Quantum three-body calculation of the nonresonant triple-α reaction rate at low temperatures

Triple-α reaction rate is re-evaluated by directly solving the three-body Schroedinger equation. The resonant and nonresonant processes are treated on the same footing using the continuum-discretized coupled-channels method for three-body scattering. An accurate description of the α-α nonresonant states significantly quenches the Coulomb barrier between the first two α-particles and the third α-particle. Consequently, the α-α nonresonant continuum states below the resonance at 92.04 keV, i.e., the ground state of 8Be, give a markedly larger contribution at low temperatures than that reported in previous studies. We show that Nomoto's method for three-body nonresonant capture processes, which is adopted in the NACRE compilation and many other studies, is a crude approximation of the accurate quantum three-body model calculation. We find an increase in triple-α reaction rate by about 20 orders of magnitude around 107 K compared with the rate of NACRE. (author)