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D0 K-,+ reconstructionwith 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
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 D0 K-,+ (by V.Friese) generators;• no Magnetic Field, but dP/P = 1%
Signal and Background simulation
Signal - 105 events D0 K-,+
Background – 104 UrQmd events
mixed 103 events
IM(GeV/c2)
Tracking & Vertexing
Tracking & Vertexing developed by I.Kisel:
CbmITrack, CbmStsmctracks2rsegs,CbmStsRefit CbmStsPerformance;
CbmStsPrimaryVertex, StsSecondaryVertex
CbmStsAnalysis: Event Topology (MC), RSEGs analysis K
(K0S; 0; -; -; D0)
K0S
0 -
IM (GeV/c2)
Tracking & Vertexing
Zv (cm)
= 57 m
MC Zv – RECO Zv (cm)
Variables and cuts. Cuts optimisation
Impact Parameter (IP > 80 m);
Z-vertex for D0 K-,+
(Z2 > 250 m);
P D0 pointing to the Primary Vertex;
Pt K-,+ > 0.5 (0.45) GeV;
P K-,+ >1.5 GeV;
2 < 5 for the Secondary vertex
(cm)
Variables and cuts. Cuts optimisation
Pt K-,+ and P K-,+
cuts optimisation
(GeV)
Signal SignalBackground Background
Variables and cuts. Cuts optimisation
P D0 pointing to
the Primary Vertex
cut optimisation
Signal Background
(cm)
Trigger feasibility studyTrigger feasibility study
11 events
Background
104 events IP,P,Pt Vz
D0pont;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/c2)
Trigger feasibility studyTrigger feasibility study
IM (GeV/c2)
MC MC
Reco
IP,P,Pt cuts
Reco
all cuts
103 mix events:
Urqmd+D0 K-,+
IP,P,Pt cuts
cut signal
IP K- + 28 %
Z-vertex 54 %
P D0
pointing99 %
Pt K-,+ 61 %
P K-,+ 58 %
all cuts 7.5 %
Trig RF ~600
S/B ratio ~0.8
OutlineOutline
• MC simulation shows feasibility to measure
D0 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