Physics Theory Seminar with Chloe Hebborn on Big Bang Nucleosynthesis Energies
The rate at which helium (4He) and deuterium (d) fuse together to produce lithium-6 (6Li) and a γ ray, is a critical puzzle piece in resolving the roughly three order of magnitude discrepancy between Big Bang predictions and astronomical observations for the primordial abundance of 6Li. Because direct measurements are hindered by the Coulomb repulsion between the 4He and d nuclei, accurate theoretical evaluations are critically needed. In this seminar, Hebborn will present an ab initio prediction of 4He(d, γ)6Li, in which all nucleons are active and interacting through chiral-EFT nucleon- and three-nucleon forces. By treating on equal footing the 4He-d dynamics and the bound 6Li, our calculation accurately and consistently determines the contributions of the main electromagnetic transitions driving the radiative capture process. Interestingly, our results reveal an enhancement of the capture probability below 100 keV owing to usually neglected magnetic dipole (M1) transitions. Our calculations agree well with the LUNA data [1], and accurately predict the S-factor over all energies relevant for the Big-Bang nucleosynthesis.
[1] Anders et al. Physical Review Letters 113, 042501 (2014).
This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under the FRIB Theory Alliance Award No. DE-SC0013617 and by LLNL under Contract No. DE-AC52-07NA27344.
Zoom link available upon request at physics@wustl.edu.
Post-docs and students' Q&A with the speaker starts at 2:15 pm. Contact Garrett King for the Q&A Zoom link.