Testing Chiral Dynamics in Pionic Atoms

Abstract

The energy dependence of chirally expanded pi N isoscalar and isovector amplitudes b_0(E) and b_1(E) respectively, for zero-momentum off shell pions near threshold, is used to impose the minimal substitution requirement E -> E - V_c on the properly constructed pion optical potential within a large-scale fit to 100 pionic-atom data across the periodic table which also include the recently established `deeply bound' pionic atoms of Pb and Sn. This fit cannot be reconciled with the well known free-space values of the pi N threshold amplitudes. In contrast, introducing the empirically known energy dependence for on-shell pions leads to a better fit and to satisfactory values for the pi N threshold amplitudes. The difference between these two approaches is briefly discussed.

10 pages, 3 figures, submitted to PLB. Discussion section rewritten, omitting an erroneous equation. Results and conclusions unchanged Accepted by PLB

References in corpus (3)

• Renormalization of the isovector $\pi N$ amplitude in pionic atoms
• Chiral dynamics and pionic 1s states of Pb and Sn isotopes
• The s-wave repulsion and deeply bound pionic atoms: fact and fancy

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