Nuclear axial polarizability and the α + α interaction

Abstract

The 27π-exchange part of the α + α interaction is studied in terms of the response of the α -particle to a static pion field which is related to the static nuclear axial polarizability. We show that the experimental α + α phase shifts for l ⩾ 4 and T_lab ⩽ 50 MeV (that probe the asymptotic tail of the potential) cannot be fitted taking only into account the nucleonic responses of the individual nucleons in the α-particle. This result is interpreted as evidence for an appreciable contribution of the nuclear polarization of the α-particle in the scattering process, nearly twice as large as the nucleonic contribution. The magnitude of this effect, as extracted from the experimental data, is consistent with the theoretical expectations.