5,634 research outputs found
Photoproduction with Nucleon Resonances
We investigate the reaction mechanism of photoproduction off
the neutron target, i.e., , in the range of GeV. We employ an effective Lagrangian method at the tree-level Born
approximation combining with a Regge approach. As a background, the
-Reggeon trajectory is taken into account in the channel and
and hyperons in the -channel Feynman diagram. In addition, the role
of various nucleon resonances listed in the Particle Data Group (PDG) is
carefully scrutinized in the channel where the resonance parameters are
extracted from the experimental data and constituent quark model. We present
our numerical results of the total and differential cross sections and compare
them with the recent CLAS data. The effect of the narrow nucleon resonance
on cross sections is studied in detail and it turns out that
its existence is essential in photoproduction to reproduce the
CLAS data.Comment: 4 pages, 3 figures, Proceedings of "8th International Conference on
Quarks and Nuclear Physics (QNP2018)", November 13-17, 2018, Tsukuba, Japa
Pion radiative weak decay from the instanton vacuum
We investigate the vector and axial-vector form factors for the pion
radiative weak decays and , based on the gauged effective chiral action from the instanton vacuum in
the large limit. The nonlocal contributions, which arise from the gauging
of the action, enhance the vector form factor by about , whereas the
axial-vector form factor is reduced by almost . Both the results for
the vector and axial-vector form factors at the zero momentum transfer are in
good agreement with the experimental data. The dependence of the form factors
on the momentum transfer is also studied. The slope parameters are computed and
compared with other works.Comment: 13 pages, 7 figures. Final version accepted for publication in
Phys.Lett.
Heavy pentaquark states and in the production induced by pion beams off the nucleon
In this study, we investigate the production induced by pion beams
off the nucleon, particularly the heavy pentaquarks and
in intermediate states, based on a hybridized Regge model. The process
involving and meson exchange in the channel is considered as
background, and the heavy pentaquark exchange is included in the channel.
The coupling constants such as the and vertices are taken
from the potentials, whereas those for the and
vertices are determined by using experimental data based on the
branching ratios. In order to estimate the and coupling
constants, we use the experimental upper limit on the total cross section as a
guide for the reaction. The background total cross section
is the order of nb. In the vicinity of the heavy pentaquark
masses, the total cross section reaches about nb.Comment: 13 pages, 6 figures. To be published in Phys. Lets.
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