Professor Daniela Bortoletto

Abstract:

We present the first measurement of the jet pseudorapidity distribution in direct photon events from a sample of (Formula presented) collisions at (Formula presented) recorded with the Collider Detector at Fermilab. Quantum chromodynamics (QCD) predicts that these events are primarily from hard quark-gluon Compton scattering, (Formula presented) with the final state quark producing the jet of hadrons. The jet pseudorapidity distribution in this model is sensitive to parton momentum fractions between 0.015 and 0.15. We find that the shape of the measured pseudorapidity distribution agrees well with next-to-leading order QCD calculations. © 1998 The American Physical Society.

Abstract:

The average bottom-hadron and individual (Formula presented), (Formula presented), and (Formula presented) meson lifetimes have been determined using decays with a (Formula presented) in the final state. The data sample consists of 110 pb(Formula presented) of (Formula presented) collisions at (Formula presented) TeV collected by the CDF detector at the Fermilab Tevatron collider during 1992–1995. For the average lifetime of (Formula presented) hadrons decaying into (Formula presented)+X, we obtain (Formula presented) For the (Formula presented) and (Formula presented) meson lifetimes, we determine (Formula presented) (Formula presented) and (Formula presented) For the (Formula presented) meson lifetime, we find (Formula presented) ps. © 1998 The American Physical Society.

Abstract:

The lifetimes of the B- and B̄0 mesons are measured using the partially reconstructed semileptonic decays B̄ → Dl- v̄X, where D0 is either a D0 or D*+ meson. The data were collected by the CDF detector at the Fermilab Tevatron collider during 1992-1995 and correspond to about 110 pb-1 of pp collisions at √s = 1.8 TeV. We measure decay lengths and extract the lifetimes to be τ(B-) = 1.637±0.058-0.043+0.045 ps and τ(B̄0) = 1.474±0.039-0.051+0.052 ps, and the ratio of the lifetimes to be τ(B-)/τ(B̄0) = 1.110±0.056-0.030+0.033, where the first uncertainties are statistical and the second are systematic.

Abstract:

We present a measurement of the B⁰ ↔ B^-0 oscillation frequency using a flavor tagging method based on correlations of B meson flavor with the charge of other particles produced in pp collisions at √ s = 1.8 TeV. Such correlations are expected to arise from b quark hadronization and from B** decays. We partially reconstruct B mesons using the semileptonic decays B⁰ → l⁺D^(*)-X and B⁺ → l⁺D^-0X. From the oscillation frequency, we obtain the mass difference between the two B⁰ mass eigenstates, Δmd = 0.471^+0.078 -0.068(stat) ± 0.034(syst) ħps^-1, and measure the efficiency and purity of this flavor tagging method for both charged and neutral B mesons. © 1998 The American Physical Society.

Abstract:

We present a measurement of the time-dependent asymmetry in the rate for B^-0 d versus B⁰ d decays to J/ψK⁰ S. A nonzero asymmetry would be an indication of CP violation, and within the standard model this may be used to measure the CP-violation parameter sin(2β)2. A total of 198 ± 17 B⁰ d/B¯⁰ d decays were observed in 99¯ collisions at √s = 1.8 TeV by the CDF detector at the Fermilab Tevatron. B⁰ d and B¯⁰ d are distinguished by a technique based on charge correlations from hadronization of the b quark. Our analysis results in sin(2β) = 1.8 ± 1.1(stat) ± 0.3(syst). © 1998 The American Physical Society.