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Search for the standard model Higgs boson in tau lepton final states
D0 Collaboration,Abazov, V.M.,Abbott, B.,Acharya, B.S.,Adams, M.,Adams, T.,Alexeev, G.D.,Alkhazov, G.,Alton, A.,Alverson, G.,Aoki, M.,Askew, A.,Atkins, S.,Augsten, K.,Avila, C.,Badaud, F.,Bagby, L.,Ba North-Holland Pub. Co 2012 Physics letters: B Vol.714 No.2
We present a search for the standard model Higgs boson in final states with an electron or muon and a hadronically decaying tau lepton in association with zero, one, or two or more jets using data corresponding to an integrated luminosity of up to 7.3 fb<SUP>-1</SUP> collected with the D0 detector at the Fermilab Tevatron collider. The analysis is sensitive to Higgs boson production via gluon-gluon fusion, associated vector boson production, and vector boson fusion, and to Higgs boson decays to ττ, WW, ZZ and bb@? pairs. Observed (expected) limits are set on the ratio of 95% C.L. upper limits on the cross section times branching ratio, relative to those predicted by the Standard Model, of 22 (14) at a Higgs boson mass of 115 GeV and 6.8 (7.7) at 165 GeV.
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.6
<P>We report on a first search for production of the lightest neutral CP-even Higgs boson (h) in the next-to-minimal supersymmetric standard model, where h decays to a pair of neutral pseudoscalar Higgs bosons (a), using 4.2 fb;{-1} of data recorded with the D0 detector at Fermilab. The a bosons are required to either both decay to micro;{+}micro;{-} or one to micro;{+}micro;{-} and the other to tau;{+}tau;{-}. No significant signal is observed, and we set limits on its production as functions of M_{a} and M_{h}.</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>
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>
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>
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
Direct Measurement of theWBoson Width
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.23
<P>We present a direct measurement of the width of the W boson using the shape of the transverse mass distribution of W --> enu candidate events. Data from approximately 1 fb(-1) of integrated luminosity recorded at square root of s = 1.96 TeV by the D0 detector at the Fermilab Tevatron pp collider are analyzed. We use the same methods and data sample that were used for our recently published W boson mass measurement, except for the modeling of the recoil, which is done with a new method based on a recoil library. Our result, 2.028 +/- 0.072 GeV, is in agreement with the predictions of the standard model.</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>
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>