321 research outputs found
Study of and structures via transitions
The helicity amplitudes of the and resonances in the
electromagnetic transition are studied in the constituent
quark model using the impulse approximation, with the proton and resonances
assumed to be in three-quark configurations. The comparison of theoretical
results and experimental data on the helicity amplitudes , ,
and indicates that the and resonances are
primarily composed of three-quark states but may contain additional
components. However, it is improbable that contributions from meson clouds will
be dominant at low .Comment: 6 pages, 3 figure
Axial transition form factors of octet baryons in the perturbative chiral quark model
We study the axial transition form factors as well as
the axial charges of the octet baryons in the perturbative
chiral quark model~(PCQM) with including both the ground and excited states in
the intermediate quark propagators. The PCQM results on the and the are found in good agreement with the existing
experimental data and the lattice-QCD values. And the study figures out that
the for all transitions behave in the dipole-like form,
which is dominantly caused by the three-quark core. The meson cloud with the
ground state quark propagator also plays an extremely important role but
results in a flat contribution. The excited state quark propagator contributing
to the could be regarded as the higher order correction
and it is very limited
Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR
Simulation results for future measurements of electromagnetic proton form
factors at \PANDA (FAIR) within the PandaRoot software framework are reported.
The statistical precision with which the proton form factors can be determined
is estimated. The signal channel is studied on the basis
of two different but consistent procedures. The suppression of the main
background channel, , is studied.
Furthermore, the background versus signal efficiency, statistical and
systematical uncertainties on the extracted proton form factors are evaluated
using two different procedures. The results are consistent with those of a
previous simulation study using an older, simplified framework. However, a
slightly better precision is achieved in the PandaRoot study in a large range
of momentum transfer, assuming the nominal beam conditions and detector
performance
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