1. Performance simulations with a realistic model of the CBM Silicon Tracking System Silicon tracking for CBM Number of integration components Ladders106 Sectors1040 Sensors1292 R/O chips16640 Channels2133k Sectors Sector typeS1S1 S S2S3S3 C2 S3 C3 Used sensors111123 Physical length [cm] 2.2 4.26.212.418.6 Physical width [cm] 6.23.16.2 Number of strips 10245121024 Strip pitch58µm Simulation & Reconstruction STS Layout Results References: [1] A.Kotynia, J.M.Heuser, W.Müller, „Simulation of realistic detector response in the CBM Silicon Tracking System”, CBM Progress Report 2009 7 [2]Nuc. Instr. Meth. A497 (2003) 389-396 [3]I.Kisel, I.Kulakov, I.Vassiliev, „A standalone package for on-line event selection in the CBM experiment”, CBM Progress Report 2008 79 Track categoryEfficiency, % Reference set (>1 GeV/c)95.2 All set (≥4 hits,>100 MeV/c)89.8 Ghost (made from fake hits)6.6 Challenge: Au+Au collisions, 25 GeV/u up to 1000 charged particles/event interaction rates up to 10 MHz STS requirements:  radiation hard and low-mass detector system  high position resolution  track reconstruction for all charged particles  momentum resolution of order 1.5% at 1GeV/c  primary vertex resolution of about 50µm  8 tracking stations: 30, 40, 50, 60, 70, 80, 90, 100 cm downstream of target, in 1 T dipole magnet;  4 m 2 active area;  The number, position and segmentation of the layers are optimized for efficient track reconstruction and high momentum resolution. Reconstructed URQMD event: central Au+Au coll. @ 25AGeV Realistic STS system in CbmRoot  The simulations include complete chain of physical processes caussed by charged particletraversing the detector [1]. Hit Finding efficiency: Primary : 98.97 % Secondary : 91.69 % Point resolution: Vertical: 60 µm Horizontal: 8 µm  In 300 µm thick silicon sensors about 23k electron-hole pairs are produced by minimum-ionizing particles.  The charge is shared by one or more collecting strips. Layout of the 8 STS stations Breakdown of STS components STS in dipole magnet Simulated track of a minimum ionizing particle in the silicon detector Influence of a magnetic field on the collection of charge on the strips [2] Charge collected on the most significant strip in cluster; different colors represent different cluster sizes Hit resolution in STS obtained using realistic detector model for vertical (green) and horizontal direction (red) Hit pull distribution in STS for vertical direction (green) and horizontal (red) Track reconstruction efficiency obtained using cellular automaton track finder [3] Signal peak height [a.u.~1ke - ] Hit resolutionHit pull  The STS stations have a modular structure and are constructed from 4 types of 300µm thick double-sided silicon micro-strip sensors, arranged on 8 types of carbon-fiber supported ladder structures. Mechanical design of a carbon fiber support structure.  Particle position obtained with Center-Of-Gravity algorithm: Anna Kotynia Goethe University, Frankfurt, Germany for the CBM Collaboration http://www-cbm.gsi.de