1. Updates on vertex detector
P. Staszel and Yasir Ali
Jagiellonian University

2. Outline 1. Outer dimensions 2. New layout based on MIMOSA -26
VTPC2
1. Outer dimensions
2. New layout based on MIMOSA -26
3. Micropatern Gaseous Detectors (MicroMegas)
4. Fluence study
5. MIMOSA-26 test (?)

3. NA61/SHINE detector – top view
VTPC2
Vertex Detector (VD)

4. Outer VDS's dimensions
VTPC2
We generated 100 k events containing only signal: 1 D0 meson decaying in to π+K pair. The rapidity and mT distributions of D0s are the same as these predicted by AMPT for Pb+Pb at 158AGeV.
The calculations were performed with relatively large stations. This allowed us to set fiducial cut on each station.
The idea for the cut was to keep the most occupied area within the cut and remove (outer) areas with low occupancy, so finally we obtain high signal acceptance using relatively small stations.

5. Signal track distribution at 158 AGeV in VDS1
VTPC2
2x4 cm2
VTPC1
The figure shows hits (x,y) distribution generated by signal tracks is Vds1. The dashed boxes represent the cuts. We found that ~99.5% of signal tracks is localized within the box 2x4cm2.
As you can see, to cover the remaining 0.5% we would need to extend the cut in the x direction for almost factor of 2.

6. Signal track distribution at 158 AGeV in VDS2
VTPC2
4x8 cm2
VTPC1
For stations Vds2-Vds4 we just extend size of the boxes in proportion to their distance from the target. So we got dimensions: 4x8 cm2, 6x12 cm2 and 8x16 cm2 for Vds2, Vds3 and Vds4, respectively. The signal lost is kept below 1 % for each station.
For Pb+Pb at 40 AGeV the signal lost is on the level of 4% for the same cuts.

7. Signal track distribution at 158 AGeV in VDS3 and VDS4
VTPC2
6x12 cm2
VTPC1
8x16 cm2

8. Charged particles produced in Pb+Pb 0-10% central interactions
VTPC2
We can expect very high hit occupancy on the level of 5 hit/mm2/event in the most inner part of the vertex detector.
→ it suggests that silicon pixel sensors would provide a good solution for us.
VTPC1 1.

9. MIMOSA-26
The following conceptual drawings are based on MIMOSA-26 chip hosting sensitive area of about 1.06 x 2.12 cm2 with the pixel pitch equal 18.4 μm (~663.5k pixels/chip):
VTPC2
These pads are for testing purpose and can be removed
VTPC1
The readout speed of the whole fame in ~100 μs (10 kHz), zero suppression circuit.
The chips are available. We can just buy them from IPHC, Strasbourg (we know also the estimated price per chip)

10. Preliminary drawing of the 1-st station
VTPC2
VTPC1
Drawn blue boxes have dimensions of the sensitive area of MOMOSA-26 sensor (~1x2cm2)
Size of the dashed box is ~ 2x4 cm2. We have to cover this area to loose less than 0.5% / 3% of signal particles for 158 / 40 GeV

11. Preliminary drawing of the 2-nd station
VTPC2
Vds2
VTPC1
MOMOSA-26 sensors (~1x2cm2)
Size of the dashed box is ~ 4x8 cm2 – same meaning as for Vds1
Full coverage with MOMOSA-26 requires 20 sensors

12. Preliminary drawing of the 3-rd station
VTPC2
MM_A
VTPC1
MM_B
Inner ring – same layout as Vds1 based on MIMOSA-26
Outer region covered with thin MicroMegas:
MM_A with dimension 2.3x4.7 cm2
MM_B with dimension 4.7x6.3 cm2
Size of the outer dashed box is 6x12 cm2

13. Preliminary drawing of the 4-th station
VTPC2
MM_B
MM_B
VTPC1
8cm
16cm
Inner ring – same layout as Vds1 based on MIMOSA-26
Outer region covered with thin MicroMegas 6 MM_B stations (4.7x6.3 cm2)
→ only 2 types of MicroMegas detectors have to be developed
→ eventually MM_A in Vds3 can be replaced with MM_B → only one type of MM

14. Preliminary drawing of the complete VD
VTPC2

15. VTPC2
VTPC1

16. VTPC2
VTPC1

17. Overview of talk in conference in Utrecht
→ In 50M events (1 month run of NA61 Experiment)
Yield for the open charm at the 158 AGeV K
Yield for the open charm at the 40 AGeV
People appreciated the idea of using MIMOSA chips as solution for dedicated vertex detector
Conclusion of the discussion with the people from GSI was that our solution is feasible and very much optimistic specially at the SPS intensities where radiation hardness is not a problem.

18. Performance of MIMOSA-26 → Beam Tests
Temperature: C
Readout Time: µs
Pitch size : µm
Irradiated with to
fluence = 3 X neq/cm2
For disc. Threshold= 5 mV:
detection efficiency ~ 99.8%,
fake hits < 10-4
resolution ~ 3.5 µm
(M.Winter, CBM Progress Report 2010)

19. Displacement Damage Function
Bulk damage exclusively depends upon non ionizing energy lose (NIEL). This is described by the displacement damage functions D(E)
Hadronic interactions:
flux = (105 * 0.005) event/s * 1.6 particles/mm2/event =
800 Hz/mm2
Electromagnetic interactions (δ-electrons):
flux = 105 event/s * particles/mm2/event =
4000 Hz/mm2
0.62
0.62/5
(A. Vasilescu, ROSE Internal Note ROSE/TN/97-2 (1997))

20. Fluence in NA61/SHINE Factor of 40 below the tested range
Φeq 1MeV = ϰΦ ϰ - radiation hardness parameter
ϰ = 0.62/5 for electrons
ϰ = for particles from hadronic interactions
Fluence for electrons in 1 month (upper limit):
Φeq 1MeV = 4 x 105 /cm2/sec X 0.62/5 X sec = 1.28 X 1011 neq/ cm2
For Spill of the beam (20%) = 2.6 X 1010 neq/cm2
Fluence for charged particles for 1 month (upper limit):
= 8 x 104 /cm2/sec X 0.62 X sec = 1.28 X 1011 neq/ cm2
For Spill of the beam (20%) = 2.6 X 1010 neq/cm2
Factor of 40 below the tested range

21. Data rates assuming full pixel coverage
Input:
max 1140 bytes/frame, fake hit probability = 10-4
max ~500 hits/frame (info from Michael Deveaux)
Vds1 consists of 6 M-26 chips:
max: 6 frames x 1140 bytes/frame x 10kHz = 7 Mbytes/s
exp: hits/station x 2.25 bytes/hit x 10 kHz = Mbytes/s
Vds2 consists of 20 M-26 chips:
max: 20 frames x 1140 bytes/frame x 10kHz = 23 Mbytes/s
exp: hits/station x 2.25 bytes/hit x 10 kHz = Mbytes/s
Vds3 consists of 36 M-26 chips:
max: 36 frames x 1140 bytes/frame x 10kHz = 41 Mbytes/s
exp: hits/station x 2.25 bytes/hit x 10 kHz = Mbytes/s
Vds4 consists of 64 M-26 chips:
max: 64 frames x 1140 bytes/frame x 10kHz = 73 Mbytes/s
exp: hits/station x 2.25 bytes/hit x 10 kHz = 12 Mbytes/s

22. Backup Slides

23. D0→ K+ π- , 200k 0-10% cent. Pb+Pb at 158 AGeV
VTPC2
S/B=13
For 50M events:
SNR = 193
40k D0+D0bar
S/B=15
For 50M events:
SNR = 178
34k D0+D0bar
VTPC1
S/B=6.6
For 50M events:
SNR = 163
31k D0+D0bar
S/B=9.6
For 50M events:
SNR = 155
26k D0+D0bar