HKS TOF hodoscopes

The HKS TOF hodoscopes determine the trigger timing and measure the velocity of the charged particles. There are three sets of hodoscopes, HTF1X, HTF1Y, and HTF2X. Each hodoscope consists of BC408 scintillator, equipped with acrylic light guides and Hamamatsu H1949-50 phototubes on both ends. Active area of the hodoscopes is 30 cm $\times$ 125 cm. Figure 21 shows the schematic drawing of HTF1X. It consists of 17 scintillator slats each of which is 20 mm thick, 75 mm wide, and 300 mm long. Figure 22 shows the schematic drawing of HTF1Y. It consists of 9 segments of scintillation counters (20 mm thick, 3.5 cm wide, and 1250 mm long). HTF2X consists similarly of 18 segments of scintillation counters with a size of 20 mm thick, 75 mm wide, and 400 mm long.

Distance between HTF1X and HTF2X was determined to allow flight time sufficient to separate kaons from pions in the momentum region of interest. Time resolution of 70 ps was achieved with a prototype, corresponding to better than 4$\sigma$ separation between 1.3 GeV/$c$ kaons and pions.