37 research outputs found
A covariant investigation of Neutral Vector Mesons: dynamical properties and electromagnetic decay widths
A simple, but fully-covariant model for describing neutral Vector Mesons, in
both light and heavy sectors, is briefly illustrated. The main ingredients of
our relativistic constituent model are i) an Ansatz for the Bethe-Salpeter
vertex for Vector Mesons, and ii) a Mandelstam-like formula for the
electromagnetic decay widths. The free parameters of our approach are fixed
through a comparison with the valence transverse-momentum distribution,
, obtained within phenomenological Light-Front Hamiltonian Dynamics
models reproducing the mass spectra. Preliminary results for the
transverse-momentum distributions, the parton distribution and the
electromagnetic decay constants are shown.Comment: 6 pages, 4 figures. Proceedings of LC2009, to appear in Nucl. Phys. B
supp
Theoretical Descriptions of the Nucleon Electromagnetic Form Factors in the Space- and Time-like regions
Some recent advances in the theoretical description of the Nucleon
electromagnetic form factors, both in the space- and time-like regions, will be
briefly illustrated. In particular, both the present stage of the lattice
calculations and updated phenomenological approaches, like the ones based on
dispersion relations and on microscopical models, will be reported.Comment: p. 6, figs. 7. Invited talk at PhiPsi 08, Frascati, April 2008. To
appear in Nucl. Phys.
Projecting the Bethe-Salpeter Equation onto the Light-Front and back: A Short Review
The technique of projecting the four-dimensional two-body Bethe-Salpeter
equation onto the three-dimensional Light-Front hypersurface, combined with the
quasi-potential approach, is briefly illustrated, by placing a particular
emphasis on the relation between the projection method and the effective
dynamics of the valence component of the Light-Front wave function. Some
details on how to construct the Fock expansion of both i) the Light-Front
effective interaction and ii) the electromagnetic current operator, satisfying
the proper Ward-Takahashi identity, will be presented, addressing the relevance
of the Fock content in the operators living onto the Light-Front hypersurface.
Finally, the generalization of the formalism to the three-particle case will
be outlined.Comment: 16 pages, macros included. Mini-review to be printed in a regular
issue of Few-Body Systems devoted to the Workshop on "Relativistic
Description of Two- and Three-body Systems in Nuclear Physics" ECT* Trento,
19 - 23 October 200
Fermion and photon gap-equations in Minkowski space within the Nakanishi integral representation method
The approach based on the Nakanishi integral representation of n-leg transition amplitudes is extended to the treatment of the self-energies of a fermion and an (IR-regulated) vector boson, in order to pave the way for constructing a comprehensive application of the technique to both gap- and Bethe-Salpeter equations, in Minkowski space. The achieved result, namely a 6-channel coupled system of integral equations, eventually allows one to determine the three Källén–Lehman weights for fully dressing the propagators of fermion and photon. A first consistency check is also provided. The presented formal elaboration points to embed the characteristics of the non-perturbative regime at a more fundamental level. It yields a viable tool in Minkowski space for the phenomenological investigation of strongly interacting theories, within a QFT framework where the dynamical ingredients are made transparent and under control
LIGHT-CONE 2015: Theoretical and experimental challenges onto the Light-Front
Editoriale di LIGHT-CONE 2015: Theoretical and experimental challenges onto the Light-Fron