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The SIDDHARTA-2 experiment installed at the DA$\mathrm{\Phi}$NE collider of INFN-LNF performed, for the first time, measurements of high-n transitions in intermediate mass kaonic atoms during the data taking campaigns of 2021 and 2022. Kaonic carbon, oxygen, nitrogen and aluminium transitions, which occur in the setup materials, were measured by using the kaons stopped in the gaseous helium target cell with aluminium frames and Kapton walls, and are reported in this paper. These new kaonic atoms measurements add valuable input to the kaonic atoms transitions data base, which is used as a reference for theories and models of the low-energy strong interaction between antikaon and nuclei. Moreover, these results pave the way for future dedicated kaonic atoms measurements through the whole periodic table and to a new era for the antikaon-nuclei studies at low energy., Comment: 8 pages, 7 figures

Background: Total-Body imaging offers high sensitivity, single-bed position, and low dose, but high construction costs limit worldwide utilization. This study compares existing and developing tomographs using plastic scintillators via simulations to propose a cost-efficient Total-Body PET scanner. Methods: Simulations of eight uEXPLORER tomographs with different scintillator materials, axial field-of-view, and detector configuration, and eight J-PET scanners with various field-of-view, plastic scintillator cross-sections, and layers were performed. Biograph Vision was also simulated. Two types of simulations were conducted with a central source and a water-filled phantom. Results: BGO crystal-based scanners showed the best sensitivity (350 cps/kBq at the center). Sparse geometry or LYSO crystals reduced sensitivity. J-PET design showed similar sensitivity to sparse LYSO detectors, with full body coverage and additional gain for brain imaging. Conclusion: The J-PET tomography system using plastic scintillators could be a cost-efficient alternative for Total-Body PET scanners, overcoming high construction costs while maintaining sensitivity

Objective: The aim of this work is to investigate the feasibility of the Jagiellonian Positron Emission Tomography (J-PET) scanner for intra-treatment proton beam range monitoring. Approach: The Monte Carlo simulation studies with GATE and PET image reconstruction with CASToR were performed in order to compare six J-PET scanner geometries (three dual-heads and three cylindrical). We simulated proton irradiation of a PMMA phantom with a Single Pencil Beam (SPB) and Spread-Out Bragg Peak (SOBP) of various ranges. The sensitivity and precision of each scanner were calculated, and considering the setup's cost-effectiveness, we indicated potentially optimal geometries for the J-PET scanner prototype dedicated to the proton beam range assessment. Main results: The investigations indicate that the double-layer cylindrical and triple-layer double-head configurations are the most promising for clinical application. We found that the scanner sensitivity is of the order of 10$^{-5}$ coincidences per primary proton, while the precision of the range assessment for both SPB and SOBP irradiation plans was found below 1 mm. Among the scanners with the same number of detector modules, the best results are found for the triple-layer dual-head geometry. Significance: We performed simulation studies demonstrating that the feasibility of the J-PET detector for PET-based proton beam therapy range monitoring is possible with reasonable sensitivity and precision enabling its pre-clinical tests in the clinical proton therapy environment. Considering the sensitivity, precision and cost-effectiveness, the double-layer cylindrical and triple-layer dual-head J-PET geometry configurations seem promising for the future clinical application. Experimental tests are needed to confirm these findings., Comment: 19 pages, 7 pages

Positronium is the simplest bound state, built of an electron and a positron. Studies of positronium in vacuum and its decays in medium tell us about Quantum Electrodynamics, QED, and about the structure of matter and biological processes of living organisms at the nanoscale, respectively. Spectroscopic measurements constrain our understanding of QED bound state theory. Searches for rare decays and measurements of the effect of gravitation on positronium are used to look for new physics phenomena. In biological materials positronium decays are sensitive to the inter- and intra-molecular structure and to the metabolism of living organisms ranging from single cells to human beings. This leads to new ideas of positronium imaging in medicine using the fact that during positron emission tomography (PET) as much as 40% of positron annihilation occurs through the production of positronium atoms inside the patient's body. A new generation of the high sensitivity and multi-photon total-body PET systems opens perspectives for clinical applications of positronium as a biomarker of tissue pathology and the degree of tissue oxidation., Comment: Colloquium, 23 pages, preprint of article in Reviews of Modern Physics

We present the tests performed by the SIDDHARTA-2 collaboration at the DA{\Phi}NE collider with a quasi-hemispherical CdZnTe detector. The very good room-temperature energy resolution and efficiency in a wide energy range show that this detector technology is ideal for studying radiative transitions in intermediate and heavy-mass kaonic atoms. The CdZnTe detector was installed for the first time in an accelerator environment to perform tests on the background rejection capabilities, which were achieved by exploiting the SIDDHARTA-2 Luminosity Monitor. A spectrum with an $^{241}Am$ source has been acquired, with beams circulating in the main rings, and peak resolutions of 6% at 60 keV and of 2.2% at 511 keV have been achieved. The background suppression factor, which turned out to be of the order of $\simeq10^{5-6}$, opens the possibility to plan for future kaonic atom measurements with CdZnTe detectors.

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.

With growing sophistication and volume of cyber attacks combined with complex network structures, it is becoming extremely difficult for security analysts to corroborate evidences to identify multistage campaigns on their network. This work develops HeAT (Heated Alert Triage): given a critical indicator of compromise (IoC), e.g., a severe IDS alert, HeAT produces a HeATed Attack Campaign (HAC) depicting the multistage activities that led up to the critical event. We define the concept of "Alert Episode Heat" to represent the analysts opinion of how much an event contributes to the attack campaign of the critical IoC given their knowledge of the network and security expertise. Leveraging a network-agnostic feature set, HeAT learns the essence of analyst's assessment of "HeAT" for a small set of IoC's, and applies the learned model to extract insightful attack campaigns for IoC's not seen before, even across networks by transferring what have been learned. We demonstrate the capabilities of HeAT with data collected in Collegiate Penetration Testing Competition (CPTC) and through collaboration with a real-world SOC. We developed HeAT-Gain metrics to demonstrate how analysts may assess and benefit from the extracted attack campaigns in comparison to common practices where IP addresses are used to corroborate evidences. Our results demonstrates the practical uses of HeAT by finding campaigns that span across diverse attack stages, remove a significant volume of irrelevant alerts, and achieve coherency to the analyst's original assessments.

Total-Body PET is one of the most promising medical diagnostics modalities. The high sensitivity provided by Total-Body technology can be advantageous for novel tomography methods like positronium imaging. Several efforts are ongoing to lower the price of the TB-PET systems. Among the alternatives, the Jagiellonian PET (J-PET) technology, based on plastic scintillator strips, offers a low-cost alternative. The work aimed to compare five Total-Body J-PET geometries as a possible next generation J-PET scanner design. We present comparative studies of performance characteristics of the cost-effective Total-Body PET scanners using J-PET technology. We investigated in silico five Total-Body scanner geometries. Monte Carlo simulations of the XCAT phantom, the 2-meter sensitivity line source and positronium sensitivity phantoms were performed. We compared the sensitivity profiles for 2-gamma and 3-gamma tomography, relative cost of the setups and performed quantitative analysis of the reconstructed images. The analysis of the reconstructed XCAT images reveals the superiority of the seven-ring scanners over the three-ring setups. However, the three-ring scanners would be approximately 2-3 times cheaper. The peak sensitivity values for two-gamma vary from 20 to 34 cps/kBq. The sensitivity curves for the positronium tomography have a similar shape to the two-gamma sensitivity profiles. The peak values are lower compared to the two-gamma cases, from about 20-28 times, with a maximum of 1.66 cps/kBq. The results show the feasibility of multi-organ imaging of all the systems to be considered for the next generation of TB J-PET designs. The relative cost for all the scanners is about 10-4 times lower compared to the cost of the uExplorer. These properties coupled together with J-PET cost-effectiveness, make the J-PET technology an attractive solution for broad application in clinics.

Tests of the T, CP and CPT symmetries in the neutral kaon system are performed by the direct comparison of the probabilities of a kaon transition process to its symmetry-conjugate. The exchange of in and out states required for a genuine test involving an anti-unitary transformation implied by time-reversal is implemented exploiting the entanglement of $K^0\bar{K}{}^0$ pairs produced at a $\phi$-factory. A data sample collected by the KLOE experiment at DA$\Phi$NE corresponding to an integrated luminosity of about 1.7 fb$^{-1}$ is analysed to study the $\Delta$t distributions of the $\phi\to K_{S}K_{L}\to \pi^+\pi^- \: \pi^{\pm}e^{\mp}\nu$ and $\phi\to K_{S}K_{L}\to \pi^{\pm}e^{\mp}\nu \: 3\pi^0$ processes, with $\Delta$t the difference of the kaon decay times. A comparison of the measured $\Delta$t distributions in the asymptotic region $\Delta t \gg \tau_{S}$ allows to test for the first time T and CPT symmetries in kaon transitions with a precision of few percent, and to observe CP violation with this novel method., Comment: 26 pages, 10 figures. Minor style corrections applied before journal submission. Sumbmitted to Physics Letters B

We report the first simultaneous and independent measurements of the K$^{-}$p $\rightarrow \Sigma^0 \, \pi^{0}$ and K$^{-}$p $\rightarrow \Lambda \, \pi^{0}$ cross sections around 100 MeV/c kaon momentum. The kaon beam delivered by the DA$\Phi$NE collider was exploited to detect K$^-$ absorptions on Hydrogen atoms, populating the gas mixture of the KLOE drift chamber. The precision of the measurements ($\sigma_{K^- p \rightarrow \Sigma^0 \pi^0} = 42.8 \pm 1.5 (stat.) ^{+2.4}_{-2.0}(syst.) \ \mathrm{mb}$ and $\sigma_{K^- p \rightarrow \Lambda \pi^0} = 31.0 \pm 0.5 (stat.) ^{+1.2}_{-1.2}(syst.) \ \mathrm{mb}\,$) is the highest yet obtained in the low kaon momentum regime.

Entanglement of photons originating from the electron-positron annihilation has not been proven experimentally. Though the independent experiments performed so far unanimously confirm that correlation between the linear polarizations of back-to-back photons from the electron-positron annihilation is consistent with the assumption that these photons are entangled in polarization. Yet, unexpectedly, recent experiments differ as regards the correlation of polarization direction of back-to-back photons after the decoherence induced by scattering of one of these photons on the electron in the scattering material. In one of the experiments, the correlation before and after the decoherence of the photon state is the same and in the other experiment the scattering of one photon leads to a significant decrease in this correlation. Here we discuss this puzzle. The decoherent states were ensured by forcing one of the annihilation photons through prior scattering before the Compton kinematics based measurement of the polarization correlation. A comparison between the experimental setups used for the different measurements and the results obtained are briefly discussed, highlighting the parameters that are important for performing such measurements. Finally, the main features of the J-PET detector are presented with the schemes for performing similar measurements so that the results can be used as conclusive remarks for solving this puzzle. Solving the decoherence puzzle will have crucial consequences for basic studies of entanglement, as well as for the proposed application of polarisation of photons in positron emission tomography. In case if the correlation of polarisation of back-to-back photons from the electron-positron annihilation is the same before and after the scattering of these photons, then it will not be useful for the reduction of the scatter fraction in PET diagnostics.

The SIDDHARTA-2 experiment at the DA$\Phi$NE collider aims to perform precision measurements of kaonic atoms X-ray spectroscopy for the investigation of the antikaon-nucleon strong interaction. To achieve this goal, novel large-area Silicon Drift Detectors (SDDs) have been developed. These devices have special geometry, field configuration and readout electronics that ensure excellent performance in terms of linearity and stability. The paper presents preliminary results for the linearity determination and stability monitoring of the SDDs system during the measurement of kaonic deuterium carried out in the summer of 2022.

The branching fraction for the decay $K_S \to \pi e \nu$ has been measured with a sample of 300 million $K_S$ mesons produced in $\phi \to K_L K_S$ decays recorded by the KLOE experiment at the DA$\Phi$NE $e^+e^-$ collider. Signal decays are selected by a boosted decision tree built with kinematic variables and time-of-flight measurements. Data control samples of $K_L \to \pi e \nu$ decays are used to evaluate signal selection efficiencies. A fit to the reconstructed electron mass distribution finds 49647$\pm$316 signal events. Normalising to the $K_S \to \pi^+\pi^-$ decay events the result for the branching fraction is $\mathcal{B}(K_S \to \pi e \nu) = (7.211 \pm 0.046_{\rm stat} \pm 0.052_{\rm syst}) \times10^{-4}$. The combination with our previous measurement gives $\mathcal{B}(K_S \to \pi e \nu) = (7.153 \pm 0.037_{\rm stat} \pm 0.043_{\rm syst}) \times10^{-4}$. From this value we derive $f_+(0)|V_{us}| = 0.2170 \pm 0.009$., Comment: arXiv admin note: substantial text overlap with arXiv:1912.05990

In this paper, we present the first tests performed after the full installation of the SIDDHARTA-2 experimental apparatus on the Interaction Region of the DA{\Phi}NE collider at the INFN National Laboratories of Frascati. Before starting the first measurement of the kaonic deuterium 2p{\rightarrow}1s transition, accurate evaluation of the background rejection. mainly achieved with the Kaon Trigger system, was required. This run, performed in the period 04-26/05/2022 with a 4 He gaseous target, confirmed the 10^5 rejection factor obtained with a reduced version of the setup and different machine conditions in 2021. This important outcome motivated the filling of the target cell with deuterium and the starting of the measurement campaign of the kaonic deuterium 2p{\rightarrow}1s transition.

The SIDDHARTA-2 experiment at the DA$\Phi$NE collider aims to perform the first kaonic deuterium X-ray transitions to the fundamental level measurement, with a systematic error at the level of a few eV. To achieve this challenging goal the experimental apparatus is equipped with 384 Silicon Drift Detectors (SDDs) distributed around its cryogenic gaseous target. The SDDs developed by the SIDDHARTA-2 collaboration are suitable for high precision kaonic atoms spectroscopy, thanks to their high energy and time resolutions combined with their radiation hardness. The energy response of each detector must be calibrated and monitored to keep the systematic error, due to processes such as gain fluctuations, at the level of 2-3 eV. This paper presents the SIDDHARTA-2 calibration method which was optimized during the preliminary phase of the experiment in the real background conditions of the DA$\Phi$NE collider, which is a fundamental tool to guarantee the high precision spectroscopic performances of the system over long periods of data taking, as that required for the kaonic deuterium measurement.

Kaonic atoms are a unique tool to explore quantum chromodynamics in the strangeness sector at low energy, with implications reaching neutron stars and dark matter. Precision X-ray spectroscopy can fully unlock the at-threshold isospin dependent antikaon-nucleon scattering lengths, via the atomic transitions to the fundamental level. While the SIDDHARTA experiment at the INFN-LNF DA$\Phi$NE collider successfully measured kaonic hydrogen, its successor SIDDHARTA-2 is starting now its data taking campaign aiming to finally fully disentangle the isoscalar and isovector scattering lengths via the measurement of kaonic deuterium. An overview of the first experimental results from a preparatory run for the SIDDAHARTA-2 experiment is presented., Comment: 13 pages, 7 figures, to be sumbitted to Phys. Scr. - Focus on New Frontiers in Physics - Selected Papers from ICNFP 2021

The SIDDHARTINO experiment at the DA{\Phi}NE Collider of INFN-LNF, the pilot run for the SIDDHARTA-2 experiment which aims to perform the measurement of kaonic deuterium transitions to the fundamental level, has successfully been concluded. The paper reports the main results of this run, including the optimization of various components of the apparatus, among which the degrader needed to maximize the fraction of kaons stopped inside the target, through measurements of kaonic helium transitions to the 2p level. The obtained shift and width values are {\epsilon}_2p = E_exp-E_e.m = 0.2 {\pm} 2.5(stat) {\pm} 2(syst) eV and {\Gamma}_2p = 8 {\pm} 10 eV (stat), respectively. This new measurement of the shift, in particular, represents the most precise one for a gaseous target and is expected to contribute to a better understanding of the kaon-nuclei interaction at low energy.

In vivo assessment of cancer and precise location of altered tissues at initial stages of molecular disorders are important diagnostic challenges. Positronium is copiously formed in the free molecular spaces in the patient's body during positron emission tomography (PET). The positronium properties vary according to the size of inter- and intramolecular voids and the concentration of molecules in them such as, e.g., molecular oxygen, O2; therefore, positronium imaging may provide information about disease progression during the initial stages of molecular alterations. Current PET systems do not allow acquisition of positronium images. This study presents a new method that enables positronium imaging by simultaneous registration of annihilation photons and deexcitation photons from pharmaceuticals labeled with radionuclides. The first positronium imaging of a phantom built from cardiac myxoma and adipose tissue is demonstrated. It is anticipated that positronium imaging will substantially enhance the specificity of PET diagnostics., Comment: 10 pages, 5 figures

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 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., Comment: This is a preprint of an article published in Nature Communications. The final version is available at https://rdcu.be/cCQqq