35 research outputs found
Form factors and branching ratio for the B -> l nu gamma decay
Form factors parameterizing radiative leptonic decays of heavy mesons for photon energy are computed in the language
of dispersion relation. The contributing states to the absorptive part in the
dispersion relation are the multiparticle continum, estimated by quark triangle
graph and resonances with quantum numbers and which includes
and and thier radial excitations, which model the higher
state contributions. Constraints provided by the asymptotic behavior of the
structure dependent amplitude, Ward Identities and gauge invariance are used to
provide useful information for parameters needed. The couplings
and are predicted if we restrict to
first radial excitation; otherwise using these as an input the radiative decay
coupling constants for radial excitations are predicted. The value of the
branching ratio for the process is found to
be in the range . A detailed comparison is given with other
approaches.Comment: 22 pages+two ps figures; Paper has been throughly revised and Sudakov
resummation has been discussed; published versio