Measurement of ^{6}H Ground State Energy in an Electron Scattering Experiment at MAMI-A1

For the first time the neutron-rich hydrogen isotope ^{6}H was produced in an electron scattering experiment in the reaction ^{7}Li(e,e^{'}pπ^{+})^{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 π^{+}, the missing mass spectrum of ^{6}H was obtained. A clear peak above ^{3}H+n+n+n energy threshold was seen resulting in a ground state energy of ^{6}H at 2.3±0.5(stat.)±0.4(syst.)  MeV with a width of 1.9±1.0(stat.)±0.4(syst.)  MeV. This Letter challenges the understandings of multinucleon interactions and presents a new method to study light neutron-rich nuclei with electron scattering experiments.