The hybrid <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si24.svg" display="inline" id="d1e493"> <mml:mi mathvariant="normal">μ</mml:mi> </mml:math> -RWELL for ePIC Endcap tracking

The Electron Ion Collider (EIC) at Brookhaven National Laboratory (BNL) aims to investigate the nuclear structure with unprecedented precision, focusing on confinement and non-perturbative QCD behavior. ePIC (Electron-Proton/Ion Collider) is the primary candidate experiment at EIC, with a hermetic design meant to measure scattered particles over a wide kinematic range. The detector’s tracking system is composed of silicon trackers and Micro Pattern Gaseous Detectors (MPGD). The MPGD Endcap Trackers consist of four G-RWELL disks, a hybrid layout integrating a GEM-based pre-amplification stage over the classic μ -RWELL, covering the region with pseudo-rapidity | η | > 2 and the entire azimuthal angle. Prototypes with an active area of 10 × 10 cm 2 were tested at CERN PS-T10 beam line with a 5 GeV/c muon beam in November 2024. The charge centroid and μ TPC reconstruction methods were used to measure spatial resolution and efficiency at various angles. The data was acquired using an SRS system with APV25 front-end electronics and analyzed with the ROOT-based Corryvreckan framework. The detectors appear stable up to very high gas gains, reach an efficiency of 96% for both perpendicular and inclined tracks, and a spatial resolution of 90 μ m and 200 μ m respectively.