  We propose a method to estimate the probability of new physics discovery in
future high energy physics experiments. Physics simulation gives both the
average numbers <Nb> of background and <Ns> of signal events. We find that the
proper definition of the significance for <Nb>, <Ns> >> 1 is S_{12} =
sqrt(<Ns>+<Nb>) - sqrt(<Nb>) in comparison with often used significances S_1 =
<Ns>/sqrt(<Nb>) and S_2 = <N_s>/sqrt(<Ns> + <Nb>). We propose a method for
taking into account the systematical errors related to nonexact knowledge of
background and signal cross sections. An account of such systematics is very
essential in the search for supersymmetry at LHC. We also propose a method for
estimation of exclusion limits on new physics in future experiments.
