316 research outputs found
Chiral unitary approach to S-wave meson baryon scattering in the strangeness S=0 sector
We study the S-wave interaction of mesons with baryons in the strangeness S=0
sector in a coupled channel unitary approach. The basic dynamics is drawn from
the lowest order meson baryon chiral Lagrangians. Small modifications inspired
by models with explicit vector meson exchange in the t-channel are also
considered. In addition the pi pi N channel is included and shown to have an
important repercussion in the results, particularly in the isospin 3/2 sector.Comment: 23 pages, LaTeX, 21 figure
Quantum Logic Gates and Nuclear Magnetic Resonance Pulse Sequences
We demonstrate how NMR can in principle be used to implement all the elements
required to build quantum computers, and briefly discuss the potential
applications of insights from quantum logic to the development of novel pulse
sequences with applications in more conventional NMR experiments.Comment: Sixteen pages, no figures. Submitted to Journal of Magnetic
Resonance. Primarily pedagogical rather than a description of novel research
result
Structure of Lambda(1405) and chiral dynamics
We report on a recent theoretical work on the structure of the Lambda(1405)
resonance within a chiral unitary approach, in which the resonance is
dynamically generated in meson-baryon scattering. Studying the analytic
structure of the scattering amplitude, we have found that there are two poles
lying around energies of Lambda(1405) with different widths and couplings to
the meson-baryon states. We discuss reactions to conform the double pole
structure in experiment and elastic K^- p scattering at low energies.Comment: 4 pages, LaTeX, 2 eps figures. Talk given at 10th International
Conference on the Structure of Baryons (Baryon 2004) at Palaiseau (France),
25-29 October 200
Baryon polarization in low-energy unpolarized meson-baryon scattering
We compute the polarization of the final-state baryon, in its rest frame, in
low-energy meson--baryon scattering with unpolarized initial state, in
Unitarized BChPT. Free parameters are determined by fitting total and
differential cross-section data (and spin-asymmetry or polarization data if
available) for , and scattering. We also compare our
results with those of leading-order BChPT
Radiative open charm decay of the Y(3940), Z(3930), X(4160) resonances
We determine the radiative decay amplitudes for decay into and , or and of some of the charmonium like
states classified as X,Y,Z resonances, plus some other hidden charm states
which are dynamically generated from the interaction of vector mesons with
charm. The mass distributions as a function of the or
invariant mass show a peculiar behavior as a consequence of
the nature of these states. The experimental search of these
magnitudes can shed light on the nature of these states.Comment: 18 pages, 9 figure
Chiral dynamics of p-wave in K^- p and coupled states
We perform an evaluation of the p-wave amplitudes of meson-baryon scattering
in the strangeness S=-1 sector starting from the lowest order chiral
Lagrangians and introducing explicitly the Sigma^* field with couplings to the
meson-baryon states obtained using SU(6) symmetry. The N/D method of
unitarization is used, equivalent, in practice, to the use of the
Bethe-Salpeter equation with a cut-off. The procedure leaves no freedom for the
p-waves once the s-waves are fixed and thus one obtains genuine predictions for
the p-wave scattering amplitudes, which are in good agreement with experimental
results for differential cross sections, as well as for the width and partial
decay widths of the Sigma^*(1385).Comment: LaTeX, 18 pages, 6 figure
Chiral Symmetry and light resonances in hot and dense matter
We present a study of the scattering amplitude in the and
channels at finite temperature and nuclear density within a chiral
unitary framework. Meson resonances are dynamically generated in our approach,
which allows us to analyze the behavior of their associated scattering poles
when the system is driven towards chiral symmetry restoration. Medium effects
are incorporated in three ways: (a) by thermal corrections of the unitarized
scattering amplitudes, (b) by finite nuclear density effects associated to a
renormalization of the pion decay constant, and complementarily (c) by
extending our calculation of the scalar-isoscalar channel to account for finite
nuclear density and temperature effects in a microscopic many-body
implementation of pion dynamics. Our results are discussed in connection with
several phenomenological aspects relevant for nuclear matter and Heavy-Ion
Collision experiments, such as mass scaling vs broadening from dilepton
spectra and chiral restoration signals in the channel. We also
elaborate on the molecular nature of resonances.Comment: 14 pages, 14 figures. Contribution to Hard Probes 2008, Illa de A
Toxa, Spain, June 8th-14th 200
Thermal rho and sigma mesons from chiral symmetry and unitarity
We study the temperature evolution of the rho and sigma mass and width, using
a unitary chiral approach. The one-loop pion-pion scattering amplitude in
Chiral Perturbation Theory at finite temperature is unitarized via the Inverse
Amplitude Method. Our results predict a clear increase with T of both the rho
and sigma widths. The masses decrease slightly for high T, while the
rho-pion-pion coupling increases. The rho behavior seems to be favored by
experimental results. In the sigma case, it signals chiral symmetry
restoration.Comment: 5 pages, 5 figures, revtex. References and brief comments added.
Final version to appear in Phys. Rev.
Separable potential model for interactions at low energies
The effective separable meson-baryon potentials are constructed to match the
equivalent chiral amplitudes up to the second order in external meson momenta.
We fit the model parameters (low energy constants) to the threshold and low
energy data. In the process, the -proton bound state problem is
solved exactly in the momentum space and the 1s level characteristics of the
kaonic hydrogen are computed simultaneously with the available low energy
cross sections. The model is also used to describe the
mass spectrum and the energy dependence of the amplitude.Comment: 31 pages, v2 - added corrections to make it compatible with the
published versio
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