[Rivet] ZFinder problem report

[Yatsenko, Elena]

Hi Andy,

I'm sorry that I didn't reply, it seems like I missed this mail.
In ZpT analysis we are considering only 4 momentum of the Z boson and we expect that clusterPhotons flag shouldn't affect on this momentum.
But during analysis we saw that it changes the momentum of Z boson in the case when we apply dR=0.1 cut.
And it seems like when clusterPhotons =<false> ZFinder takes Z bosons with decay to "bare" leptons by default.

Cheers,
Elena



09 сентября 2011, 20:29 от Andy Buckley <andy.buckley at ed.ac.uk>:
> Hi Elena,
> 
> Can you clarify what you expected the Rivet photon clustering arguments
> to do and what you are actually seeing?
> 
> Cheers,
> Andy
> 
> On 06/09/11 11:26, Andy Buckley wrote:
> > 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
> 
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.
>