Eur. Phys. J. A (2004) 19: 111-127
https://doi.org/10.1140/epjad/s2004-03-019-7

Hadrons in the nuclear medium

Inside-outside hadronization in a medium

¹ Max-Planck Institut für Kernphysik, Postfach 103980, 69029 Heidelberg, Germany
² Institut für Theoretische Physik der Universität, 93040 Regensburg, Germany
³ Institute of Experimental Physics SAV, Watsonova 47, CS-04353 Kosice, Slovakia
⁴ Dipartimento di Fisica Teorica, Università di Torino and INFN, Sezione di Torino, I-10125, Torino, Italy

Received: 30 October 2003
Published online: 12 February 2004

Abstract

Nuclei are unique analyzers for the early stage of the space-time development of hadronization. DIS at medium energies is especially suitable for this task being sensitive to hadronization dynamics, since the production length is comparable with the nuclear size. This was the driving motivation to propose an experiment at HERMES [1], and provide predictions based on a pQCD model of hadronization. Now the experiment is done and one can compare the predictions with data [2]. The model successfully describes with no adjustment the nuclear effects for various energies, z _h , p _T , and Q ², for different flavors and different nuclei. It turns out that the main source of nuclear suppression of the hadron production rate is attenuation of colorless pre-hadrons in the medium. An alternative model [11] is based upon an unjustified assumption that the struck parton keeps radiating gluons far beyond the nuclear size and the pre-hadron is produced outside the nucleus. This model has apparent problems attempting to explain certain features of the results from HERMES. A good understanding of the hadronization dynamics is important for proper interpretation of the strong suppression of high-p _T hadrons observed in heavy ion collisions at RHIC. We demonstrate that the production length is even shorter in this case and keeps contracting with rising p _T .