Constraining nuclear data via cosmological observations: Neutrino energy transport and big bang nucleosynthesis

Journal Article · 13 September 2017 · EPJ Web of Conferences

DOI: https://doi.org/10.1051/epjconf/201714601008 · OSTI ID:1412854

Paris, Mark W.  ^[1]; Fuller, George M. ^[2]; Grohs, Evan Bradley ^[3]; Kishimoto, Chad ^[4]; Vlasenko, Alexey ^[5]

---

1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. Univ. of California, San Diego, CA (United States). Dept. of Physics
3. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Physics
4. Univ. of California, San Diego, CA (United States). Dept. of Physics. Dept. of Physics and Biophysics
5. North Carolina State Univ., Raleigh, NC (United States). Dept. of Physics

Here, 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 also 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 allows a detailed account 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. We discuss the time development of neutrino spectral distortions and concomitant entropy production and extraction from the plasma. 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.

• Research Organization: Los Alamos National Laboratory (LANL)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1412854
• Report Number(s): LA-UR-16-28443
• Journal Information: EPJ Web of Conferences, Journal Name: EPJ Web of Conferences Vol. 146; ISSN 2100-014X
• Publisher: EDP SciencesCopyright Statement
• Country of Publication: United States
• Language: English