Magnetic dipole transition in proton-deuteron radiative capture at BBN energies within potential model

TL;DR

This study uses a potential model to analyze low-energy proton-deuteron radiative capture, focusing on electric and magnetic dipole transitions, providing results consistent with recent data and highlighting the sensitivity of the M1 transition to potential parameters.

Contribution

The paper presents a detailed potential model analysis of $pd$ radiative capture at BBN energies, including both $E1$ and $M1$ transitions, with improved agreement to experimental data.

Findings

Astrophysical $S$ factor at zero energy: 0.211 ± 0.016 eV b

Reaction rate agrees within 5% of recent calculations

M1 cross section sensitivity to potential depth

Abstract

The $pd$ radiative capture reaction plays a vital role in Big Bang nucleosynthesis and stellar proton-proton chain. The study of the low-energy reaction is challenging in both experiments and theories. Using the framework of potential model, we analyze $pd$ radiative capture below 1 MeV for both electric dipole ($E1$) and magnetic dipole ($M1$) transitions. The obtained astrophysical $S$ factors agree well with recent results, especially at energies relevant to sensitive deuterium abundance. The calculated reaction rate shows good agreement, with less than a 5\% difference compared to recent works. The extrapolated value for $S(0)$ including both transitions is determined to be $0.211 \pm 0.016$ eV b. A comparison with experimental data using the $\chi^2$ test reveals the sensitivity of the $M1$ cross section at low energies to the scattering potential depth.