The HARP resistive plate chambers: Characteristics and physics performance

The HARP resistive plate chamber (RPC) system was designed for time-of-flight measurement in the large-angle acceptance region of the HARP spectrometer. It comprised 46 four-gap glass RPCs covering an area of 8m2. The design of the RPCs, their operation, intrinsic properties, and system performance are described. The intrinsic time resolution of the RPCs is 127 ps leading to a system time-of-flight resolution of 175 ps. It is argued that gross differences between pion and proton timing in multi-gap timing RPCs, reported recently in the literature, do not exist.