2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/207555The influence of the hadronic ππinteraction on the wave functions of pionium (the Coulomb bound π^+π^- system) at distances less than 10 fm is calculated for s-states with principal quantum numbers n<5. Hadronic ππpotentials are used that reproduce the scattering phase shifts of two-loop chiral perturbation theory. The pionium wave functions ψ_n (r) are obtained by integrating the coupled Schrödinger equations for the (π^+π^-,π^0π^0) system. We find that, for r<10 fm, n^{3/2} ψ_n (r) is practically independent of n. From this we conclude that the production rates of the s-states of pionium are proportional to n^{-3}, a result needed for the interpretation of the DIRAC experiment currently running at CERN.9 pages including 2 figuresHigh Energy Physics - Phenomenologytext