Form factors of the isovector scalar current and the [Formula: see text] scattering phase shifts.
A model for S-wave [Formula: see text] scattering is proposed which could be realistic in an energy range from threshold up to above 1 GeV, where inelasticity is dominated by the [Formula: see text] channel. TheT-matrix, satisfying two-channel unitarity, is given in a form which matches the chiral expansion results at order [Formula: see text] exactly for the [Formula: see text], [Formula: see text] amplitudes and approximately for [Formula: see text]. 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 [Formula: see text] and [Formula: see text] form factor matrix elements of the [Formula: see text] scalar current from theT-matrix. The phenomenological parameters are determined such as to reproduce the experimental properties of the [Formula: see text], [Formula: see text] resonances, as well as the chiral results of the [Formula: see text] and [Formula: see text] scalar radii, which are predicted to be remarkably small at [Formula: see text]. ThisT-matrix model could be used for a unified treatment of the [Formula: see text] final-state interaction problem in processes such as [Formula: see text], [Formula: see text], or the [Formula: see text] initial-state interaction in [Formula: see text].
Groupe de Physique Théorique, IPN (UMR8608), Université Paris-Sud 11, Orsay, France.|Instituto de Física Corpuscular (IFIC), Centro Mixto CSIC-Universidad de Valencia, Valencia, Spain.
M
M
Albaladejo
Groupe de Physique Théorique, IPN (UMR8608), Université Paris-Sud 11, Orsay, France.
B
B
Moussallam