Observation of exclusive γγ production in pp̄ collisions at √s=1.96TeV
Physical Review Letters 108:8 (2012)
Abstract:
We have observed exclusive γγ production in proton-antiproton collisions at √s=1.96TeV, using data from 1.11±0.07fb-1 integrated luminosity taken by the Run II Collider Detector at Fermilab. We selected events with two electromagnetic showers, each with transverse energy ET>2.5GeV and pseudorapidity |η|<1.0, with no other particles detected in -7.4<η<+7.4. The two showers have similar E T and azimuthal angle separation Δψ∼π; 34 events have two charged particle tracks, consistent with the QED process pp̄→p+e+e-+p̄ by two-photon exchange, while 43 events have no charged tracks. The number of these events that are exclusive π0π0 is consistent with zero and is <15 at 95% C.L. The cross section for pp̄→p+γγ+p̄ with |η(γ)|<1.0 and ET(γ)>2.5GeV is 2.48-0.35+0.40(stat)-0.51+0.40(syst)pb. © 2012 American Physical Society.Search for Higgs bosons produced in association with b quarks
Physical Review D - Particles, Fields, Gravitation and Cosmology 85:3 (2012)
Abstract:
We present a search for neutral Higgs bosons decaying into bb̄, produced in association with b quarks in pp̄ collisions. This process could be observable in supersymmetric models with high values of tanβ. The event sample corresponds to 2.6fb -1 of integrated luminosity collected with the CDF II detector at the Fermilab Tevatron collider. We search for an enhancement in the mass of the two leading jets in events with three jets identified as coming from b quarks using a displaced vertex algorithm. A data-driven procedure is used to estimate the dijet mass spectrum of the nonresonant multijet background. The contributions of backgrounds and a possible Higgs boson signal are determined by a two-dimensional fit of the data, using the dijet mass together with an additional variable which is sensitive to the flavor composition of the three tagged jets. We set mass-dependent limits on σ(pp̄→)×B(→bb̄) which are applicable for a narrow scalar particle produced in association with b quarks. We also set limits on tanβ in supersymmetric Higgs models including the effects of the Higgs boson width. © 2012 American Physical Society.Measurement of the branching fraction B(Λb0→Λc+π -π +π -) at CDF
Physical Review D - Particles, Fields, Gravitation and Cosmology 85:3 (2012)
Abstract:
We report an analysis of the Λb0→Λc+π -π +π - decay in a data sample collected by the CDF II detector at the Fermilab Tevatron corresponding to 2.4fb -1 of integrated luminosity. We reconstruct the currently largest samples of the decay modes Λb0→Λ c(2595) +π - (with Λ c(2595) +→Λc+π +π -), Λb0→Λ c(2625) +π - (with Λ c(2625) +→Λc+π +π -), Λb0→Σ c(2455) ++π -π - (with Σ c(2455) ++→Λc+π +), and Λb0→Σ c(2455)0π +π - (with Σ c(2455)0→Λc+π -) and measure the branching fractions relative to the Λb0→Λc+π - branching fraction. We measure the ratio B(Λb0→Λc+π -π +π -)/B(Λb0→Λc+π -)=3.04±0.33(stat)-0.55+0.70(syst) which is used to derive B(Λb0→Λc+π -π +π -)= (26.8-11.2+11.9)×10 -3. © 2012 American Physical Society.Search for anomalous production of multiple leptons in association with W and Z bosons at CDF
(2012)
Search for anomalous production of multiple leptons in association with W and Z bosons at CDF
ArXiv 1202.126 (2012)