1. D 0  K -,  + reconstruction with CBM STS detector I.Vassiliev (GSI) CBM collaboration meeting 06-Oct-04 Simulation tools (cbmroot) & geometry Signal and Background simulation Tracking & Vertexing Variables and cuts. Cuts optimisation Trigger feasibility study Outline

2. Simulation tools (cbmroot) & geometry SBM framework last edition (3 first Sts in vacuum); "standard" and 700  m thickness STS geometry; 7 stations at 5, 10, 20, 40, 60, 80, 100 cm; stations at 5 and10 cm - 100  m others 200  m single Au target 500  m,  = 10  m (double) hit displacement (Gaussian smearing) at CbmStsDoubleHitProducer.cxx GEANT3, UrQmd (25 Gev) and D 0  K -,  + (by V.Friese) generators; no Magnetic Field, but dP/P = 1%

3. Signal and Background simulation Signal - 10 5 events D 0  K -,  + Background – 10 4 UrQmd events mixed 10 3 events IM(GeV/c 2 )

4. Tracking & Vertexing Tracking & Vertexing developed by I.Kisel: CbmITrack, CbmStsmctracks2rsegs,CbmStsRefit CbmStsPerformance; CbmStsPrimaryVertex, StsSecondaryVertex    CbmStsAnalysis: Event Topology (MC), RSEGs analysis K (K 0 S ;  0 ;  - ;  - ; D 0 ) K0SK0S 00  - - IM (GeV/c 2 )

5. Tracking & Vertexing Z v (cm)  = 57  m MC Z v – RECO Z v (cm)

6. Variables and cuts. Cuts optimisation Impact Parameter (IP > 80  m); Z-vertex for D 0  K -,  + (Z 2 > 250  m); P D 0 pointing to the Primary Vertex; P t K -,  + > 0.5 (0.45) GeV; P K -,  + >1.5 GeV;  2 < 5 for the Secondary vertex (cm)

7. Variables and cuts. Cuts optimisation P t K -,  + and P K -,  + cuts optimisation (GeV) Signal Background

8. Variables and cuts. Cuts optimisation P D 0 pointing to the Primary Vertex cut optimisation SignalBackground  (cm)

9. Trigger feasibility study Trigger feasibility study 11 events Background 10 4 events IP,P,P t VzVz D 0 pont;  2 all cuts –No Particle ID –realistic tracking and vertexing –~400 reduction factor –~10-3 D0 per event with –BR~3.65% –~900 charged hadrons per event IM (GeV/c 2 )

10. Trigger feasibility study Trigger feasibility study IM (GeV/c 2 ) MC Reco IP,P,P t cuts Reco all cuts 10 3 mix events: Urqmd+D 0  K -,  + IP,P,P t cuts cut signal  IP K -  + 28 % Z-vertex54 % P D 0 pointing 99 % Pt K-,+Pt K-,+ 61 % P K -,  + 58 % all cuts7.5 % Trig RF~600 S/B ratio~0.8

11. Outline Outline MC simulation shows feasibility to measure D 0  K - +  + with CBM STS "standard" detector geometry Developed cuts allows to create Trigger model with RF ~ 600 and S/B ratio ~ 0.8 (more with PID) 700  m thickness STS stations study is going on Magnetic Field