  In this article it is shown analytically that the charge spectrum generated
by ionizing particles in Resistive Plate Chambers under Townsend avalanche
conditions, that is, for sufficiently small avalanches not affected by
space-charge and considering single-electron ionization clusters follows
closely the statistical gamma distribution. This distribution describes well
comparable simulation data taken from the literature, but seems to describe as
well experimental data measured beyond these assumptions, rising some
interpretation issues.
