| 1. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the WZ -> lvll cross section and limits on anomalous triple gauge couplings in p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 695:1-4, s. 67-73
-
Tidskriftsartikel (refereegranskat)abstract
- We present a new measurement of the WZ -> lvll (l = e, mu) cross section and limits on anomalous triple gauge couplings. Using 4.1 fb(-1) of integrated luminosity of p (p) over bar collisions at root s = 1.96 TeV, we observe 34 WZ candidate events with an estimated background of 6.0 +/- 0.4 events. We measure the WZ production cross section to be 3.89(-0.90)(+1.07) pb, in good agreement with the standard model prediction. We find no evidence for anomalous WWZ couplings and set 95% C.L. limits on the coupling parameters, -0.077 < lambda(z) < 0.093 and -0.029 < Delta kappa(z) < 0.080 in the HISZ parameterization for a Lambda = 2 TeV form factor scale. These are the best limits to date obtained from the direct measurement of the WWZ vertex.
|
|
| 2. |
- Abazov, V. M., et al.
(författare)
-
Search for a heavy neutral gauge boson in the dielectron channel with 5.4 fb(-1) of p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 695:1-4, s. 88-94
-
Tidskriftsartikel (refereegranskat)abstract
- We report the results of a search for a heavy neutral gauge boson Z' decaying into the dielectron final state using data corresponding to an integrated luminosity of 5.4 fb(-1) collected by the D0 experiment at the Fermilab Tevatron Collider. No significant excess above the standard model prediction is observed in the dielectron invariant-mass spectrum. We set 95 sigma(p (p) over bar -> Z') x BR(Z' -> ee) depending on the dielectron invariant mass. These cross section limits are used to determine lower mass limits for bosons in a variety of models. For the sequential standard model boson a lower mass limit of 1023 GeV is obtained.
|
|
| 3. |
- Abazov, V. M., et al.
(författare)
-
Determination of the Width of the Top Quark
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:2, s. 022001-
-
Tidskriftsartikel (refereegranskat)abstract
- We extract the total width of the top quark, Gamma(t), from the partial decay width Gamma(t -> Wb) measured using the t-channel cross section for single top-quark production and from the branching fraction B(t -> Wb) measured in t (t) over bar t events using up to 2.3 fb(-1) of integrated luminosity collected by the D0 Collaboration at the Tevatron p (p) over bar Collider. The result is Gamma(t) = 1.99(-0.55)(+0.69) GeV, which translates to a top-quark lifetime of tau(t) = (3.3-(+1.3)(0.9)) x 10(-25) s. Assuming a high mass fourth generation b' quark and unitarity of the four-generation quark-mixing matrix, we set the first upper limit on vertical bar V-tb'vertical bar < 0.63 at 95% C.L.
|
|
| 4. |
- Abazov, V. M., et al.
(författare)
-
High mass exclusive diffractive dijet production in p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 705:3, s. 193-199
-
Tidskriftsartikel (refereegranskat)abstract
- We present evidence for diffractive exclusive dijet production with an invariant dijet mass greater than 100 GeV in data collected with the DO experiment at the Fermilab Tevatron Collider. A discriminant based on calorimeter information is used to measure a significant number of events with little energy (typically less than 10 GeV) outside the dijet system, consistent with the diffractive exclusive dijet production topology. The probability for these events to be explained by other dijet production processes is 2 x 10(-6), corresponding to a 4.7 standard deviation significance.
|
|
| 5. |
- Abazov, V. M., et al.
(författare)
-
Precise Study of the Z/gamma* Boson Transverse Momentum Distribution in p(p)over-bar Collisions Using a Novel Technique
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:12, s. 122001-
-
Tidskriftsartikel (refereegranskat)abstract
- Using 7.3 fb(-1) of p (p) over bar collisions collected by the D0 detector at the Fermilab Tevatron, we measure the distribution of the variable phi(eta)*, which probes the same physical effects as the Z/gamma* boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. A QCD prediction is found to describe the general features of the phi(eta)* distribution, but is unable to describe its detailed shape or dependence on boson rapidity. A prediction that includes a broadening of transverse momentum for small values of the parton momentum fraction is strongly disfavored.
|
|
| 6. |
- Abazov, V. M., et al.
(författare)
-
Search for pair production of the scalar top quark in the electron plus muon final state
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 696:4, s. 321-327
-
Tidskriftsartikel (refereegranskat)abstract
- We report the result of a search for the pair production of the lightest supersymmetric partner of the top quark ((t) over tilde (1)) in p (p) over bar collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider corresponding to an integrated luminosity of 5.4 fb(-1). The scalar top quarks are assumed to decay into a b quark, a charged lepton, and a scalar neutrino ((nu) over bar). and the search is performed in the electron plus muon final state. No significant excess of events above the standard model prediction is detected, and substantially improved exclusion limits at the 95% C.L. are set in the the (M-(t) over tilde1, M-(nu) over tilde mass plane.
|
|
| 7. |
- Abazov, V. M., et al.
(författare)
-
Azimuthal decorrelations and multiple parton interactions in gamma+2 jet and gamma+3 jet events in p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 83:5, s. 052008-
-
Tidskriftsartikel (refereegranskat)abstract
- Samples of inclusive gamma + 2 jet and gamma + 3 jet events collected by the D0 experiment with an integrated luminosity of about 1 fb(-1) in p (p) over bar collisions at root s = 1.96 TeV are used to measure cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (p(T)) of the gamma + leading jet system (jets are ordered in p(T)) and p(T) of the other jet for gamma + 2 jet, or p(T) sum of the two other jets for gamma + 3 jet events. The results are compared to different models of multiple parton interactions (MPI) in the PYTHIA and SHERPA Monte Carlo (MC) generators. The data indicate a contribution from events with double parton (DP) interactions and are well-described by predictions provided by the PYTHIA MPI models with p(T)-ordered showers and by SHERPA with the default MPI model. The gamma + 2 jet data are also used to determine the fraction of events with DP interactions as a function of the azimuthal angle and as a function of the second jet p(T).
|
|
| 8. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the W boson helicity in top quark decays using 5.4 fb(-1) of p(p)over-bar collision data
- 2011
-
Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 83:3, s. 032009-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the helicity of the W boson produced in top quark decays using t (t) over bar decays in the l + jets and dilepton final states selected from a sample of 5.4 fb(-1) of collisions recorded using the D0 detector at the Fermilab Tevatron p (p) over bar collider. We measure the fractions of longitudinal and right-handed W bosons to be f(0) = 0.669 +/- 0.102[+/- 0.078(stat.) +/- 0.065(syst.) +/- and f(+) = 0.023 +/- 0.053[+/- 0.041(stat.) +/- 0.034(syst.)], respectively. This result is consistent at the 98% level with the standard model. A measurement with f(0) fixed to the value from the standard model yields f(+) = 0.010 +/- 0.037[+/- 0.022(stat.) +/- 0.030(syst.).].
|
|
| 9. |
- Abazov, V. M., et al.
(författare)
-
Search for neutral Higgs bosons in the multi-b-jet topology in 5.2 fb(-1) of p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 698:2, s. 97-104
-
Tidskriftsartikel (refereegranskat)abstract
- Data recorded by the DO 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(-1). 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. (C) 2011 Elsevier B.V. All rights reserved.
|
|
| 10. |
- Abazov, V. M., et al.
(författare)
-
Search for Resonant WW and WZ Production in p(p)over-bar Collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:1, s. 011801-
-
Tidskriftsartikel (refereegranskat)abstract
- We search for resonant WW or WZ production by using up to 5: 4 fb(-1) of integrated luminosity collected by the D0 experiment in run II of the Fermilab Tevatron Collider. The data are consistent with the standard model background expectation, and we set limits on a resonance mass by using the sequential standard model W' boson and the Randall-Sundrum model graviton G as benchmarks. We exclude a sequential standard model W' boson in the mass range 180-690 GeV and a Randall-Sundrum graviton in the range 300-754 GeV at 95% C. L.
|
|
