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Studies of CPT symmetry in positronium decays with the 192 plastic strip J-PET detector

N. Chug1,2,*, S. D. Bass1,3, E. Y. Beyene1,2, C. Curceanu4, E. Czerwiński1,2, M. Das1,2, K. V. Eliyan1,2, M. Gorgol5, J. Hajduga6 et al. (J-PET Collaboration)

J. Hajduga6, S. Jalali1,2, B. Jasińska5, K. Kacprzak1,2, T. Kaplanoglu1,2, Ł. Kapłon1,2, K. Kasperska1,2, A. Khreptak1,2, A. Kierys7, G. Korcyl1,2, T. Kozik1,2, K. Kubat1,2, D. Kumar1,2, A. Kunimmal Venadan1,2, E. Lisowski8, F. Lisowski8, J. Mędrala-Sowa1,2, S. Moyo1,2, W. Mryka1,2, S. Niedźwiecki1,2, P. Pandey1,2, S. Parzych1,2, E. Pérez del Rio1,2, A. Porcelli1,9, B. Rachwał6, M. Rädler1,2, A. Sienkiewicz7, S. Sharma1,2, M. Skurzok1,2, E. Ł. Stępień1,2, T. Szumlak6, P. Tanty1,2, K. Tayefi Ardebili1,2, S. Tiwari1,2, and P. Moskal1,2,† (J-PET Collaboration)

  • 1Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, Kraków, Poland
  • 2Centre for Theranostics, Jagiellonian University, Kraków, Poland
  • 3Kitzbühel Centre for Physics, Kitzbühel, Austria
  • 4INFN, Laboratori Nazionali di Frascati, Frascati, Italy
  • 5Institute of Physics, Maria Curie-Sklodowska University, Lublin, Poland
  • 6AGH University of Cracow, Poland
  • 7Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie-Sklodowska University, Lublin, Poland
  • 8Cracow University of Technology, Faculty of Mechanical Engineering, Kraków, Poland
  • 9Centro de Investigación, Tecnología, Educación y Vinculación Astronómica, Universidad de Antofagasta, Avenida Angamos 601, Antofagasta 1240000, Chile

  • *Contact author: neha.chug@uj.edu.pl
  • †Contact author: p.moskal@uj.edu.pl
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Phys. Rev. D 113, 032003 – Published 4 February, 2026

DOI: https://doi.org/10.1103/wy7r-xgl9

Abstract

A direct test of the CPT symmetry is performed for the electromagnetic decays of ortho-positronium using the Jagiellonian positron emission tomograph (J-PET). We present the precise measurement of the CPT-sensitive angular correlation entailing the positronium spin and the momenta of its annihilation photons, surpassing previous studies utilizing the same detection system. Positrons originating from a Na22 source are emitted from the detector’s center and subsequently form positronium atoms within the spherical chamber covered with porous material. Reconstruction of annihilation locations using the 192-strip J-PET detector makes it possible to determine the positronium emission direction, which defines the quantization axis along which positronium is polarized, without the application of external magnetic fields. The measurements were performed in total for 356 days resulting in an identification of 47.8×106 events with ortho-positronium decays into three photons. The results are consistent with the exactness of CPT symmetry with measured asymmetry amplitude −0.00029±0.00022 (stat.) and with statistical error four times smaller than the previous best measurement.

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Phys. Rev. D 113, 032003– Published 4 February, 2026
  • Received 30 July 2025
  • Accepted 19 November 2025
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