arXiv subjects

K. Dulski

Publications and source records attributed to K. Dulski.

At least 19 recordsLinked to original sources

arXiv2026

High-precision measurement of the kaonic hydrogen 1s level shift and width with SIDDHARTA-2

Kaonic atoms provide a unique experimental probe of strong interaction in the low-energy regime. In particular, the strong-interaction-induced shift ($\varepsilon_{1\text{s}}$) and width ($\Gamma_{1\text{s}}$) of kaonic hydrogen directly constrain the low-energy antikaon-nucleon ($\bar{K}N$) interaction at threshold and the theoretical description of the $\Lambda$(1405) resonance. We report a new high-precision measurement of kaonic hydrogen X-ray transitions performed by the SIDDHARTA-2 experiment at the DA$\Phi$NE collider (INFN-LNF), based on an integrated luminosity of 237 pb$^{-1}$. The extracted values, $\varepsilon_{1\text{s}}\,=\,-303.0\,\pm\,17.0\,(stat.)\,\pm\,2.5\,(syst.)$ eV and $\Gamma_{1\text{s}}\,=\,607\,\pm\,62\,(stat.)\,\pm\,6\,(syst.)$ eV, represent the most precise determination to date, improving the precision by approximately a factor-of-two with respect to the previous SIDDHARTA measurement. These results significantly tighten the experimental constraints on theoretical description of the low-energy $\bar{K}N$ interaction.

nucl-ex↗

arXiv2026

Bound-state QED test above the Schwinger limit with kaonic fluorine

Kaonic atoms, formed when a negatively charged kaon replaces an electron in an atomic orbit, provide access to bound-state quantum electrodynamics (BSQED) in electromagnetic fields far stronger than in ordinary atoms. Here, we report an experimental test of BSQED in a regime where the mean Coulomb field exceeds the Schwinger limit. Using high-precision x-ray spectroscopy of kaonic fluorine with the SIDDHARTA-2 experiment at DA$\Phi$NE, corresponding to an integrated luminosity of 22.4 pb$^{-1}$, we observe transitions involving the 4f and 3d levels, probing field-to-Schwinger-limit ratios of 1.11 and 3.70, respectively. The measured transition energies agree with state-of-the-art Dirac-Fock calculations. In particular, the 5g-4f transition showing a residual of 5.8 $\pm$ 4.7 (stat.) $\pm$ 5.5 (syst.) eV and a $\sim$ 9$\sigma$ sensitivity to QED contributions. These results provide a direct test of BSQED in the strong-field regime of QED above the Schwinger limit, opening a new avenue for precision studies in extreme electromagnetic fields.

physics.atom-ph↗

arXiv2025

Precision Test of Bound-State QED at Intermediate-Z with Kaonic Neon

We report Dirac-Fock calculations of transition energies for kaonic neon (KNe). For the most intense line, the 7-6 transition, the calculated energy is 9450.28 eV, which includes a bound-state QED (BSQED) contribution of 12.66 eV. This is in excellent agreement with the recent SIDDHARTHA-2 measurement at DA$\Phi$NE of 9450.23 $\pm$ 0.37 (stat.) $\pm$ 1.50 (syst.) eV. With the QED shift far exceeding experimental uncertainty, these results establish kaonic atoms as powerful platforms for precision tests of BSQED in intermediate-Z systems.

physics.atom-ph↗

arXiv2025

Probing arbitrary polarized photon pairs undergoing double Compton scatterings by a dedicated MC simulator validated with experimental data

Quantum correlations in the polarization degrees of freedom of the two-photon system have been extensively studied and form our current understanding of the quantum nature of our world. Most of the studies are concentrated on the low-energy (optical) photon pairs, for which efficient polarization measurement devices exist. However, for high-energetic (MeV) pairs of photons, e.g. produced in the decay of positronium atoms, no polarizers are available. Partial information about the polarization degree of freedom can be extracted by exploiting the measurements of photon pairs that undergo double Compton scattering. We present a Geant4-based Monte Carlo Vienna-Warsaw model capable of simulating any initial polarization state of bipartite photons. This puts us in a position to derive the behavior of the experimental observable, the angular difference $\Delta\hat\Phi$ formed by the two scattering planes. We validate our Vienna-Warsaw simulator with the high-statistics experimental sample -- based on a total of $3 \times 10^5 $ event candidates -- of two-photon pairs measured with the J-PET Big Barrel detector. We deduce the value of the squared visibility (interference contrast) encoding the polarization in the angle difference of the two scattering planes, $\Delta\hat\Phi$. The simulated spectra are in good agreement with the experimental correlation spectra and behave as predicted by theory.

physics.ins-det↗

arXiv2024

Development of the normalization method for the first large field-of-view plastic-based PET Modular scanner

In positron emission tomography acquisition (PET), sensitivity along a line of response can vary due to crystal geometrical arrangements in the scanner and/or detector inefficiencies, leading to severe artefacts in the reconstructed image. To mitigate these effects, data must be corrected by a set of normalization coefficients applied to each line of response. The J-PET Modular scanner is a PET device made of 50 cm long plastic strips arranged axially, currently in operation at the Jagiellonian University in Krak\'ow (Poland). We have implemented a normalization method for the large field-of-view plastic-based J-PET Modular scanner using the component-based approach. We estimated the geometric normalization factors for the J-PET Modular scanner using Monte Carlo simulations. We also analysed the effects of variations in detection efficiency. A dedicated cylindrical phantom was simulated to investigate the impact of various factors on image quality. The image quality was quantified in terms of radial and axial uniformity metrics, and the standard deviation to mean intensity ratio, determined for a set of image slices. Without normalization, reconstructions of a uniform cylinder exhibit artefacts. These artefacts were satisfactorily compensated using the normalization factors. Applying geometrical corrections lowers the non-uniformity of the image expressed as a standard deviation-to-mean ratio to a range between 5.5 % to 8.5 %. Computationally, the technique is straightforward to parallelize, making it time-efficient. Preliminary estimates suggest that the method is appropriate for use with long axial field-of-view scanners, such as the total-body J-PET, currently under development at the Jagiellonian University.

physics.med-ph↗

arXiv2024

Nanoporosity imaging by positronium lifetime tomography

Positron Annihilation Lifetime Spectroscopy (PALS) is a well-established non-destructive technique used for nanostructural characterization of porous materials. It is based on the annihilation of a positron and an electron. Mean positron lifetime in the material depends on the free voids size and molecular environment, allowing the study of porosity and structural transitions in the nanometer scale. We have developed a novel method enabling spatially resolved PALS, thus providing tomography of nanostructural characterization of an extended object. Correlating space (position) and structural (lifetime) information brings new insight in materials studies, especially in the characterization of the purity and pore distribution. For the first time, a porosity image using stationary positron sources for the simultaneous measurement of the porous polymers XAD4, silica aerogel powder IC3100, and polyvinyl toluene scintillator PVT by the J-PET tomograph is demonstrated

physics.app-ph↗

arXiv2024

Investigation of Novel Preclinical Total Body PET Designed With J-PET Technology:A Simulation Study

The growing interest in human-grade total body positron emission tomography (PET) systems has also application in small animal research. Due to the existing limitations in human-based studies involving drug development and novel treatment monitoring, animal-based research became a necessary step for testing and protocol preparation. In this simulation-based study two unconventional, cost-effective small animal total body PET scanners (for mouse and rat studies) have been investigated in order to inspect their feasibility for preclinical research. They were designed with the novel technology explored by the Jagiellonian-PET (J-PET) Collaboration. Two main PET characteristics: sensitivity and spatial resolution were mainly inspected to evaluate their performance. Moreover, the impact of the scintillator dimension and time-of-flight on the latter parameter was examined in order to design the most efficient tomographs. The presented results show that for mouse TB J-PET the achievable system sensitivity is equal to 2.35% and volumetric spatial resolution to 9.46 +- 0.54 mm3, while for rat TB J-PET they are equal to 2.6% and 14.11 +- 0.80 mm3, respectively. Furthermore, it was shown that the designed tomographs are almost parallax-free systems, hence, they resolve the problem of the acceptance criterion tradeoff between enhancing spatial resolution and reducing sensitivity.

physics.med-ph↗

arXiv2024

Comparative studies of plastic scintillator strips with high technical attenuation length for the total-body J-PET scanner

Plastic scintillator strips are considered as one of the promising solutions for the cost-effective construction of total-body positron emission tomography, (PET) system. The purpose of the performed measurements is to compare the transparency of long plastic scintillators with dimensions 6 mm x 24 mm x 1000 mm and with all surfaces polished. Six different types of commercial, general purpose, blue-emitting plastic scintillators with low attenuation of visible light were tested, namely: polyvinyl toluene-based BC-408, EJ-200, RP-408, and polystyrene-based Epic, SP32 and UPS-923A. For determination of the best type of plastic scintillator for totalbody Jagiellonian positron emission tomograph (TB-J-PET) construction, emission and transmission spectra, and technical attenuation length (TAL) of blue light-emitting by the scintillators were measured and compared. The TAL values were determined with the use of UV lamp as excitation source, and photodiode as light detector. Emission spectra of investigated scintillators have maxima in the range from 420 nm to 429 nm. The BC-408 and EJ-200 have the highest transmittance values of about 90% at the maximum emission wavelength measured through a 6 mm thick scintillator strip and the highest technical attenuation length reaching about 2000 mm, allowing assembly of long detection modules for time-of-flight (TOF) J-PET scanners. Influence of the 6 mm x 6 mm, 12 mm x 6 mm, 24 mm x 6 mm cross-sections of the 1000 mm long EJ-200 plastic scintillator on the TAL and signal intensity was measured. The highest TAL value was determined for samples with 24 mm x 6 mm cross-section.

physics.ins-det↗

arXiv2024

Non-maximal entanglement of photons from positron-electron annihilation demonstrated using a novel plastic PET scanner

In state-of-the-art Positron Emission Tomography (PET), information about annihilation photon polarization is unavailable. Here, we present a PET scanner built from plastic scintillators, where annihilation photons primarily interact via the Compton effect, providing information about both photon polarization and propagation direction. Using this plastic-based PET, we determined the distribution of the relative angle between polarization planes of photons from positron-electron annihilation in a porous polymer. The amplitude of the observed distribution is smaller than predicted for maximally quantum-entangled two-photon states but larger than expected for separable photons. This result can be well explained by assuming that photons from pick-off annihilation are not entangled, while photons from direct and para-positronium annihilations are maximally entangled. Our result indicates that the degree of entanglement depends on the annihilation mechanism in matter, opening new avenues for exploring polarization correlations in PET as a diagnostic indicator.

nucl-ex↗

arXiv2024

Kaonic lead feasibility measurement at DA{\Phi}NE to solve the charged kaon mass discrepancy

An HPGe detector equipped with a transistor reset preamplifier and readout with a CAEN DT5781 fast pulse digitizer was employed in the measurement of X-rays from kaonic lead at the DA$\Phi$NE $e^+e^-$ collider at the Laboratori Nazionali di Frascati of INFN. A thin scintillator in front of a lead target was used to select kaons impinging on it and to form the trigger for the HPGe detector. We present the results of the kaonic lead feasibility measurement, where we show that the resolution of the HPGe detector in regular beam conditions remains the same as that without the beam and that a satisfactory background reduction can be achieved. This measurement serves as a test bed for future dedicated kaonic X-rays measurements for the more precise determination of the charged kaon mass.

physics.ins-det↗

arXiv2023

SIDDHARTA-2 apparatus for kaonic atoms research on the DA$\Phi$NE collider

SIDDHARTA-2 represents a state-of-the-art experiment designed to perform dedicated measurements of kaonic atoms, which are particular exotic atom configurations composed of a negatively charged kaon and a nucleus. Investigating these atoms provides an exceptional tool to comprehend the strong interactions in the non-perturbative regime involving strangeness. The experiment is installed at the DA$\Phi$NE electron-positron collider, of the INFN National Laboratory of Frascati (INFN-LNF) in Italy, aiming to perform the first-ever measurement of the 2p$\rightarrow$1s X-ray transitions in kaonic deuterium, a crucial step towards determining the isospin-dependent antikaon-nucleon scattering lengths. Based on the experience gained with the previous SIDDHARTA experiment, which performed the most precise measurement of the kaonic hydrogen 2p$\rightarrow$1s X-ray transitions, the present apparatus has been upgraded with innovative Silicon Drift Detectors (SDDs), distributed around a cryogenic gaseous target placed in a vacuum chamber at a short distance above the interaction region of the collider. We present a comprehensive description of the SIDDHARTA-2 setup including the optimization of its various components during the commissioning phase of the collider.

physics.ins-det↗

arXiv2023

Feasibility studies for imaging e$^{+}$e$^{-}$ annihilation with modular multi-strip detectors

Studies based on imaging the annihilation of the electron (e$^{-}$) and its antiparticle positron (e$^{+}$) open up several interesting applications in nuclear medicine and fundamental research. The annihilation process involves both the direct conversion of e$^{+}$e$^{-}$ into photons and the formation of their atomically bound state, the positronium atom (Ps), which can be used as a probe for fundamental studies. With the ability to produce large quantities of Ps, manipulate them in long-lived Ps states, and image their annihilations after a free fall or after passing through atomic interferometers, this purely leptonic antimatter system can be used to perform inertial sensing studies in view of a direct test of Einstein equivalence principle. It is envisioned that modular multistrip detectors can be exploited as potential detection units for this kind of studies. In this work, we report the results of the first feasibility study performed on a e$^{+}$ beamline using two detection modules to evaluate their reconstruction performance and spatial resolution for imaging e$^{+}$e$^{-}$ annihilations and thus their applicability for gravitational studies of Ps.

physics.ins-det↗

arXiv2023

TOF MLEM Adaptation for the Total-Body J-PET with a Realistic Analytical System Response Matrix

We report a study of the original image reconstruction algorithm based on the time-of-flight maximum likelihood expectation maximisation (TOF MLEM), developed for the total-body (TB) Jagiellonian PET (J-PET) scanners. The method is applicable to generic cylindrical or modular multi-layer layouts and is extendable to multi-photon 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 TOF, parallax effect and axial smearing. The algorithm was tested on datasets, simulated in GATE for the NEMA IEC and static XCAT 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, pre-filtered geometrically and with non-TOF scatter correction applied. Despite some deterioration, the obtained results still capitalise 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 multi-photon imaging and further upgrade to account for the non-collinearity, positron range and other factors.

physics.med-ph↗

arXiv2023

J-PET detection modules based on plastic scintillators for performing studies with positron and positronium beams

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 positronium decays can also be studied. Recently, a new J-PET prototype was commissioned, based on a modular design of detection units. Each module consists of 13 plastic scintillators and can be used as a stand-alone, compact and portable detection unit. In this paper, the main features of the J-PET detector, the modular prototype and their applications for possible studies with positron and positronium beams are discussed. Preliminary results of the first test experiment performed on two detection units in the continuous positron beam recently developed at the Antimatter Laboratory (AML) of Trento are also reported.

physics.ins-det↗

arXiv2021

Optimisation of the event-based TOF filtered back-projection for online imaging in total-body J-PET

We perform a parametric study of the newly developed time-of-flight (TOF) image reconstruction algorithm, proposed for the real-time imaging in total-body Jagiellonian PET (J-PET) scanners. The asymmetric 3D filtering kernel is applied at each most likely position of electron-positron annihilation, estimated from the emissions of back-to-back $γ$-photons. The optimisation of its parameters is studied using Monte Carlo simulations of a 1-mm spherical source, NEMA IEC and XCAT phantoms inside the ideal J-PET scanner. The combination of high-pass filters which included the TOF filtered back-projection (FBP), resulted in spatial resolution, 1.5 $\times$ higher in the axial direction than for the conventional 3D FBP. For realistic $10$-minute scans of NEMA IEC and XCAT, which require a trade-off between the noise and spatial resolution, the need for Gaussian TOF kernel components, coupled with median post-filtering, is demonstrated. The best sets of 3D filter parameters were obtained by the Nelder-Mead minimisation of the mean squared error between the resulting and reference images. The approach allows training the reconstruction algorithm for custom scans, using the IEC phantom, when the temporal resolution is below 50 ps. The image quality parameters, estimated for the best outcomes, were systematically better than for the non-TOF FBP.

physics.med-ph↗

arXiv2021

The J-PET detector -- a tool for precision studies of ortho-positronium decays

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 first positronium production results, its lifetime distribution measurements and discuss estimation of the influence of various background sources. The tomograph s performance demonstrated here makes it suitable for precision studies of positronium decays including entanglement of the final state photons, positron annihilation lifetime spectroscopy plus molecular imaging diagnostics.

physics.ins-det↗

arXiv2020

Synchronisation and calibration of the 24-modules J-PET prototype with 300~mm axial field of view

Research conducted in the framework of the J-PET project aims to develop a cost-effective total-body positron emission tomography scanner. As a first step on the way to construct a full-scale J-PET tomograph from long strips of plastic scintillators, a 24-strip prototype was built and tested. The prototype consists of detection modules arranged axially forming a cylindrical diagnostic chamber with the inner diameter of 360 mm and the axial field-of-view of 300 mm. Promising perspectives for a low-cost construction of a total-body PET scanner are opened due to an axial arrangement of strips of plastic scintillators, wchich have a small light attenuation, superior timing properties, and the possibility of cost-effective increase of the axial field-of-view. The presented prototype comprises dedicated solely digital front-end electronic circuits and a triggerless data acquisition system which required development of new calibration methods including time, thresholds and gain synchronization. The system and elaborated calibration methods including first results of the 24-module J-PET prototype are presented and discussed. The achieved coincidence resolving time equals to CRT = 490 $\pm$ 9 ps. This value can be translated to the position reconstruction accuracy $σ(Δl) =$ 18 mm which is fairly position-independent.

physics.ins-det↗

arXiv2020

Hit-time and hit-position reconstruction in strips of plastic scintillators using multi-threshold readouts

In this article, a new method for the reconstruction of hit-position and hit-time of photons in long scintillator detectors is investigated. This research is motivated by the recent development of the positron emission tomography scanners based on plastic scintillators. The proposed method constitutes a new way of signal processing in Multi-Voltage-Technique. It is based on the determination of the degree of similarity between the registered signals and the synchronized model signals stored in a library. The library was established for a set of well defined hit-positions along the length of the scintillator. The Mahalanobis distance was used as a measure of similarity between the two compared signals. The method was validated on the experimental data measured using two-strips J-PET prototype with dimensions of 5x9x300 mm$^3$. The obtained Time-of-Flight (TOF) and spatial resolutions amount to 325~ps (FWHM) and 25~mm (FWHM), respectively. The TOF resolution was also compared to the results of an analogous study done using Linear Fitting method. The best TOF resolution was obtained with this method at four pre-defined threshold levels which was comparable to the resolution achieved from the Mahalanobis distance at two pre-defined threshold levels. Although the algorithm of Linear Fitting method is much simpler to apply than the Mahalanobis method, the application of the Mahalanobis distance requires a lower number of applied threshold levels and, hence, decreases the costs of electronics used in PET scanner.

physics.ins-det↗