[Hps-analysis] MC Truth for Mollers

[Bradley T Yale]

Thanks, I did find another clue.

There is a particular region in the CLUSTER energy sum (~0.75 GeV) where particles are missing in MC (plot 1 Data vs. plot 2 MC). Ignore the 'V0' labels, these are for electron pairs.
Isolating this region in data, sure enough, corresponds to exactly the missing track energy at Ebeam/2, as well as perfectly matches the missing SVT hits in MC (plot 3 Data vs. plot 4 MC). Toggle these SVT plots with one on top of the other to see it.

This missing region doesn't show up in the individual cluster spectrum, only in the cluster ESum. I don't think it is trigger-related though, since the Moller gap was also present in extremely loose singles1 trigger, which has no ESum cut.

Translating this to ECal seed hits, Plot 5 (Data) is the "problem area" at the ECal, where the events show up in Data but NOT MC (crystals x = -9 and -10). The last two plots show the seed hits of the "twin peak" momentum region that exists in both Data (6) and MC (7). Cutting this twin peak region in plot 2, produces a slight dip at Ebeam/2 in data, where the dip is less pronounced than MC due to background.

There could be some other threshold difference between MC and Data. The readout steering file used for MC Mollers is
/u/group/hps/production/mc/PhysRun2016Scripts/PhysicsRun2016MollerPair0.lcsim

and the loose trigger which still produces the gap is
/u/group/hps/production/mc/PhysRun2016Scripts/LooseSingles1.lcsim

I would be happy to try or show anything else.
Explaining the missing cluster ESum events in plot 2 is the goal.
Brad
________________________________________
From: Jaros, John A. <john at slac.stanford.edu>
Sent: Monday, May 23, 2016 2:53:15 PM
To: Bradley T Yale
Cc: Graf, Norman A.
Subject: MC Truth for Mollers

Bradley,

It may be useful to follow MC truth to see where the equal energy Moller tracks disappear.

I'm thinking (very roughly) that you start with the generated distribution, which has events where the tracks have nearly equal energy, select such events, then follow them to see where they fail to satisfy acceptance or trigger cuts.  We should be able to tell what step is preventing them from showing up as "detected".

Norman is happy to help with the details of doing this.

John,
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