$\mathbf{\beta}$-delayed proton emission from $\mathbf{^{11}}$Be in effective field theory

TL;DR

This paper uses Halo effective field theory to calculate the rare beta-delayed proton emission rate from $^{11}$Be, aligning theoretical predictions with recent experimental data and showing no need for exotic physics explanations.

Contribution

It provides a novel EFT-based calculation of the decay rate and resonance parameters, confirming experimental results and exploring the impact of resonances on decay probabilities.

Findings

Calculated branching ratio consistent with experiment

Predicted resonance width around 9 keV

No exotic physics needed to explain decay rate

Abstract

We calculate the rate of the rare decay $^{11}\text{Be}$ into $^{10}\text{Be} + p +e^- + \bar{\nu}_e$ using Halo effective field theory, thereby describing the process of beta-delayed proton emission. We assume a shallow $1/2^+$ resonance in the $^{10}\text{Be}-p$ system with an energy consistent with a recent experiment by Ayyad et al. and obtain $b_p = 4.9_{-2.9}^{+5.6}\text{(exp.)}_{-0.8}^{+4.0}\text{(theo.)} \times 10^{-6}$ for the branching ratio of this decay, predicting a resonance width of $\Gamma_R = (9.0^{+4.8}_{-3.3}\text{(exp.)}^{+5.3}_{-2.2}\text{(theo.)})~\text{keV}$. Our calculation shows that the experimental branching ratio and resonance parameters of Ayyad et al. are consistent with each other. Moreover, we analyze the general impact of a resonance on the branching ratio and demonstrate that a wide range of combinations of resonance energies and widths can reproduce branching ratios of the correct order. Thus, no exotic mechanism (such as beyond the standard model physics) is needed to explain the experimental decay rate.