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 PET (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 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.
One of the features of the triplet state of positronium (ortho-Positronium)atoms is its relatively longer lifetime when compared to the singlet states ofpositronium (para-Positronium) atoms. The most probable decay of ortho-Positronium is into three annihilation photons. In order to test the discretesymmetry using the time-reversal symmetry odd-operator, it is importantto identify ortho-Positronium decay. Identification of the decay of ortho-Positronium atoms by measuring the positronium annihilation lifetime withthe Jagiellonian-Positron Emission Tomograph (J-PET) is presented in this article…
This article reports on the feasibility of testing of the symmetry under reversal in time in a purely leptonic system constituted by positronium atoms using the J-PET detector. The present state of T symmetry tests is discussed with an emphasis on the scarcely explored sector of leptonic systems. Two possible strategies of searching for manifestations of T violation in non-vanishing angular correlations of final state observables in the decays of metastable triplet states of positronium available with J-PET are proposed and discussed. Results of a pilot measurement with J-PET and assessment of…
The Jagiellonian Positron Emission Tomograph (J-PET) is a novel de- vice being developed at Jagiellonian University in Krakow, Poland based on or- ganic scintillators. J-PET is an axially symmetric and high acceptance scanner that can be used as a multi-purpose detector system. It is well suited to pur- sue tests of discrete symmetries in decays of positronium in addition to medical imaging. J-PET enables the measurement of both momenta and the polarization vectors of annihilation photons. The latter is a unique feature of the J-PET detector which allows the study of time reversal symmetry vio…
Positronium is a unique laboratory to study fundamental symmetries in the Standard Model, reflection in space ($\mathcal{P}$), reversal in time ($\mathcal{T}$), charge conjugation ($\mathcal{C}$) and their combinations. The experimental limits on the $\mathcal{C}$, $\mathcal{CP}$ and $\mathcal{CPT}$ symmetries violation in the decays of positronium are still several orders of magnitude higher than the expectations. The newly constructed Jagiellonian Positron Emission Tomograph (J-PET) was optimized for the registration of photons from the electron-positron annihilations. It enables tests of di…
The J-PET detector, which consists of inexpensive plastic scintillators, has demonstrated its potential in the study of fundamental physics. In recent years, a prototype with 192 plastic scintillators arranged in 3 layers has been optimized for the study of positronium decays. This allows performing precision tests of discrete symmetries (C, P, T) in the decays of positronium atoms. Moreover, thanks to the possibility of measuring the polarization direction of the photon based on Compton scattering, the predicted entanglement between the linear polarization of annihilation photons in positroni…
The Jagiellonian positron emission tomograph (J-PET) is a multi-purpose device built out of plastic scintillators. With large acceptance and high angular resolution, it is suitable for the studies of various phenomena such as discrete symmetries in decay of positronium atom or entangled states of photons as well as medical imaging. J-PET enables the measurement of momenta together with photon polarization related observables. Large acceptance and high granularity of the J-PET detector enables measurement of ortho-positronium decays into three photons in the whole phase-space. In this paper we …
A detection system of the conventional PET tomograph is set-up to record data from e+ e- annihilation into two photons with energy of 511 keV, and it gives information on the density distribution of a radiopharmaceutical in the body of the object. In this paper we explore the possibility of performing the three gamma photons imaging based on ortho-positronium annihilation, as well as the possibility of positronium mean lifetime imaging with the J-PET tomograph constructed from plastic scintillators. For this purposes simulations of the ortho-positronium formation and its annihilation into thre…
In living organisms the positron-electron annihilation (occurring during the PET imaging) proceeds in about 30% via creation of a metastable ortho-positronium atom. In the tissue, due to the pick-off and conversion processes, over 98% of ortho-positronia annihilate into two 511~keV photons. In this article we assess the feasibility for reconstruction of the mean ortho-positronium lifetime image based on annihilations into two photons. The main objectives of this work include: (i) estimation of the sensitivity of the total-body PET scanners for the ortho-positronium mean lifetime imaging using …
The J-PET tomograph is constructed from plastic scintillator strips arranged axially in concentric cylindrical layers. It enables investigations of positronium decays by measurement of the time, position, polarization and energy deposited by photons in the scintillators, in contrast to studies conducted so far with crystal and semiconductor based detection systems where the key selection of events is based on the measurement of the photons energies. In this article we show that the J-PET tomograph system is capable of exclusive measurements of the decays of ortho-positronium atoms. We present …
The precise measurements of the Compton scatterings of photons originating from the decay of positronium atoms can reveal information about their polarizations. J-PET detector is constructed of 192 plastic scintillators and is unique to study the scattering correlations of the annihilation photons with an angular precision of several degrees. In this work, we present the first experimental evidence showing the feasibility of measuring the photons relative polarization using the J-PET detector.
J-PET is a photon detector built of plastic scintillators, which already has been commissioned for CPT studies in the decays of positronium. In the first experiment, J-PET has achieved a sensitivity to CPT violation at a level of 10^{-4}, and now it aims to reach a level of 10^{-5}. This will be done by enhancing the three-photon registration efficiency for ortho-positronium decays using a new layer of densely packed plastic scintillators termed Modular J-PET. We present the simulation studies performed for different experimental detection setups to be used for the next CPT test with the Modul…
The Jagiellonian Positron Emission Tomograph (J-PET) is the first PET device built from plastic scintillators. It is a multi-purpose detector designed for medical imaging and for studies of properties of positronium atoms in porous matter and in living organisms. In this article we report on the commissioning of the J-PET detector in view of studies of positronium decays. We present results of analysis of the positron lifetime measured in the porous polymer. The obtained results prove that J-PET is capable of performing simultaneous imaging of the density distribution of annihilation points as…
J-PET is a detector optimized for registration of photons from the electron-positron annihilation via plastic scintillators where photons interact predominantly via Compton scattering. Registration of both primary and scattered photons enables to determinate the linear polarization of the primary photon on the event by event basis with a certain probability. Here we present quantitative results on the feasibility of such polarization measurements of photons from the decay of positronium with the J-PET and explore the physical limitations for the resolution of the polarization determination of …
The Positronium (Ps) system, a bound state of an electron and a positron, is suitable for testing the predictions of quantum electrodynamics (QED), since its properties can be perturbatively calculated to high accuracy and, unlike the hydrogen system, is not affected by the finite size or QCD effects at the current experimental precision level. This makes the Ps atom a good laboratory to test the Fundamental Symmetries of Physics and also search for new particles not included in the Standard Model (SM) of physics. On one hand, time reversal (T) and CP symmetry violation have never been observe…
This work concerned two experimental searches for the violation of fundamental discrete symmetries in physical systems originating from electron-positron interactions. The first study was a direct test of the symmetry under reversal in time in transitions of neutral K mesons, performed with quantum-entangled neutral kaon pairs. Data collected by the KLOE experiment operating at the DAFNE collider in 2004-2005 were studied to select events of the KsKl->pi e nu 3pi0 and KsKl->pi+pi- pi e nu processes and compare their rates. Rates of each process identified by two time-ordered neutral kaon decay…
Time-Over-Threshold (TOT) technique is being used widely due to its implications in developing the multi channel readouts mainly when fast signal processing is required. Using TOT technique as a measure of energy loss instead of charge integration methods significantly reduces the signals readout cost by combining the time and energy information. Therefore, this approach can potentially be used in J-PET tomograph which is build from plastic scintillators characterized by fast light signals. The drawback in adopting this technique is lying in the non-linear correlation between input energy loss…
The novel whole-body PET system based on plastic scintillators is developed by the {J-PET} Collaboration. It consists of plastic scintillator strips arranged axially in the form of a cylinder, allowing the cost-effective construction of the total-body PET. In order to determine properties of the scanner prototype and optimize its geometry, advanced computer simulations using the GATE software were performed. The spatial resolution, the sensitivity, the scatter fraction and the noise equivalent count rate were estimated according to the NEMA norm as a function of the length of the tomograph, nu…
Organ-specific, targeted Field-of-View (FoV) Positron Emission Tomography (PET)/Magnetic Resonance Imaging (MRI) inserts are viable solutions for a number of imaging tasks where whole-body PET/MRI systems lack the necessary sensitivity and resolution. To meet the required PET detector performance of these systems, high count-rates and effective spatial resolutions on the order of a few mm, a novel two-axis patterned reflector foil pixelated scintillator crystal array design is developed and its proof-of-concept illustrated in-silico with the Monte Carlo radiation transport modelling toolkit Ge…
We are investigating a prototype virtual pinhole positron emission tomography (VP-PET) system for small animal imaging applications. The PET detector modules were made up of 1.3 mm lutetium-yttrium oxyorthosilicate (LYSO) arrays, and the insert detectors consists of 0.6 mm pixelated Cadmium Zinc Telluride (CdZnTe). To validate the imaging experiment, we conducted a Monte Carlo simulation for the VP-PET system in Geant4 Application for Emission Tomography (GATE). For a point source of Na-22 with 0.5 mm diameter, the filtered back-projection (FBP) algorithm reconstructed PET image shows a resolu…
Pixelated PET systems produce higher count rates as they integrate several detecting channels per detector module. An increased data flow from the detectors posses higher needs on the bandwidth requirements. We aim to optimize the bandwidth usage efficiency by filtering on the fly the detected events with non valid energies. PET systems with a SiPM-ASIC readout scheme are being extensively used to get enhanced images on Time-Of-Flight PET scanners. These kind of digital readout systems are specially interesting for the application of on-line processing techniques given the ease of access to ea…
Current clinical PET systems utilize detectors where the scintillator typically contains single elements of 3 - 6 mm width and about 20 mm height. While providing good TOF performance, this design limits the spatial resolution and causes radial astigmatism as the DOI remains unknown. We propose an alternative, aiming to combine the advantages of current detectors with the DOI capabilities shown for monolithic concepts, based on semi-monolithic scintillators (slabs). An array of 8 monolithic LYSO slabs of dimensions 3.9 x 32 x 19 mm3 was read out by a 64-channel photosensor containing digital S…
We are exploring a scintillator-based detector with potential of high sensitivity, DOI capability and timing resolution in a single-side readout configuration. Our concept combines: 1) A design with 2+ crystal arrays stacked with relative offset, with inherent DOI information but good timing performance has not been shown with conventional light sharing readout. 2) Single crystal array with one-to-one coupling to the photodetector (PD) array, with good timing performance, but no DOI. We believe the combination, where the first layer of a staggered design is coupled one-to-one to a PD array may…
