Abstract We report a measurement of the gamma-gamma angular correlation in the 60Co cascade using a compact coincidence setup based on two unsegmented liquid-scintillator (LS) detector modules read out by photomultiplier tubes (PMTs). The beta-minus decay of 60Co produces two prompt gamma rays of 1173 keV and 1332 keV in the well-known 4+ → 2+ → 0+ cascade, whose angular correlation can be described by an even-order Legendre expansion. Although unsegmented LS detectors do not provide event-by-event interaction-point information as segmented crystal scintillators or HPGe arrays do, the correlation can be recovered statistically from coincidence timing in a fixed detector geometry. We fit the measured angular-correlation distribution with W (θ) = 1 + A2P2 (cos θ) + A4P4 (cos θ), yielding A2 = 0. 1018 ± 0. 0146 and A4 = 0. 0116 ± 0. 0183. These values are consistent with the theoretical coefficients A₂^ th=0. 102041 and A₄^ th=0. 009070 for a pure E2–E2 cascade. This work indicates that gamma-gamma angular-correlation coefficients can be quantitatively extracted with a compact, unsegmented LS system. It provides an initial benchmark for large homogeneous scintillation geometries in which event-by-event angular tagging is unavailable, and supports the feasibility of future coincidence applications with doped LS or water-based liquid scintillator (WbLS) media.
Jeong et al. (Mon,) studied this question.