[Rivet] AGILe and PYTUNE

[Andy Buckley]

On 03/12/10 16:53, Gavin Hesketh wrote:
> Dear AGILe authors,
> I've just been playing around with the fortran pythia. I'm sure you know
> recent versions have the PYTUNE function, which allows you to select any
> of the "standard" tunes, by setting the MSTP(5) parameter.
> 
> But, if I want to use this feature while also varying one parameter that
> is part of that tune, eg by passing the following parameter file when I
> call agile-runmc:
> 
> MSTP(5) 105
> PARP(64) 2
> 
> then my choice of PARP(64) is overwritten by PYTUNE. iirc, he way to
> avoid this is to set MSTP(5), call PYINIT, then set the other parameters.
> 
> I wondered if anyone had figured out how to do such a thing with agile,
> or if I simply can't use the MSTP(5)/PYTUNE functionality and have to
> set all the tune variables by hand?

Hi Gavin,

As far as I'm aware, PYTUNE will stomp all over any user-specific
settings, so slight variations on PYTUNE tunes are not possible. I
mentioned this to Peter Skands (CC'd) a while ago, so maybe the latest
version of PYTHIA does now support customising settings on top of
PYTUNE... Peter?

If not, is it possible to structure AGILe's calls to the PYTHIA routines
such that PYTUNE will be called first (with a special-case param passing
of MSTP(5)) and then PYGIVE be called for all the other params?

I'll very happily make an AGILe patch release to incorporate this (as
well as any new Fortran generator interfaces that people supply...
MC at NLO, anyone?!)

Andy

-- 
Dr Andy Buckley
SUPA Advanced Research Fellow
Particle Physics Experiment Group, University of Edinburgh