Measurement of the high energy γ-rays from heavy ion reactions using Cerenkov detector

The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as a sensitive probe for short-range correlation in atomic nuclei.The energy of the y-rays can be measured by collecting the Cerenkov light in the medium induced by the fast electrons generated in the Compton scattering or electromagnetic shower of the incident y ray.Two types of detectors based on pure water and lead glass as sensitive materials were designed for this purpose.The y response and optical photon propagation in the detectors were simulated based on electromagnetic and optical processes in Geant4.The inherent energy resolutions of 0.022(4)+0.51(2)/E1γ/2 for water and 0.0026(3)+0.446(3)/E1γ/2 for lead glass were obtained.The geometry sizes of the lead glass and water were optimized to 30 cm × 30 cm × 30 cm and 60 cm × 60 cm × 120 cm,respectively,to detect high-energy γ-rays at 160 MeV.The Hough transform method was applied to reconstruct the direction of the incident y-rays,providing the ability to experimentally distinguish the high-energy γ-rays produced in the reactions on the target from random background cosmic-ray muons.