Performances du détecteur en silicium à micropistes de l'expérience STAR à RHIC

The Silicon Strip Detector (SSD) is the fourth layer of detector using a double-sided microstrip technology of the STAR experiment at RHIC, thus completes its inner tracking device. The goal of STAR is to study heavy ions collisions in order to probe the existence of the QGP, a deconfined state of nuclear matter. Strangeness enhancement, such as $K_S^0$, $\Lambda$, $\Xi$ et $\Omega$, particles production, has been proposed to sign the formation of the QGP. Then precise measurement of secondary vertices is needed. The SSD will also permit an attempt to use the inner tracking device to measure charm and beauty with direct topological identification. It was proposed to enhance the STAR tracking capabilities by providing a better connexion between reconstructed tracks in the main tracking device (TPC) and the initial vertex detector (SVT). In this thesis, we will present the intrinsic performances of the SSD and its impact on the inner tracking system performances by studying Cu-Cu collisions occured at RHIC in 2005. Study of simulated data will also permit a better comprehension of these results.