  In this letter, a new strategy to enhance the discrimination of high energy
gamma rays from the huge charged cosmic rays background in large cosmic rays
ground arrays is presented. This strategy is based on the introduction of a new
simple variable, $P_{\gamma h}^{\alpha}$, which combines the probability of
tagging muons and/or very energetic particles in each single array station. The
discrimination power of this new variable, particularly important for and above
multi-TeV energies, is illustrated for a few specific examples in the case of a
hypothetical water Cherenkov detector cosmic ray array, both in the case of low
and high particle stations occupancy. The results are very encouraging and
hopefully will be demonstrated in the present and future gamma-ray
Observatories.
