T. Fischer, G. Martinez-Píedo, M. Hempel, M. Liebendörfer
The neutrino-driven wind, which occurs after the onset of a core-collapse
supernova explosion, has long been considered as the possible site for the
synthesis of heavy r-process elements in the Universe. Only recently, it has
been possible to simulate supernova explosions up to ~10 seconds, based on
three-flavor Boltzmann neutrino transport. These simulations show that the
neutrino luminosities and spectra of all flavors are very similar and their
difference even decreases during the deleptonization of the proto-neutron star.
As a consequence, the ejecta are always proton rich which rules out the
possible production of heavy r-process elements (Z>56). We perform a detailed
analysis of the different weak processes that determine the neutrino spectra.
Non-electron flavor (anti)neutrinos are produced and interact only via
neutral-current processes, while electron (anti)neutrinos have additional
contributions from charge-current processes. The latter are dominated by
ve-absorption on neutrons and anti- ve-absorption on protons. At early times,
charge-current processes are responsible for spectral differences between.
However, as the region of neutrino decoupling moves to higher densities during
deleptonization, charge-current reactions are suppressed by final state
Pauli-blocking. anti-ve absorption on protons is suppressed due to the
continuously increasing chemical potential of the neutrons. ve absorption on
neutrons is blocked by the increasing degeneracy of the electrons. These
effects result in negligible contributions from charge-current reactions on
timescales on the order of tens of seconds, depending on the progenitor star.
Hence, the neutrino spectra are mainly determined from neutral-current
processes which do not distinguish between the different flavors and results in
the convergence of the spectra. These findings are independent of the
charge-current reaction rates used...
View original:
http://arxiv.org/abs/1112.3842
No comments:
Post a Comment