Nuclear shadowing in DIS at moderately small x(B)

In the rest frame of the nucleus, shadowing is due to hadronic fluctuations of the incoming virtual photon, which interact with the nucleons. We expan d these fluctuations in a basis of eigenstates of the interaction and take only the q (q) over bar component of the hadronic structure of the photon i nto account. We use a representation in which the q (q) over bar-pair has a definite transverse size. Starting from the Dirac equation, we develop a p ath integral approach that allows to sum all multiple scattering terms and accounts for fluctuations of the transverse size of the pair, as well as fo r the finite lifetime of the hadronic state. First numerical results show t hat higher order scattering terms have a strong influence on the total cros s section sigma(tot)(gamma*A). The aim of this paper is to give a detailed derivation of the formula for the total cross section.