| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Aaltonen, T., et al.
(författare)
-
Evidence for a Particle Produced in Association with Weak Bosons and Decaying to a Bottom-Antibottom Quark Pair in Higgs Boson Searches at the Tevatron
- 2012
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 109:7, s. 071804-
-
Tidskriftsartikel (refereegranskat)abstract
- We combine searches by the CDF and D0 Collaborations for the associated production of a Higgs boson with a W or Z boson and subsequent decay of the Higgs boson to a bottom-antibottom quark pair. The data, originating from Fermilab Tevatron p (p) over bar collisions at root s = 1.96 TeV, correspond to integrated luminosities of up to 9.7 fb(-1). The searches are conducted for a Higgs boson with mass in the range 100-150 GeV/c(2). We observe an excess of events in the data compared with the background predictions, which is most significant in the mass range between 120 and 135 GeV/c(2). The largest local significance is 3.3 standard deviations, corresponding to a global significance of 3.1 standard deviations. We interpret this as evidence for the presence of a new particle consistent with the standard model Higgs boson, which is produced in association with a weak vector boson and decays to a bottom-antibottom quark pair.
|
|
| 5. |
- Aaltonen, T., et al.
(författare)
-
Combination of CDF and D0 measurements of the W boson helicity in top quark decays
- 2012
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:7, s. 071106-
-
Tidskriftsartikel (refereegranskat)abstract
- We report the combination of recent measurements of the helicity of the W boson from top quark decay by the CDF and D0 collaborations, based on data samples corresponding to integrated luminosities of 2.7-5.4 fb(-1) of p (p) over bar collisions collected during Run II of the Fermilab Tevatron collider. Combining measurements that simultaneously determine the fractions of W bosons with longitudinal (f(0)) and right-handed (f(+)) helicities, we find f(0) = 0.722 +/- 0.081[+/- 0.062(stat) +/- 0.052(syst)] and f(+) = -0.033 +/- 0.046[+/- 0.034(stat) +/- 0.031(syst)]. Combining measurements where one of the helicity fractions is fixed to the value expected in the standard model, we find f(0) = 0.682 +/- 0.057[+/- 0.035(stat) +/- 0.046(syst)] for fixed f(+) and f(+) = -0.015 +/- 0.035[+/- 0.018(stat) +/- 0.030(syst)] for fixed f(0). The results are consistent with standard model expectations.
|
|
| 6. |
- Abazov, V. M., et al.
(författare)
-
Determination of the pole and (MS)over-bar masses of the top quark from the t(t)over-bar cross section
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 703:4, s. 422-427
-
Tidskriftsartikel (refereegranskat)abstract
- We use higher-order quantum chromodynamics calculations to extract the mass of the top quark from the t (t) over bar cross section measured in the lepton + jets channel in p (p) over bar collisions at root s = 1.96 TeV using 5.3 fb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. The extracted top quark pole mass and (MS) over bar mass are compared to the current Tevatron average top quark mass obtained from direct measurements.
|
|
| 7. |
|
|
| 8. |
- Abazov, V. M., et al.
(författare)
-
Measurement of Spin Correlation in t(t)over-bar Production Using a Matrix Element Approach
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:3, s. 032001-
-
Tidskriftsartikel (refereegranskat)abstract
- We determine the fraction of t (t) over bar events with spin correlation, assuming that the spin of the top quark is either correlated with the spin of the top antiquark as predicted by the standard model or is uncorrelated. For the first time we use a matrix-element-based approach to study t (t) over bar spin correlation. We use t (t) over bar -> W(+)bW(-)(b) over bar -> l(+)nu bl(-)(nu) over bar(b) over bar final states produced in p (p) over bar collisions at a center- of- mass energy root s = 1: 96 TeV, where l denotes an electron or a muon. The data correspond to an integrated luminosity of 5: 4 fb(-1) and were collected with the D0 detector at the Fermilab Tevatron collider. The result agrees with the standard model prediction. We exclude the hypothesis that the spins of the t (t) over bar are uncorrelated at the 97.7% C.L.
|
|
| 9. |
- Abazov, V. M., et al.
(författare)
-
Measurement of spin correlation in t(t)over-bar production using dilepton final states
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 702:1, s. 16-23
-
Tidskriftsartikel (refereegranskat)abstract
- We measure the correlation between the spin of the top quark and the spin of the anti-top quark in t (t) over bar -> W(+)bW(-)(b) over bar -> l(+)vbl(-) (v) over bar(b) over bar final states produced in p (p) over bar collisions at a center of mass energy root s = 1.96 TeV, where l is an electron or muon. The data correspond to an integrated luminosity of 5.4 fb(-1) and were collected with the D0 detector at the Fermilab Tevatron collider. The correlation is extracted from the angles of the two leptons in the t and (t) over bar rest frames, yielding a correlation strength C = 0.10(-0.45)(+0.45). in agreement with the NLO QCD prediction within two standard deviations, but also in agreement with the no correlation hypothesis.
|
|
| 10. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the production fraction times branching fraction f(b -> Lambda(b)) . B(Lambda(b) -> J/psi Lambda)
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:3, s. 031102-
-
Tidskriftsartikel (refereegranskat)abstract
- The Lambda(b)(udb) baryon is observed in the decay Lambda(b) -> J/psi Lambda using 6.1fb(-1) of p (p) over bar collisions collected with the D0 detector at root s = 1/96 TeV. The production fraction multiplied by the branching fraction for this decay relative to that for the decay B(0) -> J/psi K(s)(0) is measured to be 0.345 +/- 0.034(stat) +/- 0.033(syst) +/- 0.003(PDG). Using the world average value of f(b -> B(0)) . B(B(0) -> J/psi K(s)(0) = (1.74 +/- 0.08) x 10(-5), we obtain f(b -> Lambda(b)) . B(Lambda(b) -> J/psi Lambda) = (6.01 +/- 0.60(stat) +/- 0.58(syst) +/- 0.28(PDG)) x 10(-5). This measurement represents an improvement in precision by about a factor of 3 with respect to the current world average.
|
|
| 11. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the t(t)over-bar production cross section using dilepton events in p(p)over-bar collisions
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 704:5, s. 403-410
-
Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the a production cross section sigma((u) over bar) in p (p) over bar collisions at root s = 1.96 TeV using 5.4 fb(-1) of integrated luminosity collected with the D0 detector. We consider final states with at least two jets and two leptons (ee, e mu, mu mu), and events with one jet for the e mu final state as well. The measured cross section is sigma((u) over bar) = 7.36(-0.79)(+0.90)(stat + syst) pb. This result combined with the cross section measurement in the lepton + jets final state yields sigma((u) over bar) = 7.56(-0.56)(+0.63)(stat + syst) pb, which agrees with the standard model expectation. The relative precision of 8% of this measurement is comparable to the precision of the latest theoretical calculations. (C) 2011 Elsevier B.V. All rights reserved.
|
|
| 12. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the ZZ production cross section in p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:1, s. 011103-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a new measurement of the production cross section sigma(p (p) over bar -> ZZ) at a center-of-mass energy root s = 1.96 TeV, obtained from the analysis of the four charged lepton final state l(+)l(-)l'(+)l'-(l,l' = e or mu). We observe ten candidate events with an expected background of 0: 37 +/- 0: 13 events. The measured cross section sigma(p (p) over bar -> ZZ) = 1.26(-0.37)(+0.47)(stat) +/- 0.14(syst) pb is in agreement with NLO QCD predictions. This result is combined with a previous result from the ZZ -> l(+)l(-)v (v) over bar channel resulting in a combined cross section of sigma(p (p) over bar -> ZZ) = 1.40(-0.37)(+0.43)(stat) +/- 0.14(syst) pb.
|
|
| 13. |
- Abazov, V. M., et al.
(författare)
-
Measurement of three-jet differential cross sections d sigma(3jet)/dM(3jet) in p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 704:5, s. 434-441
-
Tidskriftsartikel (refereegranskat)abstract
- We present the first measurement of the inclusive three-jet differential cross section as a function of the invariant mass of the three jets with the largest transverse momenta in an event in p (p) over bar collisions at root s = 1.96 TeV. The measurement is made in different rapidity regions and for different jet transverse momentum requirements and is based on a data set corresponding to an integrated luminosity of 0.7 fb(-1) collected with the DO detector at the Fermilab Tevatron Collider. The results are used to test the three-jet matrix elements in perturbative QCD calculations at next-to-leading order in the strong coupling constant. The data allow discrimination between parametrizations of the parton distribution functions of the proton. (C) 2011 Elsevier B.V. All rights reserved.
|
|
| 14. |
- Abazov, V. M., et al.
(författare)
-
Model-independent measurement of t-channel single top quark 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. ; 705:4, s. 313-319
-
Tidskriftsartikel (refereegranskat)abstract
- We present a model-independent measurement of t-channel electroweak production of single top quarks in p collisions at root s = 1.96 TeV. Using 5.4 fb(-1) of integrated luminosity collected by the DO detector at the Fermilab Tevatron Collider, and selecting events containing an isolated electron or muon, missing transverse energy and one or two jets originating from the fragmentation of b quarks, we measure a cross section sigma (p (p) over bar -> tqb + X) = 2.90 +/- 0.59 (stat + syst) pb for a top quark mass of 172.5 GeV. The probability of the background to fluctuate and produce a signal as large as the one observed is 1.6 x 10(-8), corresponding to a significance of 5.5 standard deviations. (C) 2011 Elsevier B.V. All rights reserved.
|
|
| 15. |
- Abazov, V. M., et al.
(författare)
-
Precise measurement of the top-quark mass from lepton plus jets events at D0
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:3, s. 032004-
-
Tidskriftsartikel (refereegranskat)abstract
- We report a measurement of the mass of the top quark in lepton + jets final states of p (p) over bar -> t (t) over bar data corresponding to 2.6 fb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. A matrix-element method is developed that combines an in situ jet energy calibration with our standard jet energy scale derived from studies of gamma + jet and dijet events. We then implement a flavor-dependent jet-response correction through a novel approach. This method is used to measure a top-quark mass of m(t) = 176.01 +/- 1.64 GeV. Combining this result with our previous result obtained on an independent data set, we measure a top-quark mass of m(t) = 174.94 +/- 1.49 GeV for a total integrated luminosity of 3.6 fb(-1).
|
|
| 16. |
- Abazov, V. M., et al.
(författare)
-
Precise Measurement of the Top Quark Mass in the Dilepton Channel at D0
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:8, s. 082004-
-
Tidskriftsartikel (refereegranskat)abstract
- We measure the top quark mass (m(t)) in p (p) over bar collisions at a center of mass energy root s = 1.96 TeV using dilepton t (t) over bar -> W(+)bW(-)b(-) -> l(+)nu(l)bl(-)(nu) over bar (l)(b) over bar events, where l denotes an electron, a muon, or a tau that decays leptonically. The data correspond to an integrated luminosity of 5.4 fb(-1) collected with the D0 detector at the Fermilab Tevatron Collider. We obtain m(t) = 174.0 +/- 1.8(stat) +/- 2.4(syst) GeV, which is in agreement with the current world average m(t) = 173.3 +/- 1.1 GeV. This is currently the most precise measurement of mt in the dilepton channel.
|
|
| 17. |
- Abazov, V. M., et al.
(författare)
-
Search for flavor changing neutral currents in decays of top quarks
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 701:3, s. 313-320
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for flavor changing neutral currents in decays of top quarks. The analysis is based on a search for (ℓ,ℓ′=e,μ) final states using 4.1 fb−1 of integrated luminosity of collisions at . We extract limits on the branching ratio B(t→Zq) (q=u,c quarks), assuming anomalous tuZ or tcZ couplings. We do not observe any sign of such anomalous coupling and set a limit of B<3.2% at 95% C.L.
|
|
| 18. |
- Abazov, V. M., et al.
(författare)
-
W gamma Production and Limits on Anomalous WW gamma Couplings in p(p)over-bar Collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:24, s. 241803-
-
Tidskriftsartikel (refereegranskat)abstract
- We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W(-> l nu) + gamma production in e gamma and mu gamma final states. Using data corresponding to an integrated luminosity of 4.2 fb(-1) collected with the D0 detector at the Fermilab Tevatron Collider, the measured cross section times branching fraction for the process p (p) over bar -> W gamma + X -> l nu gamma + X and the distribution of the charge-signed photon-lepton rapidity difference are found to be in agreement with the standard model. These results provide the most stringent limits on anomalous WW gamma couplings for data from hadron colliders: -0.4 < Delta kappa(gamma) < 0.4 and -0.08 < lambda(gamma) < 0.07 at the 95% C.L.
|
|
| 19. |
- Abazov, V. M., et al.
(författare)
-
Bounds on an Anomalous Dijet Resonance in W plus jets 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. 011804-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a study of the dijet invariant mass spectrum in events with two jets produced in association with a W boson in data corresponding to an integrated luminosity of 4.3 fb(-1) collected with the D0 detector at root s = 1.96 TeV. We find no evidence for anomalous resonant dijet production and derive upper limits on the production cross section of an anomalous dijet resonance recently reported by the CDF Collaboration, investigating the range of dijet invariant mass from 110 to 170 GeV/c(2). The probability of the D0 data being consistent with the presence of a dijet resonance with 4 pb production cross section at 145 GeV/c(2) is 8 x 10(-6).
|
|
| 20. |
- Abazov, V. M., et al.
(författare)
-
Direct measurement of the mass difference between top and antitop quarks
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:5, s. 052005-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a direct measurement of the mass difference between top and antitop quarks (Delta m) in lepton + jets t (t) over bar final states using the "matrix element" method. The purity of the lepton + jets sample is enhanced for t (t) over bar events by identifying at least one of the jets as originating from a b quark. The analyzed data correspond to 3.6 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV acquired by D0 in Run II of the Fermilab Tevatron Collider. The combination of the e + jets and mu + jets channels yields Delta m = 0.8 +/- 1.8(stat) +/- 0.5(syst) GeV, which is in agreement with the standard model expectation of no mass difference.
|
|
| 21. |
- Abazov, V. M., et al.
(författare)
-
Forward-backward asymmetry in top quark-antiquark production
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:11, s. 112005-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a data set corresponding to an integrated luminosity of 5.4 fb(-1), collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t (t) over bar forward-backward asymmetry to be (9.2 +/- 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 +/- 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 +/- 4.0)%. The results are compared to predictions based on the next-to-leading-order QCD generator MC@NLO. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.
|
|
| 22. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the anomalous like-sign dimuon charge asymmetry with 9 fb(-1) of p(p)over-bar collisions
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:5, s. 052007-
-
Tidskriftsartikel (refereegranskat)abstract
- We present an updated measurement of the anomalous like-sign dimuon charge asymmetry A(sl)(b) for semileptonic b-hadron decays in 9.0 fb(-1) of p (p) over bar collisions recorded with the D0 detector at a center-of-mass energy of root s = 1.96 TeV at the Fermilab Tevatron collider. We obtain A(sl)(b) = (-0.787 +/- 0.172(stat) +/- 0.093(syst)%. This result differs by 3.9 standard deviations from the prediction of the standard model and provides evidence for anomalously large CP violation in semileptonic neutral B decay. The dependence of the asymmetry on the muon impact parameter is consistent with the hypothesis that it originates from semileptonic b-hadron decays.
|
|
| 23. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the CP-violating phase phi sJ/psi phi using the flavor-tagged decay Bs(0) -> J/psi phi in 8 fb(-1) of p(p)over-bar collisions
- 2012
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:3, s. 032006-
-
Tidskriftsartikel (refereegranskat)abstract
- We report an updated measurement of the CP-violating phase, phi(J/psi phi)(s), and the decay-width difference for the two mass eigenstates, Delta Gamma(s), from the flavor-tagged decay B-s(0) -> J/psi phi. The data sample corresponds to an integrated luminosity of 8.0 fb(-1) accumulated with the D0 detector using p (p) over bar collisions at root s = 1.96 TeV produced at the Fermilab Tevatron collider. The 68% Bayesian credibility intervals, including systematic uncertainties, are Delta Gamma(s) = 0.163(-0.064)(+0.065) ps(-1) and phi(J/psi phi)(s) = -0.55(-0.36)(+0.38). The p-value for the Standard Model point is 29.8%.
|
|
| 24. |
- Abazov, V. M., et al.
(författare)
-
Measurements of inclusive W plus jets production rates as a function of jet transverse momentum in p(p)over-bar collisions root s=1.96 TeV
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 705:3, s. 200-207
-
Tidskriftsartikel (refereegranskat)abstract
- This Letter describes measurements of inclusive W (-> ev) + n jet cross sections (n = 1-4), presented as total inclusive cross sections and differentially in the nth jet transverse momentum. The measurements are made using data corresponding to an integrated luminosity of 4.2 fb(-1) collected by the DO detector at the Fermilab Tevatron Collider, and achieve considerably smaller uncertainties on W + jets production cross sections than previous measurements. The measurements are compared to next-to-leading order perturbative QCD (pQCD) calculations in the n = 1-3 jet multiplicity bins and to leading order pQCD calculations in the 4-jet bin. The measurements are generally in agreement with pQCD calculations, although certain regions of phase space are identified where these predictions could better match the data.
|
|
| 25. |
- Abazov, V. M., et al.
(författare)
-
Measurements of single top quark production cross sections and vertical bar V(tb)vertical bar in p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:11, s. 112001-
-
Tidskriftsartikel (refereegranskat)abstract
- We present measurements of production cross sections of single top quarks in p (p) over bar collisions at root s = 1.96 TeV in a data sample corresponding to an integrated luminosity of 5.4 fb(-1) collected by the D0 detector at the Fermilab Tevatron Collider. We select events with an isolated electron or muon, an imbalance in transverse energy, and two, three, or four jets, with one or two of them containing a bottom hadron. We obtain an inclusive cross section of sigma(p (p) over bar -> tb + X, tqb + X) = 3.43(-0.74)(+0.73) pb and use it to extract the CKM matrix element 0.79 < vertical bar V(tb)vertical bar <= 1 at the 95% C.L. We also measure sigma(p<(p)over bar> -> tb + X) = 0.68(-0.35)(+0.38) pb and sigma(p (p) over bar -> tqb + X) = 2.86(-0.63)(+0.69) pb when assuming, respectively, tqb and tb production rates as predicted by the standard model.
|
|
| 26. |
- Abazov, V. M., et al.
(författare)
-
Model indedpendent search for new phenomena in p(p)over-bar collisions at root s=1.96 TeV
- 2012
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:9, s. 092015-
-
Tidskriftsartikel (refereegranskat)abstract
- We describe a model-independent search for physics beyond the standard model in lepton final states. We examine 117 final states using 1.1 fb(-1) of p (p) over bar collisions data at root s = 1.96 TeV collected with the D0 detector. We conclude that all observed discrepancies between data and model can be attributed to uncertainties in the standard model background modeling, and hence we do not see any evidence for physics beyond the standard model.
|
|
| 27. |
- Abazov, V. M., et al.
(författare)
-
Precision Measurement of the Ratio B(t -> Wb)/B(t -> Wq) and Extraction of V(tb)
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:12, s. 121802-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the ratio of top quark branching fractions R = B(t -> Wb)/B(t -> Wq), where q can be a d, s, or b quark, in the lepton + jets and dilepton t (t) over bar final states. The measurement uses data from 5: 4 fb(-1) of p (p) over bar collisions collected with the D0 detector at the Fermilab Tevatron Collider. We measure R = 0.90 +/- 0.04, and we extract the Cabibbo-Kobayashi-Maskawa (CKM) matrix element vertical bar V(tb)vertical bar as vertical bar V(tb)vertical bar = 0.95 +/- 0.02, assuming unitarity of the 3 x 3 CKM matrix.
|
|
| 28. |
- Abazov, V. M., et al.
(författare)
-
Search for a Fermiophobic and Standard Model Higgs Boson in Diphoton Final States
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:15, s. 151801-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for the standard model Higgs boson and a fermiophobic Higgs boson in the diphoton final states based on 8.2 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. No excess of data above background predictions is observed and upper limits at the 95% C.L. on the cross section multiplied by the branching fraction are set which are the most restrictive to date. A fermiophobic Higgs boson with a mass below 112.9 GeV is excluded at the 95% C.L.
|
|
| 29. |
- Abazov, V. M., et al.
(författare)
-
Search for a Fourth Generation t ' Quark in p(p)over-bar Collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:8, s. 082001-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for pair production of a fourth generation t' quark and its antiparticle, followed by their decays to a W boson and a jet, based on an integrated luminosity of 5: 3 fb(-1) of proton-antiproton collisions at root s = 1.96 TeV collected by the D0 Collaboration at the Fermilab Tevatron Collider. We set upper limits on the t'(t) over bar' production cross section that exclude at the 95% C. L. a t' quark that decays exclusively to W + jet with a mass below 285 GeV. We observe a small excess in the mu + jets channel which reduces the mass range excluded compared to the expected limit of 320 GeV in the absence of a signal.
|
|
| 30. |
- Abazov, V. M., et al.
(författare)
-
Search for associated Higgs boson production using like charge dilepton events in p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84, s. 092002-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for associated Higgs boson production in the process p (p) over bar -> W/ZH -> l(+/-)l'(+/-) + X in ee, e mu, and mu mu final states. The search is based on data collected by the D0 experiment at the Fermilab Tevatron Collider at root s = 1.96 TeV corresponding to 5.3 fb(-1) of integrated luminosity. We require two isolated leptons (electrons or muons) with the same electric charge and additional kinematic requirements. No significant excess above background is observed, and we set 95% C. L. observed (expected) upper limits on ratio of the production cross section to the standard model prediction of 6.4 (7.3) for a Higgs boson mass of 165 GeV and 13.5 (19.8) for a mass of 115 GeV.
|
|
| 31. |
- Abazov, V. M., et al.
(författare)
-
Search for Doubly Charged Higgs Boson Pair Production in p(p)over-bar Collisions at root s=1.96 TeV
- 2012
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 108:2, s. 021801-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for pair production of doubly charged Higgs bosons in the processes q (q) over bar -> H(++)H(--) decaying through H(+/-+/-) ->tau(+/-)tau(+/-), mu(+/-)tau(+/-), mu(+/-)mu(+/-). The search is performed in p (p) over bar collisions at a center-of-mass energy of root s = 1:96 TeV using an integrated luminosity of up to 7:0 fb(-1) collected by the D0 experiment at the Fermilab Tevatron Collider. The results are used to set 95% C. L. limits on the pair production cross section of doubly charged Higgs bosons and on their mass for different H(+/-+/-) branching fractions. Models predicting different H(+/-+/-) decays are investigated. Assuming B(H(+/-+/-) -> tau(+/-)tau(+/-)) = 1 yields an observed (expected) lower limit on the mass of a left- handed H(L)(+/-+/-) boson of 128 (116) GeV and assuming B(H(+/-+/-) -> mu(+/-)tau(+/-)) = 1 the corresponding limits are 144 (149) GeV. In a model with B(H(+/-+/-) -> tau +/-tau(+/-) B(H(+/-+/-) -> mu(+/-)tau(+/-)) = B(H(+/-+/-) -> mu(+/-)mu(+/-) ) 1/3, we obtain M(H(L)(+/-+/-)) > 130 (138) GeV.
|
|
| 32. |
- Abazov, V. M., et al.
(författare)
-
Search for first generation leptoquark pair production in the electron plus missing energy plus jets final state
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:7, s. 071104-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for the pair production of first generation scalar leptoquarks (LQ) in data corresponding to an integrated luminosity of 5.4 fb(-1) collected with the D0 detector at the Fermilab Tevatron Collider in p (p) over bar collisions at root s = 1.96 TeV. In the channel LQLQ -> eqv(e)q', where q, q' are u or d quarks, no significant excess of data over background is observed, and we set a 95% C. L. lower limit of 326 GeV on the LQ mass, assuming equal probabilities of LQ decays to eq and v(e)q'.
|
|
| 33. |
- Abazov, V. M., et al.
(författare)
-
Search for Higgs bosons decaying to tau(+)tau(-) pairs in p(p)over-bar collisions at root s=1.96 TeV
- 2012
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 707:3-4, s. 323-329
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for the production of neutral Higgs bosons decaying into tau(+)tau(-) pairs in p (p) over bar collisions at a center-of-mass energy of 1.96 TeV. The data, corresponding to an integrated luminosity of 5.4 fb(-1), were collected by the DO experiment at the Fermilab Tevatron Collider. We set upper limits at the 95% C.L. on the product of production cross section and branching ratio for a scalar resonance decaying into tau(+)tau(-) pairs, and we interpret these limits as limits on the production of Higgs bosons in the minimal supersymmetric standard model (MSSM) and as constraints in the MSSM parameter space.
|
|
| 34. |
- Abazov, V. M., et al.
(författare)
-
Search for Neutral Minimal Supersymmetric Standard Model Higgs Bosons Decaying to Tau Pairs Produced in Association with b Quarks in p(p)over-bar Collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:12, s. 121801-
-
Tidskriftsartikel (refereegranskat)abstract
- We report results from a search for neutral Higgs bosons produced in association with b quarks using data recorded by the D0 experiment at the Fermilab Tevatron Collider and corresponding to an integrated luminosity of 7.3 fb(-1). This production mode can be enhanced in several extensions of the standard model (SM) such as in its minimal supersymmetric extension (MSSM) at high tan beta. We search for Higgs bosons decaying to tau pairs with one tau decaying to a muon and neutrinos and the other to hadrons. The data are found to be consistent with SM expectations, and we set upper limits on the cross section times branching ratio in the Higgs boson mass range from 90 to 320 GeV/c(2). We interpret our result in the MSSM parameter space, excluding tan beta values down to 25 for Higgs boson masses below 170 GeV/c(2).
|
|
| 35. |
- Abazov, V. M., et al.
(författare)
-
Combined Search for the Standard Model Higgs Boson Decaying to b(b)over-bar Using the D0 Run II Data Set
- 2012
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 109:12, s. 121802-
-
Tidskriftsartikel (refereegranskat)abstract
- We present the results of the combination of searches for the standard model Higgs boson produced in association with a W or Z boson and decaying into b (b) over bar using the data sample collected with the D0 detector in p (p) over bar collisions at root s = 1.96 TeV at the Fermilab Tevatron Collider. We derive 95% C.L. upper limits on the Higgs boson cross section relative to the standard model prediction in the mass range 100 GeV <= M-H <= 150 GeV, and we exclude Higgs bosons with masses smaller than 102 GeV at the 95% C.L. In the mass range 120 GeV <= M-H <= 145 GeV, the data exhibit an excess above the background prediction with a global significance of 1.5 standard deviations, consistent with the expectation in the presence of a standard model Higgs boson.
|
|
| 36. |
- Abazov, V. M., et al.
(författare)
-
Measurement of angular correlations of jets at s=1.96 TeV and determination of the strong coupling at high momentum transfers
- 2012
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 718:1, s. 56-63
-
Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the average value of a new observable at hadron colliders that is sensitive to QCD dynamics and to the strong coupling constant, while being only weakly sensitive to parton distribution functions. The observable measures the angular correlations of jets and is defined as the number of neighboring jets above a given transverse momentum threshold which accompany a given jet within a given distance δR in the plane of rapidity and azimuthal angle. The ensemble average over all jets in an inclusive jet sample is measured and the results are presented as a function of transverse momentum of the inclusive jets, in different regions of δR and for different transverse momentum requirements for the neighboring jets. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb -1 collected with the D0 detector at the Fermilab Tevatron Collider in pp- collisions at s=1.96 TeV. The results are well described by a perturbative QCD calculation in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects. From these results, we extract the strong coupling and test the QCD predictions for its running over a range of momentum transfers of 50-400 GeV.
|
|
| 37. |
- Abazov, V. M., et al.
(författare)
-
Measurement of leptonic asymmetries and top-quark polarization in t(t)over-bar production
- 2013
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 87:1, s. 011103-
-
Tidskriftsartikel (refereegranskat)abstract
- We present measurements of lepton (l) angular distributions in top-quark (t) pair production and t (t) over bar -> W(+)bW-(b) over bar -> l(+) vbl-(v) over bar(b) over bar decays produced in p (p) over bar collisions at a center-of-mass energy of root s = 1.96 TeV, where l is an electron or muon. Using data corresponding to an integrated luminosity of 5.4 fb(-1), collected with the D0 detector at the Fermilab Tevatron Collider, we measure for the first time the leptonic forward-backward asymmetry in dilepton final states and obtain A(FB)(l) = (5.8 +/- 5.1(stat) +/- 1.3(syst))%, corrected for detector acceptance. This is compared to the standard model prediction of A(FB)(l)(predicted) = (4.7 +/- 0.1)%. A deviation from the standard model prediction as previously seen in a D0 measurement based on the analysis of the l + jets final state is not observed in these dilepton final states. The two results differ from each other by 1.4 standard deviations and are combined to obtain A(FB)(l) = (11.8 +/- 3.2)%. Furthermore, we present a first study of the top-quark polarization.
|
|
| 38. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the Semileptonic Charge Asymmetry using B-S(0) -> D-s mu X Decays
- 2013
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 110:1, s. 011801-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the time-integrated flavor-specific semileptonic charge asymmetry in the decays of B-s(0) mesons that have undergone flavor mixing, a(sl)(s), using B-s(0)((B) over bar (0)(s)) -> D-s(-/+) mu(+/-) X decays, with D-s(-/+) -> phi pi(-/+) and phi -> K+K-, using 10.4 fb(-1) of proton-antiproton collisions collected by the D0 detector during Run II at the Fermilab Tevatron Collider. A fit to the difference between the time-integrated D0 detector during Run II at the Fermilab Tevatron Colllider. A fit to the difference between the time-integrated D-s(-) and D-s(+) mass distributions of the B-s(0) and ($) over bar (0)(s) candidates yields the flavor-specific asymmetry a(sl)(s) = [-1.12 +/- 0.74(stat) +/- 0.17(syst)]%, which is the most precise measurement and in agreement with the standard model prediction.
|
|
| 39. |
- Abazov, V. M., et al.
(författare)
-
Search for Higgs boson production in oppositely charged dilepton and missing energy events in p(p)over-bar collisions at root s=1.96 TeV
- 2012
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 86:3, s. 032010-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for the standard model Higgs boson using events with two oppositely charged leptons and large missing transverse energy as expected in H -> WW decays. The events are selected from data corresponding to 8.6 fb(-1) of integrated luminosity in p (p) over bar collisions at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. No significant excess above the standard model background expectation in the Higgs boson mass range this search is sensitive to is observed, and upper limits on the Higgs boson production cross section are derived.
|
|
| 40. |
- Abazov, V. M., et al.
(författare)
-
Search for the Standard Model Higgs Boson in Associated WH Production in 9.7 fb(-1) of p(p)over-bar Collisions with the D0 Detector
- 2012
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 109:12, s. 121804-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for the standard model Higgs boson in final states with a charged lepton (electron or muon), missing transverse energy, and two or three jets, at least one of which is identified as a b-quark jet. The search is primarily sensitive to WH -> lvb (b) over bar production and uses data corresponding to 9.7 fb(-1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron p (p) over bar Collider at root s = 1.96 TeV. We observe agreement between the data and the expected background. 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 5.2 x sigma(SM), where sigma(SM) is the standard model Higgs boson production cross section, while the expected limit is 4: 7 x sigma(SM).
|
|
| 41. |
- Abazov, V. M., et al.
(författare)
-
Search for the standard model Higgs boson in the ZH -> nu(nu)over-barb(b)over-bar channel in 9.5 fb(-1) of p(p)over-bar collisions at root s=1.96 TeV
- 2012
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 716:2, s. 285-293
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for the standard model Higgs boson in 9.5 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 final state considered contains a pair of b jets and is characterized by an imbalance in transverse energy, as expected from p (p) over bar -> ZH -> nu(nu) over barb (b) over bar production. The search is also sensitive to the WH -> l nu b (b) over bar channel when the charged lepton is not identified. The data are found to be in good agreement with the expected background. For a Higgs boson mass of 125 GeV, we set a limit at the 95% C.L. on the cross section sigma(p (p) over bar -> vertical bar Z/W vertical bar H), assuming standard model branching fractions, that is a factor of 4.3 times larger than the theoretical standard model value, while the expected factor is 3.9. The search is also used to measure a combined WZ and ZZ production cross section that is a factor of 0.94 +/- 0.31 (stat) +/- 0.34 (syst) times the standard model prediction of 4.4 pb, with an observed significance of 2.0 standard deviations. (C) 2012 Elsevier B.V. All rights reserved.
|
|
| 42. |
- Abazov, V. M., et al.
(författare)
-
Search for the Standard Model Higgs Boson in ZH -> l(+) l(-) b(b)over-bar Production with the D0 Detector in 9.7 fb(-1)of p(p)over-bar Collisions at root s=1.96 TeV
- 2012
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 109:12, s. 121803-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for the standard model (SM) 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 -> e(+) e(-) or Z -> mu(+) mu(-)candidate and at least two jets, including at least one jet identified as likely to contain a b quark. To validate the search procedure, we also measure the cross section for ZZ production in the same final state. It is found to be consistent with its SM prediction. We set upper limits on the ZH production cross section times branching ratio for H -> b (b) over bar at the 95% C.L. for Higgs boson masses 90 <= M-H <= 150 GeV. The observed (expected) limit for M-H = 125 GeV is 7.1 (5.1) times the SM cross section.
|
|
| 43. |
- Abazov, V. M., et al.
(författare)
-
Improved determination of the width of the top quark
- 2012
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:9, s. 091104-
-
Tidskriftsartikel (refereegranskat)abstract
- We present an improved determination of the total width of the top quark, Gamma(t), using 5.4 fb(-1) of integrated luminosity collected by the D0 Collaboration at the Tevatron p (p) over bar Collider. The total width Gamma(t) is extracted from the partial decay width Gamma(t -> Wb) and the branching fraction B(t -> Wb). Gamma(t -> Wb) is obtained from the t-channel single top-quark production cross section and B(t -> Wb) is measured in t (t) over bar events. For a top mass of 172.5 GeV, the resulting width is Gamma(t) = 2.00(-0.43)(+0.47) GeV. This translates to a top-quark lifetime of tau(t) = (3.29(-0.63)(+0.90)) x 10(-25) s. We also extract an improved direct limit on the Cabibbo-Kobayashi-Maskawa quark-mixing matrix element 0.81 < vertical bar V-tb vertical bar <= 1 at 95% C.L. and a limit of vertical bar V-tb'vertical bar < 0.59 for a high-mass fourth-generation bottom quark assuming unitarity of the fourth-generation quark-mixing matrix.
|
|
| 44. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the differential cross section d sigma/dt in elastic p(p)over-bar scattering at root s=1.96 TeV
- 2012
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 86:1, s. 012009-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the elastic differential cross section dσ(pp̅ →pp̅ )/dt as a function of the four-momentum-transfer squared t. The data sample corresponds to an integrated luminosity of ≈31 nb-1 collected with the D0 detector using dedicated Tevatron pp̅ Collider operating conditions at √s=1.96 TeV and covers the range 0.26<|t|<1.2 GeV2. For |t|<0.6 GeV2, dσ/dt is described by an exponential function of the form Ae-b|t| with a slope parameter b=16.86±0.10(stat)±0.20(syst) GeV-2. A change in slope is observed at |t|≈0.6 GeV2, followed by a more gradual |t| dependence with increasing values of |t|.
|
|
| 45. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the top-quark mass in p(p)over-bar collisions using events with two leptons
- 2012
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 86:5
-
Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the top-quark mass (m(t)) in p (p) over bar collisions at root s = 1.96 TeV using t (t) over bar events with two leptons (ee, e mu, or mu mu) and accompanying jets in 4.3 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron collider. We analyze the kinematically underconstrained dilepton events by integrating over their neutrino rapidity distributions. We reduce the dominant systematic uncertainties from the calibration of jet energy using a correction obtained from t (t) over bar events with a final state of a single lepton plus jets. We also correct jets in simulated events to replicate the quark flavor dependence of the jet response in data. We measure m(t) = 173.7 +/- 2.8 (stat) +/- 1.5 (syst) GeV and combining with our analysis in 1 fb(-1) of preceding data we measure m(t) = 174.0 +/- 2.4 (stat) +/- 1.4 (syst) GeV. Taking into account statistical and systematic correlations, a combination with the D0 matrix element result from both data sets yields m(t) = 173.9 +/- 1.9 (stat) +/- 1.6 (syst) GeV.
|
|
| 46. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the W Boson Mass with the D0 Detector
- 2012
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 108:15, s. 151804-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the W boson mass using data corresponding to 4: 3 fb(-1) of integrated luminosity collected with the D0 detector during Run II at the Fermilab Tevatron p (p) over tilde collider. With a sample of 1 677 394 W -> e nu candidate events, we measure M-W = 80.367 +/- 0.026 GeV. This result is combined with an earlier D0 result determined using an independent Run II data sample, corresponding to 1 fb(-1) of integrated luminosity, to yield MW 80.375 +/- 0.023 GeV.
|
|
| 47. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the WZ and ZZ production cross sections using leptonic final states in 8.6 fb(-1) of p(p)over-bar collisions
- 2012
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:11, s. 112005-
-
Tidskriftsartikel (refereegranskat)abstract
- We study the processes p (p) over bar -> WZ -> l(+) vl(+) l(-) and p (p) over bar -> ZZ -> l(+) l(-) v (v) over bar, where l = e or mu. Using 8: 6 fb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron collider, we measure the WZ production cross section to be 4.50(-0.66)(+0.63) pb which is consistent with, but slightly larger than, the prediction of the standard model. The ZZ cross section is measured to be 1: 64 +/- 0: 46 pb, in agreement with a prediction of the standard model. Combination with an earlier analysis of the ZZ -> l(+) l(-) l(+) l(-) channel yields a ZZ cross section of 1.44(-0.34)(+0.35) pb.
|
|
| 48. |
- Abazov, V. M., et al.
(författare)
-
Search for Higgs bosons of the minimal supersymmetric standard model in p(p)over-bar collisions at root s=1.96 TeV D0 Collaboration
- 2012
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 710:4-5, s. 569-577
-
Tidskriftsartikel (refereegranskat)abstract
- We report results from searches for neutral Higgs bosons produced in p (p) over bar collisions recorded by the D0 experiment at the Fermilab Tevatron Collider. We study the production of inclusive neutral Higgs boson in the tau tau final state and in association with a b quark in the b tau tau and bbb final states. These results are combined to improve the sensitivity to the production of neutral Higgs bosons in the context of the minimal supersymmetric standard model (MSSM). The data are found to be consistent with expectation from background processes. Upper limits on MSSM Higgs boson production are set for Higgs boson masses ranging from 90 to 300 GeV. We exclude tan beta > 20-30 for Higgs boson masses below 180 GeV. These are the most stringent constraints on MSSM Higgs boson production in p (p) over bar collisions.
|
|
| 49. |
- Abazov, V. M., et al.
(författare)
-
Search for pair production of the scalar top quark in muon plus tau final states D0 Collaboration
- 2012
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 710:4-5, s. 578-586
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for the pair production of scalar top quarks ((t) over tilde (1)), the lightest supersymmetric partners of the top quarks, in p (p) over bar collisions at a center-of-mass energy of 1.96 TeV, using data corresponding to an integrated luminosity of 7.3 fb(-1) collected with the D0 experiment at the Fermilab Tevatron Collider. Each scalar top quark is assumed to decay into a b quark, a charged lepton, and a scalar neutrino ((nu) over bar). We investigate final states arising from (t) over tilde (1)(t) over tilde (1) -> b (b) over bar mu tau(nu nu) over tilde and (t) over tilde (1)(t) over tilde (1) -> b (b) over bar tau tau(nu nu) over tilde. With no significant excess of events observed above the background expected from the standard model, we set exclusion limits on this production process in the (m((t) over tilde1), m((nu) over tilde)) plane.
|
|
| 50. |
- Abazov, V. M., et al.
(författare)
-
Search for Universal Extra Dimensions in p(p)over-bar Collisions
- 2012
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 108:13, s. 131802-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for Kaluza-Klein (KK) particles predicted by models with universal extra dimensions (UED) using a data set corresponding to an integrated luminosity of 7.3 fb(-1), collected by the D0 detector at a p (p) over bar center-of-mass energy of 1.96 TeV. The decay chain of KK particles can lead to a final state with two muons of the same charge. This signature is used to set a lower limit on the compactification scale of R-1 > 260 GeV in a minimal UED model.
|
|
