Eur. Phys. J. C 20, 479-486 (2001)
DOI: 10.1007/s100520100697

Hadron formation in deep-inelastic positron scattering in a nuclear environment

The HERMES Collaboration A. Airapetian and et al.

Yerevan Physics Institute, 375036, Yerevan, Armenia

(Received: 20 February 2001 / Revised version: 3 May 2001 / Published online: 8 June 2001 -© Springer-Verlag / Società Italiana di Fisica 2001)

Abstract
The influence of the nuclear medium on the production of charged hadrons in semi-inclusive deep-inelastic scattering has been studied by the HERMES experiment at DESY using a 27.5 GeV positron beam. The differential multiplicity of charged hadrons and identified charged pions from nitrogen relative to that from deuterium has been measured as a function of the virtual photon energy and the fraction z of this energy transferred to the hadron. There are observed substantial reductions of the multiplicity ratio R_M^h at low and at high z, both of which are well described by a gluon-bremsstrahlung model of hadronization. A significant difference of the -dependence of R_M^h is found between positive and negative hadrons. This is interpreted in terms of a difference between the formation times of protons and pions, using a phenomenological model to describe the - and z-dependence of R_M^h.

© Società Italiana di Fisica, Springer-Verlag 2001