Performance of the LHCb tracking system in Run I of the LHC

Abstract

The LHCb tracking system consists of a Vertex Locator around the interaction point, a tracking station with four layers of silicon strip detectors in front of the magnet, and three straw-tube and silicon strip tracking stations behind the magnet. This system allows reconstruction of charged particles with a high efficiency (>95% for particles with momentum p>5GeV) and excellent momentum resolution (0.5% for particles with p<20GeV). The high momentum resolution results in narrow mass peaks, leading to a high signal-to-background ratio in such key channels as Bs0→μμ. The excellent performance of the tracking system yields a decay time resolution of ~50fs, allowing to resolve the fast B0s oscillation with a mixing frequency of 17.7ps−1. Such a decay time resolution is an essential element in studies of time dependent CP violation. I present an overview of the track reconstruction in LHCb and its performance in Run I of the LHC. I highlight the challenges and improvements of the track reconstruction from Run II onward, including efforts to improve the timing of the online reconstruction and approaches to unify the online and offline reconstruction.