Questioning MAMI's recent determination of $B_{\Lambda}({_{\Lambda}^3}{\rm H})$

TL;DR

This paper questions the recent MAMI experiment's large determination of the hypernucleus ${_{\Lambda}^3}{ m H}$ binding energy, proposing an alternative interpretation involving a different hypernucleus decay.

Contribution

It offers an alternative explanation for the observed spectral line, challenging the previous assignment and discussing model dependence in hypernuclear binding energy measurements.

Findings

The observed spectral line may originate from ${_{\Lambda}^7}{ m He}$ decay, not ${_{\Lambda}^3}{ m H}$.

The interpretation of hypernuclear decay lines is model-dependent.

The proposed reinterpretation affects the estimated binding energy of ${_{\Lambda}^3}{ m H}$.

Abstract

A recent report on ${^7{\rm Li}}(e,e'K^+)$ electroproduction runs by the A1 collaboration at the Mainz Microtron (MAMI) assigns a sharp pion-momentum line at $p_{\pi^-}\approx 113.8\pm 0.1$ MeV/c to ${_{\Lambda}^3}{\rm H}\to\pi^-+{^3{\rm He}}$ weak decay, resulting in exceptionally large ${_{\Lambda}^3}{\rm H}$ binding-energy $B_{\Lambda}({_{\Lambda}^3}{\rm H})=0.523\pm 0.013\pm 0.075$ MeV. Here I suggest an alternative interpretation of the observed sharp line in terms of ${_{\Lambda}^7}{\rm He}_{\rm g.s.}\to\pi^-+{^7{\rm Li}}(E_{\rm x}=478$ keV) weak decay, discussing also the model dependence of $B_{\Lambda}({_{\Lambda}^7}{\rm He})$.