Multiplicity of Charged and Neutral Pions in Deep-Inelastic Scattering of 27.5 GeV Positrons on Hydrogen

TL;DR

This study measures the production rates of charged and neutral pions in deep-inelastic scattering of 27.5 GeV positrons on hydrogen, confirming isospin invariance and exploring dependencies on Q^2 and x with results aligning with QCD predictions.

Contribution

First detailed comparison of charged and neutral pion multiplicities in deep-inelastic scattering at this energy, confirming isospin symmetry and QCD-based evolution.

Findings

Charged and neutral pion multiplicities are equal up to z=0.7.

Total energy fractions are approximately 0.51 for charged and 0.26 for neutral pions.

Multiplicity dependencies on Q^2 and x are consistent with theoretical expectations.

Abstract

Measurements of the individual multiplicities of pi+, pi- and pi0 produced in the deep-inelastic scattering of 27.5 GeV positrons on hydrogen are presented. The average charged pion multiplicity is the same as for neutral pions, up to approximately z= 0.7, where z is the fraction of the energy transferred in the scattering process carried by the pion. This result (below z= 0.7) is consistent with isospin invariance. The total energy fraction associated with charged and neutral pions is 0.51 +/- 0.01 (stat.) +/- 0.08 (syst.) and 0.26 +/- 0.01 (stat.) +/- 0.04 (syst.), respectively. For fixed z, the measured multiplicities depend on both the negative squared four momentum transfer Q^2 and the Bjorken variable x. The observed dependence on Q^2 agrees qualitatively with the expected behaviour based on NLO-QCD evolution, while the dependence on x is consistent with that of previous data after corrections have been made for the expected Q^2-dependence.