Strong evidence for ZZ production in pp̄ collisions at s=1.96TeV
Physical Review Letters 100:20 (2008)
Abstract:
We report the first evidence of Z boson pair production at a hadron collider with a significance exceeding 4 standard deviations. This result is based on a data sample corresponding to 1.9fb-1 of integrated luminosity from pp̄ collisions at s=1.96TeV collected with the Collider Detector at Fermilab II detector. In the ′ ′ channel, we observe three ZZ candidates with an expected background of 0.096-0.063+0.092 events. In the νν channel, we use a leading-order calculation of the relative ZZ and WW event probabilities to discriminate between signal and background. In the combination of ′ ′ and νν channels, we observe an excess of events with a probability of 5.1×10-6 to be due to the expected background. This corresponds to a significance of 4.4 standard deviations. The measured cross section is σ(pp̄→ZZ)=1.4-0.6+0.7(stat+syst)pb, consistent with the standard model expectation. © 2008 The American Physical Society.Measurement of the tt[over] production cross section in pp[over] collisions at sqrt(s)=1.96 TeV.
Phys Rev Lett 100:19 (2008) 192004
Abstract:
We measure the tt[over] production cross section in pp[over] collisions at sqrt(s)=1.96 TeV in the lepton + jets channel. Two complementary methods discriminate between signal and background: b tagging and a kinematic likelihood discriminant. Based on 0.9 fb(-1) of data collected by the D0 detector at the Fermilab Tevatron Collider, we measure sigma(tt[over])=7.62+/-0.85 pb, assuming the current world average m(t)=172.6 GeV. We compare our cross section measurement with theory predictions to determine a value for the top-quark mass of 170+/-7 GeV.Simultaneous measurement of the ratio R=B(t --> Wb)/B(t --> Wq) and the top-quark pair production cross section with the D0 detector at sqrt(s) = 1.96 TeV.
Phys Rev Lett 100:19 (2008) 192003
Abstract:
We present the first simultaneous measurement of the ratio of branching fractions, R=B(t --> Wb)/B(t --> Wq), with q being a d, s, or b quark, and the top-quark pair production cross section sigma(tt[over]) in the lepton plus jets channel using 0.9 fb(-1) of pp[over] collision data at sqrt(s)=1.96 TeV collected with the D0 detector. We extract R and sigma(tt[over]) by analyzing samples of events with 0, 1, and > or =2 identified b jets. We measure R=0.97(+0.09)/(-0.08)(stat+syst) and sigma(tt[over])=8.18(+0.09)(-0.84)(stat+syst) +/- 0.50(lumi) pb, in agreement with the standard model prediction.Two-particle momentum correlations in jets produced in pp̄ collisions at s=1.96TeV
Physical Review D - Particles, Fields, Gravitation and Cosmology 77:9 (2008)
Abstract:
We present the first measurement of two-particle momentum correlations in jets produced in pp̄ collisions at s=1.96TeV. Results are obtained for charged particles within a restricted cone with an opening angle of 0.5 radians around the jet axis and for events with dijet masses between 66 and 563GeV/c2. A comparison of the experimental data to theoretical predictions obtained for partons within the framework of resummed perturbative QCD in the next-to-leading log approximation shows that the parton momentum correlations survive the hadronization stage of jet fragmentation, giving further support to the hypothesis of local parton-hadron duality. The extracted value of the next-to-leading-log-approximation parton shower cutoff scale Qeff set equal to ΛQCD is found to be (1.4-0.7+0.9)×100MeV. © 2008 The American Physical Society.A combined search for the standard model Higgs boson at sqrt(s) = 1.96 TeV
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 663:1-2 (2008) 26-36