Discrete symmetries tested at 10${}^{-4}$ precision using linear polarization of photons from positronium annihilations

Abstract

Discrete symmetries play an important role in particle physics with violation of CP connected to the matter-antimatter imbalance in the Universe. We report the most precise test of P, T and CP invariance in decays of ortho-positronium, performed with methodology involving polarization of photons from these decays. Positronium, the simplest bound state of an electron and positron, is of recent interest with discrepancies reported between measured hyperfine energy structure and theory at the level of $10^{-4}$ signaling a need for better understanding of the positronium system at this level. We test discrete symmetries using photon polarizations determined via Compton scattering in the dedicated J-PET tomograph on an event-by-event basis and without the need to control the spin of the positronium with an external magnetic field, in contrast to previous experiments. Our result is consistent with QED expectations at the level of 0.0007 and one standard deviation.

17 pages, 10 figures

References in corpus (10)

• Test of a single module of the J-PET scanner based on plastic scintillators
• Positronium imaging with the novel multiphoton PET scanner
• J-PET: a new technology for the whole-body PET imaging
• Testing CPT symmetry in ortho-positronium decays with positronium annihilation tomography
• Simulating NEMA characteristics of the modular total-body J-PET scanner -- an economic total-body PET from plastic scintillators
• Multichannel FPGA based MVT system for high precision time (20~ps~RMS) and charge measurement
• A feasibility study of ortho-positronium decays measurement with the J-PET scanner based on plastic scintillators
• QED and Fundamental Symmetries in Positronium Decays
• Commissioning of the J-PET detector for studies of decays of positronium atoms
• Comparative studies of plastic scintillator strips with high technical attenuation length for the total-body J-PET scanner