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