1,349 research outputs found
meson transparency in nuclei from resonant interactions
We investigate the meson nuclear transparency using some recent
theoretical developments on the in medium self-energy. The inclusion of
direct resonant -scattering and the kaon decay mechanisms leads to a
width much larger than in most previous theoretical approaches. The
model has been confronted with photoproduction data from CLAS and LEPS and the
recent proton induced production from COSY finding an overall good
agreement. The results support the need of a quite large direct -scattering contribution to the self-energy
Polarized proton structure in the resonance region
In view of the precise data available on inclusive polarized electron
scattering off polarized proton targets in the nucleon resonance excitation
region, we compare these results with the coherent sum of resonant
contributions to the polarized structure function and virtual photon
asymmetry . To this goal, we employ the nucleon resonance
electroexcitation amplitudes determined for photon virtualities 5.0
GeV from analyses of the CLAS data on exclusive electroproduction off
protons in the resonance region. Most of the well established resonances of
four star PDG status in the mass range up to 1.75~GeV are included. We find
that the resonance-like structures observed in the inclusive data are
related to the resonant contributions in the entire range of photon virtuality
where the data on are available. In the range of invariant mass of
the final hadron system 1.5 GeV, the data on the asymmetry are
well reproduced even when accounting for resonant contributions only,
especially for the larger values of and energies analysed. This
observation offers an interesting hint to quark-hadron duality seen in
polarized inclusive electron scattering observables.Comment: Contribution to proceedings: Emergence and Structure of Baryons -
Selected Contributions from the International Conference Baryons 202
Studying the Pc(4450) resonance in J/psi photoproduction off protons
The LHCb has reported the observation of a resonancelike structure, the
Pc(4450), in the J/psi p invariant masses. In our work, we discuss the
feasibility of detecting this structure in J/psi photoproduction, e.g. in the
measurements that have been approved for the experiments in Hall A/C and in
Hall B with CLAS12 at JLab. Also the GlueX Collaboration has already reported
preliminary results. We take into account the experimental resolution effects,
and perform a global fit to world J/psi photoproduction data in order to study
the possibility of observing the Pc(4450) signal in future JLab data. We
present a first estimate of the upper limit for the branching ratio of the
Pc(4450) into the J/psi p channel, and we study the angular distributions of
the differential cross sections. This will shed light on the nature and
couplings of the Pc(4450) structure in the future photoproduction experiments.Comment: NSTAR 2017 conference proceeding
Relating CP-violating decays to the neutron EDM
We use the present upper bound on the neutron electric dipole moment to give
an estimate for the upper limit of the CP-violating couplings of the
meson to the neutron. Using this result, we derive constraints on
the CP-violating two-pion decays of the . Our results are relevant
for the running and planned GlueX and LHCb measurements of rare meson decays.Comment: NSTAR 2017 conference proceeding
Structure of Pion Photoproduction Amplitudes
We derive and apply the finite energy sum rules to pion photoproduction. We
evaluate the low energy part of the sum rules using several state-of-the-art
models. We show how the differences in the low energy side of the sum rules
might originate from different quantum number assignments of baryon resonances.
We interpret the observed features in the low energy side of the sum rules with
the expectation from Regge theory. Finally, we present a model, in terms of a
Regge-pole expansion, that matches the sum rules and the high-energy
observables.Comment: 19 pages, 15 figures and 4 table
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