R-matrix analysis of reactions in the 9B compound system

TL;DR

This paper uses R-matrix analysis to study reactions in the 9B system, providing new resonance data that challenge the idea of resonance-enhanced destruction of 7Li in big bang nucleosynthesis.

Contribution

It applies a multichannel R-matrix method to analyze 9B reactions with extensive data, identifying previously unknown resonances and refuting the existence of certain threshold resonances.

Findings

No near-threshold resonances with large widths were found.

Results reduce the likelihood of resonance-driven 7Li destruction.

New resonance parameters were identified and compared with existing data.

Abstract

Recent activity in solving the 'lithium problem' in big bang nucleosynthesis has focused on the role that putative resonances may play in resonance-enhanced destruction of 7Li. Particular attention has been paid to the reactions involving the 9B compound nuclear system, d+7Be->9B. These reactions are analyzed via the multichannel, two-body unitary R-matrix method using code (EDA) developed by Hale and collaborators. We employ much of the known elastic and reaction data, in a four-channel treatment. The data include elastic 3He+6Li differential cross sections from 0.7 to 2.0 MeV, integrated reaction cross sections for energies from 0.7 to 5.0 MeV for 6Li(3He,p)8Be* and from 0.4 to 5.0 MeV for the 6Li(3He,d)7Be reaction. Capture data have been added to an earlier analysis with integrated cross section measurements from 0.7 to 0.825 MeV for 6Li(3He,gamma)9B. The resulting resonance parameters are compared with tabulated values, and previously unidentified resonances are noted. Our results show that there are no near d+7Be threshold resonances with widths that are 10's of keV and reduce the likelihood that a resonance-enhanced mass-7 destruction mechanism, as suggested in recently published work, can explain the 7Li problem.