1,759 research outputs found

    Ultrasoft contribution to heavy-quark pair production near threshold

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    We compute the third-order correction to the heavy-quark current correlation function due to the emission and absorption of an ultrasoft gluon. Our result supplies a missing contribution to top-quark pair production near threshold and the determination of the bottom quark mass from QCD sum rules.Comment: 10 pages, LaTe

    QCD factorization for exclusive, non-leptonic B decays

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    Exclusive, non-leptonic, two-body decays of B mesons simplify greatly in the heavy quark limit. In this talk I discuss the factorized structure that holds in this limit and some of its consequences: (a) naive factorization is recovered in a certain limit; (b) `non-factorizable' effects are hard and can be calculated; (c) strong interaction phases vanish in the heavy quark limit (and can be calculated as well). As an illustration, I compute the penguin contribution to the decay Bd→π+π−B_d\to\pi^+\pi^- and its effect on the determination of sin⁥2α\sin 2\alpha.Comment: 4 pages, LaTeX, Talk presented at the `International Europhysics Conference on High Energy Physics' (EPS99), 15-21 July 1999, Tampere, Finlan

    Quarkonium polarization as a test of non-relativistic effective theory

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    I compare current approaches to quarkonium production with regard to what they tell us about quarkonium polarization. Predictions for J/ψJ/\psi polarization in hadron-hadron and photon-hadron collisions are summarized.Comment: 6 pages, LaTeX, 3 figures included via epsf.sty, uses sprocl.sty (provided

    Spectator scattering at NLO in non-leptonic B decays: Tree amplitudes

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    We compute the 1-loop (alpha_s^2) correction to hard spectator scattering in non-leptonic B decay tree amplitudes. This forms part of the NNLO contribution to the QCD factorization formula for hadronic B decays, and introduces a new rescattering phase that corrects the leading-order result for direct CP asymmetries. Among the technical issues, we discuss the cancellation of infrared divergences, and the treatment of evanescent four-quark operators. The infrared finiteness of our result establishes factorization of spectator scattering at the 1-loop order. Depending on the values of hadronic input parameters, the new 1-loop correction may have a significant impact on tree-dominated decays such as B -> pi pi.Comment: 28 pages, 5 figures, LaTe

    Signatures of Color-Octet Quarkonium Production

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    I briefly review the nonrelativistic QCD picture of quarkonium production and its confrontation with experiment in various production processes.Comment: 17 pages, LaTeX, 1 figure, sprocl.sty provided (To appear in the Proceedings of the Second Workshop on Continuous Advances in QCD, Minneapolis, U.S.A., March 1996

    CP Violation

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    Several pieces of direct and indirect evidence now suggest that the Kobayashi-Maskawa mechanism plays a distinguished role for CP violation at the electroweak scale. This talk provides a general overview of CP violation in its various contexts, emphasizing CP violation in flavour-violating interactions, such as due to the Kobayashi-Maskawa mechanism. I then review a few recent theoretical developments relevant to the interpretation of CP violation.Comment: 27 pages, LaTeX; plenary talk presented at the International Europhysics Conference on High Energy Physics, Budapest, July 2001; manuscript has some overlap with hep-lat/020101