Centrality dependence of π±, K±, baryon and antibaryon production in Pb + Pb collisions at 158 A GeV

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Abstract
We present new results of the CERN experiment NA52 on the centrality dependence of π±, K±, p, d, and production yields near zero transverse momentum and at several rapidities, from 64% to 4% of the total Pb + Pb cross section. Baryon yields increase nearly linearly and K± yields faster than linearly with the number of participating nucleons Np. The antibaryon yields increase less than linearly with Np, indicating absorption. The centrality and rapidity dependence of the π−/π+ ratio indicates Coulomb interaction of the pions with the projectile spectator protons. Within the framework of a coalescence model the radius of the particle source has been estimated from the ratios d/p2 and /2. The source radii are similar for matter and antimatter and are found to increase with ~ Np0.30−0.36.