Use of Lepton Containers in (selector)

[Wolfgang.Mader@cern.ch]

Dear Authors.

Recently we have come across a feature in the (selector). We looked at ttbar production with fully leptonic final states. We used the lepton containers (90, 91) in order to define the decay modes of the top quark in (processes). We then used the same lepton containers in (selector) to define cuts on the invariant mass of the top candidate. What we observed then were large discrepancies in all kinds of distributions of SHERPA generated ttbar events with respect to MC@NLO generated events. When changing the (selector) section to include cuts on explicit leptonic final states (like 11 -12 5, or 13 -14 5) rather than using the lepton containers, we observed a much better agreement.

Our suspicion is now that the seletor in SHERPA also accepts 'unphysical' combinations like e-nu_mu and so on in order to select valid events. There have been several inquiries from the ATLAS community to me wheter such selectors could be used. According to our experience I asked them to use explicit final state definitions for now. I think it would be much more intuitive if the selector in SHERPA would only accept valid combinations of particles.

Cheers, -Wolfgang

[Frank Siegert]

Dear Wolfgang,

I don't yet understand your proposed solution to the problem. How do you suggest the selector should define "valid combinations of particles"? If you tell the selector to cut [90 (lepton), 91 (neutrino)] by a single range, it will look for the first 90/91 pair it can find in the event, and apply the cut. How do you want to define in general, which lepton/neutrino combination it should look for, without actually specifying it in the selector?

But maybe I misunderstood your proposal?

Frank

[Frank Siegert]

After the discussion we had via email, I propose to close this bug as "wontfix". I hope we agree that there is no automated way of determining valid combinations of particles, as in some cases you might indeed want to look at e.g. separation between e/mu.

Also, it is not a big issue to make the selectors explicit.

Thanks, Frank

[Stefan Hoeche]

Milestone old deleted