  We present a new detection scheme for rejecting backgrounds in neutrino less
double beta decay experiments. It relies on the detection of Cherenkov light
emitted by electrons in the MeV region. The momentum threshold is tuned to
reach a good discrimination between background and good events. We consider
many detector concepts and a range of target materials. The most promising is a
high-pressure 136Xe emitter for which the required energy threshold is easily
adjusted. Combination of this concept and a high pressure Time Projection
Chamber could provide an optimal solution. A simple and low cost effective
solution is to use the Spherical Proportional Counter that provides two delayed
signals from ionization and Cherenkov light.
  In solid-state double beta decay emitters, because of their higher density,
the considered process is out of energy range. An alternative solution could be
the development of double decay emitters with lower density by using for
instance the aerogel technique. It is surprising that a technology used for
particle identification in high-energy physics becomes a powerful tool for
rejecting backgrounds in such low-energy experiments.
