Positronium signature in organic liquid scintillators for neutrino experiments
- 27 January 2011
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review C
- Vol. 83 (1)
- https://doi.org/10.1103/physrevc.83.015504
Abstract
Electron antineutrinos are commonly detected in liquid scintillator experiments via inverse decay by looking at the coincidence between the reaction products: neutrons and positrons. Prior to positron annihilation, an electron-positron pair may form an orthopositronium (o-Ps) state, with a mean lifetime of a few nanoseconds. Even if the o-Ps decay is speeded up by spin-flip or pick-off effects, it may introduce distortions in the photon emission time distribution, crucial for position reconstruction and pulse shape discrimination algorithms in antineutrino experiments. Reversing the problem, the o-Ps-induced time distortion represents a new signature for tagging antineutrinos in liquid scintillator. In this article, we report the results of measurements of the o-Ps formation probability and lifetime for the most used solvents for organic liquid scintillators in neutrino physics (pseudocumene, linear alkyl benzene, phenylxylylethane, and dodecane). We characterize also a mixture of pseudocumene 1.5 g/l of 2,5-diphenyloxazole, a fluor acting as wavelength shifter. In the second part of the article, we demonstrate that the o-Ps-induced distortion of the scintillation photon emission time distributions represent an optimal signature for tagging positrons on an event by event basis, potentially enhancing the antineutrino detection. DOI: http://dx.doi.org/10.1103/PhysRevC.83.015504 © 2011 American Physical Society
Other Versions
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