New approach to the search for neutrinoless double beta decay

Sub-eV Majorana neutrino masses 〈${\mathit{m}}_{\nu }$〉, can be explored by a new approach to neutrinoless double β decay using ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$ in a Xe gas-loaded, multiton liquid scintillator installed in a very low background detector such as the Kamiokande facility. With enriched ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$, a readily implementable, 10 ton detector experiment can establish an 〈${\mathit{m}}_{\nu }$〉=0.45 eV at 3σ in 1 yr (or exclude an 〈${\mathit{m}}_{\nu }$〉<0.23 eV in 2 yr). A 100 ton detector can extend the limit to 〈${\mathit{m}}_{\nu }$〉<0.1 eV, compared with the present limit of 〈${\mathit{m}}_{\nu }$〉<1.3 eV.