The Phase1 CMS Pixel detector upgrade

Abstract

The pixel detector of the CMS experiment will be replaced in an extended end-of-year shutdown during winter 2016/2017 with an upgraded one able to cope with peak instantaneous luminosities beyond the nominal LHC instantaneous luminosity of 1 × 1034 cm−2 s−1. Under the conditions expected in the coming years, which will see an increase of a factor two in instantaneous luminosity, the present system would experience a dynamic inefficiency caused mainly by data losses due to buffer overflows. The Phase I upgrade of the CMS pixel detector, described in this paper, will operate at full efficiency at an instantaneous luminosity of 2 × 1034 cm−2 s−1 and beyond, thanks to a new readout chip. The new detector will feature one additional tracking point both in the barrel and in the forward regions, while reducing the material budget as a result of a new CO2 cooling system and optimised layout of the services. In this paper, the design and the technological choices of the Phase I detector will be reviewed and the status of the construction of the detector and the performance of its components will be discussed.