Speaker
Description
Since 2010, the LHCb experiment at CERN has been accumulating 1--2 fb−1 of pp collision data every year. This b- and c-hadron rich data sample, together with the detector's excellent performance, has allowed LHCb to carry out world leading measurements in the field of flavor physics. However, many of these results will benefit from datasets significantly larger than what the current detector would be able to record in a reasonable amount of time. This challenge is being overcome via a major upgrade of the LHCb detector scheduled to be completed in 2021. With three completely new trackers as well as more powerful electronics, LHCb will be able to read out the collision data at the unprecedented rate of 30 MHz, with all trigger decisions performed at the software level. The data collection is expected to exceed 5 fb−1 a year. This contribution will describe the two new trackers that are based on silicon technology: the Vertex Locator(VELO) and the Upstream Tracker (UT). The new VELO is a hybrid pixel detector with 55×55μm2silicon pixels read out every pp bunch crossing by the VeloPix ASIC. This subdetector will be moved closer to the proton beams, only 3.5~mm apart, to further improve the vertexing precision. The modules are separated from the beam vacuum by a custom-made foil that can now be thinner thanks to a novel milling process and chemical etching. It will withstand a total ionization dose (TID) of about 400 MRad, leading to a bias voltage of 1000~V by the end of its 10-year lifetime. The sensors will be cooled by bi-phase CO2 flowing under the chips via microchannels etched on the silicon substrate. The UT is a new silicon microstrip detector placed between the VELO and the LHCb dipole magnet that will have finer granularity (down to 95 μm pitch close to the beam), improved coverage, and smaller material budget than those of the Tracker Turicens is that it replaces. The UT is composed of four planes of silicon sensors cooled by evaporative CO2 and read out by a dedicated front-end ASIC (SALT). This chip provides pulse shaping, digitization, and digital signal processing including pedestal and common-mode noise subtraction as well as zero-suppression, allowing too for the readout of the charge deposition on the silicon sensors after every pp bunch crossing. In this contribution we will describe these two detectors as well as their current installation and commissioning status.
