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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>
Search for pair production of first-generation leptoquarks in pp¯ collisions at s=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.,Ancu, L.S.,Andeen, T.,Anzelc, M.S.,Aoki, M.,Arn Elsevier 2009 Physics letters: B Vol.681 No.3
<P><B>Abstract</B></P><P>A search for pair production of first-generation leptoquarks (<I>LQ</I>) is performed with data collected by the DØ experiment in pp¯ collisions at s=1.96 TeV at the Fermilab Tevatron Collider. In a sample of data corresponding to ∼1<SUP> fb−1</SUP> the search has been performed on the final states with two electrons and two jets or one electron, two jets and missing transverse energy. We find our data consistent with standard model expectations. The results are combined with those found in a previous analysis of events with two jets and missing transverse energy to obtain scalar <I>LQ</I> mass limits. We set 95% C.L. lower limits on a scalar <I>LQ</I> mass of 299 GeV, 284 GeV and 216 GeV for β=1, β=0.5 and β=0.02 respectively, where <I>β</I> is the <I>LQ</I> branching ratio in the <I>eq</I> channel. This improves the results obtained with a lower luminosity sample from Run II of the Tevatron. Lower limits on vector <I>LQ</I> masses with different couplings from 357 GeV to 464 GeV for β=0.5 are also set using this analysis.</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>
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.,Ancu, L.S.,Andeen, T.,Anzelc, M.S.,Aoki, M.,Arn Elsevier 2009 Physics letters: B Vol.680 No.1
<P><B>Abstract</B></P><P>A search for supersymmetric partners of quarks is performed in the topology of multijet events accompanied by at least one tau lepton decaying hadronically and large missing transverse energy. Approximately 1 fb<SUP>−1</SUP> of pp¯ collision data from the Fermilab Tevatron Collider at a center of mass energy of 1.96 TeV recorded by the DØ detector is analyzed. Results are combined with the previously published DØ inclusive search for squarks and gluinos. No evidence of physics beyond the Standard Model is found and lower limits on the squark mass up to 410 GeV are derived in the framework of minimal supergravity with tanβ=15, <SUB>A0</SUB>=−2<SUB>m0</SUB> and μ<0, in the region where decays to tau leptons dominate. Gaugino masses <SUB>m1/2</SUB> are excluded up to 172 GeV.</P>
DO Collaboration,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.,And North-Holland Pub. Co 2009 Physics letters: B Vol.679 No.3
We present a measurement of the top quark pair production cross section in pp@? collisions at s=1.96 TeV using approximately 1 fb<SUP>-1</SUP> collected with the DO detector. We consider decay channels containing two high p<SUB>T</SUB> 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 τ lepton. For a mass of the top quark of 170 GeV, the measured cross section is 7.5<SUB>-1.0</SUB><SUP>+1.0</SUP>(stat)<SUB>-0.6</SUB><SUP>+0.7</SUP>(syst)<SUB>-0.5</SUB><SUP>+0.6</SUP>(lumi) pb. Using @?τ events only, we measure: σ<SUB>tt@</SUB>?xB(tt@?->@?τbb@?)=0.13<SUB>-0.08</SUB><SUP>+0.09</SUP>(stat)<SUB>-0.06</SUB><SUP>+0.06</SUP>(syst)<SUB>-0.02</SUB><SUP>+0.02</SUP>(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 Chromodynamics theoretical prediction, we extract a mass of the top quark of 171.5<SUB>-8.8</SUB><SUP>+9.9</SUP> GeV, in agreement with direct measurements.
Search for admixture of scalar top quarks in the tt@? lepton + jets final state at s=1.96 TeV
DO Collaboration,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.,And North-Holland Pub. Co 2009 Physics letters: B Vol.674 No.1
A search for pair production of the lightest supersymmetric partner of the top quark, t@?<SUB>1</SUB>, is performed in the lepton+jets channel using 0.9 fb<SUP>-1</SUP> of data collected by the DO experiment. Kinematic differences between t@?<SUB>1</SUB>t@?@?<SUB>1</SUB> 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@?<SUB>1</SUB>->χ@?<SUB>1</SUB><SUP>+</SUP>b) are obtained for scalar top quark masses of 130-190 GeV and chargino masses of 90-150 GeV.
D0 Collaboration,Abazov, V.M.,Abbott, B.,Acharya, B.S.,Adams, M.,Adams, T.,Alexeev, G.D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G.A.,Ancu, L.S.,Aoki, M.,Arnoud, Y.,Arov, M.,Askew, A.,Asman, B.,Atr North-Holland Pub. Co 2011 Physics letters: B Vol.698 No.2
Data recorded by the D0 experiment at the Fermilab Tevatron Collider are analyzed to search for neutral Higgs bosons produced in association with b quarks. The search is performed in the three-b-quark channel using multijet-triggered events corresponding to an integrated luminosity of 5.2 fb<SUP>-1</SUP>. In the absence of any significant excess above background, limits are set on the cross section multiplied by the branching ratio in the Higgs boson mass range 90 to 300 GeV, extending the excluded regions in the parameter space of the minimal supersymmetric standard model.
Measurement of trilinear gauge boson couplings fromWW+WZ→lνjjevents 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.,Ancu, L. S.,Anzelc, M. S.,Aoki, M.,Arnoud, American Physical Society 2009 PHYSICAL REVIEW D - Vol.80 No.5
Search forW′Boson Resonances Decaying to a Top Quark and a Bottom Quark
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.21
<P>We search for the production of a heavy W' gauge boson that decays to third generation quarks in 0.9 fb-1 of pp collisions at square root(s)=1.96 TeV, collected with the D0 detector at the Fermilab Tevatron collider. We find no significant excess in the final-state invariant mass distribution and set upper limits on the production cross section times branching fraction. For a left-handed W' boson with SM couplings, we set a lower mass limit of 731 GeV. For right-handed W' bosons, we set lower mass limits of 739 GeV if the W' boson decays to both leptons and quarks and 768 GeV if the W' boson decays only to quarks. We also set limits on the coupling of the W' boson to fermions as a function of its mass.</P>
Observation of Single Top-Quark Production
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.,Ancu, L. S.,Andeen, T.,Anzelc, M. S.,Aoki, American Physical Society 2009 Physical Review Letters Vol.103 No.9
<P>We report observation of the electroweak production of single top quarks in pp[over ] collisions at sqrt[s]=1.96 TeV based on 2.3 fb(-1) of data collected by the D0 detector at the Fermilab Tevatron Collider. Using events containing an isolated electron or muon and missing transverse energy, together with jets originating from the fragmentation of b quarks, we measure a cross section of sigma(pp[over ]--> tb + X, tqb + X) = 3.94 + or - 0.88 pb. The probability to measure a cross section at this value or higher in the absence of signal is 2.5 x 10(-7), corresponding to a 5.0 standard deviation significance for the observation.</P>