Transverse mass distributions of neutral pions from $^{208}$Pb-induced reactions at 158$\cdot A$ GeV

Abstract

Results on transverse mass spectra of neutral pions measured at central rapidity are presented for impact parameter selected 158$\cdot A$ GeV Pb + Pb, and Pb + Nb collisions. The distributions cover the range $0.5 \mathrm{GeV}/c^{2} \le m_{T} - m_{0} \le 4 \mathrm{GeV}/c^{2}$. The change of the spectral shape with centrality is studied in detail. In going from peripheral to medium central collisions there is a nuclear enhancement increasing with transverse mass similar to the well known Cronin effect, while for very central collisions this enhancement appears to be weaker than expected.