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1.
  • Abazov, V. M., et al. (författare)
  • Measurement of the differential cross sections for isolated direct photon pair production in p(p)over-bar collisions at root s=1.96 TeV
  • 2013
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 725:1-3, s. 6-14
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present measurements of direct photon pair production cross sections using 8.5 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron p (p) over bar collider. The results are presented as differential distributions of the photon pair invariant mass d sigma/dM(gamma gamma), pair transverse momentum d sigma/dp(T)(gamma gamma) azimuthal angle between the photons d sigma/d Delta(phi)(gamma gamma), and polar scattering angle in the Collins-Soper frame d sigma/d vertical bar cos theta*vertical bar. Measurements are performed for isolated photons with transverse momenta p(T)(gamma) &gt; 18 (17) GeV for the leading (next-to-leading) photon in P-T, pseudorapidities vertical bar eta(gamma)vertical bar &lt; 0.9, and a separation in eta-phi space Delta R-gamma gamma &gt; 0.4. We present comparisons with the predictions from Monte Carlo event generators DIPHOX and RESBOS implementing QCD calculations at next-to-leading order, 2 gamma NNLO at next-to-next-to-leading order, and SHERPA using matrix elements with higher-order real emissions matched to parton shower. </p>
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2.
  • Abazov, V. M., et al. (författare)
  • Search for a Higgs boson in diphoton final states with the D0 detector in 9.6 fb(-1) of p(p)over-bar collisions at root s=1.96 TeV
  • 2013
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052007
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present a search for a Higgs boson decaying into a pair of photons based on 9.6 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The search employs multivariate techniques to discriminate signal from the nonresonant background and is separately optimized for a standard model and a fermiophobic Higgs boson. No significant excess of data above the background prediction is observed and upper limits on the product of the cross section and branching fraction are derived at the 95% confidence level as a function of Higgs boson mass. For a standard model Higgs boson with mass of 125 GeV, the observed (expected) upper limits are a factor of 12.8 (8.7) above the standard model prediction. The existence of a fermiophobic Higgs boson with mass in the 100-113 GeV range is excluded at the 95% confidence level.</p>
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3.
  • Abazov, V. M., et al. (författare)
  • Search for Higgs boson production in trilepton and like-charge electron-muon final states with the D0 detector
  • 2013
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052009
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present a search for Higgs bosons in multilepton final states in p (p) over bar collisions at root s = 1.96 TeV recorded with the D0 detector at the Fermilab Tevatron Collider, using the full Run II data set with integrated luminosities of up to 9.7 fb(-1). The multilepton states considered are ee mu, e mu mu, mu tau(h)tau(h) , and like-charge e(+/-) mu(+/-) pairs. These channels directly probe the HVV (V = W, Z) coupling of the Higgs boson in production and decay. The mu tau(h)tau(h) channel is also sensitive to H -&gt; tau(+)tau(-) decays. Upper limits at the 95% C.L on the rate of standard model Higgs boson production are derived in the mass range 100 &lt;= M-H &lt;= 200 GeV. The expected and observed limits are a factor of 6.3 and 8.4 above the predicted standard model cross section at M-H = 125 GeV. We also interpret the data in a fermiophobic Higgs boson model.</p>
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4.
  • Abazov, V. M., et al. (författare)
  • Search for the rare decay B-s(0) -&gt; mu(+) mu(-)
  • 2013
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 87:7, s. 072006
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We perform a search for the rare decay B-s(0) -&gt; mu(+) mu(-) using data collected by the D0 experiment at the Fermilab Tevatron Collider. This result is based on the full D0 Run II data set corresponding to 10.4 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV. We use a multivariate analysis to increase the sensitivity of the search. In the absence of an observed number of events above the expected background, we set an upper limit on the decay branching fraction of B(B-s(0) -&gt; mu(+) mu(-)) &lt; 15 x 10(-9) (12 x 10(-9)) at the 95% (90%) C.L. </p>
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5.
  • Abazov, V. M., et al. (författare)
  • Search for the standard model Higgs boson in lv plus jets final states in 9.7 fb(-1) of p(p)over-bar collisions with the D0 detector
  • 2013
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052008
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present, in detail, a search for the standard model Higgs boson, H, in final states with a charged lepton (electron or muon), missing energy, and two or more jets in data corresponding to 9.7 fb(-1) of integrated luminosity collected at a center-of-mass energy of root s = 1.96 TeV with the D0 detector at the Fermilab Tevatron p (p) over bar Collider. The search uses b-jet identification to categorize events for improved signal versus background separation and is sensitive to associated production of the H with a W boson, WH -&gt; lvb(b)over bar&gt;; gluon fusion with the Higgs decaying to W-boson pairs, H -&gt; WW -&gt; lvjj; and associated production with a vector boson where the Higgs decays to W-boson pairs, VH -&gt; VWW -&gt; lvjjjj production (where V = W or Z). We observe good agreement between data and expected background. We test our method by measuring WZ and ZZ production with Z -&gt; b(b)over bar&gt; and find production rates consistent with the standard model prediction. For a Higgs boson mass of 125 GeV, we set a 95% C. L. upper limit on the production of a standard model Higgs boson of 5.8 sigma(SM) SM, where sigma(SM) is the standard model Higgs boson production cross section, while the expected limit is 4.7 X sigma(SM). We also interpret the data considering models with fourth generation fermions, or a fermiophobic Higgs boson.</p>
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6.
  • Abazov, V. M., et al. (författare)
  • Search for ZH -&gt; l(+)l(-)b(b)over-bar production in 9.7 fb(-1) of p(p)over-bar collisions with the D0 detector
  • 2013
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052010
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present a search for the standard model Higgs boson produced in association with a Z boson in 9.7 fb(-1) of p (p) over bar collisions collected with the D0 detector at the Fermilab Tevatron Collider at root s = 1.96 TeV. Selected events contain one reconstructed Z -&gt; e(+)e(-) or Z -&gt; mu(+)mu(-) candidate and at least two jets, including at least one jet likely to contain a b quark. To validate the search procedure, we also measure the cross section for ZZ production and find that it is consistent with the standard model expectation. We set upper limits at the 95% C.L. on the product of the ZH production cross section and branching ratio B(H -&gt; b (b) over bar) for Higgs boson masses 90 &lt;= M-H &lt;= 150 GeV. The observed (expected) limit for M-H = 125 GeV is a factor of 7.1 (5.1) larger than the standard model prediction.</p>
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7.
  • Abazov, V. M., et al. (författare)
  • Studies of W boson plus jets production in p(p)over-bar collisions at root s=1.96 TeV
  • 2013
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:9, s. 092001
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present a comprehensive analysis of inclusive W(-&gt; ev) + n-jet (n &gt;= 1, 2, 3, 4) production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV at the Tevatron collider using a 3.7 fb(-1) data set collected by the D0 detector. Differential cross sections are presented as a function of the jet rapidities (y), lepton transverse momentum (P-T) and pseudorapidity (eta), the scalar sum of the transverse energies of the W boson and all jets (H-T), leading dijet P-T and invariant mass, dijet rapidity separations for a variety of jet pairings for P-T-ordered and angular-ordered jets, dijet opening angle, dijet azimuthal angular separations for P-T-ordered and angular-ordered jets, and W boson transverse momentum. The mean number of jets in an event containing a W boson is measured as a function of H-T, and as a function of the rapidity separations between the two highest-P-T jets and between the most widely separated jets in rapidity. Finally, the probability for third-jet emission in events containing a W boson and at least two jets is studied by measuring the fraction of events in the inclusive W + 2-jet sample that contain a third jet over a P-T threshold. The analysis employs a regularized singular value decomposition technique to accurately correct for detector effects and for the presence of backgrounds. The corrected data are compared to particle level next-to-leading-order perturbative QCD predictions, predictions from all-order resummation approaches, and a variety of leading-order and matrix element plus parton shower event generators. Regions of the phase space where there is agreement or disagreement with the data are discussed for the different models tested.</p>
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8.
  • Abazov, V. M., et al. (författare)
  • Combined search for the Higgs boson with the D0 experiment
  • 2013
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052011
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We perform a combination of searches for standard model Higgs boson production in p (p) over bar collisions recorded by the D0 detector at the Fermilab Tevatron Collider at a center of mass energy of root s = 1.96 TeV. The different production and decay channels have been analyzed separately, with integrated luminosities of up to 9.7 fb(-1) and for Higgs boson masses 90 &lt;= M-H &lt;= 200 GeV. We combine these final states to achieve optimal sensitivity to the production of the Higgs boson. We also interpret the combination in terms of models with a fourth generation of fermions, and models with suppressed Higgs boson couplings to fermions. The result excludes a standard model Higgs boson at 95% C.L. in the ranges 90 &lt; M-H &lt; 101 GeV and 157 &lt; M-H &lt; 178 GeV, with an expected exclusion of 155 &lt; M-H &lt; 175 GeV. In the range 120 &lt; M-H &lt; 145 GeV, the data exhibit an excess over the expected background of up to 2 standard deviations, consistent with the presence of a standard model Higgs boson of mass 125 GeV.</p>
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9.
  • Abazov, V. M., et al. (författare)
  • Evidence for s-channel single top quark production in p(p)over-bar collisions at root s=1.96 TeV
  • 2013
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 726:4-5, s. 656-664
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present measurements of the cross sections for the two main production modes of single top quarks in p (p) over bar collisions at root s = 1.96 TeV in the Run II data collected with the DO detector at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of 9.7 fb(-1). The s-channel cross section is measured to be sigma(p (p) over bar -&gt; tb + X) = 1.10(-0.31)(+0.33) pb with no assumptions on the value of the t-channel cross section. Similarly, the t-channel cross section is measured to be sigma(p (p) over bar -&gt; tqb + X) = 3.07(-0.49)(+0.54) pb. We also measure the s + t combined cross section as sigma(p (p) over bar -&gt; tb + X, tqb + X) = 4.11(-0.55)(+0.60) ph and set a lower limit on the CKM matrix element vertical bar V-tb vertical bar&gt; 0.92 at 95% C.L., assuming mt = 172.5 GeV. The probability to measure a cross section for the s channel at the observed value or higher in the absence of signal is 1.0 x 10(-4), corresponding to a significance of 3.7 standard deviations. </p>
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10.
  • Abazov, V. M., et al. (författare)
  • Measurement of differential tt production cross sections in pp collisions
  • 2014
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 90:9, s. 092006
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The production of top quark-antiquark pair events in pp collisions at root s= 1.96 TeV is studied as a function of the transverse momentum and absolute value of the rapidity of the top quarks as well as of the invariant mass of the tt pair. We select events containing an isolated lepton, a large imbalance in transverse momentum, and four or more jets with at least one jet identified as originating from a b quark. The data sample corresponds to 9.7 fb(-1) of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Observed differential cross sections are consistent with standard model predictions.</p>
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