933 research outputs found
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
Free-field Representations and Geometry of some Gepner models
The geometry of Gepner model, where is investigated by
free-field representation known as "bc\bet\gm"-system. Using this
representation it is shown directly that internal sector of the model is given
by Landau-Ginzburg -orbifold. Then we consider
the deformation of the orbifold by marginal anti-chiral-chiral operator.
Analyzing the holomorphic sector of the deformed space of states we show that
it has chiral de Rham complex structure of some toric manifold, where toric
dates are given by certain fermionic screening currents. It allows to relate
the Gepner model deformed by the marginal operator to the -model on CY
manifold realized as double cover of with ramification along
certain submanifold.Comment: LaTex, 14 pages, some acknowledgments adde
Mass Shift of Axion in Magnetic Field
A mass-shift of the axion propagating in an external constant homogenious
magnetic field is calculated. The contributions via an electron loop and a
virtual photon are examined. It is shown that the virtual photon contribution
dominates substantially over the electron-loop one. Under the conditions of the
early Universe the electron-loop contribution to the massless axion mass-shift
is equal to zero while the virtual photon contribution is finite and can be of
order of the recent restrictions on the axion mass.Comment: 4 pages, latex2e, 2 PS figures, uses ws-p8-50x6-00.sty (included) and
amssymb.sty. Talk at the International Workshop on Particle Physics and the
Early Universe (COSMO-99), Trieste, Italy, 27 September - 3 October 199
Double radiative decay in the Standard Model
Z-boson decay in the Standard Model is
analysed. The distribution function on the invariant masses of the photon and
fermion pairs is calculated in the leading logarithmic approximation. It is
shown that this distribution function has a specific shape of a ``crest''. (To
be published in Mod.Phys.Lett.A)Comment: 6 pages, LaTeX, (the figures are not included), Yaroslavl, Yaroslavl
State University preprint YARU-HE-94/0
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