  We calculate factorized cross sections for lepton pair production mediated by
a virtual photon in hadron-hadron collisions using the jet calculus scheme, in
which a kinematical constraint due to parton radiation is taken into account.
This method guarantees a proper phase space boundary for subtraction terms.
Some properties of the calculated cross sections are examined. We also discuss
matching between the hard scattering cross sections and parton showers at the
next-to-leading logarithmic (NLL) order of quantum chromodynamics (QCD).
