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

Abstract

For the first time the neutron-rich hydrogen isotope ${}^6\mathrm{H}$ was produced in an electron scattering experiment in the reaction ${}^7\mathrm{Li}(\mathrm{e},{\mathrm{e}}^{\prime }\mathrm{p}\ddot{\mathrm{I}}{€}^{+}{)}^6\mathrm{H}$ 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 $\ddot{I}{€}^{+}$, the missing mass spectrum of ${}^6\mathrm{H}$ was obtained. A clear peak above ${}^3$H+n+n+n energy threshold was seen resulting in a ground state energy of ${}^6\mathrm{H}$ at $2.3\pm 0.5(stat.)\pm 0.4(syst.)$ MeV with a width of $1.9\pm 1.0(stat.)\pm 0.4(syst.)$ 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.

6 pages, 4 figures