1. Retrieve stereo hits in Hough tracking

2. Tracking efficiency status
(1)
(2)
Figure(1) efficiency : events found at least 1 track/all events
Figure(2) efficiency : events found at least 1 track past track quality/all events
Track quality cut: |Δpt|<10MeV |Δp |<15MeV |Δvr|<1cm |Δvz|<10cm
When |cos|>0.8 , efficiency drop fast

3. Method to get back lost hit when large |cos|
Use 2d circle information after 2d fit
Calculate distance of every stereo hit position to the 2d circle(mid point position)
Use drift information to help to reject noise hit
Retrieve lost stereo hits inside a certain distance cut and reject noise hits

4. Some Explain
Aim to deal with stereo hits when |cos|>0.8 to adjust the bin cut in Hough Map
When |cos|>0.8 peak width get larger ,so lost more stereo hits
Cause this is used to retrieve lost hits , use a strict condition to reject noise hits
Sensitive to multi turn tracks , so want it only for |cos|>0.8

5. Layer <8 (drift distance cut)
Noise stereo hit drift distance
signal stereo hit drift distance
(cm)
(cm)
When cut at drift distance 0.6 , cut more noise stereo hits

6. Layer<8 (distance to circle)
signal stereo hit distance to circle
noise stereo hit distance to circle
(cm)
(cm)
Next try different cut to get more signal hits and reject noise hits

7. Layer<8 (distance to circle cut)
proportion of signal hit/all hits vary with different cut
Number of signal hits vary with different cut
rate
Signal hits
(cm)
(cm)
We want high signal rate and more signal hits
use cut distance=3.0 cm ,means when distance of a stereo hits to circle<3.0cm , retrieve the hit

8. Layer>=8(drift distance cut)
Noise stereo hit drift distance
signal stereo hit drift distance
(cm)
(cm)
When cut at drift distance 0.8 , cut more noise stereo hits

9. Layer>=8 (distance to circle)
signal stereo hit distance to circle
noise stereo hit distance to circle
(cm)
(cm)
Next try different cut to get more signal hits and reject noise hits

10. Layer<8 (distance to circle cut)
proportion of signal hit/all hits vary with different cut
Number of signal hits vary with different cut
rate
Signal hits
(cm)
(cm)
use cut distance=4.0 cm

11. Tracking efficiency status
before get back lost hits
events found at least 1 track/all events
Add quality cut
After get back lost hits
events found at least 1 track/all events
Add quality cut
Track quality cut: |Δpt|<10MeV |Δp |<15MeV |Δvr|<1cm |Δvz|<10cm
Tracking efficiency upgrate ~15% when |cos|>0.8
Influence on multi turn tracks when |cos| is small

12. signal hits distribution on track
Hit number on track
|Cos|>0.8
signal hits distribution on track
After get back lost hits
before get back lost hits
After this method , signal hits number on track increase
Noise ghost track decline