QED and Fundamental Symmetries in Positronium Decays

Bass, Steven D.

doi:10.5506/aphyspolb.50.1319

Cited by 33 publications

(29 citation statements)

References 60 publications

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“…Systems consisting of charged leptons, in contrast, are governed by quantum electrodynamics (QED), supported by experimental evidence of unparalleled precision. The most recent measurements of the electron anomalous magnetic moment [11], and its QED predictions based on the recent precise measurement of the fine structure constant [12] agree to 1 part in 10 12 , indicating that no new CPT-violating interactions coupling to the electron could be observed to this level of precision [13]. Nonetheless, the recently discovered deviations from QED predictions in the fine structure of the positronium atom, that is, the bound state of an electron and positron [14], suggest that diverse experimental studies of charged lepton systems should not be hastily abandoned.…”

mentioning

confidence: 83%

Testing CPT symmetry in ortho-positronium decays with positronium annihilation tomography

Moskal

Gajos

Mohammed

et al. 2021

Preprint

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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 as a high-acceptance photon detector to study CPT-prohibited angular correlation in ortho-positronium (o-Ps) annihilations. We record an unprecedented range of kinematical configurations of o-Ps annihilations into three photons. Tomographic reconstruction of the annihilation points in a large medium allows single-event estimation of positronium spin orientation and, consequently, determination of the complete spectrum of angular correlation between the annihilation plane orientation and positronium spin, the non-vanishing expectation value of which would manifest CPT-violating effects. We find no violation at the precision level of 10^{−4}, with a fourfold improvement on the previous measurement. This work enables application of positronium-imaging techniques to study discrete symmetries in positronium decays.

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mentioning

confidence: 83%

Testing CPT symmetry in ortho-positronium decays with positronium annihilation tomography

Moskal

Gajos

Mohammed

et al. 2021

Preprint

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“…In addition, low-energy precision experiments are used to look for possible new sources of CP violation. Key experiments involve the search for electric dipole moments [62,63,64] plus precision measurements of CP sensitive observables in positronium decays [65,66,67]. So far there is no evidence for new extra sources of CP violation from these low-energy precision experiments.…”

Section: Particle Physics Today -The Very Successful Standard Modelmentioning

confidence: 99%

Emergent gauge symmetries and particle physics

Bass

2020

Progress in Particle and Nuclear Physics

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Hadron properties and interactions are emergent from QCD. Atomic and condensed matter physics are emergent from QED. Could the local gauge symmetries of particle physics also be emergent? We give an introduction to this question and recent ideas connecting it to the (meta)stability of the Standard Model Higgs vacuum. With an emergent Standard Model the gauge symmetries would "dissolve" in the ultraviolet. This scenario differs from unification models which exhibit maximum symmetry in the extreme ultraviolet. With emergence, new global symmetry violations would appear in higher dimensional operators.

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“…Time reversal symmetry violations have not been observed in purely leptonic systems, so far [2][3][4][5]. The Standard Model predicts photon-photon or weak interaction to both give rise to phenomena mimicking a violation of the symmetry in the order of 10 −9 (photonphoton interaction) and 10 −13 (weak interactions), respectively [3,4,[11][12][13].…”

Section: Time-reversal Symmetrymentioning

confidence: 99%

“…Only the most probable decay of o-Ps into (137) three photons BR(o-Ps → 4γ/o-Ps → 3γ) < 2.6 × 10 −6 at 90% C.L. [3,10] is implemented in the J-PET-Geant4 simulator [17]. Since the aim of this research is testing T-symmetry at the sensitivity level of 10 −4 , the less frequent decays of o-Ps are neglected.…”

Section: Monte-carlo Simulationmentioning

confidence: 99%

“…The demonstration of the mirror symmetry being violated by the weak interaction was the first discovery in this domain [1]. So far, there has not been any experimental evidence of a violation of these discrete symmetries in the charged leptonic sector [2][3][4][5]. The Jagiellonian Positron Emission Tomograph (J-PET) is the first PET scanner making use of plastic scintillators [6,7], which is capable of positronium imaging [8,9] as well as testing discrete symmetries in the decay of positronium atoms [10].…”

Section: Introductionmentioning

confidence: 99%

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J-PET Monte Carlo Simulations for Time-Reversal Symmetry Test in Ortho-Positronium Decay

2020

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This article reports the development of Monte Carlo simulations of the J-PET detector using the Geant4 toolkit aimed at serving as a foundation for testing the time-reversal symmetry in the decay of ortho-Positronium (o-Ps) atoms. In order to observe asymmetries in time-reversal, it is important to understand the physical properties of the signal candidates (o-Ps → 3γ) recorded by the detector setup. The simulations aim at replicating the experimental procedure of producing meta-stable triplet states of positronium and testing the T-symmetry using symmetry-odd operators with the Jagiellonian-Positron Emission Tomograph (J-PET) detector.

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QED and Fundamental Symmetries in Positronium Decays

Abstract: We discuss positronium decays with emphasis on tests of fundamental symmetries and the constraints from measurements of other precision observables involving electrons and photons.(1)

Cited by 33 publications

References 60 publications

Testing CPT symmetry in ortho-positronium decays with positronium annihilation tomography

Testing CPT symmetry in ortho-positronium decays with positronium annihilation tomography

Emergent gauge symmetries and particle physics

J-PET Monte Carlo Simulations for Time-Reversal Symmetry Test in Ortho-Positronium Decay

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