The silicon pixel tracking system for the ATLAS experiment at the Large Hadron Collider is described and the performance requirements are summarized. Detailed descriptions of the pixel detector electronics and the silicon sensors are given. The design, fabrication, assembly and performance of the pixel detector modules are presented. Data obtained from test beams as well as studies using cosmic rays are also discussed.

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We con rm the existence of the two I G (J PC ) = 0 + (0 ++ ) resonances f 0 (1370) and f 0 (1500) reported by us in earlier analyses. The analysis presented here couples the nal states 0 0 0 , 0 0 and 0 of pp annihilation at rest. It is based on a 3 3 K{matrix. We nd masses and widths of M = (1390 30)MeV , ; = (380 80)MeV and M = (1500 10) MeV , ; = (154 30)MeV , respectively. The product branching ratios for the production and decay i n to 0 0 and of the f 0 (1500) are (1:27 0:33) 10 ;3 and (0:60 0:17) 10 ;3 , respectively.