STAR QA Board

[Geary Eppley <eppley@rice.edu>]

Hi Hongwei:

Thanks for the info. Yet L4 produces substantially the same result  
that Gene gets from Fast offline.

-Geary

Quoting "Ke, Hongwei" <kehw@bnl.gov>:

> Hi Geary and Gene,
>
> L4 still uses a VPD calibration table generated Feb 2021. I do not  
> know how good it is to the current pp run.
>
> For the primary vertex reconstruction of L4, it Is basically the  
> average position of DCA points of associated tracks.
> It is biased toward the beam line in x-y plane, but no real constrain.
> The algorithm only select one primary vertex and it is biased toward  
> the candidate with the most associated tracks.
>
> Best regards,
> Hongwei Ke
>
> On Dec 27, 2021, at 9:08 PM, Van Buren, Gene via STAR-QAboard-l  
> <star-qaboard-l@lists.bnl.gov<mailto:star-qaboard-l@lists.bnl.gov>>  
> wrote:
>
> Hi, Geary
>
> We have FastOffline _with_ the BeamLine constraint. The result of  
> that is the data that was shown earlier in this thread, though it  
> essentially showed the two components of the two different BeamLine  
> constraints.
>
> Then we have data I processed _without_ any BeamLine constraint.  
> That's what my (Vtx_z,tpc - Vtpx_z,vpd) plot was made from, and the  
> attached Vy vs. Vx plot is made from.
>
> Hope that helps,
> -Gene
>
> <PastedGraphic-3.png>
>
> On Dec 27, 2021, at 5:58 PM, Geary Eppley  
> <eppley@rice.edu<mailto:eppley@rice.edu>> wrote:
>
> Hi Gene:
>
> Thanks. The offset matches L4 which does VPD-TPC gets -2. The RMS is  
> also about the same as L4 and about the same as Run 17.
>
> If I understand the earlier emails, you use fast offline with  
> modified parameters to get this data.
>
> Do you have a Vx vs Vy plot for this data?
>
> -Geary
>
> Quoting "Van Buren, Gene" <gene@bnl.gov<mailto:gene@bnl.gov>>:
>
> Hi, Geary
>
> On Dec 27, 2021, at 1:02 PM, Geary Eppley  
> <eppley@rice.edu<mailto:eppley@rice.edu><mailto:eppley@rice.edu>>  
> wrote:
> The central Vx vs Vy central distribution shown Friday has a radius  
> of order 1mm. The L4 distribution has a radius of order 1 cm. Do you  
> know what causes that difference?
>
> I do not know exactly what L4 is doing, but my best guess is that  
> they are using no BeamLine constraint at all.
>
>
> We are interested in VPD-TPC Vz offset to see if any adjustments  
> need to be made. L4 consistently shows and offset of -2 cm or less.  
> The RMS is just slightly worse than Run 17, which is not bad  
> considering the current problems with the active splitter.
>
> What offset do you see in your analysis?
>
>
> I'm attaching a histogram of (Vtx_z,tpc - Vtpx_z,vpd) from the data  
> I used to determine the BeamLine last Tuesday. Hope that's useful.
>
> -Gene
>
> [cid:5FA1EB5A-4C18-43E5-B139-E2BF69938FDB@attlocal.net]
>
>
>
>
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