Why is the universe composed only of matter, with negligible anti-matter? Is the neutrino its own anti-particle? These two seemingly disparate questions are linked through the ideas of leptogenesis. In the most attractive formulation, massive neutrinos break matter-antimatter asymmetry and yield the universe we observe, inhabit and explore today. But leptogenesis also forces today’s neutrinos to be their own anti-particles, with mass in the range of 50 meV, close to the measured value. The only practical avenue for determining the neutrino nature is the search for an almost unimaginably rare nuclear decay, neutrinoless double beta decay, possible in a few neutron-rich isotopes. I focus on NEXT, an experimental program based on 136Xe, in a high-pressure xenon gas Time Projection Chamber that combines excellent energy resolution and rejection of backgrounds through event topology. Strangely, a biochemistry technique might make success possible.
Perhaps an exciting discovery awaits, one that may indicate how the universe chose to keep about one part per billion of matter.
