[Rivet] Overriding settings of pytune

[James Monk]

Hi, (this is an AGILe-related question, but the AGILe list doesn't see much action these days)

I'm running Perugia 2011 by calling pytune with 350, but then trying to override the PDF to use LHAPDF instead of the internal set.  Parameters are:

#Turn on Perugia 2011
MSTP(5) 350
# Set CTau cut on (default to 10mm from PARJ(71))
MSTJ(22) 2

#set PDF to CTEQ 5L
MSTP(51) 19070
# Use LHAPDF
MSTP(52) 2

The problem is, in some cases it still attempts to use the internal PDF set number (7), but from LHAPDF.  This obviously doesn't work.  As far as I can tell, the determining factor is whether or not I set a particular process, or just use the default QCD process.  If I don't set a process then it uses the proper LHAPDF set number.  If I set a process then it tries to use the PDF set number of 7 from the tune.

Any ideas?  Could this be an internal Pythia problem, rather than an AGILe one?

cheers,

James