# Direct observation of proton emission in 11Be

## TL;DR

This paper reports the first direct measurement of proton emission from $^{11}$Be's $eta^- ext{p}^+$ decay, revealing a much larger branching ratio than predicted, explained by a resonance in $^{11}$B.

## Contribution

It provides the first direct observation and measurement of $eta^- ext{p}^+$ decay in $^{11}$Be using a novel detector, challenging existing theoretical models.

## Key findings

- Measured $eta^- ext{p}^+$ branching ratio is significantly larger than predicted.
- Detected a narrow resonance in $^{11}$B above the proton separation energy.
- First direct measurement of this decay mode in $^{11}$Be.

## Abstract

The elusive $\beta^-\text{p}^+$ decay was observed in $^{11}$Be by directly measuring the emitted protons and their energy distribution for the first time with the prototype Active Target Time Projection Chamber (pAT-TPC) in an experiment performed at ISAC-TRIUMF. The measured $\beta^-\text{p}^+$ branching ratio is orders of magnitude larger than any previous theoretical model predicted. This can be explained by the presence of a narrow resonance in $^{11}$B above the proton separation energy.