  We present a technique for separating nuclear double beta decay
($\beta\beta$-decay) events from background neutrino interactions due to
$^{8}$B decays in the sun. This background becomes dominant in a kiloton-scale
liquid-scintillator detector deep underground and is usually considered as
irreducible due to an overlap in deposited energy with the signal. However,
electrons from 0$\nu\beta\beta$-decay often exceed the Cherenkov threshold in
liquid scintillator, producing photons that are prompt and correlated in
direction with the initial electron direction. The use of large-area fast
photodetectors allows some separation of these prompt photons from delayed
isotropic scintillation light and, thus, the possibility of reconstructing the
event topology. Using a simulation of a 6.5~m radius liquid scintillator
detector with 100~ps resolution photodetectors, we show that a spherical
harmonics analysis of early-arrival light can discriminate between
0$\nu\beta\beta$-decay signal and $^{8}$B solar neutrino background events on a
statistical basis. Good separation will require the development of a slow
scintillator with a 5 nsec risetime.
