Process 51 is identical to 50 except for the fact that the bottom quark mass is neglected. This allows the calculation to be performed up to NLO. The other processes 52 and 53,also with massless b-quarks account for the decays into neutrinos (nproc=52) and bottom quarks (nproc=53). Note that the NLO calculation of process 53 does not currently include radiation from the bottom quarks produced in the decay.
When removebr is true in process 51, the Z boson does not decay.
nplotter_Zbbbar.f is the default plotting routine.