  We apply Laplace method for the tree diagrams to calculate the interference
terms arising as a result of summation of particles permutations in the final
state of scattering. These terms significantly influence the values of
experimentally observed quantities. We show that the tree diagram with a single
input line and an arbitrary number of output lines has a maximum value for the
equal four-momenta of secondary particles. It means the tree diagrams of
inelastic scattering describe the formation of parton and hadron showers. We
also demonstrate the need to take into account the contributions from
interference between different showers.
