Cosmic-ray test of a time-of-flight detector for double-strangeness experiments at J-PARC

Abstract

We have developed a time-of-flight (ToF) array consisting of 24 plastic scintillators for triggering and timing measurements in a series of planned experiments to study double-strangeness hadronic and nuclear systems at the K1.8 beamline of J-PARC. Each ToF scintillator is 180<!-- --> <!-- -->cm long with a cross-section of $8\times 3{\mathrm{cm}}^2$, and is read out by H1949-50 photomultiplier tubes at both ends. The timing and attenuation properties of the scintillators are measured using cosmic-ray muons and β rays from ⁹⁰Sr. The cosmic-ray muon events are triggered by three pairs of 120-cm-long plastic scintillators, sandwiching the ToF array. The intrinsic time resolutions of the scintillators are estimated to be in the range 60–100<!-- --> <!-- -->ps, which is adequate for reliable separation between π and K at $1.2\mathrm{GeV}/c$. The attenuation length is measured to be approximately 210<!-- --> <!-- -->cm, which is half that for a bulk scintillator.