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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.