scholarly journals Sensitivity of Discrete Symmetry Tests in the Positronium System with the J-PET Detector

Symmetry ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1268
Author(s):  
Aleksander Gajos
Keyword(s):  
Detection System ◽  
Discrete Symmetry ◽  
Bound State ◽  
Emission Tomography ◽  
Angular Correlations ◽  
Leptonic Sector ◽  
Positron Emission ◽  
Electron Positron ◽  
Order Of Magnitude ◽  
Symmetry Tests

Study of certain angular correlations in the three-photon annihilations of the triplet state of positronium, the electron–positron bound state, may be used as a probe of potential CP and CPT-violating effects in the leptonic sector. We present the perspectives of CP and CPT tests using this process recorded with a novel detection system for photons in the positron annihilation energy range, the Jagiellonian Positron Emission Tomography (J-PET). We demonstrate the capability of this system to register three-photon annihilations with an unprecedented range of kinematical configurations and to measure the CPT-odd correlation between positronium spin and annihilation plane orientation with a precision improved by at least an order of magnitude with respect to present results. We also discuss the means to control and reduce detector asymmetries in order to allow J-PET to set the first measurement of the correlation between positronium spin and momentum of the most energetic annihilation photon which has never been studied to date.

scholarly journals Increased Functional Vascular Response in the Region of a Glioma

1998 ◽  
Vol 18 (2) ◽  
pp. 148-153 ◽  
Author(s):  
Jeffrey G. Ojemann ◽  
John M. Neil ◽  
Ann-Mary MacLeod ◽  
Daniel L. Silbergeld ◽  
Ralph G. Dacey ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Word Reading ◽  
Preoperative Assessment ◽  
Normal Subjects ◽  
Emission Tomography ◽  
Vascular Response ◽  
Positron Emission ◽  
Order Of Magnitude ◽  
Verb Generation ◽  
Increased Blood Flow

Functional imaging of a language task using positron emission tomography was performed as part of the preoperative assessment of a patient with a left supplementary motor area (SMA) tumor. Positron emission tomography scans were obtained during language tasks (verb generation and word reading of visually presented nouns) that normally lead to increased blood flow in the SMA relative to a control condition (visual fixation). In the patient, the normal SMA response was an order of magnitude larger in the region of the tumor. Other regions, such as left inferior frontal cortex and right cerebellum, showed equivalent activation in the patient and normal subjects. Histopathologic study revealed an anaplastic astrocytoma. Thus, this exaggerated vascular response to local neuronal activation occurred in the setting of a proliferation of glial cells. This is consistent with models of coupling of regional CBF and neuronal activity that implicate glia as the mediatol between neurons and vasculature. The concept that tumoral disruption of normal vascular responses could, in some cases, potentially enhance rather than dampen the response is proposed.

scholarly journals The tests of CP and CPT symmetry using the J-PET detector

2019 ◽  
Vol 199 ◽  
pp. 05027
Author(s):  
Muhsin Mohammed ◽  
Aleksander Gajos
Keyword(s):  
Particle Physics ◽  
Detection System ◽  
Experimental Tests ◽  
Reconstruction Technique ◽  
Positronium Atom ◽  
Cpt Symmetry ◽  
Elementary Particle Physics ◽  
Positron Emission ◽  
Cp Symmetry ◽  
Symmetry Tests

Symmetries under the parity transformation (P), charge-conjugation (C) and time reversal (T) are of fundamental importance in nuclear and elementary particle physics. Studies of the observables violating the combined CP symmetry constitute precise tests of the Standard Model. However, CP violation was observed to date only for systems involving quarks, raising the importance of searches its manifestations e.g. in purely leptonic systems. The 3γ decay of spin-aligned ortho-positronium atoms (o-Ps) can be used to test CP invariance in such a purely leptonic system. The Jagiellonian Positron Emission Tomograph (J-PET) detection system enables experimental tests of CP and CPT through measurement of the expectation values of angular correlation operators odd under these transformations and constructed from (i) spin vector of the ortho-positronium atom, (ii) co-planar momentum vectors of photons originating from the decay of the positronium atom, and (iii) linear polarization direction of annihilation photons. Precise experimental symmetry tests with J-PET are possible thanks to a dedicated reconstruction technique of 3γ ortho-positronium decays and a positronium production chamber including a highly porous aerogel target, whose setup allows for determining the orthopositronium spin polarization without the use of an external magnetic field.

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

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
P. Moskal ◽  
A. Gajos ◽  
M. Mohammed ◽  
J. Chhokar ◽  
N. Chug ◽  
...  
Keyword(s):  
Tomographic Reconstruction ◽  
Bound State ◽  
Cpt Symmetry ◽  
Final State ◽  
Positron Emission Tomography Scanner ◽  
Correlation Operator ◽  
Angular Correlations ◽  
Fundamental Symmetry ◽  
Positron Emission ◽  
Charge Parity

AbstractCharged 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.

Positron Emission Tomography of Cocaine Binding Sites on the Dopamine Transporter

1994 ◽  
Author(s):  
Bertha K. Madras ◽  
◽  
David R. Elmaleh ◽  
Peter C. Meltzer ◽  
Anna Y. Liung ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Dopamine Transporter ◽  
Binding Sites ◽  
Emission Tomography ◽  
Positron Emission
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