At the last HFTsoft meeting, it has been shown than increasing the precision of the LADR volume (PIXL geometry) removes the slope seen for the
residuals (hit position - track projection) in the v direction ( v = longitudinal to Z, relative to the sensor).
Increasing the precision gives yLOCAL close to 0 (~1micron) whereas it was previously ~ 8 microns.

1) simu setup
The simulation input had he following setup :

 detp geom y2013
 gexec $STAR_LIB/xgeometry.so
 gclose all
 user/vsig 0.01 .1
 gfile o test_default_precision.fz
 aguser/gkine 200 8 0.1 5.0 -1.0 +1.0 0 6.28
 trig 100

Especially Zvertex is closed to 0.

Vertex positions are shown below.

One question asked was to see the residuals plots for vertices [relatively] displaced from 0

2) new setup

 detp geom y2013
 gexec $STAR_LIB/xgeometry.so
 gclose all
 user/vxyz 0 0 1.5
 user/vsig .01 .1
 gfile o vertex_shift_1cm_test_default_precision.fz
 aguser/gkine 200 8 0.1 5.0 -1.0 +1.0 0 6.28
 trig 100

1. vertexZ is set at 1.5 cm and smeared by .1 cm
2. vertex XY is set at 0 and smeared by .01 cm

3) Results
The results are below. The plot shows :

• left   : residuals in u direction (transverse to beam) vs Zglobal (of pixel hits)
• right : residuals in v direction (transverse to beam) vs Zglobal (of pixel hits)

This plot has to be compared with the same plots for which vertexZ was at 0 (shown below)


4) comments

1. The slope is still present for the residuals in v direction 
2. the split appears now for Z (hits in PXL) ~ Zvertex (1.5 cm)