ONE-PARTICLE INCLUSIVE PROCESSES IN DEEPLY INELASTIC LEPTON-NUCLEON SCATTERING

The one-particle inclusive cross section in deeply inelastic lepton-nu cleon scattering, expressed in terms of parton densities and fragmenta tion functions being differential in the invariant mass of the observe d hadron and of the incoming nucleon, diverges if this invariant mass vanishes. This divergence can be traced back to the kinematical config uration where the parent parton of the observed hadron is emitted coll inearly from the incoming parton of the QCD subprocess. By using the c oncept of ''fracture functions'', which has recently been introduced b y Trentadue and Veneziano, it is possible to absorb this divergence in these new distribution functions as long as the observed hadron is no t soft. This procedure allows the determination of a finite one-partic le inclusive cross section in next-to-leading order QCD perturbation t heory. We give details of the calculation and the explicit form of the bare fracture functions in terms of the renormalized ones.