During the checking of D0 and D0bar spectra. we find an interesting performance about the single track  HFT matching ratio do have some charge dependence.

The final D0 D0bar efficiency looks like doesnot suffer this effect, since the pion and kaon HFT matching ratio is very similar. And D0 decay to pi+K- and D0bar to pi-K+. So The final eff doesn't not effect from this. 

The positive particle looks like have higher matching ratio compare to negative particle at some specific range (pt/eta/phi/vz).

We do compared the charge dependence for HFT Matching ratio, the plots can be found in the attached documents. 

https://drupal.star.bnl.gov/STAR/system/files/HFT_Ratio_VsPt_Centrality_Eta_Phi_Vz_Zdcx_170813_combineCharge.pdf

We suspect this is due to the geometry effect. such as the HFT edge effect or dead sensors. Two different charge tracks, even though they have the same eta/vz/phi value at the original point. But due to charge difference, they do have different moving directions and hit on different sensors.

We also select high pt tracks with a narrow eta range |eta|<0.1, and check the Vz and phi dependence. The one can be used to study the HFT dead sensors.
The plots can be found in the attached file.

https://drupal.star.bnl.gov/STAR/system/files/HFTRatio_highpT.pdf

As clearly see, there are some dead and "inefficiency" sensors. And around those sensors, the HFT matching ratio have charge dependence.
Especially for phi around -0.91 to 0.338, those two sectors looks like have more non-uniform "dead" or "inefficiency" sectors 


If you compere the positive and negative hight pt tracks, the Vz vs Phi distribution looks similar, but some small inefficiency structure was shifted to lower phi range for positive track. This is reasonable. The Higher Matching ratio for positive particle compared to negative particles, could be due to the HFT structure, the HFT was rotated align clockwise. Which could make positive particle have more change hit the sensor perpendicular. (just some naive thought) If we have reversed Magnetic, this suspicion can be checked.