Positronium Formation and Decay in Organic Scintillators for Neutrino Detection
The detection of electron anti-neutrinos is generally carried out by searching for the coincidence of the reaction products, neutron and positron, in liquid scintillators. However, in these last a positron may form positronium (Ps) with an electron of the medium; efficiency of the process may be high. Furthermore, the triplet ground state sublevel (o-Ps) has lifetimes of a few ns. These features introduce distortions in the time distribution of the emitted photons, which is essential for position reconstruction and pulse shape discrimination algorithms in anti-neutrino experiments. This drawback can be favorably exploited by using o-Ps as a probe to detect anti-neutrinos in the scintillator. We report results of positron annihilation lifetime measurements in some organic liquid scintillators used for neutrino experiments. The o-Ps induced distortion of the scintillation photon emission time distribution may enhance the anti-neutrino detection.
Jozef Krištiak, Jan Kuriplach and Pradeep K. Pujari
G. Consolati et al., "Positronium Formation and Decay in Organic Scintillators for Neutrino Detection", Materials Science Forum, Vol. 733, pp. 306-309, 2013