528 research outputs found

### Weak Decays of Heavy-Quark Systems

The recent theoretical progress in the description of semileptonic decays in
the framework of the heavy mass expansion is summarized. Both inclusive and
exclusive decays are considered.Comment: Contribution to the XXIXth Rencontres de Moriond (Electroweak
Interactions and Unified Theories}, Meribel, France, March 12-19, 1994,
LaTeX, 10 pages, two figues appended after \end{document} as uu-encoded and
compressed .eps files, uses epsf., CERN-TH.7264/9

### Subleading Light-cone distributions functions in the decays Lambda(b) --> X(s) Gamma and Lambda(b) --> X(u) Lepton Anti-Nu

In this paper we investigate the subleading twist corrections to the photon
energy spectrum in the decay Lambda_b -> X_s \gamma and to the lepton energy
spectrum in Lambda_b -> X_u l \bar{\nu}. As a first step we rederive the
matching coefficients of the subleading twist using a much simpler method.
Parametrizing the matrix elements for Lambda_b and using reparametrization
invariance, we show that the energy spectra close to the endpoints are given in
terms of only a single universal function.Comment: LATEX,The complete paper is also available via the www at
http://www-ttp.physik.uni-karlsruhe.de/Preprints/ . Discussion section
improve

### Light-Quark Decays in Heavy Hadrons

We consider weak decays of heavy hadrons (bottom and charmed) where the heavy
quark acts as a spectator. Theses decays are heavily phase-space suppressed but
may become experimentally accessible in the near future. These decays are
interesting as a QCD laboratory to study the behaviour of the light quarks in
the colour-background field of the heavy spectator.Comment: 11 pages, 6 table

### Direct CP Violation In Radiative B Decays

We discuss the role of the radiative B decays $B \to X_{s/d} \gamma$ in our
search for new physics focusing on the issue of direct CP violation. We discuss
in some detail a SM prediction for the CP asymmetries in inclusive $b \to s/d$
transitions, namely $\mid \Delta {\cal B}(B \to X_s \gamma) + \Delta {\cal B}(B
\to X_d \gamma) \mid \sim 1 \cdot 10^{-9}$. Any measured value in significant
deviation of this estimate would indicate new sources of CP violation beyond
the CKM phase.Comment: latex, 8 pages, 3 figure

### Improved Estimates for the Parameters of the Heavy Quark Expansion

We give improved estimates for the non-perturbative parameters appearing in
the heavy quark expansion for inclusive decays. While the parameters appearing
in low orders of this expansion can be extracted from data, the number of
parameters in higher orders proliferates strongly, making a determination of
these parameters from data impossible. Thus, one has to rely on theoretical
estimates which may be obtained from an insertion of intermediate states. In
this paper we refine this method and attempt to estimate the uncertainties of
this approach.Comment: 18 pages (v2: Fixed sign error in section 3. conclusions unchanged

### Zero-Recoil Sum Rules for $\Lambda_b \to \Lambda_c$ Form Factors

We set up a zero recoil sum rule to constrain the form factors of the
$\Lambda_b \to \Lambda_c$ transition. Our results are compared with the recent
lattice calculation for these transitions. We find the same situation as in the
case for $B \to D^*$: The lattice results practically saturate the sum rules,
leaving basically no room for excited states.Comment: 8 pages, 5 figure

### Parton--Hadron Duality in B Meson Decays

We summarize the current view on Parton-Hadron duality as it applies to B
meson decays. It is emphasized that an OPE treatment is essential for properly
formulating duality and its limitations. Duality violations are unlikely to
become the limiting factor in describing semileptonic B width vis-a-vie higher
order corrections. The consistent extraction of the b quark mass from B
production and decays provides a striking example of the theoretical control
achieved.Comment: Contribution to the CKM workshop, held at CERN, Geneva,
Feb.15.-18.2002, LaTeX, 13 pages, 2 figure

### 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

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