The CMS pixel detector and challenges (prospectives) for its upgrade

The CMS pixel detector was installed in July 2008 in the innermost region of CMS. It consists of 66 million pixels of 100 μ m by 150 μ m size over 3 barrel layers and 2 forward disks. The pixel system has been successfully commissioned. Over 80 K muon tracks were taken during the CMS cosmic runs and the detector is ready for the first physics run. The pixel detector, so close to the interaction point, will be exposed to a very high radiation dose. The estimation is that the first barrel layer, located at 4.3 cm from the beam pipe, after 3 years of LHC running at full luminosity will become inefficient for position reconstruction. For this reason, a susbstitution of a new pixel detector in 2014 has been already scheduled. At the same time an LHC luminosity upgrade is also planned. While a simple rebuild of the current detector could be done, the expectation is to design a new one, optimized for higher luminosity. This paper describes the present system and its performance as well as possible solutions for the upgrade.