SwePub - search: WFRF:(Williams B)

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1.	Schael, S, et al. (author) Precision electroweak measurements on the Z resonance 2006 In: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454 Research review (peer-reviewed)abstract We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
2.	Aamodt, K., et al. (author) The ALICE experiment at the CERN LHC 2008 In: Journal of Instrumentation. - 1748-0221. ; 3:S08002 Research review (peer-reviewed)abstract ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries, Its overall dimensions are 16 x 16 x 26 m(3) with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.
3.	Fox, Z, et al. (author) Predictors of CD4 count change over 8 months of follow up in HIV-1-infected patients with a CD4 count>or=300 cells/microL who were assigned to 7.5 MIU interleukin-2 2007 In: HIV medicine. - : Wiley. - 1464-2662 .- 1468-1293. ; 8:2, s. 112-123 Journal article (peer-reviewed)
4.	Abazov, V. M., et al. (author) Properties of l=1 B-1 and B(2) Mesons 2007 In:* Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:17, s. 172001- 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.
5.	Abazov, V. M., et al. (author) Evidence for the Decay B-s(0)->(DsDs())-D-() and a Measurement of Delta Gamma(CP)(s)/Gamma(s) 2009 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:9, s. 091801- Journal article (peer-reviewed)abstract We search for the semi-inclusive process B-s(0)->(DsDs())-D-() using 2.8 fb(-1) of pp collisions at s=1.96 TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We observe 26.6 +/- 8.4 signal events with a significance above background of 3.2 standard deviations yielding a branching ratio of B(B-s(0)->(DsDs())-D-())=0.035 +/- 0.010(stat.)+/- 0.011(syst.). Under certain theoretical assumptions, these double-charm final states saturate CP-even eigenstates in the B-s(0) decays resulting in a width difference of Delta Gamma(CP)(s)/Gamma(s)=0.072 +/- 0.021(stat.)+/- 0.022(syst.).
6.	Abazov, V. M., et al. (author) Measurement of sigma(p(p)over-bar -> Z plus X)Br(Z -> tau(+)tau(-)) at root s=1.96 TeV 2009 In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 670:4-5, s. 292-299 Journal article (peer-reviewed)abstract We present a measurement of the cross section for Z boson production times the branching fraction to tau lepton pairs sigma(p (p) over bar -> Z + X)Br(Z -> tau(+)tau(-)) in p (p) over bar collisions at root s = 1.96 TeV. The measurement is performed in the channel in which one tau lepton decays into a muon and neutrinos. and the other tau lepton decays hadronically or into an electron and neutrinos. The data sample corresponds to an integrated luminosity of 1.0 fb(-1) collected with the DO detector at the Fermilab Tevatron Collider. The sample contains 1511 candidate events with an estimated 20% background from jets or muons misidentified as tau leptons. We obtain sigma . Br = 240 +/- 8 (star) +/- 12 (sys) +/- 15 (lum) pb, which is consistent with the standard model prediction.
7.	Abazov, V. M., et al. (author) Measurement of the Angular and Lifetime Parameters of the Decays B-d(0) -> J/psi K(0) and B-s(0) -> J/psi phi 2009 In:* Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:3, s. 032001-:102, s. 032001- Journal article (peer-reviewed)abstract We present measurements of the linear polarization amplitudes and the strong relative phases that describe the flavor-untagged decays B-d(0) --> J/psi K(0) and B-s(0) --> J/psi phi in the transversity basis. We also measure the mean lifetime (tau) over bar (s) of the B-s(0) mass eigenstates and the lifetime ratio (tau) over bar (s)/tau(d). The analyses are based on approximately 2.8 fb(-1) of data recorded with the D0 detector. From our measurements of the angular parameters we conclude that there is no evidence for a deviation from flavor SU( 3) symmetry for these decays and that the factorization assumption is not valid for the B-d(0) --> J/psi K(0) decay.
8.	Abazov, V. M., et al. (author) Observation of ZZ Production in p(p)over-bar Collisions at root s=1.96 TeV 2008 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 101:17, s. 171803-:101, s. 171803- Journal article (peer-reviewed)abstract We present an observation for ZZ -> l(+) l(-) l'(+) l'(-) (l, l' =e or mu) production in p (p) over bar collisions at a center-of-mass energy of root s = 1.96 TeV. Using 1.7 fb(-1) of data collected by the D0 experiment at the Fermilab Tevatron Collider, we observe three candidate events with an expected background of 0.14(-0.02)(+0.03) events. The significance of this observation is 5.3 standard deviations. The combination of D0 results in this channel, as well as in ZZ -> l(+) l(-) v (v) over bar yields a significance of 5.7 standard deviations and a combined cross section of sigma(ZZ) = 1.60 +/- 0.63(stat)(-0.17)(+0.16)(syst) pb.
9.	Abazov, V. M., et al. (author) Search for Associated W and Higgs Boson Production in p(p)over-bar Collisions at root s=1.96 TeV 2009 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:5, s. 051803-:102, s. 051803- Journal article (peer-reviewed)abstract We present results of a search for WH -> l nu b (b) over bar production in p (p) over bar collisions based on the analysis of 1.05 fb(-1) of data collected by the D0 experiment at the Fermilab Tevatron, using a neural network for separating the signal from backgrounds. No signal-like excess is observed, and we set 95% C. L. upper limits on the WH production cross section multiplied by the branching ratio for H -> b (b) over bar for Higgs boson masses between 100 and 150 GeV. For a mass of 115 GeV, we obtain an observed (expected) limit of 1.5 (1.4) pb, a factor of 11.4 (10.7) times larger than the standard model prediction.
10.	Abazov, V. M., et al. (author) Search for Large Extra Spatial Dimensions in the Dielectron and Diphoton Channels in p(p)over-bar Collisions at root s=1.96 TeV 2009 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:5, s. 051601-:102, s. 051601- Journal article (peer-reviewed)abstract We report on a search for large extra spatial dimensions in the dielectron and diphoton channels using a data sample of 1: 05 fb(-1) of p (p) over bar collisions at a center-of-mass energy of 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. The invariant mass spectrum of the data agrees well with the prediction of the standard model. We find the most restrictive 95% C. L. lower limits on the effective Planck scale between 2.1 and 1.3 TeV for 2 to 7 extra dimensions.
11.	Abazov, V. M., et al. (author) Search for Neutral Higgs Bosons at High tan beta in the b(h/H/A) -> b tau(+)tau(-) Channel 2009 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:5, s. 051804-:102, s. 051804- Journal article (peer-reviewed)abstract The first search in p (p) over bar collisions at root s = 1.96 TeV for the production of neutral Higgs bosons in association with bottom quarks and decaying in two tau leptons is presented. The cross section for this process is enhanced in many extensions of the standard model, such as its minimal supersymmetric extension (MSSM) at large tan beta. The data, corresponding to an integrated luminosity of 328 pb(-1), were collected with the D0 detector at the Fermilab Tevatron Collider. An upper limit is set on the production cross section of neutral Higgs bosons in the mass range of 90 to 150 GeV, and this limit is used to exclude part of the MSSM parameter space.
12.	Abazov, V. M., et al. (author) Search for pair production of second generation scalar leptoquarks 2009 In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 671:2, s. 224-232 Journal article (peer-reviewed)abstract We report on a search for the pair production of second generation scalar leptoquarks (LQ) in p (p) over bar collisions at the center of mass energy root s- = 1.96 TeV using a data set corresponding to an integrated luminosity of 1.0 fb(-1) collected with the D empty set experiment at the Fermilab Tevatron Collider. Topologies arising from the LQ (LQ) over bar -> mu q nu q and LQ (LQ) over bar -> mu q mu q decay modes are investigated. No excess of data over the standard model prediction is observed and upper limits on the leptoquark pair production cross section are derived at the 95% C.L. as a function of the leptoquark mass and the branching fraction beta for the decay LQ -> mu q. These are interpreted as lower limits on the leptoquark mass as a function of beta. For beta = 1 (0.5), scalar second generation leptoquarks with masses up to 316 GeV (270 GeV) are excluded.
13.	Abazov, V. M., et al. (author) Search for Anomalous Top-Quark Couplings with the D0 Detector 2009 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:9, s. 092002- Journal article (peer-reviewed)abstract Anomalous Wtb couplings modify the angular correlations of the top-quark decay products and change the single top-quark production cross section. We present limits on anomalous top-quark couplings by combining information from W boson helicity measurements in top-quark decays and anomalous coupling searches in the single top-quark final state. We set limits on right-handed vector couplings as well as left-handed and right-handed tensor couplings based on about 1 fb(-1) of data collected by the D0 experiment.
14.	Abazov, M, et al. (author) Search for admixture of scalar top quarks in the t(t)over-bar lepton + jets final state at root s=1.96 TeV 2009 In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 674:1, s. 4-10 Journal article (peer-reviewed)abstract A search for pair production of the lightest supersymmetric partner of the top quark, (t) over tilde (1), is performed in the lepton + jets channel using 0.9 fb(-1) of data collected by the D circle divide experiment. Kinematic differences between (t) over tilde (1)(t) over tilde (1) and the dominant top quark pair production background are used to separate the two processes. First limits from Run II of the Fermilab Tevatron Collider for the scalar top quark decaying to a chargino and a b quark ((t) over tilde1 -> (chi) over tilde (+)(1)b) are obtained for scalar top quark masses of 130-190 GeV and chargino masses of 90-150 GeV.
15.	Abazov, V. M., et al. (author) Observation and properties of the orbitally excited B-s2* meson 2008 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:8, s. 082002-:100, s. 082002- Journal article (peer-reviewed)abstract We report the direct observation of the excited L=1 state B-s2* in fully reconstructed decays to B+K-. The mass of the B-s2* meson is measured to be 5839.6 +/- 1.1(stat)+/- 0.7(syst) MeV/c(2), and its production rate relative to the B+ meson is measured to be [1.15 +/- 0.23(stat)+/- 0.13(syst)]%.
16.	Abazov, V. M., et al. (author) Study of direct CP violation in B-+/--> J/psi K-+/-(pi(+/-)) decays 2008 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:21, s. 211802- Journal article (peer-reviewed)abstract We present a search for direct CP violation in B-+/- -> J/psi K-+/- (pi(+/-)) decays. The event sample is selected from 2: 8 fb(-1) of p (p) over bar collisions recorded by D0 experiment in run II of the Fermilab Tevatron Collider. The charge asymmetry A(CP)(B+ -> J/psi K+) = +0: 0075 +/- 0: 0061(stat) +/- 0: 0030 (syst) is obtained using a sample of approximately 40 000 B-+/- -> J/psi K-+/- decays. The achieved precision is of the same level as the expected deviation predicted by some extensions of the standard model. We also measured the charge asymmetry A(CP) (B+ -> J/psi pi(+)) = - 0: 09 +/- 0: 08(stat) +/- 0: 03(syst).
17.	Abazov, M, et al. (author) Measurement of differential Z/gamma* plus jet plus X cross sections in p(p)over-bar collisions at root S=1.96 TeV 2008 In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 669:5, s. 278-286 Journal article (peer-reviewed)abstract We present new measurements of differential cross sections for Z/gamma* (-> mu mu) + jet + X production in a 1 fb(-1) data sample collected with the DO detector in p (p) over bar collisions at root s = 1.96 TeV. Results include the first measurements differential in the Z/gamma* transverse momentum and rapidity, as well as new measurements differential in the leading jet transverse momentum and rapidity. Next-to-leading order perturbative QCD predictions are compared to the measurements, and reasonable agreement is observed, except in the region of low Z/gamma* transverse momentum. Predictions from two event generators based on matrix elements and parton showers, and one pure parton shower event generator are also compared to the measurements. These show significant overall normalization differences to the data and have varied success in describing the shape of the distributions.
18.	Abazov, M, et al. (author) Measurement of gamma + b + X and gamma + c + X Production Cross Sections in pp > Collisions at s=1.96 TeV 2009 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:19, s. 192002- Journal article (peer-reviewed)abstract First measurements of the differential cross sections d(3)sigma/(dp(T)(gamma)dy(gamma)dy(jet)) for the inclusive production of a photon in association with a heavy quark (b, c) jet are presented, covering photon transverse momenta 30 < p(T)(gamma)< 150 GeV, photon rapidities \|y(gamma)\|< 1.0, jet rapidities \|y(jet)\|< 0.8, and jet transverse momenta p(T)(jet)> 15 GeV. The results are based on an integrated luminosity of 1 fb(-1) in pp collisions at s=1.96 TeV recorded with the D0 detector at the Fermilab Tevatron Collider. The results are compared with next-to-leading order perturbative QCD predictions.
19.	Abazov, M, et al. (author) Measurement of the t(t)over-bar production cross section and top quark mass extraction using dilepton events in p(p)over-bar collisions 2009 In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 679:3, s. 177-185 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 using approximately 1 fb(-1) collected with the DO detector. We consider decay channels containing two high p(T) charged leptons where one lepton is identified as an electron or a muon while the other lepton can be an electron, a muon or a hadronically decaying tau lepton. For a mass of the top quark of 170 GeV, the measured cross section is 7.5(-1.0)(+1.0)(stat)(-0.6)(+0.7)(syst)(-0.5)(+0.6)(lumi) pb. Using l tau events only, we measure: sigma(t (t) over bar) x B(t (t) over bar -> l tau b (b) over bar) = 0.13(-0.08)(+0.09)(stat)(-0.06)(+0.06)(syst)(-0.02)(+0.02)(lumi) pb. Comparing the measured cross section as a function of the mass of the top quark with a partial next-to-next-to leading order Quantum Chroniodynamics theoretical prediction, we extract a mass of the top quark of 171.5(-8.8)(+9-9) GeV, in agreement with direct measurements.
20.	Abazov, M, et al. (author) Search for associated production of charginos and neutralinos in the trilepton final state using 2.3 fb(-1) of data 2009 In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 680:1, s. 34-43 Journal article (peer-reviewed)abstract We report the results of a search for associated production of charginos and neutralinos using a data set corresponding to an integrated luminosity of 2.3 fb(-1) collected with the Demptyset experiment during Run II of the Tevatron proton-antiproton collider. Final states containing three charged leptons and missing transverse energy are probed for a signal from supersymmetry with four dedicated trilepton event selections. No evidence for a signal is observed, and we set limits on the product of production cross section and leptonic branching fraction. Within minimal supergravity, these limits translate into bounds on m(0) and m(1/2) that are well beyond existing limits.
21.	Abazov, M, et al. (author) Search for Resonant Diphoton Production with the D0 Detector 2009 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:23, s. 231801- Journal article (peer-reviewed)abstract We present a search for a narrow resonance in the inclusive diphoton final state using similar to 2.7 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron p (p) over bar Collider. We observe good agreement between the data and the background prediction, and set the first 95% C. L. upper limits on the production cross section times the branching ratio for decay into a pair of photons for resonance masses between 100 and 150 GeV. This search is also interpreted in the context of several models of electroweak symmetry breaking with a Higgs boson decaying into two photons.
22.	Abazov, M, et al. (author) Search for the Standard Model Higgs Boson in the Missing Energy and Acoplanar b-Jet Topology at root s=1.96 TeV 2008 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 101:25, s. 251802- Journal article (peer-reviewed)abstract We report a search for the standard model Higgs boson in the missing energy and acoplanar b-jet topology, using an integrated luminosity of 0.93 fb(-1) recorded by the D0 detector at the Fermilab Tevatron p (p) over bar Collider. The analysis includes signal contributions from p (p) over bar -> ZH -> v (v) over barb (b) over bar, as well as from WH production in which the charged lepton from the W boson decay is undetected. Neural networks are used to separate signal from background. In the absence of a signal, we set limits on sigma(p (p) over bar -> VH) x B(H -> b (b) over bar) at the 95% C.L. of 2.6-2.3 pb, for Higgs boson masses in the range 105-135 GeV, where V W, Z. The corresponding expected limits range from 2.8 to 2.0 pb.
23.	Abazov, M, et al. (author) Evidence of WW and WZ Production with lepton plus jets Final States in pp Collisions at root s=1.96 TeV 2009 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:16, s. 161801- Journal article (peer-reviewed)abstract We present first evidence for WW+WZ production in lepton+jets final states at a hadron collider. The data correspond to 1.07 fb(-1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron in pp collisions at root s=1.96 TeV. The observed cross section for WW+WZ production is 20.2 +/- 4.5 pb, consistent with the standard model and more precise than previous measurements in fully leptonic final states. The probability that background fluctuations alone produce this excess is < 5.4x10(-6), which corresponds to a significance of 4.4 standard deviations.
24.	Abazov, M, et al. (author) Measurement of the WW Production Cross Section with Dilepton Final States in pp Collisions at s=1.96 TeV and Limits on Anomalous Trilinear Gauge Couplings 2009 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 103:19, s. 191801- Journal article (peer-reviewed)abstract We provide the most precise measurement of the WW production cross section in pp collisions to date at a center of mass energy of 1.96 TeV, and set limits on the associated trilinear gauge couplings. The WW -> l nu l(')nu (l, l(')=e, mu) decay channels are analyzed in 1 fb(-1) of data collected by the D0 detector at the Fermilab Tevatron Collider. The measured cross section is sigma(pp -> WW)=11.5 +/- 2.1(stat+syst)+/- 0.7(lumi) pb. One- and two-dimensional 95% C.L. limits on trilinear gauge couplings are provided.
25.	Abazov, M, et al. (author) Measurement of the Z gamma -> nu(nu)over-bar gamma Production Cross Section and Limits on Anomalous ZZ gamma and Z gamma gamma Couplings in p(p)over-bar Collisions at root s=1.96 TeV 2009 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:20, s. 201802- Journal article (peer-reviewed)abstract We present the first observation of the Z gamma -> nu(nu) over bar gamma process at the Fermilab Tevatron at 5.1 standard deviations significance, based on 3.6 fb(-1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron p (p) over bar Collider at root s = 1.96 TeV. The measured Z gamma production cross section multiplied by the branching fraction of Z -> nu(nu) over bar is 32 +/- 9(stat + syst) +/- 2(lumi) fb for the photon E-T > 90 GeV. It is in agreement with the standard model prediction of 39 +/- 4 fb. We set limits on anomalous trilinear Z gamma gamma and ZZ gamma gauge boson couplings, most of which are the most restrictive to date.

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