1,143 research outputs found
Effective Field Theory and Heavy Quark Physics
These notes are based on five lectures presented at the 2004 Theoretical
Advanced Study Institute (TASI) on ``Physics in D>=4''. After a brief
motivation of flavor physics, they provide a pedagogical introduction to
effective field theory, the effective weak Lagrangian, and the technology of
renormalization-group improved perturbation theory. These general methods are
then applied in the context of heavy-quarks physics, introducing the concepts
of heavy-quark and soft-collinear effective theory.Comment: Lectures presented at TASI 2004 (39 pages
Uncertainties in the Determination of
I discuss the theoretical uncertainties in the extraction of
from semilep\-to\-nic decays of mesons, taking into account the most recent
theoretical developments. The main sources of uncertainty are identified both
for the exclusive decay mode and for the inclusive
channel . From an analysis of the available experimental
data, I obtain from the exclusive mode, and from the inclusive mode. I also give a prediction for
the slope of the form factor at zero recoil, which is
.Comment: Proceedings of 1995 Moriond Conference on Electroweak Interactions
and Unified Theories, 11 pages, 3 figures available as uu-encoded postscript
file
Heavy Flavour Physics
The current status of the theory and phenomenology of weak decays of hadrons
containing a heavy quark is reviewed. Exclusive semileptonic and rare decays of
mesons are discussed, as well as inclusive decay rates, the semileptonic
branching ratio of the meson, and the lifetimes of -flavoured hadrons.
Determinations of from spectroscopy are briefly
presented.Comment: 27 pages, 7 figures, discussion of the theory of the B semileptonic
branching ratio has been revise
Soft-Collinear Factorization and the Calculation of the B->Xs+gamma Rate
Using results on soft-collinear factorization for inclusive B-meson decay
distributions, a systematic study of the partial B->Xs+gamma decay rate with a
cut E_gamma<E_0 on photon energy is performed. For values E_0<1.9 GeV the rate
can be calculated without reference to shape functions. The result depends on
three large scales: m_b, \sqrt{m_b Delta}, and Delta=m_b-2E_0. The sensitivity
to the scale Delta=1.1 GeV (for E_0=1.8 GeV) introduces significant
uncertainties, which have been ignored in the past. Our new prediction for the
B->Xs+gamma branching ratio with E_gamma<1.8 GeV is
Br(B->Xs+gamma)=(3.44+-0.53+-0.35)*10^{-4}, where the errors refer to
perturbative and parameter uncertainties, respectively. The implications of
larger theory uncertainties for New Physics searches are explored with the
example of the type-II two-Higgs-doublet model.Comment: Invited talk presented at the 39th Rencontres de Moriond: Electroweak
Interactions and Unified Theories (La Thuile, Italy, 21-28 March 2004), and
at Continuous Advances in QCD 2004 (Minneapolis, Minnesota, 13--16 May 2004).
11 pages, 1 figur
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