STAR task force for evaluating tracking efficiency uncertainty

[yh66 <yh66 AT rice.edu>]

Hi Petr,
   Thank you, this is an excellent explanation. And the effect of the  
iTPC update may be very interesting for this study.

BW,
Yiding
Quoting Petr Chaloupka via Star-tf-trkeff-l <star-tf-trkeff-l AT lists.bnl.gov>:

> Dear Yiding,
>
> thank you for the question. Let me explain.
> The discrepancy (large increase) from nhits>15 to nits>20 comes from  
> the fact that we use charged tracks from decay K→3pi. This means  
> that what is shown is a comparison of tracking efficiency for a  
> tracks belonging to the primary kaon. However the primary kaon can  
> never reach full way to the outer edge of the TPC (as most of  
> primary tracks do) otherwise we would not be able to reconstruct its  
> decay. In other words such track cannot have the maximum of 45 hits.  
> In run18 (which data do you use?) we get to maximum of 30 possible  
> hits, the average is about 25. So when you look at the results for  
> nhits>20 it is quite an extreme cut for such tracks and hence there  
> is a significant difference between data and simulation. One should  
> be carefull to extrapolate to full lenght tracks (nhitPossible~45).  
> I can argue that for a full lenght track the systematic error will  
> not be larger that what is in the table so for example for the cut  
> of dca<2cm and nhits>15 the 5% is reasonable upper estimate. The  
> situation will be different for run19 with iTPC where we will have  
> acces to tracks with more points. Then the estimates for nhits>20  
> should be closer to full lenght tracks.
>
> With best regards,
> Petr
>
> On 08. 06. 23 1:08, yh66 via Star-tf-trkeff-l wrote:
> > Dear experts,
> >      This is Yiding from Rice. Recently I am working on the  
> > systematic uncertainty of di-electron analysis. I plan to add  
> > embedding/data mismatching uncertainty specifically referenced in  
> > your presentation slide available at:  
> > https://urldefense.com/v3/__https://drupal.star.bnl.gov/STAR/system/files/TrkEff.pdf__;!!BuQPrrmRaQ!hhfhZsWQCHurYChjT15Xy9i3REkW3jV-y0OLxbJY6S8R15zcOYmMDBLdqswClEKJ_udpYq2IIodkTNxLpPNGHa0PZc4aIgAi98Bal9gbZnQ$ . And I have one question about  
> > it.
> >      In Slide 15 of your presentation, you demonstrate the effect  
> > of different cuts on mismatching. I observed two intriguing aspects  
> > in this analysis. Firstly, the mismatching appears to be sensitive  
> > to the DCA cut, which aligns with similar observations made in  
> > various studies. However, what caught my attention is the  
> > substantial difference in mismatching between nHitsFit>15 and  
> > nHitsFit>20. To the best of my knowledge, previous di-electron  
> > analyses utilizing Run18 Au-Au 27GeV data did not report such a  
> > significant mismatching discrepancy between data and embedded  
> > electrons. Could you kindly shed some light on the underlying  
> > reasons behind this discrepancy?
> >      I appreciate your great study on the track efficiency  
> > uncertainty and would be grateful for any insights you can provide  
> > to help me better understand the question.
> >
> > BW,
> > Yiding Han
> >
> > _______________________________________________
> > Star-tf-trkeff-l mailing list
> > Star-tf-trkeff-l AT lists.bnl.gov
> > https://urldefense.com/v3/__https://lists.bnl.gov/mailman/listinfo/star-tf-trkeff-l__;!!BuQPrrmRaQ!hhfhZsWQCHurYChjT15Xy9i3REkW3jV-y0OLxbJY6S8R15zcOYmMDBLdqswClEKJ_udpYq2IIodkTNxLpPNGHa0PZc4aIgAi98Bazry4zyg$