Small scale CMB fluctuations as a probe of the mass of Dark Matter particles

The CMB anisotropy on arc second range is examined to test the power spectrum of perturbations in the small scale region and, in particular, to estimate the mass of dominant dark matter particles. It is shown that for the simplest evolutionary history with standard recombination, three and four beam observations could discriminate the mass of dark matter particles in the interval $0.5 KeV\leq M_{DM}\leq 4 KeV$ with an antenna beam (0.5 - 0.25) arc minute with amplitude $\approx 10^{-7}$.