Measurement of inclusiveπ 0 production in hadronicZ 0 decays

Abstract

An analysis is presented of inclusiveπ0 production inZ0 decays measured with the DELPHI detector. At low energies,π0 decays are reconstructed by using pairs of converted photons and combinations of converted photons and photons reconstructed in the barrel electromagnetic calorimeter (HPC). At high energies (up to\(x_p = 2 \cdot p_\pi /\sqrt s = 0.75\)) the excellent granularity of the HPC is exploited to search for two-photon substructures in single showers. The inclusive differential cross section is measured as a function of energy forqq andbb events. The number ofπ0’s per hadronicZ0 event isN(π0)/Zhad0=9.2±0.2(stat)±1.0(syst) and forbb events the number ofπ0’s is N(π0)/bb=10.1±0.4(stat)±1.1(syst). The ratio of the number ofπ0’s inbb events to hadronicZ0 events is less affected by the systematic errors and is found to be 1.09±0.05±0.01. The measuredπ0 cross sections are compared with the predictions of different parton shower models. For hadronic events, the peak position in theξp=ln(1/xp) distribution isξ*p=3.90−0.14+0.24. The average number ofπ0’s from the decay of primary B hadrons is found to be N(B→π0X)/B hadron=2.78±0.15(stat)±0.60(syst).