# Muon capture in nuclei: an ab initio approach based on quantum Monte Carlo methods

## TL;DR

This paper introduces an ab initio quantum Monte Carlo method to calculate muon capture rates in light nuclei, applying it to helium-4 with realistic nuclear interactions and weak currents, highlighting uncertainties in experimental data.

## Contribution

The paper presents a novel quantum Monte Carlo approach for muon capture in nuclei, incorporating realistic interactions and weak currents constrained by empirical data.

## Key findings

- Calculated muon capture rate in helium-4 using realistic interactions.
- Analyzed sensitivity to weak current parametrizations.
- Identified large uncertainties in experimental measurements.

## Abstract

An ab initio quantum Monte Carlo method is introduced for calculating total rates of muon weak capture in light nuclei with mass number $A \leq 12$. As a first application of the method, we perform a calculation of the rate in $^4$He in a dynamical framework based on realistic two- and three-nucleon interactions and realistic nuclear charge-changing weak currents. The currents include one- and two-body terms induced by $\pi$- and $\rho$-meson exchange, and $N$-to-$\Delta$ excitation, and are constrained to reproduce the empirical value of the Gamow-Teller matrix element in tritium. We investigate the sensitivity of theoretical predictions to current parametrizations of the nucleon axial and induced pseudoscalar form factors as well as to two-body contributions in the weak currents. The large uncertainties in the measured values obtained from bubble-chamber experiments (carried out over 50 years ago) prevent us from drawing any definite conclusions.