A cylindrical GEM inner tracker for the BESIII experiment at IHEP

Abstract

The Beijing Electron Spectrometer III (BESIII) [1] is a multi-purpose detector that collects data provided by the collision in the Beijing Electron Positron Collider II (BEPCII), hosted at the Institute of High Energy Physics of Beijing. Since the beginning of its operation, BESIII has collected the world largest sample of J/Ψ and Ψ (2s). Due to the increase of the luminosity up to its nominal value of 1033 cm-2 s-11 and aging effect, the MDC decreases its efficiency in the first layers up to 35 % with respect to the value in 2014. Since BESIII has to take data up to 2022 with the chance to continue up to 2027, the Italian collaboration proposed to replace the inner part of the MDC with three independent layers of Cylindrical triple-GEM (CGEM). The CGEM-IT project will deploy several new features and innovation with respect the other current GEM based detector: the μ TPC and analog readout, with time and charge measurements will allow to reach the 130 μm spatial resolution in 1 T magnetic field requested by the BESIII collaboration. In this proceeding, an update of the status of the project will be presented, with a particular focus on the results with planar and cylindrical prototypes with test beams data. These results are beyond the state of the art for GEM technology in magnetic field.