Attenuation of Hadron in Nuclei

The influence of the nuclear medium on the production of charged hadrons in semi-inclusive DIS has been studied by the HERMES experiment at DESY with a 27.5 GeV positron beam. The hadron multiplicity has been measured for helium, neon and krypton relative to that of deuterium. The multiplicity ratio is strongly reduced at high values of the atomic number A. The Aα-dependence of HERMES data on krypton and nitrogen is discussed and is compared to two theoretical models. Assuming a simple Aα-dependence of the nuclear attenuation, the HERMES data are found to be closer to the A2/3-dependence predicted by some pQCD-based models than to the A1/3-dependence that follows from models based on nuclear absorption only. (author)