Hi Oliver,
I have no doubt that your approach is valuable and I am happy to see it
carried on. I would spend one word on why it would be nice to have the
possibility to look at the other "biased" approach, though.
To say it in simple words, I would like to be able (also) to apply the
neutrino mass constraint and look at the chi^2 for this fit. If you wish
it is just an hypothesis testing: "is it true that in this event we are
missing only a neutrino?"
>
> So all missing momentum and energy from lost particles will be blamed
> on the neutrino and you naturally will get biased kinematic
> estimators. Even worse is the fact, that the chi^2 will not reflect
> this behavior because the neutrino, as unmeasured quantity, does not
> enter in the chi^2 definition -> You get a biased kinematic with
> a normal chi^2 behavior. No way to separate good from bad events.
I would say that the chi^2 will reflect that there is a problem if the
neutrino mass constraint is imposed: you are just imposing a constraint
which does not apply.
If you wish this approach is the same as cutting on the Prob(chi2) of a
track fit or a vertex fit: if the background is due to tracks that do not
actually come from the same vertex ,cutting on the chi2 makes sense.
This said I am happy with your approach, I am just suggesting one more
knob. We can discuss this by phone either offline (in particular if I am
misunderstanding what you say) or on monday.
thanks
ric
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