STS simulations: Layout, digitizers, performance Radoslaw Karabowicz GSI

2 STS detector Tracking detector: - low-mass detector - full azimuthal angle coverage - polar angle coverage: from 2.5° to 25° - high track density in the inner-most region - high collision rate - vertical magnetic field

3 STS design Silicon Tracking System: 8 stations (at 30, 35, 40, 50, 60, 75, 90 and 100cm away from the target) build from micro-strip double-sided silicon sensors (~300  m thick, 6cm wide, 2÷6 cm high) with narrow strips (60  m): vertically oriented on the front side and slightly rotated on the back side (by 15°) readout electronics located in the bottom and top parts outside of defined acceptance sensor readout ensured by low-mass microcables small sensors in the inner region to reduce the occupancy, outer regions covered by larger sensors, or even chained sensors, to minimize number of channels

4 n-XY TER FEB with 8 s Module Silicon sensor Cable n-XY TER FEB with 8 s Cable ~6cm 2-6cm

5 Overlaps vs gaps Example realizations of the station #3 at z=40cm gaps overlaps intermediate

6 Overlaps vs gaps – tracking efficiency Overlap geometryGap geometry overall efficiency 1 gap, 2 gaps 1 overlap, 2 overlaps Traversing overlaps does not change tracking efficiency Traversing gaps does change tracking efficiency Work done by the GSI Summer Student Maksym Zyzak from National University, Kyiv

7 Overlaps vs gaps – momentum resolution Overlap geometryGap geometry overall resolution 1 gap, 2 gaps 1 overlap, 2 overlaps Traversing overlaps does not change momentum resolution Traversing gaps does change momentum resolution Work done by the GSI Summer Student Maksym Zyzak from National University, Kyiv

8 Realistic detector response The hit is determined by the track position in the center of the silicon detector Ideal response: Physical processes: -charge smearing -collection efficiency -Lorentz angle due to magnetic field Realistic response:

9 Realistic response - models w/2p/2transverse tracks LHC CBM: |B| = 1T Holes:  = 1.5°,  x = 8  m Electrons:  = 7.5°,  x = 40  m

10 Hit density 0-35 hits/cm hits/cm %0-11% Strip occupancy Ideal Realistic

11 = 98.6% % = 91.9% 54-99% strips Cluster length Hit finding efficiency Ideal Realistic 1 strip from definition of ideal response

12 Realistic response - results Ideal response:Realistic response:

13 Ideal

14 Realistic

15 Detector X-ray x[cm] y[cm] - silicon detector thickness: currently 0.3% x 0 (300  m) - station with cables and support structure: up to 1% x 0 -total vertex/tracking system: < 15% x 0 x/x 0 Radiation length thickness station 5 (z = 60cm) STS detector 6 million 10 GeV/c pions in Geant

16 Summary (more) Realistic geometry that matches recent discussions on construction possibilities available (thanks to Sergey Belogurov) The geometry has been tested by Irina Rostovtseva, Maksym Zyzak and me More discussion with engineers needed The realistic digitizer and cluster finder ready Detector response study essential

17 Deltas – expected behavior Station e- / beam particle Station e- / beam particle Station e- / beam particle

18 Deltas – surprising feature HEAR MORE ABOUT THIS FROM YOURI’s PRESENTATION Station e- / beam particle Station e- / beam particle 0.05 – 0.1 Station e- / beam particle 0.03 – 0.12

19 Delta electrons study by Iouri Vassiliev

20 Left-right asymmetry

21 Hit density 0-35 hits/cm hits/cm %0-11% Strip occupancy Ideal Realistic

22 = 98.6% % = 91.9% 54-99% strips Cluster length Hit finding efficiency Ideal Realistic 1 strip from definition of ideal response

STS test beam early results Radoslaw Karabowicz GSI

24 Silicon sensor Test beam setup Silicon sensor n-XY TER FEB with n-XY TER FEB with

25 First signals from beta source 90 Sr Time in epochs yield source

26 First signals from beta source 90 Sr ADC channels yield Noise Beta source

27 Beam in Cave C!!! Time in epochs yield Playing with threshold Screams: Do we have beam??

28 Beam bunches time [a.u.]. Hits Beam counter Yield

29 Channel number correlations Horizontal strips Vertical strips channel number on detector 1 on detector 2 channel number Vertical strips Horizontal strips on detector 1 on detector 2

30 Time correlations beam detector time – hit time [a.u.] channel number on roc1 (n side)

31 Time correlations Run020 Run015

32 Summary LOTS TO DO!!! to analyze and understand the data to prepare for next beam time Conclusions