Search for V+A current in top-quark decays in pp̄ collisions at s=1.96TeV
Physical Review Letters 98:7 (2007)
Abstract:
We report an upper limit on the fraction of V+A current, fV+A, in top-quark decays, using approximately 700pb-1 of pp̄ collisions at s=1.96TeV acquired by the upgraded Collider Detector at Fermilab. For the decay t→Wb→ νb (where =e or μ), the invariant mass of the charged lepton and the bottom quark jet is sensitive to the polarization of the W boson. We determine fV+A=-0.06±0.25 given a top-quark mass of 175GeV/c2. We set an upper limit on fV+A of 0.29 at the 95% confidence level, an improvement by a factor of 2 on the previous best direct limit. © 2007 The American Physical Society.Measurement of the ratios of branching fractions B(B0s --> Ds- pi+ pi+ pi-)/B(B0-->D- pi+ pi+ pi-) and B(B0s --> Ds- pi+)/B(B0-->D- pi+).
Phys Rev Lett 98:6 (2007) 061802
Abstract:
Using 355 pb;{-1} of data collected by the CDF II detector in pp[over ] collisions at sqrt[s]=1.96 TeV at the Fermilab Tevatron, we study the fully reconstructed hadronic decays B_{(s)};{0}-->D_{(s)};{-}pi;{+} and B_{(s)};{0}-->D_{(s)};{-}pi;{+}pi;{+}pi;{-}. We present the first measurement of the ratio of branching fractions B(B_{s};{0}-->D_{s};{-}pi;{+}pi;{+}pi;{-})/B(B;{0}-->D;{-}pi;{+}pi;{+}pi;{-})=1.05+/-0.10(stat)+/-0.22(syst). We also update our measurement of B(B_{s};{0}-->D_{s};{-}pi;{+})/B(B;{0}-->D;{-}pi;{+}) to 1.13+/-0.08(stat)+/-0.23(syst), improving the statistical uncertainty by more than a factor of 2. We find B(B_{s};{0}-->D_{s};{-}pi;{+})=[3.8+/-0.3(stat)+/-1.3(syst)]x10;{-3} and B(B_{s};{0}-->D_{s};{-}pi;{+}pi;{+}pi;{-})=[8.4+/-0.8(stat)+/-3.2(syst)]x10;{-3}.Search for exotic S=-2 baryons in pp̄ collisions at s=1.96TeV
Physical Review D - Particles, Fields, Gravitation and Cosmology 75:3 (2007)
Abstract:
A search for a manifestly exotic S=-2 baryon state decaying to Ξ-π-, and its neutral partner decaying to Ξ-π+, has been performed using 220pb-1 of pp̄ collisions at s=1.96TeV collected by the Collider Detector at Fermilab. The Ξ- trajectories were measured in a silicon tracker before their decay, resulting in a sample with low background and excellent position resolution. No evidence was found for S=-2 pentaquark candidates in the invariant mass range of 1600-2100MeV/c2. Upper limits on the product of pentaquark production cross section times its branching fraction to Ξ-π+,-, relative to the cross section of the well-established Ξ(1530) resonance, are presented for neutral and doubly negative candidates with pT>2GeV/c and |y|<1 as a function of pentaquark mass. At 1862MeV/c2, these upper limits for neutral and doubly negative final states were found to be 3.2% and 1.7% at the 90% confidence level, respectively. © 2007 The American Physical Society.Search for the pair production of scalar top quarks in the acoplanar charm jet final state in p over(p, ̄) collisions at sqrt(s) = 1.96 TeV
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 645:2-3 (2007) 119-127
Abstract:
A search for the pair production of scalar top quarks, over(t, ̃), has been performed in 360 pb-1 of data from p over(p, ̄) collisions at a center-of-mass energy of 1.96 TeV, collected by the DØ detector at the Fermilab Tevatron collider. The over(t, ̃) decay mode considered is over(t, ̃) → c over(χ, ̃)10, where over(χ, ̃)10 is the lightest supersymmetric particle. The topology analyzed therefore consists of a pair of acoplanar heavy-flavor jets with missing transverse energy. The data and standard model expectation are in agreement, and a 95% C.L. exclusion domain in the (mover(t, ̃), mover(χ, ̃)10) plane has been determined, extending the domain excluded by previous experiments. © 2006 Elsevier B.V. All rights reserved.Measurement of the ratios of branching fractions B(Bs0→Ds- π+π+π-)/B(B0→D-π+π+π-) and B(Bs0→Ds-π+)/ B(B0→D-π+)
Physical Review Letters 98:6 (2007)