Hadronization in semi-inclusive deep-inelastic scattering on nuclei Original Research Article

A series of semi-inclusive deep-inelastic scattering measurements on deuterium, helium, neon, krypton, and xenon targets has been performed in order to study hadronization. The data were collected with the HERMES detector at the DESY laboratory using a 27.6 GeV positron or electron beam. Hadron multiplicities on nucleus A relative to those on the deuteron, image, are presented for various hadrons (image, image, image, image, image, p, and image) as a function of the virtual-photon energy ν, the fraction z of this energy transferred to the hadron, the photon virtuality image, and the hadron transverse momentum squared image. The data reveal a systematic decrease of image with the mass number A for each hadron type h. Furthermore, image increases (decreases) with increasing values of ν (z), increases slightly with increasing image, and is almost independent of image, except at large values of image. For pions two-dimensional distributions also are presented. These indicate that the dependences of image on ν and z can largely be described as a dependence on a single variable image, which is a combination of ν and z. The dependence on image suggests in which kinematic conditions partonic and hadronic mechanisms may be dominant. The behaviour of image at large image constitutes tentative evidence for a partonic energy-loss mechanism. The A-dependence of image is investigated as a function of ν, z, and of image. It approximately follows an image form with image.