IFLP   13074
INSTITUTO DE FISICA LA PLATA
Unidad Ejecutora - UE
artículos
Título:
About the validity of complex mass scheme for the Δ resonance and higher energy region approaches
Autor/es:
C. BARBERO AND A. MARIANO
Revista:
JOURNAL OF PHYSICS G. NUCLEAR PHYSICS
Editorial:
IOP PUBLISHING LTD
Referencias:
Año: 2015 vol. 42 p. 1 - 12
ISSN:
0305-4616
Resumen:
It is a well known fact that when a resonance (R) is produced and decays, itsunperturbed propagator will be singular at p^2=m_R^2 when it appears in ans-type Feynman pole graph. Nevertheless this is not a problem, since it mustbe dressed by the successive re-interactions of the resonance with itself to allorders through the non-pole T-matrix, which we include in this work for theself-energy one-loop pion?nucleon contributions. Recently, we have shownthat within the one-loop approximation for the absorptive part it is possible tojustify the use of the complex-mass description m -> m - iG/2 over theunperturbed propagator, adopted in previous calculations to treat pion?nucleonelastic and radiative scattering, and photo and weak pion production in theresonance region. Here we discuss the limits of the validity of this approximation, since in actual calculations we must go over this range. We show that, when the resonance energy is increased above p^2 ~ 1400 MeV, thisapproach becomes invalid and an alternative approximation should be considered.In addition, we discuss the usual energy dependent width approximation,present in several actual isobar models used to analyze the last neutrino scattering experiments, and show that also it could be unappropriate.