ND-IFUNAM-ININ-LIP-USevilla-UHuelva

ND - IFUNAM - ININ - LIP - U. Sevilla - U. Huelva collaboration for the measurement of the reaction rate in alpha(nn,gamma)⁶He and its impact on the r-process.

The Physics of Compact Binary Mergers (CBM) has been strongly enhanced in the last five years thanks to the experimental evidence that has made it possible to identify these systems as a scenario where the astrophysical process r occurs [1,2], a process in which the nucleosynthesis of elements with masses up to A=50-80 occurs. In this context, two possible paths appear through which to synthesize ¹²C, the seed nucleus of the r process, starting from alpha particles and neutrons and overcoming the instabilities of A=5, 8:

a) alpha(alpha n,gamma)⁹Be(alpha,n)¹²C; b) alpha(nn,gamma)⁶He(alpha,n)⁹Be(alpha,n)¹²C.

The relative weight of these two paths depends on the reaction rates of the alpha(nn,gamma)⁶He and alpha(alpha n,gamma)⁹Be reactions and on a wide variety of astrophysical conditions. In this context, the collaboration has proposed the measurement of the alpha(nn,gamma)⁶He reaction rate at the NSL laboratory at the University of Notre Dame. The experimental approach adopted consists of measuring the Coulomb breakup channel in the ⁶He(gamma,nn)alpha reverse reaction, applying the theoretical framework shown in [3], developed by members of the collaboration.

[1] Piean, E. et al. "Spectroscopic identification of r-process nucleosynthesis in a double neutron-star merger", Nature 551(2017)67-70

[2] Kasen, D. et al. "Origin of the heavy elements in binary neutron-star mergers from a gravitational-wave event", Nature 551(2017)80-84

[3] Casal, J. et al. "Determining astrophysical three-body radiative capture reaction rates from inclusive Coulomb break-up measurements", Physical Review C 93(2016)041602