These processes represent the production of a Z boson that decays into a pair of electrons, in association with a heavy quark, Q. For more details on this calculation, please see Ref. [1].
For processes 261, 262, 266 and 267 the initial state at lowest order is the heavy quark and a gluon and the calculation may be performed at NLO. As for H + b production, the matrix elements are divided into two sub-processes at NLO. Thus the user must sum over these after performing more runs than usual. At lowest order one can proceed as normal, using nproc=261 (for Z + b) or nproc=262 (for Z + c). For a NLO calculation, the sequence of runs is as follows:
Run nproc=261 (or 262) with part=virt and part=real (or, both at the same time using part=tota);
Run nproc=266 (or 267) with part=real.
The sum of these yields the cross-section with one identified heavy quark in the final state when inclusive is set to .false. . To calculate the rate for at least one heavy quark, inclusive should be .true..
For processes 263 and 264, the calculation uses the matrix elements for the production of a Z and a heavy quark pair and demands that one of the heavy quarks is not observed. It may either lie outside the range of pT and η required for a jet, or both quarks may be contained in the same jet. Due to the extra complexity (the calculation must retain the full dependence on the heavy quark mass), this can only be computed at LO.
When removebr is true, the Z boson does not decay.
nplotter_auto.f is the default plotting routine.
[1] J.M. Campbell, R.K. Ellis, F. Maltoni and S. Willenbrock, Associated production of a Z Boson and a single heavy quark jet, Phys. Rev. D 69 (2004) 074021 [hep-ph/0312024].