1. Primary Vertex with Pixel and Stripixel
30th Jun 2011
Maki Kurosawa
Yasuyuki Akiba
Rachid Nouicer

2. Previous Algorithm for Determination of Cluster Combination
Previous algorithm : determine search window starting from bbcz.
edge y
edge
First Selection
Outer layer
1st search window
Inner layer Z
bbcz
Second Selection
Previous algorithm y
2nd search window
Search region was changed.
Outer layer
Inner layer
cluster[0]
bbcz Z
Dzbbc = ± 5 mm

3. New Algorithm for Determination of Cluster Combination
Previous algorithm : determine search window starting from bbcz.
Updated algorithm : determine search window starting form each cluster on outer layer.
Cluster search window on inner layer y
cluster[1]
Outer layer
Inner layer
search window
bbcz Z
Dzbbc
New algorithm

4. SvxClusterContainer::find_clusters
100 pitch (100 x dz) z0
cls0
cls1
cls3
Inner layer
cls2
-dz
+dz
The “find_clusters” searchs clusters within z0 ± dz
Each layer has 100 pitch along z direction.
Dz is dependent on the ration of “a” and “b” in bottom figure.
For the most nearest layers, a = 13.14, b = Then Dzbbc is calculated to be 27 mm.
dz = 22 (cm) / 100 = 2.2 (mm) for pixel
dz = 39 (cm) / 100 = 3.9 (mm) for stripixel y
cluster[1]
Outer layer b
search window
Inner layer a
bbcz Z
Dzbbc = ± 4.5 ~ 27 mm

5. Short Summary
Calculation time is almost same for previous and new algorithm.
Calculation time is 300 sec / 5,000 events with both algorithm.
Especially, for the strip layers, Dz is changed ladder by ladder.
To improve the resolution of primary z-vertex, some modification of code is needed.
Previous algorithm will be used.

6. Number of Track vs BBC Charge
Pixel
Stripixel

7. Number of Track vs BBC Charge with Cut of abs(bbcz) < 5 cm
Pixel
Stripixel
abs(bbcz) < 5 cm
abs(bbcz) < 5 cm

8. Two Ways for Determination of Primary Z-Vertex
Peak position
Mean Position :
Peak Position ± 10 bin
Bin width is 500 um and 1000 um for pixel and stripixel, respectively.
Each bin width corresponds to each pixel size.
Peak position :
hist->GetMaximamBin()

9. Primary Z-Vertex vs BBC Z (Peak Position)

10. Primary Z-Vertex vs BBC Z (Mean Position)

11. Deference between Primary Z-Vertex and BBC Z
Peak position
Mean position
bbcz-pxlz (cm) bbcz-strpxlz (cm)
bbcz-pxlz (cm) bbcz-strpxlz (cm)
Resolution of calculated primary z-vertex was improved.

12. New Class
Code : SvxSeedZVertexFinder.C
Class : SvxSeedZVertexFinder()
Determination of temporary primary z-vertex by using cluster combination for pixel/stripixel layers.
Temporary primary z-vertex will be used as a seed to determine primary vertex.
Calculated z-vertex will be stored in VtxOut.
Summary
Previous algorithm will be used in calculation for a primary z-vertex.
Mean value was used to determine the primary z-vertex. Difference between the primary z-vertex and the bbc z-vertex was reduced for pixel.
Start to create new class for temporary z-vertex.

13. Pixel Detector Status

14. Sense Voltage Measurements on 29th Jun
Sense voltage of GND and VDD for all ladders were measured on 29th Jun.
Data will be summarized and used for QA test at Chemistry as reference.
SPIRO ID of B1-L0-S could not be taken with OPS.
During physics run, the data packet from this ladder had been always bad.
This is because transfer of DAC values is always failed.
Some inspection will be needed for this SPIRO module.

15. Backup Slides

16. Beam Profile (Intersection Point with X-Z and Y-Z Plane)
Pixel
Stripixel

17. Simple Tracking Third Selection cluster Cluster combination selection
abs(Df) < (radian) Df
(0, 0, 0)
Z vertex ::
Intersection point between simple track and a plane perpendicular to phi angle component of simple track.