Structure of the $σ$-meson and diamagnetism of the nucleon

M. I. Levchuk; A. I. L'vov; A. I. Milstein; M. Schumacher

doi:10.1142/9789812773333_0057

paper

Structure of the $σ$ -meson and diamagnetism of the nucleon

arXiv:hep-ph/0511193 · doi:10.1142/9789812773333_0057

Abstract

The structure of the $σ$ meson and the diamagnetism of the nucleon are shown to be topics which are closely related to each other. Arguments are found that the $σ$ meson couples to two photons via its non-strange $q q ˉ$ structure component. This ansatz leads to a quantitative explanation of the $t$ -channel component of the difference of electromagnetic polarizabilities, (α-β)^t $, co n t ainin g t h e d iama g n e t i s m o f t h e n u c l eo n . T h e p r e d i c t i o ni s$ (α-β)^t_{p,n}=(5α_e g_{πMM})/(6π^2 m^2_σf_π)=15.3 $in u ni t so f$ 10^{-4}{\rm fm}^3 $t o b eco m p a r e d w i t h t h ee x p er im e n t a l v a l u e$ (α-β)^t_p=15.1\pm 1.3 $f or t h e p r o t o nan d$ (α-β)^t_n=14.8\pm 2.7 $f or t h e n e u t r o n . T h ee q u i v a l e n t a pp r o a c h t oe x pl o i tt h e$ ππ $s t r u c t u r eco m p o n e n t o f t h e$ σ $m eso n v ia t h e B E F T s u m r u l e l e a d s t o$ (α-β)^t_{p,n}=14\pm 2$, what also is in agreement with the experimental results.

Contribution made by Martin Schumacher to the International Workshop on the Physics of Excited Baryons, 12 - 15 Oct. 2005, Tallahasse, Florida USA

Structure of the σ-meson and diamagnetism of the nucleon

Abstract

Structure of the $σ$ -meson and diamagnetism of the nucleon