418 research outputs found
Hints on the quadrupole deformation of the (1232)
The E2/M1 ratio (EMR) of the (1232) is extracted from the world data
in pion photoproduction by means of an Effective Lagrangian Approach (ELA).This
quantity has been derived within a crossing symmetric, gauge invariant, and
chiral symmetric Lagrangian model which also contains a consistent modern
treatment of the (1232) resonance. The \textit{bare} s-channel
(1232) contribution is well isolated and Final State Interactions (FSI)
are effectively taken into account fulfilling Watson's theorem. The obtained
EMR value, EMR%, is in good agreement with the latest lattice
QCD calculations [Phys. Rev. Lett. 94, 021601 (2005)] and disagrees with
results of current quark model calculations.Comment: Enlarged conclusions and explanations on the E2/M1 ratio. Figure 3
improved. References updated. 5 pages. 3 figures. 2 tables. Accepted for
publication in Physical Review
Nonfactorization and the decays and
In six chosen scenarios for the dependence of the form factors involved
in transition, we have determined the allowed domain
of and from the experimentally measured
ratios and in a scheme that uses the value of the phenomenological parameter and includes nonfactorized
contribution. We find that the experimentally measured values of and
from semileptonic decays of favor solutions which have significant
nonfactorized contribution, and, in particular, favors solutions in
scenarios where is either flat or decreasing with .Comment: 15 pages, Latex, four figure (available on request)
Heavy-to-Light Meson Transitions in QCD
I discuss QCD sum rules determinations of the form factors governing the
decay . For some of these form factors the computed
dependence on the momentum transferred does not agree with the expectation from
the nearest pole dominance hypothesis. Relations are observed among the form
factors, that seem to be compatible with equations recently derived by B.Stech.
The measurement of a number of color suppressed nonleptonic B decay rates could
shed light on the accuracy of the calculation of these form factors and on the
factorization approximation.Comment: LaTex, 7 pages, 2 figures (files included). Talk given at the 6th
International Symposium on Heavy Flavours, Pisa, 6-10 June 199
The Absence of Positive Energy Bound States for a Class of Nonlocal Potentials
We generalize in this paper a theorem of Titchmarsh for the positivity of
Fourier sine integrals. We apply then the theorem to derive simple conditions
for the absence of positive energy bound states (bound states embedded in the
continuum) for the radial Schr\"odinger equation with nonlocal potentials which
are superposition of a local potential and separable potentials.Comment: 23 page
The Mass Splitting Problem
It is discussed the problem of the mass splitting. It is
suggested to use the decay to measure the
mass splitting.Comment: 7 pages, revtex, a few typos fixed, to be published in Pis'ma v
ZHETF, V. 69, No 1, pp. 8-11, 10 January 199
Nonfactorization in Hadronic Two-body Cabibbo-favored decays of D^0 and D^+
With the inclusion of nonfactorized amplitudes in a scheme with , we
have studied Cabibbo-favored decays of and into two-body hadronic
states involving two isospins in the final state. We have shown that it is
possible to understand the measured branching ratios and determined the sizes
and signs of nonfactorized amplitudes required.Comment: 15 pages, Late
Nonfactorization and Color-Suppressed Decays
Using value of the parameter but including a modest
nonfactorized amplitude, we show that it is possible to understand all data,
including polarization, for color-suppressed
decays in all commonly used models of form factors. We show that for decay one can define an effective , which is process-dependent and,
in general, complex; but it is not possible to define an effective for
decay. We also explain why nonfactorized amplitudes do not
play a significant role in color-favored B decays.Comment: 13 pages, Latex, one figure (not included
Hyperon-Nucleon Final State Interaction in Kaon Photoproduction of the Deuteron
Final state hyperon-nucleon interaction in strangeness photoproduction of the
deuteron is investigated making use of the covariant reaction formalism and the
P-matrix approach to the YN system. Remarkably simple analytical expression for
the amplitude is obtained. Pronounced effects due to final state interaction
are predicted including the manifestation of the 2.13 GeV resonance.Comment: LaTeX, 13 page
Decay
Motivated by the experimental measurement of the decay rate, , and
the longitudinal polarization, , in the Cabibbo favored decay , we have studied theoretical prediction within the context of
factorization approximation invoking several form factors models. We were able
to obtain agreement with experiment for both and by using
experimentally measured values of the form factors ,
and in the semi-leptonic decay . We have also included in our calculation the effect of the
final state interaction () by working with the partial waves amplitudes
, and . Numerical calculation shows that the decay amplitude is
dominated by wave, and that the polarization is sensitive to the
interference between and waves. The range of the phase difference
accommodated by experimental error in
is large.Comment: 7 pages, LaTe
Form factors of the exotic baryons with isospin I=5/2
The electromagnetic form factors of the exotic baryons are calculated in the
framework of the relativistic quark model at small and intermediate momentum
transfer. The charge radii of the E+++ baryons are determined.Comment: 12pages, 2 figure
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