/ Experiment-HEP hep-ex/0104004

Multiplicity of charged and neutral pions in deep inelastic scattering of 27.5-GeV positrons on hydrogen

Airapetian, A. ; Akopov, N. ; Akopov, Z. ; Amarian, M. ; Arrington, J. ; Aschenauer, E.C. ; Avakian, H. ; Avakian, R. ; Avetisian, A. ; Avetisian, E. ; Bailey, P. ; Bains, B. ; Baumgarten, C. ; Beckmann, M. ; Belostotski, S. ; Bernreuther, S. ; Bianchi, N. ; Bottcher, H. ; Borissov, A. ; Bouwhuis, M. ; Brack, J. ; Brauksiepe, S. ; Braun, B. ; Bruckner, W. ; Brull, A.

Published in: Eur.Phys.J.
Year: 2001
Vol.: C21
Page No: 599-606
Pages: 10

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.

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