Precise measurement of the $\Lambda$-binding energy difference between $^3_\Lambda$H and $^4_\Lambda$H via decay-pion spectroscopy at MAMI

TL;DR

This study achieved high-precision measurement of the $ extLambda$ binding energy in light hypernuclei, revealing a deeper binding than previous data and constraining hyperon-nucleon interactions.

Contribution

First high-precision decay-pion spectroscopy measurement of $^3_ extLambda$H binding energy at MAMI, providing more accurate data for hypernuclear physics.

Findings

Measured $B_ extLambda(^3_ extLambda ext{H})$ as 0.523 MeV with improved accuracy.

Result aligns with STAR but shows deeper binding than earlier measurements.

Suggests a stronger $ extLambda$-deuteron interaction.

Abstract

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