Triple α Resonances and Possible Link to the Efimov Trimers

The basic condition for Efimov states is the existence of resonant two-body forces. A system of three particles with resonant two-body interactions may form bound states, the so called Efimov trimers, even when any two of the particles are unable to bind. Inspired by this idea we have analysed a set of data from the6Li +6Li → 3 α reaction measured in a kinematically complete experiment at 3.1 MeV of beam energy, corresponding to 29.6 MeV of excitation energy in12C , with the characteristic that the 3α channel is fed by three8Be states in the same event. A strong enhancement in the coincidence yield is experienced for these events. Evidence of three8Be levels within the same 3α event suggests that one particle is exchanged between the other two. According to quantum mechanics, this is a condition for Efimov states to occur and for which no observation exists yet in nuclei. The hyperspherical formalism for the low-energy three-body problem has been applied to point out the 3α particle correlation.