How well do we understand Beryllium-7 + proton -> Boron-8 + photon? An Effective Field Theory perspective

TL;DR

This paper uses effective field theory and Bayesian analysis to improve the understanding and precision of the Beryllium-7 + proton reaction rate, crucial for solar neutrino predictions.

Contribution

It introduces a Bayesian constrained NLO EFT framework for the 7Be(p,γ)8B reaction, refining the S-factor estimate at solar energies.

Findings

Tight constraints on the S-factor at solar energies.

Uncertainty in S(0) reduced by half compared to previous estimates.

Demonstrated the impact of input data choices on EFT parameter estimation.

Abstract

We have studied the 7Be(p,photon)8B reaction in the Halo effective field theory (EFT) framework. The leading order (LO) results were published in Phys.Rev.C89,051602(2014) after the isospin mirror process, 7Li(n,photon)8Li, was addressed in Phys.Rev.C89,024613(2014). In both calculations, one key step was using the final shallow bound state asymptotic normalization coefficients (ANCs) computed by ab initio methods to fix the EFT couplings. Recently we have developed the next-to-LO (NLO) formalism (to appear soon), which could reproduce other model results by no worse than 1% when the 7Be-p energy was between 0 and 0.5 MeV. In our recent report (arXiv:1507.07239), a different approach from that in Phys.Rev.C89,051602(2014) was used. We applied Bayesian analysis to constrain all the NLO-EFT parameters based on measured S-factors, and found tight constraints on the S-factor at solar energies. Our S(E=0 MeV)= 21.3 + - 0.7 eV b. The uncertainty is half of that previously recommended. In this proceeding, we provide extra details of the Bayesian analysis, including the computed EFT parameters' probability distribution functions (PDFs) and how the choice of input data impacts final results.