• ~6k events AuAu run14, run 15160040
• cuts : pT>1 & # tracks <500 & (pxl + ist) >2

1) Results with survey tables : dU , dV
correction to be applied :

1. dY = -750 microns
2. dZ = +550 microns

2) Results after correction : dU , dV

3) comparison plots : dU, dV

4) Residuals vs ladder vs Pt cut
data sample : 20.5k events , AuAu @ 200 GeV
base cut : # tracks <500 && (pxl+ist)>2
dU : here 
dV : here

5) Residuals vs wafer (within a ladder)
data sample : 54 events , AuAu @ 200 GeV
base cut : # tracks <500 && (pxl+ist)>2 && Pt>1.5
(before corrections)

dU : here
left panel : each point is the mean of a gaus+pol1 fit, done wafer by wafer
The red line is a pol1 fit, where wafer 1,2 and wafer 15,16 are excluded
right panel : each point is the result of FitSlicesY() method from ROOT (which may be biased sometimes)
Color histos are the residuals themselves

dV, Fit : here

dU, dV , Correlation : here 
Each slide (= 1 wafer) shows the residual distribution and the 2D correlation between the hit position and the track projection on the SSD wafer

6) Occupancy (hardware efficiency)
To define the occupancy, we looked at the distributions od hits in local coordinates. The goal is to know the occupancy at the chip level.
Within the same cut (# tracks <500 && (pxl+ist)>2 && Pt>1.0), we plot the local coordinates of hits per ladder :
here

The occupancy is define as a fraction of the number of total chips. Therefore a full wafer will have an occupancy of 1 (explanation / drawings here) 

The distribution of occupancy is here ; the breadown per wafer/ladder is here 

If we exclude from the calculation the 1st and the last wafer of each ladder (because they do not see any tracks anyway), the average number for hardware efficiency is 67%
If we include those wafers, the efficiency drops to 60% (but it's not fair)
It appears that the SSD software clean-up cuts reduce the efficiency another 10% ( correlation of SSD to IST hits to about 1:2)

Note : the 2D plots are sensibly the same within the cuts (# tracks <500 && (pxl+ist)>2 && Pt>1.5) and the cuts (# tracks <500 && (pxl+ist)>2 && Pt>1.0 &&|ZVertex|<10)

7) Estimation hit errors

Rerun run14 data without SSD in tracking and look at the residuals in r/phi
Files from day 160 analyzed : ~71k events before cuts, ~47k after |zvertex| <10 cm && |tof-TPC|<5cm : plot
Tracks selection : e.fMatchHits.pT>.5 && (e.fMatchHits.pxlFit+e.fMatchHits.istFit)>2

dU vs Pt : plot
dU vs 1/Pt : plot (same as above but linear fit)

However ladder 2 and 3 seem to show a residual mis-alignment of the order of 200-300 microns (plot) that bias the residuals (plot)

dU vs Pt (w/o ladder 2 and 3) : plot
dU vs 1/Pt (w/o ladder 2 and 3) : plot
The linear fit suggests that at infinite momentum, the residuals is ~38microns

8) Estimation hit errors (pass2)
run14 data with SST in reco (no tracking), SL15k :1.3M events ; 850k events after |zvertex|<10 && |zvertex(TPC) - zvertex(VPD)|<3  : plot here
tracks cut : pt>1, (pxl+ist)>2
Residuals (track projection - hit position) are fitted as :

• dU vs 1/Pt (10 bins), per wafer, f = sqrt[a*a + (b/pt)*(b/pt)] [example 1, example 2]
• dV vs 1/P (10 bins), per wafer, f = pol1 [example 1, example 2]

mean of dU over good wafers : ~45 microns [detail 1, detail 2]
mean of dV over good wafers : ~950 microns [detail 1, detail 2]