The Upgrade of LHCb VELO

Abstract

LHCb physics achievements to date include some of the world’s most precise flavour physics measurements, including the CKM phase γ and the discovery of CP violation in the charm sector. These achievements have been possible thanks to the enormous data samples collected and the performance of the subdetectors, with the efficiency and precision of the silicon vertex detector (VELO) being a major contributor to this success. The experiment has been upgraded to run at higher luminosity, requiring 40 MHz readout. The VELO Upgrade modules are composed of hybrid pixel detectors and electronics circuits glued onto a cooling substrate, made of thin silicon plates with embedded micro-channels, allowing for the circulation of evaporative CO 2 . The detectors are located in vacuum, separated from the beam by a thin aluminium box. The upgraded VELO is composed of 52 modules placed along the beam axis divided into two retractable halves. The design, production, installation and commissioning of the VELO Upgrade system is presented together with test results. • LHCb experiment relies on the VELO detector for accurate vertex reconstruction. • The VELO Upgrade is the brand new silicon pixel tracker of LHCb. • Detector comprises 52 double sided modules with 4 pixel sensors each. • Micro-channels circulating evaporative CO 2 allows for efficient heat dissipation. • Modules Electrical and thermal performance validated in operation conditions.