  We have studied the widths of the rapidity distributions of particles
produced in nucleus-nucleus collisions at various center of mass energies and
as a function of centrality at SPS energies. We show that the width of the
rapidity distribution is sensitive to longitudinal flow, velocity of sound in
the medium, and rescattering of particles. We explore the possibility of
distinguishing the initial hard scattering regime from final state effects by
studying the variation in the width of the rapidity distribution of the
particles with centrality for various pT values.
