Measurement of $\rm ^{6}H$ ground state energy in an electron scattering experiment at MAMI-A1

TL;DR

This paper reports the first measurement of the ground state energy of the neutron-rich isotope H using electron scattering at MAMI, revealing a peak that challenges existing models of multi-nucleon interactions.

Contribution

It introduces a novel electron scattering method to produce and study light neutron-rich nuclei, specifically H, and measures its ground state energy for the first time.

Findings

H ground state energy measured at 2.3 MeV

Clear peak observed above the H threshold

Method provides new insights into multi-nucleon interactions

Abstract

For the first time the neutron-rich hydrogen isotope $\rm ^{6}H$ was produced in an electron scattering experiment in the reaction $\rm ^{7}Li(e,~e'p\pi^{+})^{6}H$ using the spectrometer facility of the A1 Collaboration at the Mainz Microtron accelerator. By measuring the triple coincidence between the scattered electron, the produced proton, and $\pi^{+}$, the missing mass spectrum of $\rm ^{6}H$ was obtained. A clear peak above $^3$H+n+n+n energy threshold was seen resulting in a ground state energy of $\rm ^{6}H$ at $2.3\pm0.5({\rm stat.})\pm0.4({\rm syst.})$ MeV with a width of $1.9\pm1.0({\rm stat.})\pm0.4({\rm syst.})$ MeV. This work challenges the understandings of multi-nucleon interactions and presents a new method to study light neutron-rich nuclei with electron scattering experiments.