1 Open charm simulations ( D +, D 0,  + c ) Sts geometry: 2MAPS +6strip (Strasbourg geo) or 2M2H4S (D+ and D - at 25AGeV); TOOLS: signal (D +  K -  +  + ;  + c  pK -  + and D 0  K -  +  +  - ), and background (central UrQMD) simulation; 15,25,35 AGeV; Pythia signal generator by D.Bertini; Tracking (fast), Primary Vertex Reconstruction, Background study. Cuts optimization. S/BG ratios; D +  K -  +  + ; D 0  K -  +  +  - and  + c  pK -  + reconstruction; Summary & plans I.Vassiliev, S.Gorbunov, I. Kisel, S. Seddiki and I. Sevastiuk CBM Collaboration Meeting 26-Sep-07

2 CBM (light) setup Sts + TOF 8 stations (10,20,30,50,62.5,75,87.5,100 cm) 2 first in vacuum Topology: stations 1,2 – MAPS, 3-8 – Strips or (3,4Hybrids) "MAPS" (150  m), first two station with 10x10  m cell size "Strip"-detectors (400  m), 50  m strip-pitch, ½ strip length; Realistic hit producers sts_digi_new_standard-3.par

3 Tracking in STS Algorithm: “Cellular Automaton + Kalman Filter” by I.Kisel Momentum resolution: ~ 1% 697 rec. tracks ~ 1% ghost tracks central collision Au beam, 25 AGeV, on Au target efficiency [%] momentum [GeV/c] MAPS + strips: ± 0.09 (D + ) MAPS +strips: ± 0.14 Tracking efficiency: primary tracks (signal) all rec. tracks 78 ms on Pentium 4

4 primary vertex reconstruction pv sv K-K- ++ 5.7 µm -- ++ z mc -z reco (cm)

5 D +  K -  +  + ;  + c  pK -  + and D 0  K -  +  +  - z-vertex reconstruction D+K-+ +D+K-+ + old p ++ K-K- sv ++ c pv new

6 Strategy: background suppression keeping maximum of efficiency single track parameters based cuts:  χ 2 prim on the impact parameter (lower value)   IP impact parameter cut (upper value) 1mm  track momentum cut p > 1.0 GeV/c  track transverse momentum p t > 0.25 GeV/c multiple track (particle) parameters based cuts:  χ 2 GEO geometrical constrained fit 3.0   χ 2 TOPO topological constrained fit 2.0 

7 Background study; tracks xz y zRzR xRxR central UrQMD

8 Cut optimization D +  K -  +  25 AGeV χ 2 prim on the impact parameter (lower value) S/  B

9 Cut optimization CutsBg track loss (%)ε (D + tracks) (%) P >1 (GeV/c) P t > 0.25 (GeV/c) χ 2 > 6.5 (  P + P t P + χ P + P t + χ ( 2368 tracks)35.9 P + P t + χ 2 +Ip99.67(1750 tracks)34 χ 2 prim > 6.5  p t > 0.25 GeV/c, p > 1 GeV/c, Ip < 1 mm : 1k central UrQMD  ~2.8x10 15 “triplets" 1k central UrQMD  ~10 8 “triplets" after the cuts D +  K -  +  25 AGeV

10 Background study, tracks and vertices cτ D + = 312  m cτ D 0 = 123  m cτ  + = 59  m c

11 D + ->K -  +  + geometrical and topological constrain CutsBg loss (%)ε (D + ) (%) χ 2 geo < 3 σ χ 2 topo < 2 σ

12 M = 4.17 ·10 -5 BR = 9.51 % χ 2 = 5 σ Eff = 5.47 % S/B 2σ = 1.33 D + = 20.7K per central ev. χ 2 = 9 σ Eff = 2.5 % S/B 2σ = 42.4 D+ = 10.8K Cut optimization S/B Efficiency

13 D + ->K - π + π + all cuts 25AGeV Eff = 1.84 % S/B 2σ = K D + per central events M = 4.17 ·10 -5 BR = 9.51 % 2m2h4s 2m6s 16K D + /10 11 central ev.

14 D + ->K - π + π + at 35 and 15 AGeV 35 AGeV 15 AGeV M = 2.67 ·10 -4 BR = 9.51 % Eff = 5.64 % S/B 2σ = 15.6 D + =135K per central ev. M = 3.34 ·10 -7 BR = 9.51 % Eff = 1.97 % S/B 2σ = 0.5 D + =62 per central ev.

15 D 0 ->K -  -  +  + topological constrain

16 D 0 ->K -  -  +  + (25 AGeV) 8.1  10 9 central events (300 central UrQMD) 3.2K D 0 + 1K D 0 per central events Systematic!

17  +  pK -  + c M = 4.88·10 -4 (A.Andronic) BR = 5% 10.7(4.4) K  c + per central events

18 Summary and plans Fast (SIMDized) CA tracking works fine; D +  K -  +  + ;  + c  pK -  + and D 0  K -  +  +  - looks very promising for the CBM experiment: collection rates about 16K D +, 32K D -, 3.2K D 0, 1KD 0, 4.4K  + c per at 25 AGeV with excellent S/B ratio; next steps: More realistic Sts (cables and support structures) TOF particle ID including K -(+) identification; D s detection possibility study; Open charm common trigger feasibility study.