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Abazov, V.M.,Abbott, B.,Abolins, M.,Acharya, B.S.,Adams, M.,Adams, T.,Aguilo, E.,Ahsan, M.,Alexeev, G.D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G.A.,Anastasoaie, M.,Ancu, L.S.,Andeen, T.,Andrieu, Elsevier 2009 Physics letters: B Vol.680 No.1
<P><B>Abstract</B></P><P>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<SUP>−1</SUP> collected with the DØ 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 <SUB>m0</SUB> and <SUB>m1/2</SUB> that are well beyond existing limits.</P>
Measurement of the Angular and Lifetime Parameters of the DecaysBd0→J/ψK*0andBs0→J/ψϕ
Abazov, V. M.,Abbott, B.,Abolins, M.,Acharya, B. S.,Adams, M.,Adams, T.,Aguilo, E.,Ahsan, M.,Alexeev, G. D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G. A.,Anastasoaie, M.,Ancu, L. S.,Andeen, T.,Andr American Physical Society 2009 Physical Review Letters Vol.102 No.3
<P>We present measurements of the linear polarization amplitudes and the strong relative phases that describe the flavor-untagged decays Bd0-->J/psiK*0 and Bs0-->J/psiphi in the transversity basis. We also measure the mean lifetime taus of the Bs0 mass eigenstates and the lifetime ratio taus/taud. 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 Bd0-->J/psiK*0 decay.</P>
Search for AssociatedWand Higgs Boson Production inpp¯Collisions ats=1.96 TeV
Abazov, V. M.,Abbott, B.,Abolins, M.,Acharya, B. S.,Adams, M.,Adams, T.,Aguilo, E.,Ahsan, M.,Alexeev, G. D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G. A.,Anastasoaie, M.,Ancu, L. S.,Andeen, T.,Andr American Physical Society 2009 Physical Review Letters Vol.102 No.5
<P>We present results of a search for WH-->lnubb[over ] production in pp[over ] 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-->bb[over ] 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.</P>
Zγ production and limits on anomalous ZZγ and Zγγ couplings in pp@? collisions at s=1.96 TeV
DO Collaboration,Abazov, V.M.,Abbott, B.,Abolins, M.,Acharya, B.S.,Adams, M.,Adams, T.,Aguilo, E.,Ahn, S.H.,Ahsan, M.,Alexeev, G.D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G.A.,Anastasoaie, M.,Ancu North-Holland Pub. Co 2007 Physics letters: B Vol.653 No.5
We present a study of eeγ and μμγ events using 1109 (1009) pb<SUP>-1</SUP> of data in the electron (muon) channel, respectively. These data were collected with the DO detector at the Fermilab Tevatron pp@? collider at s=1.96 TeV. Having observed 453 (515) candidates in the eeγ (μμγ) final state, we measure the Zγ production cross section for a photon with transverse energy E<SUB>T</SUB>>7 GeV, separation between the photon and leptons ΔR<SUB>@</SUB>?<SUB>&</SUB>gamma;>0.7, and invariant mass of the di-lepton pair M<SUB>@</SUB>?<SUB>@</SUB>?>30 GeV/c<SUP>2</SUP>, to be 4.96+/-0.30(stat.+syst.)+/-0.30(lumi.) pb, in agreement with the Standard Model prediction of 4.74+/-0.22 pb. This is the most precise Zγ cross section measurement at a hadron collider. We set limits on anomalous trilinear Zγγ and ZZγ gauge boson couplings of -0.085<h<SUB>30</SUB><SUP>&</SUP>gamma;<0.084, -0.0053<h<SUB>40</SUB><SUP>&</SUP>gamma;<0.0054 and -0.083<h<SUB>30</SUB><SUP>Z</SUP><0.082, -0.0053<h<SUB>40</SUB><SUP>Z</SUP><0.0054 at the 95% C.L. for the form-factor scale Λ=1.2 TeV.
Measurement ofBs0Mixing Parameters from the Flavor-Tagged DecayBs0→J/ψϕ
Abazov, V. M.,Abbott, B.,Abolins, M.,Acharya, B. S.,Adams, M.,Adams, T.,Aguilo, E.,Ahn, S. H.,Ahsan, M.,Alexeev, G. D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G. A.,Anastasoaie, M.,Ancu, L. S.,Ande American Physical Society 2008 Physical review letters Vol.101 No.24
<P>From an analysis of the flavor-tagged decay Bs0-->J/psiphi we obtain the width difference between the Bs0 light and heavy mass eigenstates, DeltaGammas = 0.19+/-0.07(stat)(-0.01)+0.02(syst) ps(-1), and the CP-violating phase, phi s= -0.57(-0.30)+0.24(stat)(-0.02)+0.08(syst). The allowed 90% CL intervals of DeltaGammas and phi s are 0.06 < DeltaGammas < 0.30 ps(-1) and -1.20 < phi s < 0.06, respectively. The data sample corresponds to an integrated luminosity of 2.8 fb(-1) accumulated with the D0 detector at the Fermilab Tevatron collider.</P>
Abazov, V. M.,Abbott, B.,Abolins, M.,Acharya, B. S.,Adams, M.,Adams, T.,Aguilo, E.,Ahn, S. H.,Ahsan, M.,Alexeev, G. D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G. A.,Anastasoaie, M.,Ancu, L. S.,Ande American Physical Society 2008 Physical review letters Vol.100 No.10
<P>We present a measurement of the shape of the Z/gamma* boson transverse momentum (q(T)) distribution in pp --> Z/gamma* --> e(+)e(-) + X events at a center-of-mass energy of 1.96 TeV using 0.98 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron collider. The data are found to be consistent with the resummation prediction at low q(T), but above the perturbative QCD calculation in the region of q(T)>30 GeV/c. Using events with q(T)<30 GeV/c, we extract the value of g(2), one of the nonperturbative parameters for the resummation calculation. Data at large boson rapidity y are compared with the prediction of resummation and with alternative models that employ a resummed form factor with modifications in the small Bjorken x region of the proton wave function.</P>
Search for supersymmetry in di-photon final states at s=1.96 TeV
Abazov, V.M.,Abbott, B.,Abolins, M.,Acharya, B.S.,Adams, M.,Adams, T.,Aguilo, E.,Ahn, S.H.,Ahsan, M.,Alexeev, G.D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G.A.,Anastasoaie, M.,Ancu, L.S.,Andeen, T. Elsevier 2008 Physics letters: B Vol.659 No.5
<P><B>Abstract</B></P><P>We report results of a search for supersymmetry (SUSY) with gauge-mediated symmetry breaking in di-photon events collected by the D0 experiment at the Fermilab Tevatron Collider in 2002–2006. In 1.1 fb<SUP>−1</SUP> of data, we find no significant excess beyond the background expected from the standard model and set the most stringent lower limits to date for a standard benchmark model on the lightest neutralino and chargino masses of 125 GeV and 229 GeV, respectively, at 95% confidence.</P>
DO Collaboration,Abazov, V.M.,Abbott, B.,Abolins, M.,Acharya, B.S.,Adams, M.,Adams, T.,Aguilo, E.,Ahn, S.H.,Ahsan, M.,Alexeev, G.D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G.A.,Anastasoaie, M.,Ancu North-Holland Pub. Co 2008 Physics letters: B Vol.666 No.5
The process pp@?->γ+jet+X is studied using 1.0 fb<SUP>-1</SUP> of data collected by the D0 detector at the Fermilab Tevatron pp@? collider at a center-of-mass energy s=1.96 TeV. Photons are reconstructed in the central rapidity region |y<SUP>&</SUP>gamma;|<1.0 with transverse momenta in the range 30<p<SUB>T</SUB><SUP>&</SUP>gamma;<400 GeV while jets are reconstructed in either the central |y<SUP>jet</SUP>|<0.8 or forward 1.5<|y<SUP>jet</SUP>|<2.5 rapidity intervals with p<SUB>T</SUB><SUP>jet</SUP>>15 GeV. The differential cross section d<SUP>3</SUP>σ/dp<SUB>T</SUB><SUP>&</SUP>gamma;dy<SUP>&</SUP>gamma;dy<SUP>jet</SUP> is measured as a function of p<SUB>T</SUB><SUP>&</SUP>gamma; in four regions, differing by the relative orientations of the photon and the jet in rapidity. Ratios between the differential cross sections in each region are also presented. Next-to-leading order QCD predictions using different parameterizations of parton distribution functions and theoretical scale choices are compared to the data. The predictions do not simultaneously describe the measured normalization and p<SUB>T</SUB><SUP>&</SUP>gamma; dependence of the cross section in the four measured regions.
A combined search for the standard model Higgs boson at s=1.96 TeV
DO Collaboration,Abazov, V.M.,Abbott, B.,Abolins, M.,Acharya, B.S.,Adams, M.,Adams, T.,Aguilo, E.,Ahn, S.H.,Ahsan, M.,Alexeev, G.D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G.A.,Anastasoaie, M.,Ancu North-Holland Pub. Co 2008 Physics letters: B Vol.663 No.1
We present new results of the search for WH->@?νbb@? production in pp@? collisions at a center-of-mass energy of s=1.96 TeV, based on a dataset with integrated luminosity of 0.44 fb<SUP>-1</SUP>. We combine these new results with previously published searches by the D0 collaboration, for WH and ZH production analyzed in the E@?<SUB>T</SUB>bb@? final state, for ZH (->@?<SUP>+</SUP>@?<SUP>-</SUP>bb@?) production, for WH (->WWW) production, and for H (->WW) direct production. No signal-like excess is observed either in the WH analysis or in the combination of all D0 Higgs boson analyses. We set 95% C.L. (expected) upper limits on σ(pp@?->WH)xB(H->bb@?) ranging from 1.6 (2.2) pb to 1.9 (3.3) pb for Higgs boson masses between 105 and 145 GeV, to be compared to the theoretical prediction of 0.13 pb for a Standard Model (SM) Higgs boson with mass m<SUB>H</SUB>=115 GeV. After combination with the other D0 Higgs boson searches, we obtain for m<SUB>H</SUB>=115 GeV an observed (expected) limit 8.5 (12.1) times higher than the SM predicted Higgs boson production cross section. For m<SUB>H</SUB>=160 GeV, the corresponding observed (expected) ratio is 10.2 (9.0).
Evidence for Production of Single Top Quarks and First Direct Measurement of|Vtb|
Abazov, V. M.,Abbott, B.,Abolins, M.,Acharya, B. S.,Adams, M.,Adams, T.,Aguilo, E.,Ahn, S. H.,Ahsan, M.,Alexeev, G. D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G. A.,Anastasoaie, M.,Ancu, L. S.,Ande American Physical Society 2007 Physical Review Letters Vol.98 No.18