136 research outputs found
Short- and long-distance QCD effects in B-meson decays
Various exclusive and inclusive decays of B mesons are studied, at present,
with dedicated experiments at ``B factories''. In order to compete with the
experimental accuracy, we need a reliable theoretical framework to compute
strong interaction effects in a hadronic environment. I discuss how the
separation of (perturbatively calculable) short-distance QCD effects from
(non-perturbative) long-distance phenomena helps to obtain precise theoretical
predictions.Comment: Invited talk given at Hadrons 03, Aschaffenburg, Germany; 10 pages, 6
figures, uses aipproc.cl
Renormalization Group Evolution of Flavour Invariants
The fermion spectrum in the Standard Model (SM) exhibits hierarchical
structures between the eigenvalues of the Yukawa matrices which determine the
fermion masses, as well as certain hierarchical patterns in the mixing matrix
that describes weak transitions between different fermion generations. A
basis-independent description of the SM flavour structure can be given in terms
of a complete set of flavour invariants. In this paper, we construct a
convenient set of such invariants, and discuss the general form of the
renormalization-group equations. We also discuss the simplifications that arise
from exploiting hierarchies in Yukwawa couplings and mixings which are present
in the SM or its minimal-flavour violating extensions.Comment: 27 pages, 3 figure
Is there a non-Standard-Model contribution in non-leptonic b -> s decays?
Precision measurements of branching fractions and CP asymmetries in
non-leptonic b -> s decays reveal certain "puzzles" when compared with Standard
Model expectations based on a global fit of the CKM triangle and general
theoretical expectations. Without reference to a particular model, we
investigate to what extent the (small) discrepancies observed in (B -> J/psi
K), (B -> phi K) and (B -> K pi) may constrain new physics in (b -> s q qbar)
operators. In particular, we compare on a quantitative level the relative
impact of different quark flavours q=c,s,u,d.Comment: 25 pages, 7 figures, some references added, brief discussion of B ->
J/psi \pi include
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