[Rivet] WFinder

[Jon Butterworth]

Hi Chris, David, all,

Sorry I missed the discussion last week... this may be hopelessly out of 
date, if so apologies.

Is the "total missing four-vector" counted before or after hadronic decays?

If it's before (as I hope it is), then surely for the samples the 
experiments actually *used* in their unfolding, the "truth MET" and 
"neutrino ET" are identical, so both are ok and the measurements are 
fine. But if (in nature or a new MC process) a different particle gives 
rise to that MET, the WFinder gives an unphysical result, which can't be 
compared properly to data, whereas using truth MET would be robust 
against this.

Given that, I'm puzzled what "signal efficiency dropping massively" 
means. I would hope the change makes almost no difference (though of 
course it would require re-validation). I think having a WFinder which 
relies on physics, pre-hadron-decay observables something rivet needs...

Cheers,
Jon





On 06/07/2015 15:48, Chris Pollard wrote:
> Hi David,
>
>     I'm tempted to deprecate WFinder immediately, leave it as is for one
>     more release, but mark all analyses using it as UNVALIDATED.
>
>
>     There are also other analyses that explicitly count neutrinos without
>     using WFinder. Should those be UNVALIDATED, too?
>
>
> I'm not sure this is the correct thing to do. If the experiments
> unfolded to neutrino four momenta instead of truth MET, that doesn't
> make the measurement wrong. It just makes it less portable and useful.
> We can't change this now---the data are only useable when compared to
> this truth definition.
>
> My opinion is that we should mark the WFinder as deprecated now and be
> prepared to manually rewrite analyses that unfold to the neutrino
> without the WFinder. Those that unfold to the truth MET should still
> work, though.
>
> Chris
>
>
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-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Prof. Jonathan Butterworth,              http://www.hep.ucl.ac.uk/~jmb/
Head, Physics and Astronomy Department            Tel: +44 20 7679 3444
University College London                 Gower St, London WC1E 6BT, UK
ATLAS, CERN                                       Tel: +41 22 76  72340
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