Nuclear, Particle, Astroparticle and Cosmology (NUPAC) Seminars
Neutrino energy transport and precision primordial nucleosynthesis
Presented by Mark Paris, LANL
We introduce a new computational capability that moves toward a
self-consistent calculation of neutrino transport and nuclear reactions
for big bang nucleosynthesis (BBN). Such a self-consistent approach is
needed to be able to extract detailed information about nuclear
reactions and physics beyond the standard model from precision
cosmological observations of primordial nuclides and the cosmic
microwave background radiation. We calculate the evolution of the early
universe through the epochs of weak decoupling, weak freeze-out and big
bang nucleosynthesis (BBN) by simultaneously coupling a full strong,
electromagnetic, and weak nuclear reaction network with a multi-energy
group Boltzmann neutrino energy transport scheme. The modular structure
of our approach allows the dissection of the relative contributions of
each process responsible for evolving the dynamics of the early
universe. Such an approach affords a detailed accounting of the
evolution of the active neutrino energy distribution functions alongside
and self-consistently with the nuclear reactions and entropy/heat
generation and flow between the neutrino and
photon/electron/positron/baryon plasma components. Our calculations
reveal nonlinear feedback in the time evolution of neutrino distribution
functions and plasma thermodynamic conditions. The time development of
neutrino spectral distortions and concomitant entropy production and
extraction from the plasma will be discussed in some detail. These
effects result in changes in the computed values of the BBN deuterium
and helium-4 yields that are on the order of a half-percent relative to
a baseline standard BBN calculation with no neutrino transport. This is
an order of magnitude larger effect than in previous estimates. For
particular implementations of quantum corrections in plasma
thermodynamics, our calculations show a 0.4% increase in deuterium and a
0.6% decrease in 4He over our baseline. The magnitude of these changes
are on the order of uncertainties in the nuclear physics for the case of
deuterium and are potentially significant for the error budget of helium
in upcoming cosmological observations.
2:00 pm, Tuesday, January 26, 2016
PAIS-2540, PAIS
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