2,185 research outputs found
Ultrasoft contribution to heavy-quark pair production near threshold
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
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 and its effect on the
determination of .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
I compare current approaches to quarkonium production with regard to what
they tell us about quarkonium polarization. Predictions for
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
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
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