Search for the higgs boson in events with missing transverse energy and b quark jets produced in pp̄ collisions at s=1.96TeV
Physical Review Letters 100:21 (2008)
Abstract:
We search for the standard model Higgs boson produced in association with an electroweak vector boson in events with no identified charged leptons, large imbalance in transverse momentum, and two jets where at least one contains a secondary vertex consistent with the decay of b hadrons. We use ∼1fb-1 integrated luminosity of pp̄ collisions at s=1.96TeV recorded by the Collider Detector at Fermilab II experiment at the Tevatron. We find 268 (16) single (double) b-tagged candidate events, where 248±43 (14.4±2.7) are expected from standard model background processes. We observe no significant excess over the expected background and thus set 95% confidence level upper limits on the Higgs boson production cross section for several Higgs boson masses ranging from 110 to 140GeV/c2. For a mass of 115GeV/c2, the observed (expected) limit is 20.4 (14.2) times the standard model prediction. © 2008 The American Physical Society.Strong evidence for ZZ production in pp[over] collisions at sqrt[s]=1.96 TeV.
Phys Rev Lett 100:20 (2008) 201801
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 1.9 fb(-1) of integrated luminosity from pp[over] collisions at sqrt[s]=1.96 TeV collected with the Collider Detector at Fermilab II detector. In the lll'l' channel, we observe three ZZ candidates with an expected background of 0.096(-0.063)+0.092 events. In the llnunu 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 lll'l' and llnunu channels, we observe an excess of events with a probability of 5.1 x 10(-6) to be due to the expected background. This corresponds to a significance of 4.4 standard deviations. The measured cross section is sigma(pp[over]-->ZZ)=1.4(-0.6)+0.7(stat+syst) pb, consistent with the standard model expectation.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.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.Measurement of the tt̄ production cross section in pp̄ collisions at s=1.96TeV
Physical Review Letters 100:19 (2008)