On Tue, 14 Oct 2014, [log in to unmask] wrote:

> Hi Matt,
>
> and others responsible for generated/simulated data, I have a question:
>
> I took your data from:
>
> /mss/hallb/hps/production/readout/tritrig-beam-tri/2pt2/
>
> 
>
> tritrigv1-egsv3-triv2-g4v1_s2d6-readout20140522_[1-10000].slcio
>
>
> and from description I thought this was a right mix of trident data and beam 
> background. However, I found some difficulty interpreting these files:
>
> 1. there is no distinction between "signal" (trident) and background, if you 
> select events produced at t=0 and having no parents they are still not 
> distinguishable completely (usually >3 particles/event);

For tridents, the signal particles should share a parent, and the parent 
should have PDG ID 622. There should be exactly one such trident in every 
event in the files you're looking at.

There may be other tridents ("background tridents") in the event, which 
will not be labeled in this way; if they occur in the same beam bunch as 
the signal trident, they can be identified in the way you describe.

>
> 2. even if you find a combination of 3 particles with close missing mass it 
> is >10^-2 GeV (varying), while I expected <10^-4 GeV^2 (fixed).

Since tridents are produced at random Z within the target, they are 
affected by multiple scattering. Since we don't use SLIC to simulate 
target interactions, the MS is applied outside of SLIC, and so the 
particles listed in SLIC have already been smeared by MS.

Matt should confirm that the mass you're seeing is consistent with this 
explanation.

>
> Any suggestion?
>
> Best Regards,
>             Mikhail.
>
>
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