STAR MAPS Vertex Detector operational experience

Abstract

The Heavy Flavor Tracker (HFT) is a set of silicon tracking detectors, which are used by the Solenoidal Tracker at RHIC (STAR) to extend its measurement capabilities in the heavy flavor domain. STAR takes data at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. This system took data in Au+Au collisions, p+p, p+Au and d+Au collisions at √$s_{NN}$ = 200 GeV at RHIC, during the period 2014 - 2016. The innermost high resolution PiXeL detector (PXL) is the first application of the state-of-the-art thin Monolithic Active Pixel Sensors (MAPS) technology in a collider environment. The PXL detector is based on 50 μm-thin MAPS sensors with a pitch of 20.7 μm. Each sensor includes an array of nearly 1 million pixels, read out in a column parallel rolling shutter mode with an integration time 185.6 μs. The 170 mW/$cm^{2}$ power dissipation allows for air cooling and contributes to reduce the global material budget to 0.4% radiation length on the innermost layer. The experience and lessons learned from construction and operations of this novel detector are presented. Detector performance and results from 2014 Au+Au data analysis, demonstrating the STAR capabilities of charm reconstruction, are described.