2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/82901Using effective field theory for a proton and antiproton bound in a Coulomb potential, the shift of the ground state energy level is calculated to arbitrary order in the scattering length. Including the next order contact interaction, the correction due to the effective range parameter can also be obtained.7 pages, 1 figuresNuclear TheoryHigh Energy Physics - Phenomenologytext