1 open charm simulations ( d +, d 0, + c ) sts geometry: 2maps +6strip (strasbourg geo) or 2m2h4s...
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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;
• Tracking (fast),
• Primary Vertex Reconstruction,
• Background study. Cuts optimization. S/BG ratios;
• D+ K-+ +; D0K-+ +- and +c pK-+ reconstruction;
• Summary & plans
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 :
1k central UrQMD ~2.8x1015 “triplets"
1k central UrQMD ~108 “triplets" after the cuts
D+K-+ + @ 25 AGeV
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Background study, tracks and vertices
cτD+ = 312 m
cτD0 = 123 m
cτ+ = 59 mc
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D+->K- ++ geometrical and topological
constrain
Cuts Bg loss (%) ε (D+) (%)
χ2geo < 3 σ 79.7 4.56
χ2topo < 2 σ 99.95 4.17
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M = 4.17 ·10-5
BR = 9.51 %
χ2 = 5 σEff = 5.47 %S/B 2σ = 1.33D+ = 20.7K per 1011central ev.
χ2 = 9 σ Eff = 2.5 %S/B 2σ = 42.4D+ = 10.8K
Cut optimization
S/BEfficiency
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D+ ->K-π+π+ all cuts 25AGeV
Eff = 1.84 %S/B 2σ = 1.47.1K D+ per 1011
central events
M = 4.17 ·10-5
BR = 9.51 %
2m2h4s2m6s
16K D+/1011 central ev.
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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 = 15.6D+=135Kper 1011
central ev.
M = 3.34 ·10-7
BR = 9.51 %Eff = 1.97 %S/B 2σ = 0.5D+=62per 1011 central ev.
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D0 ->K- - ++
topological constrain
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D0 ->K- - ++ (25 AGeV)
8.1109central events (300 central UrQMD)
3.2K D0 + 1K D0 per 1011 central events
Systematic!
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+ pK-+c
M<y=1> = 4.88·10-4 (A.Andronic)
BR = 5%
10.7(4.4) K c+ per 1011 central events
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Summary and plans
Fast (SIMDized) CA tracking works fine;D+K-+ +; +
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.
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