1,842 research outputs found
Distribution Amplitudes of Heavy Hadrons: Theory and Applications
The physics of heavy quarks becomes a very reach area of study thanks to an
excellent operation of hadron colliders and -factories and exciting results
from them. Experimental data obtained allows to get some information about the
heavy hadron dynamics. In this case, the models for the heavy hadron
wave-functions are required to do theoretical predictions for concrete
processes under study. In many cases, the light-cone description is enough to
obtain theoretical estimates for heavy hadron decays. A discussion of the
wave-functions of the -meson and heavy bottom baryons in terms of the
light-cone distribution amplitudes is given in this paper. Simple models for
the distribution amplitudes are presented and their scale dependence is
discussed. Moments of the distribution amplitudes which are entering the
branching fractions of radiative, leptonic and semileptonic -mesons decays
are also briefly discussed.Comment: 17 pages, 4 figures, lecture at the Helmholtz International Summer
School and Dubna International Advanced School on Theoretical Physics
"Quantum Field Theory at the Limits: from Strong Fields to Heavy Quarks",
JINR, Dubna, Russia, July 18--30, 201
Line bundle twisted chiral de Rham complex and bound states of D-branes on toric manifolds
In this note we calculate elliptic genus in various examples of twisted
chiral de Rham complex on two dimensional toric compact manifolds and
Calabi-Yau hypersurfaces in toric manifolds. At first the elliptic genus is
calculated for the line bundle twisted chiral de Rham complex on a compact
smooth toric manifold and K3 hypersurface in \mathbb{P}^{3} . Then we twist
chiral de Rham complex by sheaves localized on positive codimension
submanifolds in \mathbb{P}^{2} and calculate in each case the elliptic genus.
In the last example the elliptic genus of chiral de Rham complex on
\mathbb{P}^{2} twisted by SL(N) vector bundle with instanton number k is
calculated. In all cases considered we find the infinite tower of open string
oscillator contributions of the corresponding bound state of D-branes and
identify directly the open string boundary conditions and D-brane charges.Comment: 14 pages, LaTex, some comments and references adde
Poisson-Lie T-duality and N=2 superconformal WZNW models on compact groups
The supersymmetric generalization of Pisson-Lie T-duality in N=2
superconformal WZNW models on the compact groups is considered. It is shown
that the role of Drinfeld's doubles play the complexifications of the
corresponding compact groups. These complex doubles are used to define the
natural actions of the isotropic subgroups forming the doubles on the group
manifolds of the N=2 superconformal WZNW models. The Poisson- Lie T-duality in
N=2 superconformal U(2)-WZNW model considered in details. It is shown that this
model admits Poisson-Lie symmetries with respect to the isotropic subgroups
forming Drinfeld's double Gl(2,C). Poisson-Lie T-duality transformation maps
this model into itself but acts nontrivialy on the space of classical
solutions. Supersymmetric generalization of Poisson-Lie T-duality in N=2
superconformal WZNW models on the compact groups of higher dimensions is
proposed.Comment: 12 pages, latex, misprints correcte
Supersymmetric gauged WZNW models as dressing cosets
The domain of applicability of the Poisson-Lie T-duality is enlarged to
include the gauged WZNW models.Comment: 10 pages, LaTeX, reference adde
Improved -Meson Distribution Amplitudes from Inclusive Decay
We calculate the -meson energy spectrum in the decay in the leading-order
perturbative QCD in the static-quark limit for the orthoquarkonium.Our
principal result is the extraction of parameters of the
effective vertex function (EVF) involving a virtual and a real gluon from the
available data on the hard part of the -meson energy spectrum. The
perturbative-QCD based framework provides a good description of the available
CLEO data, allowing one to constrain the lowest Gegenbauer coefficients
and of the quark-antiquark and gluonic distribution
amplitudes of the -meson. The resulting constraints are combined
with the existing ones on these coefficients from an analysis of the
transition form factor and the requirement of positivity
of the EVF, yielding and for . This reduces significantly
the current uncertainty on these coefficients.Comment: 4 pages, 4 figures, use svjour.cls and svepj.clo; talk given at the
International Europhysics Conference on High-Energy Physics (HEP 2003), 17-23
July 2003, Aachen, Germany. Title change
Branching Ratios for and Decays in Next-to-Leading Order in the Large Eneregy Effective Theory
We calculate the so-called hard spectator corrections in in the leading-twist approximation to the decay widths for and decays and their charge conjugates, using
the Large Energy Effective Theory (LEET) techniques. Combined with the hard
vertex and annihilation contributions, they are used to compute the branching
ratios for these decays in the next-to-leading order (NLO) in the strong
coupling and in leading power in . These
corrections are found to be large, leading to the inference that the
theoretical branching ratios for the decays in the LEET
approach can be reconciled with current data only for significantly lower
values of the form factors than their estimates in the QCD sum rule and Lattice
QCD approaches. However, the form factor related uncertainties mostly cancel in
the ratios and , where , and hence their
measurements will provide quantitative information on the standard model
parameters, in particular the ratio of the CKM matrix elements and the inner angle of the CKM-unitarity triangle. We
also calculate direct CP asymmetries for the decays
and and find, in conformity with the
observations made in the existing literature, that the hard spectator
contributions significantly reduce the asymmetries arising from the vertex
corrections.Comment: 45 pages, 18 figures (requires amssymb and epsf); replaced with the
revised versio
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