[Halld-cal] Shower Quality Cut

[Shepherd, Matthew]

Dear George,

Very roughly, the efficiency for the quality cut is in the neighborhood of 85% - 95% per photon.  It depends on energy and also number of tracks in the event.  When we look at an inclusive pi0 sample, we see that we retain 85% of pi0's after a cut of 0.5.

So, you have 6 photons, and I would predict an efficiency of roughly (0.85)^3 = 60%.  You state that you loose 1/3 of events:  it seems that is perfectly consistent with my rough prediction.

The cut will not affect BCAL showers as they all have a quality set to 1 by default.

As with any cut, if there is no advantage to using it, then it is best to leave it off.  It will just introduce a systematic uncertainty in your analysis.  

The cut is really designed to eliminate detached showers caused by a nearby hadronic interaction.  There should be relatively few of those in your all neutral topology, so I'm not sure that the quality score will be particularly helpful.

Matt

---------------------------------------------------------------------
Matthew Shepherd, Professor
Department of Physics, Indiana University, Swain West 265
727 East Third Street, Bloomington, IN 47405

Office Phone:  +1 812 856 5808

> On Jul 16, 2019, at 7:17 AM, Georgios Vasileiadis <gvasil at jlab.org> wrote:
> 
> Dear Rebecca and Matt,
> 
> During yesterday's eta/eta' meeting we discussed the Shower Quality cut and how it affects the eta pi+ pi- and eta pi0 pi0 final states. I put together some slides in order to show you the result of using this cut in my analyses. As you can see in the attached slides, this cut is very efficient for the eta pi+ pi- final state (I think the algorithm was trained using the very similar reaction omega -> pi+ pi- pi0). However, it is disastrous for the eta pi0 pi0 final state (6 photons and no charged tracks, besides the recoiling proton). Some details on the application of the cut:
> 
> a) A combo is cut even if just one of the photons fails the cut
> 
> b) I didn't check whether the showers end up in the FCAL or the BCAL, prior to applying the cut
> 
> Given the above, I would like to ask you:
> 
> 1) Can this cut be used for final states with only neutral particles?
> 
> 2) Should I be checking for the location of the shower (FCAL/BCAL) before using this cut (i.e. apply it ony to FCAL showers)?
> 
> 
> Thank you in advance,
> George
> 
> 
> <shower_quality_cut.pdf>_______________________________________________
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