[Rivet] DressedLeptons and photons from tau decays

[Andy Buckley]

On 06/02/17 15:07, Markus Seidel wrote:
> Dear all,
>
> what is the reason for excluding photons from tau decays from the
> DressedLeptons?
>
> Doesn't this prevent to cluster photons from electrons from taus?

Hi Markus,

I think the projection was probably written considering (as is usually 
the case, in my experience) leptonic taus to only be observed via their 
muon or electron child -- and it is the child rather than the parent 
whose momentum vector is used as the centre of the dressing cone.

DressedLeptons isn't designed for hadronic taus, and I suspect this rule 
is in there to avoid "contamination" from hadronic tau decay photons 
into prompt electron or muon dressing.

You're probably right that there's an issue in how it's implemented, 
though: it does seem reasonable, or at least would be a reasonable 
option, to include photons directly from a prompt leptonic tau when 
dressing that tau's electron/muon child. The neutrinos are still 
"missing", so it may not help much, but is physically well-defined. I 
*could* add an option flag of that sort, to restrict the veto to 
*hadronic* taus only: is that what you had in mind?

Frank Siegert may know more: he originally implemented DressedLeptons 
(then called ClusteredLeptons), and I can'd remember if he or I added 
the tau photon veto! Frank??

Andy

-- 
Dr Andy Buckley, Lecturer / Royal Society University Research Fellow
Particle Physics Expt Group, University of Glasgow