58 research outputs found
Plan lechero Colombo-Holandés en Obonuco, unidad confinamiento.
Ganado de leche-Ganadería lech
A Non-Perturbative Chiral Approach for Meson-Meson Interactions
A non-perturbative method which combines constraints from chiral symmetry
breaking and coupled channel unitarity is used to describe meson-meson
interactions up to \sqrt{s}\lesssim 1.2 GeV, extending in this way the range of
applicability of the information contained in Chiral Perturbation Theory (\chi
PT), since this perturbative series is typically restricted to \sqrt{s}\lesssim
500 MeV. The approach uses the O(p^2) and O(p^4) \chiPT Lagrangians. The seven
free parameters resulting from the O(p^4) Lagrangian are fitted to the
experimental data. The approach makes use of the expansion of T^{-1} instead of
the amplitude itself as done in \chiPT. The former expansion is suggested by
analogy with the effective range approximation in Quantum Mechanics and it
appears to be very useful. The results, in fact, are in good agreement with a
vast amount of experimental analyses.Comment: 4 pages, 2 figures, LaTeX, Talk given at PANIC99, Uppsala (Sweden),
June 10-16, 199
Resonances, Chiral Symmetry, Coupled Channel Unitarity and Effective Lagrangians
By means of a coupled channel non-perturbative unitary approach, it is
possible to extend the strong constrains of Chiral Perturbation Theory to
higher energies. In particular, it is possible to reproduce the lowest lying
resonances in meson-meson scattering up to 1.2 GeV using the parameters of the
O(p^2) and O(p^4) Chiral Lagrangian. We report on an update of these results
examining their possible relevance for meson spectroscopy.Comment: To appear in the proceedings of the 8th International Conference on
Hadron Spectroscopy, HADROn 99, August 24-28, 1999, Beijing, China. Four
pages, uses espcrc1.sty (included
Chiral dynamics in U(3) unitary chiral perturbation theory
We perform a complete one-loop calculation of meson-meson scattering, and of
the scalar and pseudoscalar form factors in U(3) chiral perturbation theory
with the inclusion of explicit resonance fields. This effective field theory
takes into account the low-energy effects of the QCD U_A(1) anomaly explicitly
in the dynamics. The calculations are supplied by non-perturbative
unitarization techniques that provide the final results for the meson-meson
scattering partial waves and the scalar form factors considered. We present
thorough analyses on the scattering data, resonance spectroscopy, spectral
functions, Weinberg-like sum rules and semi-local duality. The last two
requirements establish relations between the scalar spectrum with the
pseudoscalar and vector ones, respectively. The Nc extrapolation of the various
quantities is studied as well. The fulfillment of all these non-trivial aspects
of the QCD dynamics by our results gives a strong support to the emerging
picture for the scalar dynamics and its related spectrum.Comment: To match the version accepted by Phys.Lett.
Chiral Perturbation Theory and the f2(1270) resonance
Within Chiral Perturbation Theory, we study elastic pion scattering in the
I=0, J=2, channel, whose main features are the f2(1270) resonance and the
vanishing of the lowest order. By means of a chiral model that includes an
explicit resonance coupled to pions, we describe the data and calculate the
resonance contribution to the O(p^4) and O(p^6) chiral parameters. We also
generalize the Inverse Amplitude Method to higher orders, which allows us to
study channels with vanishing lowest order. In particular, we apply it to the
I=0,J=2 case, finding a good description of the f2(1270) resonance, as a pole
in the second Riemann sheet.Comment: 4 pages,1 figur
Energetic and spatial characterization of seismicity in the Algeria–Morocco region
We estimate the energetic and spatial characteristics of seismicity in the
Algeria–Morocco region using a variety of seismic and statistical parameters, as a first step
in a detailed investigation of regional seismic hazard. We divide the region into five
seismotectonic regions, comprising the most important tectonic domains in the studied
area: the Moroccan Meseta, the Rif, the Tell, the High Plateau, and the Atlas. Characteristic
seismic hazard parameters, including the Gutenberg–Richter b-value, mean seismic
activity rate, and maximum possible earthquake magnitude, were computed using an
extension of the Aki–Utsu procedure for incomplete earthquake catalogs for each domain,
based on recent earthquake catalogs compiled for northern Morocco and northern Algeria.
Gutenberg–Richter b-values for each zone were initially estimated using the approach of
Weichert (Bull Seismol Soc Am 70:1337–1346, 1980): the estimated b-values are
1.04 ± 0.04, 0.93 ± 0.10, 0.72 ± 0.03, 0.87 ± 0.02, and 0.77 ± 0.02 for the Atlas,
Meseta, High Plateau, Rif, and Tell seismogenic zones, respectively. The fractal dimension
D2 was also estimated for each zone. From the ratio D2/b, it appears that the Tell and Rif
zones, with ratios of 2.09 and 2.12, respectively, have the highest potential earthquake
hazard in the region. The Gutenberg–Richter relationship analysis allows us to derive that
in the Tell and Rif, the number of earthquake with magnitude above Mw 4.0, since 1925
normalized to decade and to square cell with 100-km sides is equal to 2.6 and 1.91,
respectively. This study provides the first detailed information about the potential seismicity
of these large domains, including maximum regional magnitudes, characteristics of
spatial clustering, and distribution of seismic energy release.The Algerian CRAAG, the Spanish Seismic Hazard and Active Tectonics research group, and the Spanish MINECO CGL2015-
65602-R project.http://link.springer.com/journal/110692018-04-30hb2016Physic
The SU(2) and SU(3) chiral phase transitions within Chiral Perturbation Theory
The SU(2) and SU(3) chiral phase transitions in a hot gas made of pions,
kaons and etas are studied within the framework of Chiral Perturbation Theory.
By using the meson meson scattering phase shifts in a second order virial
expansion, we are able to describe the temperature dependence of the quark
condensates. We have estimated the critical temperatures where the different
condensates melt. In particular, the SU(3) formalism yields a lower critical
temperature for the non-strange condensates than within SU(2), and also
suggests that the strange condensate may melt at a somewhat higher temperature,
due to the different strange and non-strange quark masses.Comment: 4 pages, two figures. Final version to appear in Phys Rev D. Complete
model independent calculation. Unitarized ChPt only used to check
extrapolation at high T. References added and numerical bug correcte
- …