[Rivet] Boosts in FinalStates/ParticleFinders

[Leif Lönnblad]

I think the TransformationFinder idea sounds like the most reasonable 
idea. Can we find another use case for manipulating particles in the 
ParticleFinder?

The DISKinematics class was something I added in the very early days of 
Rivet since I wanted to compare some stuff with HZTOOL. As far as I can 
see it is not used at all, and should maybe be removed completely.

Cheers,
Leif

On 2016-04-07 22:59, Andy Buckley wrote:
> One of the things that we were asked to provide in Rivet recently was
> automatic frame transformation of projections, e.g. to return particles
> or jets computed in the beam centre-of-mass.
>
> I've added some tools to the Beam projection to compute (I hope
> correctly...) the appropriate boost for that case, but it's not clear
> how to propagate it to the projections. I can't just make a
> BoostedFinalState, then pass that (maybe wrapped in another FinalState)
> to FastJets, for example, because then the tagging ghosts mode via an
> internal HeavyHadrons projection will be in a different frame from the
> jets they're being clustered into: not good.
>
> Any ideas how we should go about doing this? We could maybe go down the
> rabbit-hole above, but I feel it gets very complex very quickly. Another
> way is to add an optional TransformationFinder projection argument to
> the ParticleFinder base class, so that the boost is computed
> event-by-event by that projection before being applied to the found
> particles. BeamBoostFinder would then be one of several implementations
> of TransformationFinder, and perhaps the existing but little-used
> DISKinematics projection would also be retrofitted that way.
>
> This feels quite neat to me, but isn't quite as minor a bit of surgery
> as I'd hoped for. Any thoughts / much easier ways that I've not seen?
>
> Cheers!
> Andy
>