413 research outputs found
Bound states of in nuclei
We study the binding energy and the width of the in nuclei,
associated to the and components. The first one leads to
negligible contributions while the second one leads to a sizeable attraction,
enough to bind the in nuclei. Pauli blocking and binding effects on
the decay reduce considerably the decay width in nuclei and
medium effects associated to the component also lead to a very small
width, as a consequence of which one finds separation between the bound levels
considerably larger than the width of the states.Comment: Presentation in the 10th International Baryon Conference BARYON0
Phi meson mass and decay width in nuclear matter
The meson spectrum, which in vacuum is dominated by its coupling to
the system, is modified in nuclear matter. Following a model based
on chiral SU(3) dynamics we calculate the meson selfenergy in nuclear
matter considering the and in-medium properties. For the latter
we use the results of previous calculations which account for and wave
kaon-nucleon interactions based on the lowest order meson-baryon chiral
effective Lagrangian, and this leads to a dressing of the kaon propagators in
the medium. In addition, a set of vertex corrections is evaluated to fulfill
gauge invariance, which involves contact couplings of the meson to
wave and wave kaon-baryon vertices. Within this scheme the mass shift
and decay width of the meson in nuclear matter are studied.Comment: 19 pages, 10 figures in EPS format, revtex4; One section modified,
some references update
The baryon-decuplet in the chiral dynamics of Lambda-hyperons in nuclear matter
We study the long range part of the -hyperon optical potential in
nuclei using Quantum Many Body techniques and flavor-SU(3) Chiral Lagrangians
as starting point. More precisely, we study the contributions to the
-hyperon optical potential due to the long-range two-pion exchange,
with and baryons in the internal baryonic lines and
considering Nh and h excitations. We also consider the contribution to
the spin-orbit potentials that comes out from these terms. Our results support
a natural explanation of the smallness of the -nuclear spin-orbit
interaction and shows the importance of the and degrees of
freedom for the hyperon-nucleus interactions.Comment: 8 pages, 5 figure
Baryonic Resonances from the Interactions of the Baryon Decuplet and Meson Octet
We study -wave interactions of the baryon decuplet with the octet of
pseudoscalar mesons using the lowest order chiral Lagrangian. We find two bound
states in the SU(3) limit corresponding to the octet and decuplet
representations. These are found to split into eight different trajectories in
the complex plane when the SU(3) symmetry is broken gradually. Finally, we are
able to provide a reasonable description for a good number of 4-star
resonances listed by the Particle Data Group. In particular, the
, the and the states are well
reproduced. We predict a few other resonances and also evaluate the couplings
of the observed resonances to the various channels from the residues at the
poles of the scattering matrix from where partial decay widths into different
channels can be evaluated.Comment: Contribution to the HADRON05 Conference, Rio de Janeiro, September
200
Threshold Neutral Pion Photoproduction on the Proton
The neutral pion photoproduction on the proton near threshold has a very
small scattering cross section when compared to the charged channels, which in
ChPT is explained by strong cancellations between the lowest order pieces.
Therefore it is very sensitive to higher-order corrections of chiral
perturbation theory. We perform a fully covariant calculation up to chiral
order p^3 and we investigate the effect of the inclusion of the Delta(1232)
resonance as an explicit degree of freedom. We show that the convergence
improves, leading to a much better agreement with data at a wide range of
energies.Comment: Proceedings to the NSTAR2015 conference, which will be published in
JPS conference proceeding
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