, 12(1): 5658. September 2021.\n
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@article{moskal_testing_2021,\n\ttitle = {Testing {CPT} symmetry in ortho-positronium decays with positronium annihilation tomography},\n\tvolume = {12},\n\tcopyright = {2021 The Author(s)},\n\tissn = {2041-1723},\n\turl = {https://www.nature.com/articles/s41467-021-25905-9},\n\tdoi = {10.1038/s41467-021-25905-9},\n\tabstract = {Charged lepton system symmetry under combined charge, parity, and time-reversal transformation (CPT) remains scarcely tested. Despite stringent quantum-electrodynamic limits, discrepancies in predictions for the electron–positron bound state (positronium atom) motivate further investigation, including fundamental symmetry tests. While CPT noninvariance effects could be manifested in non-vanishing angular correlations between final-state photons and spin of annihilating positronium, measurements were previously limited by knowledge of the latter. Here, we demonstrate tomographic reconstruction techniques applied to three-photon annihilations of ortho-positronium atoms to estimate their spin polarisation without magnetic field or polarised positronium source. We use a plastic-scintillator-based positron-emission-tomography scanner to record ortho-positronium (o-Ps) annihilations with single-event estimation of o-Ps spin and determine the complete spectrum of an angular correlation operator sensitive to CPT-violating effects. We find no violation at the precision level of 10−4, with an over threefold improvement on the previous measurement.},\n\tlanguage = {en},\n\tnumber = {1},\n\turldate = {2021-09-29},\n\tjournal = {Nature Communications},\n\tauthor = {Moskal, P. and Gajos, A. and Mohammed, M. and Chhokar, J. and Chug, N. and Curceanu, C. and Czerwiński, E. and Dadgar, M. and Dulski, K. and Gorgol, M. and Goworek, J. and Hiesmayr, B. C. and Jasińska, B. and Kacprzak, K. and Kapłon, Ł and Karimi, H. and Kisielewska, D. and Klimaszewski, K. and Korcyl, G. and Kowalski, P. and Krawczyk, N. and Krzemień, W. and Kozik, T. and Kubicz, E. and Niedźwiecki, S. and Parzych, S. and Pawlik-Niedźwiecka, M. and Raczyński, L. and Raj, J. and Sharma, S. and Choudhary, S. and Shopa, R. Y. and Sienkiewicz, A. and Silarski, M. and Skurzok, M. and Stępień, E. Ł and Tayefi, F. and Wiślicki, W.},\n\tmonth = sep,\n\tyear = {2021},\n\tnote = {Bandiera\\_abtest: a\nCc\\_license\\_type: cc\\_by\nCg\\_type: Nature Research Journals\nNumber: 1\nPrimary\\_atype: Research\nPublisher: Nature Publishing Group\nSubject\\_term: Experimental nuclear physics;Experimental particle physics;Imaging techniques\nSubject\\_term\\_id: experimental-nuclear-physics;experimental-particle-physics;imaging-techniques},\n\tpages = {5658},\n}\n
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\n Charged lepton system symmetry under combined charge, parity, and time-reversal transformation (CPT) remains scarcely tested. Despite stringent quantum-electrodynamic limits, discrepancies in predictions for the electron–positron bound state (positronium atom) motivate further investigation, including fundamental symmetry tests. While CPT noninvariance effects could be manifested in non-vanishing angular correlations between final-state photons and spin of annihilating positronium, measurements were previously limited by knowledge of the latter. Here, we demonstrate tomographic reconstruction techniques applied to three-photon annihilations of ortho-positronium atoms to estimate their spin polarisation without magnetic field or polarised positronium source. We use a plastic-scintillator-based positron-emission-tomography scanner to record ortho-positronium (o-Ps) annihilations with single-event estimation of o-Ps spin and determine the complete spectrum of an angular correlation operator sensitive to CPT-violating effects. We find no violation at the precision level of 10−4, with an over threefold improvement on the previous measurement.\n