Hypersharp Resonant Capture of Neutrinos as a Laboratory Probe of the Planck Length

Abstract

The 18.6 keV antineutrino line from 2-body decay of 3H in crystals can be emitted with natural width because of motional averaging by lattice vibrations despite the very long lifetime of 3H and contrary to commonly held views of linewidths in such a case. It can be resonantly captured in 3He with geometrical cross section sigma ~10-17 cm2. Using its hypersharp sensitivity DELTAE/E ~10-29 and the method of time-filtered resonance, the basic energy width ~10-24 eV expected of the 3H state can be measured to test if ultimate nuclear widths are limited by the Planck length rather than time-energy uncertainty.