730 research outputs found
Electromagnetic form factors of the baryon octet in the perturbative chiral quark model
We apply the perturbative chiral quark model at one loop to analyze the
electromagnetic form factors of the baryon octet. The analytic expressions for
baryon form factors, which are given in terms of fundamental parameters of
low-energy pion-nucleon physics (weak pion decay constant, axial nucleon
coupling, strong pion-nucleon form factor), and the numerical results for
baryon magnetic moments, charge and magnetic radii are presented. Our results
are in good agreement with experimental data.Comment: 15 pages, 6 figures, to be published in Eur. Phys. J.
Relativistic Quark Model Based Description of Low Energy NN Scattering
A description of the NN scattering is constructed starting from the pseudoscalar-, the vector-, and the
scalar - meson-nucleon coupling constants,
which we obtain within a relativistic quark model. Working within the
Blankenbecler-Sugar-Logunov-Tavkhelidze quasipotential dynamics we thus
describe the NN phase shifts in a relativistically invariant way. In this
procedure we use the phenomenological form factor cutoff masses and the
effective and meson-nucleon coupling constants, only.
The comparison of our NN phase shifts to the both empirical data and the Bonn
OBEP fit shows good agreement -- the ratio of the for the present
results to the for Bonn OBEP description is 1.2.Comment: 20 LaTeX pages, 2 postscript figures are available on request.
Preprint IPSAS-RA-940
Neutrino mediated muon--electron conversion in nuclei revisited
The non-photonic neutrino exchange mechanism of the lepton flavor violating
muon-electron conversion in nuclei is revisited. First we determine the nucleon
coupling constants for the neutrino exchange mechanism in a relativistic quark
model taking into account quark confinement and chiral symmetry requirements.
This includes a new, previously overlooked tree-level contribution from
neutrino exchange between two quarks in the same nucleon. Then for the case of
an additional sterile neutrino we reconsider the coherent mode of this process.
The presence of a mixed sterile-active neutrino state heavier than the quark
confinement scale Lambda_c (~1 GeV) may significantly improve the prospects for
observation of this process in future experiments as compared to the
conventional scenario with only light neutrinos. Turning the arguments around
we derive new experimental constraints on |U_(mu h)| and |U_(e h)| mixing
matrix elements from the non-observation of muon--electron conversion.Comment: 13 pages, RevTex, 1 Postscript figur
piN scattering and electromagnetic corrections in the perturbative chiral quark model
We apply the perturbative chiral quark model to give predictions for the
electromagnetic O(p^2) low-energy couplings of the ChPT effective Lagrangian
that define the electromagnetic mass shifts of nucleons and first-order (e^2)
radiative corrections to the piN scattering amplitude. We estimate the leading
isospin-breaking correction to the strong energy shift of the pi(-)p atom in
the 1s state, which is relevant for the experiment "Pionic Hydrogen" at PSI.Comment: 12 pages, 2 figure
Possible hadronic molecule structure of the Y(3940) and Y(4140)
In the present article we report on evidence for hadronic molecule structures
in the charmonium sector. In particular we discuss the Y(3940) and the recently
observed Y(4140) as heavy hadron molecule states with quantum numbers or . The Y(3940) state is considered to be a superposition of
and , while the
Y(4140) is a bound state of and mesons. We give
predictions for both the strong Y(3940) to J/psi omega, Y(4140) to J/psi phi
and radiative Y(3940)/Y(4140) to gamma gamma decay widths in a phenomenological
Lagrangian approach. The results for the strong hidden charm decay modes
clearly support the molecular interpretation of the Y(3940) and Y(4140), while
our estimates for the radiative decays provide a sensitive test for the
underlying meson structure of the two Y mesons discussed here. The alternative
assignment of is also tested, giving similar results for the
strong decay widths.Comment: 5 pages, 2 figures. To appear in the Proceedings of XIII
International Conference on Hadron Spectroscopy, November 29 - December 4,
2009, Florida State Universit
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