1. Status of straw-tube tracker V.Peshekhonov, D.Peshekhonov, A.Zinchenko JINR, Dubna V.Tikhomirov P.N.Lebedev Physics Institute, Moscow Presented on the 10 th CBM Collaboration Meeting, 25-28 September 2007, Dresden

2. Status of straw-tube tracker2 Straw tube detectors are widely used for accelerators and astrophysics experiments. Straw transition radiation detectors for the balloon investigation ATLAS TRT COMPASS straw tracker (straw length – up to 3.6 m) CBM straw TRD: in the angle range 50 mrad – 200 mrad hit rate per 1 cm.sq. of the straw – from 1.2 MHz to ~200 kHz (central AuAu collisions, CBM detector setup with RICH) To reduce the occupancy we propose to use segmented straws

3. Status of straw-tube tracker3 What the segmented straws are: Anode consists of some independent part of the anode wires (segments) Each segment has own HV and readout channel Length of segments may be from few cm up to ~70cm Readout: low-mass transmission line (TL) from segment to FEE length of the TL up to 2m; drop of the signals - ~3% for TL 1.5m long and ~30% for 2m long Energy resolution ~24% Signal amplitude non-uniformity between segments – below ~5% Two segmented straw prototypes have been built and tested in JINR (results have been presented to the CBM Collaboration on March-2007 Meeting)

4. Status of straw-tube tracker4 New prototype is now under development: It will be two-layer chamber with size 40 x 40 cm.sq. ~200 straws (4mm) Segmentation of straw: 4-5 segments with length from ~5 to 10 cm Should be ready for testing before spring-2008 Now: simulation and tests of transmission lines samples Problems: FEE, purchase of XC160 kapton film,…….

5. Status of straw-tube tracker5 MD M1 TOF M3 M2 Straw Tracker: Distance – 4 m, 6 m and 8 m for 1-st, 2-d and 3-d module Each module consist of three double layers: one for X coordinate measurement and two inclined at ±10 degrees (U and V) layers.

6. Status of straw-tube tracker6 To estimate the possibility of straw tube detectors using in the CBM muon detector setup, some Monte Carlo simulation has been performed. AuAu central collisions at 25 GeV “Compact” muon system and the system with additional absorbers have been considered Hit rate has been estimated Track reconstruction efficiency is evaluated Accuracy of straw tracker and TOF matching is estimated

7. Status of straw-tube tracker7 HIT RATE Here – for version of muon system with additional absorbers

8. Status of straw-tube tracker8 HIT RATE Slices of occupancy map at Y=0 and X=0 Maximum expected rate ~0.005 hits/cm 2 or ~2% occupancy for 10 cm straw with 4 mm diameter

9. Status of straw-tube tracker9 HIT RATE “Compact” version of muon system Version with additional absorbers

10. Status of straw-tube tracker10 < 0.0005 cm -2 0.001÷0.0005 cm -2 0.002÷0.001 cm -2 0.003÷0.002 cm -2 0.005÷0.003 cm -2 S: 270 x 220 m 2 (X,Y) S: 320 x 170 m 2 (X,Y) Segmented straws, both side readout Terminated straws, readout – from outside ends Ch.1 Ch.2 General straw tracker layout (1-st module; muon system with additional absorbers)

11. Status of straw-tube tracker11 Area, mradOccupancy, % Straw length, cm ± X± Y 1-st module (Ǿ 4mm) centre~100~75≤ 520÷ 25 periphery150÷50090÷500~5≤ 150 2-d moduleª (Ǿ 4mm) centre~90~70≤ 520÷ 25 peripheryªª150÷500170÷500~5≤ 150 GRANULARITY (configuration of the muon detector with additional absorbers) ª ) 3-d module - 6 mm in diameter straws can be used ªª ) Far periphery – long terminated straws ( 2÷4 m) can be used

12. Status of straw-tube tracker12 Rate: 0.05÷0.02 1/cm 2 Rate: 0.02÷0.005 1/cm 2 Rate: 0.005÷0.002 1/cm 2 Rate: < 0.002 1/cm 2 300 450 500 300 400 500 600 GRANULARITY (1-st module, compact version of muon system) Rate for the nearest area to the beam pipe Granularity and occupancy of the central area 1-1 1-2

13. Status of straw-tube tracker13 TRACKING EFFICIENCY Very simple tracking procedure: at least one hit in each of three tracker modules with the same track ID hit smearing with coordinate resolution – 200 µm on X, 200 µm/sin(10 o ) on Y straight line fit with χ 2 /NDF<10 Without multiple scattering With multiple scattering

14. Status of straw-tube tracker14 STRAW TRACKER – TOF MATCHING X: σ = 1.7 mm 14 Y: σ = 2.3 mm

15. Status of straw-tube tracker15 Conclusions The concept of straw tube tracker for the CBM experiment with muon detector system is observed Preliminary estimation of expected hit rate is obtained To reduce the occupancy of the tracker in the central region, the segmented straws can be used The preliminary estimation of tracker efficiency and coordinate matching with TOF is obtained The straw tube tracker can be used in the CBM experiment with muon system option