3,924 research outputs found
Renormalization of the 1S0 One-Pion-Exchange NN Interaction in Presence of Derivative Contact Interactions
We use standard distorted wave theory techniques and dimensional
regularization to find out solutions of the nucleon-nucleon Lippman--Schwinger
equation with a kernel determined by the Weinberg's next-to-leading potential,
which consists of one--pion exchange and additional contact terms with
derivatives. Though for simplicity, we restrict the discussion to the
channel and to contact terms containing up to two derivatives, the
generalization to higher waves and/or number of derivatives is straightforward.
The undetermined low energy constants emerging out of the renormalization
procedure are fitted to data.Comment: 7 pages, revtex4, Phys. Lett. B in prin
Study of the strong and in a non-relativistic quark model
We present results for the strong widths corresponding to the and decays. We apply our
model in Ref. Phys. Rev. D 72, 094022 (2005) where we previously studied the
corresponding transitions in the charmed sector. Our non-relativistic
constituent quark model uses wave functions that take advantage of the
constraints imposed by heavy quark symmetry. Partial conservation of axial
current hypothesis allows us to determine the strong vertices from an analysis
of the axial current matrix elements.Comment: 6 latex pages, 1 table, new references adde
Meson Resonances at large Nc: Complex Poles vs Breit-Wigner Masses
The rigorous quantum mechanical definition of a resonance requires
determining the pole position in the second Riemann sheet of the analytically
continued partial wave scattering amplitude in the complex Mandelstam
s-variable plane. For meson resonances we investigate the alternative
Breit-Wigner (BW) definition within the large Nc expansion. By assuming that
the pole position is and exploiting unitarity, we show
that the BW determination of the resonance mass differs from the pole position
by terms, which can be extracted from pi-pi scattering
data. For the case of the f0(600) pole, the BW scalar mass is predicted to
occur at about 700 MeV while the true value is located at about 800 MeV.Comment: 7 pages. No figures. (elsevier preprint
Wave functions for dynamically generated resonances; the two and
In this work we develop a formalism to evaluate wave functions in momentum
and coordinate space for the resonant states dynamically generated in a unitary
coupled channel approach. The on shell approach for the scattering matrix,
commonly used, is also obtained in Quantum Mechanics with a separable
potential, which allows one to write wave functions in a trivial way. We
develop useful relationships among the couplings of the dynamically generated
resonances to the different channels and the wave functions at the origin. The
formalism provides an intuitive picture of the resonances in the coupled
channel approach, as bound states of one bound channel, which decays into open
ones. It also provides an insight and practical rules for evaluating couplings
of the resonances to external sources and how to deal with final state
interaction in production processes. As an application of the formalism we
evaluate the wave functions of the two states in the , and other coupled channels. It also offers a practical way
to study three body systems when two of them cluster into a resonance.Comment: 5pages, 1 figure. To appear in the proceedings of the International
Workshop on Chiral Symmetry in Hadrons and Nuclei (Chiral10), Valencia,
Spain, Jun 21-24, 201
Non-universal gravitational couplings of neutrinos in matter
When neutrinos travel through a normal matter medium, the electron neutrinos
couple differently to gravity compared to the other neutrinos, due to the
presence of electrons in the medium and the absence of the other charged
leptons. The matter-induced gravitational couplings of the neutrinos under such
conditions are calculated and their contribution to the neutrino index of
refraction in the presence of a gravitational potential is determined.Comment: Latex, 10 page
Radiative pion capture in nuclei: a continuum shell-model approach
The radiative pion capture process in nuclei is approached by using a
continuum shell-model description of the nucleus, together with a
phenomenological treatment of the two particle-two hole effects. It is found
that these effects play an important role to reproduce the observed
experimental photon energy distribution. This distribution as well as the
integrated one depends significantly on the details of the mean field
potential. This makes this process interesting to investigate the nuclear
structure dynamics.Comment: 21 pages, LateX file + 5 figures, epsf.st
Study of semileptonic and nonleptonic decays of the meson
We evaluate semileptonic and two--meson nonleptonic decays of the
meson in the framework of a nonrelativistic quark model. The former are done in
spectator approximation using one--body current operators at the quark level.
Our model reproduces the constraints of heavy quark spin symmetry obtained in
the limit of infinite heavy quark mass. For the two--meson nonleptonic decays
we work in factorization approximation. We compare our results to the ones
obtained in different relativistic approaches.Comment: Talk given at the IVth International Conference on Quarks an Nuclear
Physics, Madrid, June 5th-10th 200
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