O potencial nucleon-nucleon e a troca de dois píons relativística / Nucleon-nucleon potential and the relativistic exchange of two pions

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

21/08/2003

RESUMO

This work is devoted to the construction of a two-pion Exchange nucleon-nucleon potential in the framework of the relativist chiral perturbation theory, formulated by Becher and Leutwyler. In their study of pion-nucleon scattering they developed a method to regain the Power counting rules while keeping Lorentz invariance. These authors also Drew attention to a problem present in the heavy baryon formulation, that is chiral serie does not converge in the low-energy region around t=4µ2, where µ is the pions mass. We have shown that this problem is rather relevant to nucleon-nucleon potential, mainly due to the fact that this range of energy determines its asymptotic properties. The dynamics of the two-pion Exchange nucleon-nucleon interaction is determined by pion-nucleon sub-amplitudes. Starting from Becher and Letwylers sub-amplitude, we obtain diagrams classified in three families, according to their topology and the coupling constants involved. In the definition of the potential we substract, from the relativist amplitude, the iteration o fone-pion Exchange, following the prescription of Blankenbecler and Sugar. Our potential up to order q4 is expressed in terms of six basic functions associated to relativistic loop integrals. It keeps the correct asymptotic properties, as long as we do not expand the basic integrals. Forcing such na expansio, in order to compare it with the results from Entem and Machleidt, we observe na agreement in the majority o terms. Some differrences are associated to the Goldberg-Treiman discrepancy, indicated by GT, and two terms come from two loop calculations. The remaining ones are probably related to the prescription adopted for the iteration o fone-pion exchange. In configuration space we compare our results with the médium-range component of two versions of the Argonne potential, AV14 and AV18. We obtain agreement only for the central isoscalar potential, the most important to phenomenology. Regarding other channels, we observe discrepancies even between AV14 and AV18. Based on the classification of the dynamics in three families and analysing their contributions to each component, we propose a way to overcome such ambiguities in the construction of phenomenological potentials.

ASSUNTO(S)

chiral symmetry simetria quiral infrared regularization nucleon-nucleon potential potencial nucleon-nucleon regularização lnfravermelha relatividade relativity

ACESSO AO ARTIGO

Documentos Relacionados