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
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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 -
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Open charm simulations (D+, D0, +c)
• Sts geometry: 2MAPS +6strip (Strasbourg geo) or 2M2H4S (D+ and D- at 25AGeV);
• TOOLS: signal (D+K-+ +; +c pK-+ and D0K-+ +- ) , and
background (central UrQMD) simulation; 15,25,35 AGeV; Pythia signal generator by D.Bertini;
I.Vassiliev, S.Gorbunov, I. Kisel, S. Seddiki and I. SevastiukCBM Collaboration Meeting 26-Sep-07
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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
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Tracking in STSTracking 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
effi
cien
cy [
%]
momentum [GeV/c]
MAPS + strips: 96.23 ± 0.09 (D+)
MAPS +strips: 92.87 ± 0.14
Tracking efficiency: primary tracks (signal) all rec. tracks
78 ms on Pentium 4
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primary vertex reconstruction
pvsv K-
+
5.7 µm
-+
zmc-zreco (cm)
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D+K-+ +; +c pK-+
and D0K-+ +- z-vertex reconstruction
D+K-+ +
old p+
K-sv
+c
pv
new
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Strategy: background suppression keeping maximum of efficiency
single track parameters based cuts: χ2
prim on the impact parameter (lower value) 4.5-6.5 IP impact parameter cut (upper value) 1mm track momentum cut p > 1.0 GeV/c track transverse momentum pt > 0.25 GeV/c
multiple track (particle) parameters based cuts: χ2
GEO geometrical constrained fit 3.0 χ2
TOPO topological constrained fit 2.0
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Background study; tracks
x z
y
zRxR
central UrQMD
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Cut optimization
D+K-+ + @ 25 AGeV
χ2prim
on the impact parameter (lower value)
S/B
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Cut optimization
Cuts Bg track loss (%) ε (D+ tracks) (%)
P >1 (GeV/c) 37.7 94
Pt > 0.25 (GeV/c) 55.1 86.6
χ2 > 6.5 ( 99.0 38.6
P + Pt 57.6 85.1
P + χ2 99.24 37.9
P + Pt + χ2 99.55( 2368 tracks) 35.9
P + Pt + χ2+Ip 99.67(1750 tracks) 34
χ2prim > 6.5 pt > 0.25 GeV/c, p > 1 GeV/c, Ip < 1 mm :
c pK-+ and D0K-+ +- looks very promising for the CBM experiment: collection rates about16K D+, 32K D-, 3.2K D0, 1KD0, 4.4K+
c per 1011 at 25 AGeV with excellent S/B ratio;next steps:More realistic Sts (cables and support structures)TOF particle ID including K-(+) identification;Ds detection possibility study;Open charm common trigger feasibility study.