A new approach for the ortho-positronium lifetime determination in a vacuum cavity

TL;DR

This paper proposes a novel experimental method to measure the ortho-positronium decay rate with 100 ppm accuracy, aiming to test higher-order QED corrections and explore potential new physics such as hidden sectors related to dark matter.

Contribution

A new experimental approach using a vacuum cavity and advanced subtraction techniques to improve the precision of ortho-positronium lifetime measurements.

Findings

Potential to reach 100 ppm measurement accuracy

Development of a new technique for confining o-Ps in vacuum

Method to subtract pick-off annihilation rate effectively

Abstract

Currently, the experimental uncertainty for the determination of the ortho-positronium (o-Ps) decay rate is at 150 ppm precision; this is two orders of magnitude lower than the theoretical one, at 1 ppm level. Here we propose a new proof of concept experiment aiming for an accuracy of 100 ppm to be able to test the second-order correction in the calculations, which is $\simeq 45\left(\frac{\alpha}{\pi}\right)^2\approx 200$ ppm. The improvement relies on a new technique to confine the o-Ps in a vacuum cavity. Moreover, a new method was developed to subtract the time dependent pick-off annihilation rate of the fast backscattered positronium from the o-Ps decay rate prior to fitting the distribution. Therefore, this measurement will be free from the systematic errors present in the previous experiments. The same experimental setup developed for our recent search for invisible decay of ortho-positronium is being used. The precision will be limited by the statistical uncertainty, thus, if the expectations are fulfilled, this experiment could pave the way to reach the ultimate accuracy of a few ppm level to confirm or confront directly the higher order QED corrections. This will provide a sensitive test for new physics, e.g. a discrepancy between theoretical prediction and measurements could hint the existence of an hidden sector which is a possible dark matter candidate.