https://doi.org/10.1140/epjc/s10052-015-3715-z
Regular Article - Theoretical Physics
Form factors of the isovector scalar current and the 
scattering phase shifts
1
Groupe de Physique Théorique, IPN (UMR8608), Université Paris-Sud 11, Orsay, France
2
Instituto de Física Corpuscular (IFIC), Centro Mixto CSIC-Universidad de Valencia, Valencia, Spain
* e-mail: moussall@ipno.in2p3.fr
Received:
20
July
2015
Accepted:
2
October
2015
Published online:
13
October
2015
A model for S-wave scattering is proposed which could be realistic in an energy range from threshold up to above 1 GeV, where inelasticity is dominated by the 
channel. The T-matrix, satisfying two-channel unitarity, is given in a form which matches the chiral expansion results at order 
exactly for the 
, 
amplitudes and approximately for 
. It contains six phenomenological parameters. Asymptotic conditions are imposed which ensure a minimal solution of the Muskhelishvili–Omnès problem, thus allowing one to compute the and form factor matrix elements of the 
scalar current from the T-matrix. The phenomenological parameters are determined such as to reproduce the experimental properties of the 
, 
resonances, as well as the chiral results of the and scalar radii, which are predicted to be remarkably small at 
. This T-matrix model could be used for a unified treatment of the final-state interaction problem in processes such as 
, 
, or the initial-state interaction in 
.
© SIF and Springer-Verlag Berlin Heidelberg, 2015
