Alpha-Alpha scattering, chiral symmetry and 8Be lifetime

Alpha-alpha scattering is discussed in terms of a chiral two pion exchange potential which turns out to be attractive and singular at the origin, hence demanding renormalization. When 8Be is treated as a resonance state a model independent correlation between the Q-factor and lifetime 1/Gamma for the decay into two alpha particles arises. For a wide range of parameters compatible with potential model analyses of low energy pi-alpha scattering it is found Gamma = 4.4(4)eV} in fairly good agreement with the experimental value Gamma = 5.57 (25) eV. The remaining discrepancy as well as the phase shift up to ELAB=15MeV could be accommodated by the leading nuclear peripheral contributions due to the 3H+p and 3He+n continuum.