TargetTarget & VDS Hera-B

One of the most important parts in the data analysis is Tracking and Vertexing (now). The Vertex Detector is a central after Target (of course!) smile component in the HERA-B detector. It has to provide the track coordinates for reconstruction the J/psy decay vertices and the impact parameters of all tagging particles. It provides a unique possibility to "see" beam-target interaction points (vertices)

8 targets

Since two: HOLMES by Michael Schmelling

and CATS by charming Silvia Masciocchi

and not charming smile  Ivan (The Terrible) Kisel
tracking programs are available, both of them have been used for the target spot reconstruction.

 Several problems have been solved and some interesting effects were observed in the 99a-00 Run period. The current version of CATS allows significantly improuve target alignment procedure, using both tracks and vertex information.

Target alignment

Using multiwire runs the Beam Position Monitor (BPM) data have been calibrated:
target spot

X(VDS) = X(bpm) - 1.083 (mm)*
Y(VDS) = Y(bpm) + 0.322 (mm)*


*depends of RUN#
 

Target alignment procedure is based on comparison of actual target position (measured by an optical and mechanical devices) and position of vertices reconstructed in the VDS co-ordinate system. X-projection for the Inner  wire (as well as the Y-projection for the Above and Below wires) reconstructed in the VDS is shown below:
 


Typical X(Y) resolution is about 55 -65 mkm.

Z-projections of vertices for the  wires have resolution in the range of 440-630 mkm :


 
 
 
Target
Radial resolution (mkm)
Longitudinal resolution (mkm)
Systematic shift (mm)
Z-size (mkm) Z-pozition (cm)
Above 1
62 +/-  10
460
0.14
500
-1.42
Below 1
57 +/- 8
440
0.34
500
-1.50
Inner 1
58 +/- 9
460
0.01
500
-0.99
Outer 1
64 +/- 10
470
0.20
500
-1.18
Above 2
67 +/- 10
600
0.97
500
-5.45
Below 2
55 +/- 8
540
0.26
500
-5.67
Inner 2
69 +/- 8
630
0.71
1000
-4.83
Outer 2
65 +/- 13
540
0.35
50
-5.06

 

I*** This site is under construction, sorry for the inconveniences ***


Youri Vassiliev

Last modified: Tue Sep 18 16:02:57 MEST 2001