Suppression of High-p_T Neutral Pion Production in Central Pb+Pb Collisions at sqrt{s_NN} = 17.3 GeV Relative to p+C and p+Pb Collisions

TL;DR

This study measures neutral pion production in various collision systems at 17.4 GeV, revealing suppression in high-p_T pi0 yields in central Pb+Pb collisions compared to p+C and p+Pb, indicating possible medium effects.

Contribution

First detailed comparison of neutral pion spectra across p+C, p+Pb, and Pb+Pb collisions at this energy, highlighting suppression in central heavy-ion collisions.

Findings

High-p_T pi0 yields are enhanced or consistent with scaled p+C and p+Pb yields in peripheral collisions.

Suppression of high-p_T pi0 observed in central Pb+Pb collisions with N_part > 350.

Results suggest medium-induced effects in central heavy-ion collisions at SPS energies.

Abstract

Neutral pion transverse momentum spectra were measured in p+C and p+Pb collisions at sqrt{s_NN} = 17.4 GeV at mid-rapidity 2.3 < eta_lab < 3.0 over the range 0.7< p_T < 3.5 GeV/c. The spectra are compared to pi0 spectra measured in Pb+Pb collisions at sqrt{s_NN} = 17.3 GeV in the same experiment. For a wide range of Pb+Pb centralities (N_part < 300) the yield of pi0's with p_T > 2 GeV/c is larger than or consistent with the p+C or p+Pb yields scaled with the number of nucleon-nucleon collisions (N_coll), while for central Pb+Pb collisions with N_part > 350 the pi0 yield is suppressed.