In-beam measurements of the HADES-TOF RPC wall

A full size prototype of the new inner High-Acceptance DiElectron Spectrometer (HADES)-TOF wall based on Resistive Plate Chambers (RPCs) was mounted and exposed to secondaries from C reactions on Be and Nb targets at 2 AGeV kinetic energy and typical HADES particle fluxes. The tested sextant is constituted by 187 individual 4-gap glass–aluminium shielded RPC cells distributed in three columns and two layers, covering an area of 1.26m2.An average timing resolution of 73 ps σσ was measured with 99%99% intrinsic efficiency, on a random location, and moderate timing tails, along with an average longitudinal position resolution of 7.7 mm σσ, in the range from a few Hz/cm2Hz/cm2 up to 80Hz/cm2 without noticeable degradation of performance. Additionally, the matching efficiency was estimated using the tracking system of HADES, yielding an average value of 97.5%.