High precision light kaonic atoms X-ray spectroscopy is a unique tool for performing experiments equivalent to scattering at vanishing relative energies, to determine the antikaon–nucleus interaction ...at threshold without the need of extrapolation to zero energy. The SIDDHARTA-2 collaboration is going to perform the first measurement of kaonic deuterium transitions to the fundamental level, which is mandatory to extract the isospin dependent antikaon–nucleon scattering lengths. The SIDDHARTA-2 experiment is presently installed on the DA
Φ
NE collider of INFN-LNF. The preliminary results obtained during the machine commissioning phase in preparation for the kaonic deuterium data taking campaign, together with future perspectives for extreme precision kaonic atoms studies at DA
Φ
NE are presented.
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 well as positron annihilation lifetime spectroscopy.
The determination of low-energy cross sections and branching ratios of the
K
-
multi-nucleon absorption processes in
Λ
p
and
Σ
0
p
final states performed by the AMADEUS collaboration is presented. ...Low momentum
K
-
(
p
K
≃
127
MeV
/
c
) produced at the
DA
Φ
NE
collider are impinged on a Carbon target within the KLOE detector and the two and three nucleon absorption processes are disentangled by comparing the experimental data to phenomenological calculations. The
Λ
p
spectra are interpreted in terms of
K
-
multi-nucleon absorption processes; the possible contribution of a
K
-
pp
bound state is demonstrated to overlap with the two nucleon capture process, its absolute yield thus resulting indistinguishable.
Purpose
The time-over-threshold (TOT) technique is being used widely due to itsimplications in developing the multi-channel readouts, mainly when fast signal processing is required. Using the TOT ...technique, as a measure of energy loss instead of charge integration methods, significantly reduces the signal readout costs by combining the time and energy information. Therefore, this approach can potentially be utilized in J-PET tomograph which is built from plastic scintillators characterized by fast light signals. The drawback in adopting this technique lies in the non-linear correlation between input energy loss and TOT of the signal. The main motivation behind this work is to develop the relationship between TOT and energy loss and validate it by the J-PET tomograph setup.
Methods
The experiment was performed using a
22
Na beta emitter source placed in the center of the J-PET tomograph. This isotope produces photons of two different energies: 511 keV photons from the positron annihilation (direct annihilation or through the formation of a para-positronium atom or pick-off process of ortho-positronium atoms) and a 1275 keV prompt photon. This allows the study of the correlation between TOT values and energy loss for energy ranges up to 1000 keV. Since the photon interacts predominantly via Compton scattering inside the plastic scintillator, there is no direct information of the energy deposition. However, using the J-PET geometry, one can measure the scattering angle of the interacting photon. Since the
22
Na source emits photons of two different energies, it is necessary to know unambiguously the energy of incident photons and their corresponding scattering angles in order to estimate energy deposition. In summary, this work presents a dedicated algorithm developed to tag photons of different energies and studying their scattering angles to calculate the energy deposition by the interacting photons.
Results
A new method was elaborated to measure the energy loss by photons interacting with plastic scintillators used in the J-PET tomograph. We find the relationship between the energy loss and TOT is non-linear and can be described by the functions TOT = A0 + A1 * ln(E
dep
+ A2) + A3 * (ln(E
dep
+ A2))
2
and TOT = A0 - A1 * A2
E
dep
. In addition, we also introduced a theoretical model to calculate the TOT as a function of energy loss in plastic scintillators.
Conclusions
A relationship between TOT and energy loss by photons interacting inside the plastic scintillators used in J-PET scanner is established for a deposited energy range of 100–1000 keV.
We report a study of the original image reconstruction algorithm based on the time-of-flight maximum-likelihood expectation-maximization (TOF MLEM), developed for the total-body (TB) Jagiellonian PET ...(J-PET) scanners. The method is applicable to generic cylindrical or modular multilayer layouts and is extendable to multiphoton imaging. The system response matrix (SRM) is represented as a set of analytical functions, uniquely defined for each pair of plastic scintillator strips used for the detection. A realistic resolution model (RM) in detector space is derived from fitting the Monte Carlo simulated emissions and detections of annihilation photons on oblique transverse planes. Additional kernels embedded in SRM account for time-of-flight (TOF), parallax effect, and axial smearing. The algorithm was tested on datasets, simulated in GATE for the NEMA IEC and static extended cardiac-torso phantoms inside a 24-module 2-layer TB J-PET. Compared to the reference TOF MLEM with none or a shift-invariant RM, an improvement was observed, as evaluated by the analysis of image quality, difference images, and ground-truth metrics. We also reconstructed the data with additive contributions, prefiltered geometrically and with non-TOF scatter correction applied. Despite some deterioration, the obtained results still capitalize on the realistic RM with better edge preservation and superior ground-truth metrics. The envisioned prospects of the TOF MLEM with analytical SRM include its application in multiphoton imaging and further upgrade to account for the noncollinearity, positron range, and other factors.
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 nonvanishing angular correlations of final state observables in the decay 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 its performance in reconstruction of three-photon decays are shown along with an analysis of its impact on the sensitivity of the detector for the determination of T-violation sensitive observables.
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