More NFlavours: support NFlavour=3,4,5,6 and new parameter isFFNS
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Added support for NFlavour=3,4,5,6 in QCDNUM and APFEL (but not APFEL++) evolutions.
Before only NFlavour=3 and NFlavour=5 were available (moreover NFlavour=5 was actually NFlavour=6).
New parameter isFFNS (in constants.yaml) controls whether it is FFNS or VFNS:
Thus now the following scenarios are available:
@aglazov could you please check the modification to the QCDNUM evolution, in particular to qcdnumDef
? It was needed to have FFNS with 4, 5 or 6 flavours and avoid Input quark densities not linearly independent
error from QCDNUM, but I do not have much experience with QCDNUM routines and do not know if what I did was optimal?
This MR was initially triggered by the request from Sara to have FFNS with 4 flavours (apparently, a VFNS with 3 to 4 flavours was requested), even though in the old xFitter: https://groups.google.com/forum/#!msg/xfitter-users/tcuwZNDEgpc/wm0Eagr1AAAJ
Also four tests VFNS4-QCDNUM
, FFNS4-QCDNUM
, VFNS4-APFEL
, FFNS4-APFEL
are added (QCDNUM and APFEL produce identical evolved PDFs).