Characterization of positronium properties in doped liquid scintillators

TL;DR

This study investigates how doping liquid scintillators with various elements affects the formation and decay of ortho-positronium, aiming to enhance neutrino detection and background suppression in future experiments.

Contribution

It provides the first detailed characterization of o-Ps properties in doped liquid scintillators with different elements relevant to neutrino research.

Findings

Gadolinium and lithium doping influence o-Ps formation probability and decay time.

Neodymium and tellurium doping also affect o-Ps properties, relevant for double beta decay studies.

Results can guide scintillator preparation to optimize neutrino detection signatures.

Abstract

Ortho-positronium (o-Ps) formation and decay can replace the annihilation process, when positron interacts in liquid scintillator media. The delay induced by the positronium decay represents either a potential signature for anti-neutrino detection, via inverse beta decay, or to identify and suppress positron background, as recently demonstrated by the Borexino experiment. The formation probability and decay time of o-Ps depend strongly on the surrounding material. In this paper, we characterize the o-Ps properties in liquid scintillators as function of concentrations of gadolinium, lithium, neodymium, and tellurium, dopers used by present and future neutrino experiments. In particular, gadolinium and lithium are high neutron cross section isotopes, widely used in reactor anti-neutrino experiments, while neodymium and tellurium are double beta decay emitters, employed to investigates the Majorana neutrino nature. Future neutrino experiments may profit from the performed measurements to tune the preparation of the scintillator in order to maximize the o-Ps signature, and therefore the discrimination power.