  For a set of N identical massive boson wavepackets with optimal initial
quantum mechanical localization, we calculate the Hanbury-Brown/Twiss (HBT)
two-particle correlation function. Our result provides an algorithm for
calculating one-particle spectra and two-particle correlations from an
arbitrary phase space occupation (q_i,p_i,t_i)_{i=1,N} as e.g. returned by
event generators. It is a microscopic derivation of the result of the coherent
state formalism, providing explicit finite multiplicity corrections. Both the
one- and two-particle spectra depend explicitly on the initial spatial
wavepacket width which parametrizes the quantum mechanical wavepacket
localization. They provide upper and lower bounds which suggest that a
realistic value for this width has the order of the Compton wavelength.
