Intrinsic time resolution of a hexagonal BC404 scintillator: A Monte Carlo study of interaction geometry and optical reflectivity

RESUMO

Time resolution is an important parameter in particle detectors, as it determines their ability to distinguish between two temporally separated events. It can be decomposed into electronic and intrinsic contributions, the latter being influenced by scintillation, optical transport, detector geometry, particle type and energy, and the sensitive area of the photosensor. In this work, a Monte Carlo simulation based on Geant4 is used to investigate the intrinsic time resolution of a hexagonal BC404 plastic scintillator. The analysis includes the evaluation of the optical-photon distribution over the hexagonal surfaces and the characterization of the intrinsic time resolution for different interaction configurations. The intrinsic time resolution is investigated using muons as cosmic-ray proxies with energies ranging from 4~GeV to 1~TeV. In addition, the effect of surface reflectivity on optical-photon transport and timing performance is studied for reflectivities ranging from 0\% to 100\%. The results show that the intrinsic time resolution exhibits little dependence on the incident muon energy, while a clear dependence on the interaction position is observed. Furthermore, although the number of detected photons varies with the interaction position and surface reflectivity, the intrinsic time resolution is not solely determined by photon statistics, indicating that optical transport and geometrical effects play an important role in the timing performance. Across the investigated configurations, intrinsic time resolutions ranging from approximately 15 to 100~ps are obtained. These findings highlight the importance of the interaction position, optical transport, photon statistics, and surface reflectivity in determining the timing performance of hexagonal plastic scintillators and provide guidance for the optimization of their optical properties and geometry for timing-sensitive applications.