[Rivet] lifetimes in rivet

[Andy Buckley]

On 01/04/10 09:43, Alexander Richards wrote:
> Hi Andy,
> Was wondering if there was a nice Rivety was of cutting of particle
> lifetimes such as a lifetime projection or something? I think I can
> directly get the lifetime of the particles from the GenParticle but was
> wondering if there was an easier way?

(Copying to Rivet list: please send to the list if possible!)

I don't *think* there is a way to get the generator's take on the
lifetime from the GenParticle: at least, I don't see anything in the
GenParticle interface that does this. HepPDT could probably be used to
get this info from the PID, but there's no guarantee that the number
matches that used by the generator.

If there is such a mechanism in HepMC (and it's used, including in the
translation from the Fortran HEPEVT event record), then I'd be very
happy: we could move a lot of restrictions on particle lifetime cuts
from how the generator has to be configured into the Rivet analysis
code, and a lifetime-sensitive projection of some sort would indeed be
useful. But I don't know of such a mechanism: maybe someone can correct me?

Andy

PS. There is a GenParticle::generated_mass property... adding a
GenParticle::generated_lifetime seems quite sensible to me. But it would
only be likely to be used by new generators, after some active
migration. And the experiments are still several HepMC versions behind!

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