Precise measurement of the $\hat{I}›$-binding energy difference between ${}_{\hat{I}}^3›$H and ${}_{\hat{I}}^4›$H via decay-pion spectroscopy at MAMI

Abstract

We performed high-precision decay-pion spectroscopy of light $\hat{I}›$ hypernuclei at the Mainz Microtron (MAMI) using the A1 spectrometer facility. By measuring the monochromatic $\ddot{I}{€}^{-}$ momentum from the two-body weak decay ${}_{\hat{I}}^3›\mathrm{H}\to {}^3\mathrm{He}+\ddot{I}{€}^{-}$ and referencing it to the ${}_{\hat{I}}^4›\mathrm{H}\to {}^4\mathrm{He}+\ddot{I}{€}^{-}$ decay, we determined the $\hat{I}›$ binding energy of ${}_{\hat{I}}^3›\mathrm{H}$ with unprecedented accuracy. The obtained value, $B_{\hat{I}}›{(}_{\hat{I}}^3›\mathrm{H})=0.523\pm 0.013(stat.)\pm 0.075(syst.)$~MeV, is consistent with the STAR result, but indicates a significantly deeper binding than inferred from earlier measurements. This result implies a stronger $\hat{I}›$-deuteron interaction and provides stringent constraints on hyperon-nucleon interactions.