Star-tpc-l mailing list

["Van Buren, Gene" <gene AT bnl.gov>]

Hi, Mathias

The "last hit at z = -40 cm" tracks are dominated by pile-up from 
post-trigger-crossing collisions & backgrounds.... Either they are completely 
pile-up tracks, or potentially they are tracks with many pile-up hits and a 
few non-pile-up hits.

I do want to make sure you are aware (though maybe you already are?) that we 
read out the TPC for longer than the full drift time, specifically so that 
tracks are more easily identified as being from post-trigger-crossings 
because they include hits that are reconstructed "beyond" the central 
membrane (i.e. they have the wrong sign z for the side of the TPC from which 
they were detected). These tracks are called PCTs (post-crossing tracks. In 
FXT data, the last hit on PCTs should be between approximately -40 cm < z < 
0, and should be visible in your plots as an excess of such hits.

Likewise, PCTs in FXT should have a first hit excess for 0 < z < +40 cm.

It is not obvious to me why there would be an excess specifically at last z = 
-40 cm or first z = +40 cm, without an excess between there and zero.

-Gene

p.s. I see no flag for PCTs in either StMuTrack or StPicoTrack. It's there in 
StEvent/StTrack, but I guess no one thought it worth a single bit in DSTs  :-(
  bool StTrack::isPostXTrack()
I also see no count of PCT daughters in the StPicoDst vertex information, but 
this count is in StEvent and StMuDst (which just re-uses StEvent's 
StPrimaryVertex):
  UShort_t StPrimaryVertex::numPostXTracks()
This leaves you with no handle on PCTs and vertices that use them at the 
PicoDst level.




> On Oct 31, 2024, at 8:22 PM, Mathias Labonte <Star-tpc-l AT lists.bnl.gov> 
> wrote:
> 
> Hi Everyone,
> 
> Here are comparisons between gene’s production, and the TFG24e production. 
> Please see the slides below.
> 
> 
> Some things to highlight:
> 
> 
> 
> I observe that the change in the vertexer cuts do not resolve the DCA y 
> distributions. I include a slide explaining why we may have initially 
> thought this.
> 
> There are differences between there two productions in the first and last 
> hit distributions that I find hard to explain.
> 
> 
> 
> 
> 
> Any comments, suggestions, or otherwise are welcome and I look forward to a 
> discussion on these studies. If you have any ideas to explore further 
> before the TPC meeting, I would like to hear those too.
> 
> Mathias 
> 
> 
> 
> 
> 
> 
> 
> <latest_test_production_comparisons.pdf>