at the 68% (95%) confidence level.

Journal ArticleDOI
P. Del Amo Sanchez1, J. P. Lees1, V. Poireau1, E. Prencipe1  +439 moreInstitutions (73)
TL;DR: In this article, a search for the rare decays B+→K+νν and B0→K0νν using 459×106 BB pairs collected with the BABAR detector at the SLAC National Accelerator Laboratory is presented.
Abstract: We present a search for the rare decays B+→K+νν and B0→K0νν using 459×106 BB pairs collected with the BABAR detector at the SLAC National Accelerator Laboratory. Flavor-changing neutral-current decays such as these are forbidden at tree level but can occur through one-loop diagrams in the standard model (SM), with possible contributions from new physics at the same order. The presence of two neutrinos in the final state makes identification of signal events challenging, so reconstruction in the semileptonic decay channels B→D(*)lν of the B meson recoiling from the signal B is used to suppress backgrounds. We set an upper limit at the 90% confidence level (CL) of 1.3×10-5 on the total branching fraction for B+→K+νν , and 5.6×10-5 for B0→K0νν . We additionally report 90% CL upper limits on partial branching fractions in two ranges of dineutrino mass squared for B+→K+νν .

Journal ArticleDOI
Bernard Aubert1, Y. Karyotakis1, J. P. Lees1, V. Poireau1  +492 moreInstitutions (80)
TL;DR: In this article, the moments of observed spectra in inclusive semileptonic B-meson decays to charm hadrons (B) over bar -> X(c)l(- )) over bar events, collected with the BABAR detector at SLAC.
Abstract: We present results for the moments of observed spectra in inclusive semileptonic B-meson decays to charm hadrons (B) over bar -> X(c)l(-)(nu) over bar. Moments of the hadronic-mass and the combined mass-and-energy spectra for different minimum electron or muon momenta between 0.8 and 1: 9 GeV/c are obtained from a sample of 232 X 10(6) Gamma(4S) -> B (B) over bar events, collected with the BABAR detector at the PEP-II asymmetric-energy B-meson factory at SLAC. We also present a reevaluation of the moments of electron-energy spectra and partial decay fractions B((B) over bar -> X(c)e(-)(nu) over bar) for minimum electron momenta between 0.6 and 1: 5 GeV/c based on a sample of 51 X 10(6) Gamma(4S) -> B (B) over bar events. The measurements are used for the extraction of the total decay fraction, the Cabibbo-Kobayashi-Maskawa (CKM) matrix element vertical bar V-cb vertical bar, the quark masses m(b) and m(c), and four heavy-quark QCD parameters in the framework of a Heavy-Quark Expansion (HQE). We find B((B) over bar -> X(c)l(-)(nu) over bar = (10.64 +/- 0.17 +/- 0.06)% and vertical bar V-cb vertical bar = (42.05 +/- 0.45 +/- 0.70) X 10(-3).

Journal ArticleDOI
P. Del Amo Sanchez1, J. P. Lees1, V. Poireau1, E. Prencipe1  +441 moreInstitutions (75)
TL;DR: The absolute branching fractions for the decays D^-_s → l^- ν_ l (l = e,µ, or τ) are measured using a data sample corresponding to an integrated luminosity of 521 fb^(-1) collected at center-of-mass energies near 10.58 GeV with the BABAR detector at the PEP-II e^+e^- collider at SLAC.
Abstract: The absolute branching fractions for the decays D^-_s → l^- ν_ l (l = e,µ, or τ) are measured using a data sample corresponding to an integrated luminosity of 521 fb^(-1) collected at center-of-mass energies near 10.58 GeV with the BABAR detector at the PEP-II e^+e^- collider at SLAC. The number of D^-_s mesons is determined by reconstructing the recoiling system DKXγ in events of the type e^+e^- → DKXD^(*-)_s , where D^(*-) → D^-_s γ and X represents additional pions from fragmentation. The D^-_s → l^- events are detected by full or partial reconstruction of the recoiling system DKXγl. The branching fraction measurements are combined to determine the D^-_s decay constant f_(ds) =(258.6 ± 6:4 ± 7.5) MeV, where the first uncertainty is statistical and the second is systematic.

Journal ArticleDOI
Georges Aad1, Brad Abbott2, Jalal Abdallah3, A. A. Abdelalim4  +2853 moreInstitutions (180)
TL;DR: In this article, the ionization signals in the liquid argon of the ATLAS electromagnetic calorimeter are studied in detail using cosmic muons, and the drift time of the ionisation electrons is measured and used to assess the intrinsic uniformity of the CALorimeter gaps and estimate its impact on the constant term of the energy resolution.
Abstract: The ionization signals in the liquid argon of the ATLAS electromagnetic calorimeter are studied in detail using cosmic muons. In particular, the drift time of the ionization electrons is measured and used to assess the intrinsic uniformity of the calorimeter gaps and estimate its impact on the constant term of the energy resolution. The drift times of electrons in the cells of the second layer of the calorimeter are uniform at the level of 1.3% in the barrel and 2.8% in the endcaps. This leads to an estimated contribution to the constant term of (0.29(-0.04)(+0.05))% in the barrel and (0.54(-0.04)(+0.06))% in the endcaps. The same data are used to measure the drift velocity of ionization electrons in liquid argon, which is found to be 4.61 +/- 0.07 mm/mu s at 88.5 K and 1 kV/mm.

Journal ArticleDOI
P. Del Amo Sanchez1, J. P. Lees1, V. Poireau1, E. Prencipe1  +442 moreInstitutions (73)
TL;DR: In this article, an updated study of the suppressed decays B^-→DK^- and B^ −→D^*K^- followed by D→K^+π^-, where D * indicates a D * meson, and D *→Dπ^0 or D*→Dγ.
Abstract: We report results from an updated study of the suppressed decays B^-→DK^- and B^-→D^*K^- followed by D→K^+π^-, where D^(*) indicates a D^((*)0) or a D^((*)0) meson, and D^*→Dπ^0 or D^*→Dγ. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity triangle angle γ due to interference between the b→c transition B^-→D^((*))0K^- followed by the doubly Cabibbo-suppressed decay D^0→K^+π^-, and the b→u transition B^-→D^((*)0)K^- followed by the Cabibbo-favored decay D^0→K^+π^-. We also report an analysis of the decay B^-→D^(*)π^- with the D decaying into the doubly Cabibbo-suppressed mode D→K^+π^-. Our results are based on 467× 10^6 Υ(4S)→BB decays collected with the BABAR detector at SLAC. We measure the ratios R^(*) of the suppressed ([K^+π^-]_DK^-/π^-) to favored ([K^-π^+]_DK^-/π^-) branching fractions as well as the CP asymmetries A^(*) of those modes. We see indications of signals for the B^-→DK^- and B^-→D_(Dπ0)^*K^- suppressed modes, with statistical significances of 2.1 and 2.2σ, respectively, and we measure: RDK=(1.1±0.6±0.2)×10^(-2), ADK=-0.86±0.47_(-0.16)^(+0.12), R_((Dπ0))K^*=(1.8±0.9± 0.4)×10^-2, A_((Dπ0))K^*=+0.77±0.35±0.12, R_((Dγ))K^*=(1.3±1.4±0.8)×10^-2,A_((Dγ))K^*=+0.36 ±0.94-_(0.41)^(+0.25), where the first uncertainty is statistical and the second is systematic. We use a frequentist approach to obtain the magnitude of the ratio r_B≡|A(B^-→D ^0K^-)/A(B^-→D^0K^-)|=(9.5_(-4.1)^(+5.1))%, with r_B<16.7% at 90% confidence level. In the case of B^-→D^*K^- we find r_B^*≡|A(B^-→D ^*0K^-)/A(B^-→D^*0K^-)|=(9.6_(-5.1)^(+3.5))%, with rB*<15.0% at 90% confidence level.

Journal ArticleDOI
P. Del Amo Sanchez1, J. P. Lees1, V. Poireau1, E. Prencipe1  +439 moreInstitutions (76)
TL;DR: In this article, the authors performed a study of exclusive production of D{sub s}{sup +}D{subs}{sup -, D{ sub s {sub s} *+}D {sub S {sub n} *-}, and D{Sub s{sub n{sub ns} * +}d{sub S} * -} final states in initial state-radiation events from e{sup+}e{sup -} annihilations.
Abstract: We perform a study of exclusive production of D{sub s}{sup +}D{sub s}{sup -}, D{sub s}{sup *+}D{sub s}{sup -}, and D{sub s}{sup *+}D{sub s}{sup *-} final states in initial-state-radiation events from e{sup +}e{sup -} annihilations at a center-of-mass energy near 10.58 GeV, to search for charmonium 1{sup --} states. The data sample corresponds to an integrated luminosity of 525 fb{sup -1} and was recorded by the BABAR experiment at the PEP-II storage ring. The D{sub s}{sup +}D{sub s}{sup -}, D{sub s}{sup *+}D{sub s}{sup -}, and D{sub s}{sup *+}D{sub s}{sup *-} mass spectra show evidence of the known {psi} resonances. Limits are extracted for the branching ratios of the decays X(4260){yields}D{sub s}{sup (*)+}D{sub s}{sup (*)-}.

Journal ArticleDOI
P. Del Amo Sanchez1, J. P. Lees1, V. Poireau1, E. Prencipe1  +450 moreInstitutions (78)
TL;DR: In this paper, the authors measured the ratio R_(τμ)(Υ(1S)) = 1.005±0.013(stat)± 0.022(syst) in the standard model (SM) with no deviation from the expected SM value.
Abstract: The ratio R_(τμ)(Υ(1S)) = Γ_(Υ(1S)→τ^+^τ-)/Γ_(Υ(1S)→μ^+μ^-) is measured using a sample of (121.8±1.2) × 10^(6)Υ(3S) events recorded by the BABAR detector. This measurement is intended as a test of lepton universality and as a search for a possible light pseudoscalar Higgs boson. In the standard model (SM) this ratio is expected to be close to 1. Any significant deviations would violate lepton universality and could be introduced by the coupling to a light pseudoscalar Higgs boson. The analysis studies the decays Υ(3S)→Υ(1S)π^+π^-, Υ(1S)→l^+l^-, where l = μ, τ. The result, R_(τμ)(Υ(1S)) = 1.005±0.013(stat)±0.022(syst), shows no deviation from the expected SM value, while improving the precision with respect to previous measurements.

Journal ArticleDOI
Bernard Aubert1, Y. Karyotakis1, J. P. Lees1, V. Poireau1  +491 moreInstitutions (78)
TL;DR: In this article, the branching fractions of neutral and charged B meson decays to final states containing a K_1(1270) or K_ 1(1400) meson and a charged pion.
Abstract: We report measurements of the branching fractions of neutral and charged B meson decays to final states containing a K_1(1270) or K_1(1400) meson and a charged pion. The data, collected with the BABAR detector at the SLAC National Accelerator Laboratory, correspond to 454×10^6 BB pairs produced in e^+e^- annihilation. We measure the branching fractions B(B^0→K_1(1270)^+π-+K_1(1400)^+π-)=3.1_(-0.7)^(+0.8)×10^(-5) and B(B^+→K_1(1270)^0π^++K_1(1400)^0π^+)=2.9_(-1.7)^(+2.9)×10^(-5) (<8.2×10^(-5) at 90% confidence level), where the errors are statistical and systematic combined. The B^0 decay mode is observed with a significance of 7.5σ, while a significance of 3.2σ is obtained for the B^+ decay mode. Based on these results, we estimate the weak phase α=(79±7±11)° from the time-dependent CP asymmetries in B^0→a1(1260)^±π^∓ decays.

Journal ArticleDOI
P. Del Amo Sanchez1, J. P. Lees1, V. Poireau1, E. Prencipe1  +442 moreInstitutions (74)
TL;DR: In this paper, the authors used the π+π-invariant mass distribution to confirm the consistency of the observed state with the orbital angular momentum assignment of the Υ(13DJ) triplet.
Abstract: Based on 122×106Υ(3S) events collected with the BABAR detector, we have observed the Υ(13DJ) bottomonium state through the Υ(3S)→γγΥ(13DJ)→γγπ+π-Υ(1S) decay chain. The significance for the J=2 member of the Υ(13DJ) triplet is 5.8 standard deviations including systematic uncertainties. The mass of the J=2 state is determined to be 10 164.5±0.8(stat)±0.5(syst) MeV/c2. We use the π+π- invariant mass distribution to confirm the consistency of the observed state with the orbital angular momentum assignment of the Υ(13DJ).