  The effect of altered hadron masses is studied for its effect with regard to
final-state hadronic observables. It is shown that the final phase space
densities of pions and kaons, which can be inferred experimentally, are
sensitive to in-medium properties of the excited matter at earlier stages of
the collision, but that the sensitivity is significantly moderated by
interactions that change the effective numbers of pions and kaons during the
latter part of the collision.
