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 the 6 Li + 6 Li → 3 α reaction measured in a kinematically complete experiment at 3.1MeV of beam energy, corresponding to 29.6MeV of excitation energy in 12 C, with the characteristic that the 3 α channel is fed by three 8 Be states in the same event. A strong enhancement in the α – α coincidence yield is experienced for these events. Evidence of three 8 Be levels within the same 3 α 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 3 α particle correlation.