[Rivet] ZFinder problem report

[Andy Buckley]

On 30/08/11 19:19, Yatsenko, Elena wrote:
> Hello,
>
> During implementation of the ATLAS ZpT analysis with Rivet v1.6.0 we've found a problem in ZFinder class with clusterPhotons flag.
> If clusterPhotons =«false» dR cut is not effective for the 4 momentum of the Z boson .
> So in our case
>
> ZFinder zfinder_dressed_el(-2.4, 2.4, 20, ELECTRON, 66.0*GeV, 116.0*GeV, 0.1, false, false);
>   and
> ZFinder zfinder_bare_el(-2.4, 2.4, 20, ELECTRON, 66.0*GeV, 116.0*GeV, 0.0, false, false);
>
> will give the same results. While the class documentation suggest that clusterPhotons is meant to only correct the 4 vectors of the decay lepton.

Hi again Elena,

I think that the main issue here is that the class documentation needs 
to be improved on W/ZFinder and LeptonClusters to explain exactly what 
these bool flags imply. It's been redeveloped a bit recently and *I'm* 
not entirely sure what Frank intended!

What do *you* expect these flags to do? My understanding is that if you 
set clusterPhotons=false then the Z mass will be constructed without 
using dR: I'm not sure why we have a separate flag for that, but 
presumably there has been a use case for it. I think that the 
trackPhotons flag is used to decide whether or not the photons are 
attached to the returned leptons, from my reading of the docstring, but 
Frank should clarify that: it is a bit confusing.

Cheers,
Andy

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

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