Here you find a list of parameters available in OpenLoops. Within the general purpose Monte Carlo frameworks (e.g. Sherpa or Herwig++) these parameters are synchronised automatically.
Unstable particles with a finite width are by default treated in the complex mass scheme. The cosine of the weak mixing angle cW is always defined as cW=MW/MZ and thus in general a complex valued parameter.
By default all quark flavours are included at one-loop. More precisely, the number of quark flavours that contribute to the renormalisation (and evolution) of αs is chosen as max(number of massless quarks, minnf_alphasrun). Thus, by default only massless quarks are treated as active flavours, while the contribution of massive quarks is effectively decoupled from the running of αs by renormalising it via zero-momentum subtraction. In this approach, above threshold the heavy-quark (with mass Mq) contributions to any renormalised one-loop amplitudes generate logarithms of μR/Mq that are not present in the evolution of αs above threshold. This behaviour can be altered specifying the parameter minnf_alphasrun. If set to a value larger then the number of massless quark flavours, also the corresponding heavy quarks are assumed to contribute to the running of the strong coupling (above the respective thresholds).
A more detailed documentation will soon be available.
These order_ew, and order_qcd selectors are used for the bookkeping of different perturbative orders as explained here.
Further technical parameters affecting the stability system are listed here.