Kaonic Atoms Research Articles

Development of high-efficiency X-ray detectors based on 1 mm thick monolithic SDD arrays

We present the novel 2× 4 monolithic Silicon Drift Detectors (SDD) array of 1 mm thickness developed within the context of the SIDDHARTA-2 experiment for high-energy X-ray spectroscopy measurements of light kaonic atom transitions. It represents a state-of-the-art advancement in terms of detection efficiency with respect to the previous generation of detectors, having a thickness of 450 μm. The sensor features eight square SDD units with an active area of 8 × 8 mm2 each, arranged in a 2 × 4 matrix. Therefore, the total active area of the array is 32 × 16 mm2 while the total chip area is 36 × 20 mm2, including a 2-mm dead region on each side of the array. This new version of SDD arrays, manufactured by Fondazione Bruno Kessler (FBK), includes an additional electrode on its entrance window, designed to reduce charge sharing between adjacent channels and improve energy resolution. This article describes two different detection modules based on these arrays: the first module includes a single array, whereas the second one is composed of two 1 mm thick SDD arrays in a stacked configuration, in order to reach 2 mm of effective thickness and further increase the module detection efficiency. The first spectroscopic measurements obtained with the two modules will be also reported in the paper, showing the spectroscopic improvements that can be obtained with the additional electrode on the window and the efficiency improvements that can be obtained with the stacked module.

First measurement of kaonic helium-4 M-series transitions

In this paper we present the results of a new kaonic helium-4 measurement with a 1.37 g l−1 gaseous target by the SIDDHARTA-2 experiment at the DAΦNE collider. We measured, for the first time, the energies and yields of three transitions belonging to the M-series. Moreover, we improved by a factor about three, the statistical precision of the 2p level energy shift and width induced by the strong interaction, obtaining the most precise measurement for gaseous kaonic helium, and measured the yield of the L α transition at the employed density, providing a new experimental input to investigate the density dependence of kaonic atoms transitions yield.

On the Importance of Future, Precise, X-ray Measurements in Kaonic Atoms

Progress in the construction of precise X-ray detectors allows measurements of energies and widths of “upper levels” in K− mesic atoms. These can be used to determine sub-threshold Kaon-nucleon amplitudes, which are important in investigations of nuclear states of these mesons. The special case of the 2P state in Kaonic Helium is discussed and used to check the properties of the K− proton quasi-bound state. Similar attempts in other elements indicate a need for new, precise measurements.

The measurement of the E2 nuclear resonance effects in kaonic atoms at DAΦNE: The KAMEO proposal

KAMEO (Kaonic Atoms Measuring Nuclear Resonance Effects Ob-servables) is a proposal for an experiment aiming to perform the first consistent measurement of the E2 nuclear resonance effects in kaonic molybdenum A=94,96,98,100 isotopes. The E2 nuclear resonance mixes atomic states, due to the electrical quadrupole excitation of nuclear rotational states. It occurs in atoms having the energy of a nuclear excitation state closely matching an atomic de-excitation state energy, and affects the rates of X-ray atomic transitions matching the energy of the resonance. The measurement E2 nuclear resonance effect in KMO isotopes allows the study of the strong kaon-nucleus interaction in a rotational excited nuclear state. Moreover, the effect enables the K- to access an inner atomic level not easily reachable by the kaon normal cascade, due to the nuclear absorption. The KAMEO proposed apparatus consists of 4 enriched Mo A=94,96,98,100 isotope strips, exposed to the kaons produced by the DAφNE collider, for kaonic atoms formation, with a high-purity germanium detector, cooled with liquid nitrogen, used to measure the X-ray atomic transitions. The DAφNE collider is located at the National Laboratories of Frascati (LNF-INFN), in Italy. It is already suited for kaonic atoms measurement by the SIDDHARTA-2 collaboration.

Kaonic atoms with SIDDHARTA-2 at the DAΦNE collider

The most important information still missing in the field of the low-energy antikaon-nucleon inter actions studies is the experimental determination of the hadronic energy shift and width of kaonic deuterium. This measurement will be performed by the SIDDHARTA-2 experiment, installed at the DAΦNE collider and presently in data taking campaign. The precise measurement of the shift and width of the 1s level with respect to the purely electromagnetic calculated values, generated by the presence of the strong interaction, through the measurement of the X-ray transitions to this level, in kaonic hydrogen, was performed by the SIDDHARTA collaboration, the kaonic deuterium is underway by SIDDHARTA-2. These measurement will allow the first precise experimental extraction of the isospin dependent antikaon-nucleon scattering lengths, funda mental quantities for understanding low-energy QCD in the strangeness sector. The experimental challenge of the kaonic deuterium measurement is the very small X-rays yield, the even larger width (compared to kaonic hy drogen), and the difficulty to perform X-rays spectroscopy with weak signals in the high radiation environment of DAΦNE. It was, therefore, crucial to develop a new apparatus involving large-area X-rays detector system, to optimize the signal and to control and by improve the signal-to-background ratio by gaining in solid angle, increasing the timing capability, and as well implementing additional charge particle tracking veto systems.

Intermediate Mass Kaonic Atoms at DA\(\Phi \)NE

Intermediate Mass Kaonic Atoms at DA\(\Phi \)NE

The Odyssey of Kaonic Atoms Studies at the DA\(\Phi \)NE Collider: From DEAR to SIDDHARTA-2

The Odyssey of Kaonic Atoms Studies at the DA\(\Phi \)NE Collider: From DEAR to SIDDHARTA-2

CdZnTe detectors tested at the [formula omitted] collider for future kaonic atoms measurements

The SIDDHARTA-2 collaboration at the INFN Laboratories of Frascati (LNF) aims to perform important measurements on kaonic atoms. In parallel to the groundbreaking kaonic deuterium measurement, presently running on the DAΦNE collider at LNF, we plan to install additional detectors. The aim is to perform further kaonic atoms’ studies, taking advantage of the unique low energy and low momentum spread K− beam delivered by the at-rest decay of the ϕ meson.CdZnTe devices are ideal for detecting transitions toward both the upper and lower levels of intermediate-mass kaonic atoms, like kaonic carbon and aluminium. Measuring these transitions can have an important impact on the strangeness sector of nuclear physics.We present the results obtained in two preliminary tests conducted at DAΦNE in view of measurements foreseen in 2024, with the twofold aim to tune the timing window required to reject the extremely high electromagnetic background, and to quantify the readout saturation effect due to the high rate when placed close to the Interaction Region (IR). In the first test we used a RITEC device and electronics, while for the second one commercial REDLEN detectors were coupled to a frontend electronics customized at the University of Palermo.The results confirmed the possibility of finding and matching a proper timing window to identify the signal events and proved the better performance in terms of energy resolution of the REDLEN technology with a custom frontend electronics. In both cases, strong saturation effects were confirmed, accounting for a loss of almost 90% of the events, which will be overcome by a dedicated shielding structure foreseen for the final experimental setup.

Study of the p–p–K+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{+}$$\\end{document} and p–p–K-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-}$$\\end{document} dynamics using the femtoscopy technique

The interactions of kaons (K) and antikaons (K¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm {\\overline{K}}$$\\end{document}) with few nucleons (N) were studied so far using kaonic atom data and measurements of kaon production and interaction yields in nuclei. Some details of the three-body KNN and K¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm {\\overline{K}}$$\\end{document}NN dynamics are still not well understood, mainly due to the overlap with multi-nucleon interactions in nuclei. An alternative method to probe the dynamics of three-body systems with kaons is to study the final state interaction within triplet of particles emitted in pp collisions at the Large Hadron Collider, which are free from effects due to the presence of bound nucleons. This Letter reports the first femtoscopic study of p–p–K+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^+$$\\end{document} and p–p–K-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^-$$\\end{document} correlations measured in high-multiplicity pp collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{s}$$\\end{document} = 13 TeV by the ALICE Collaboration. The analysis shows that the measured p–p–K+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^+$$\\end{document} and p–p–K-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^-$$\\end{document} correlation functions can be interpreted in terms of pairwise interactions in the triplets, indicating that the dynamics of such systems is dominated by the two-body interactions without significant contributions from three-body effects or bound states.

The SIDDHARTA-2 Veto-2 system for X-ray spectroscopy of kaonic atoms at DAΦNE

The Veto-2 is a fundamental component of a multiple-stage veto system for the SIDDHARTA-2 experiment installed at the DAΦNE collider at INFN-LNF in Italy. It was developed to improve the signal-to-background ratio for the challenging measurement of X-ray transitions to the fundamental level in kaonic deuterium. Its purpose is the suppression of hadronic background in the form of Minimum Ionizing Particles by using the topological correlation between signals in the X-ray and Veto-2 detectors. The Veto-2 system consists of a barrel of plastic scintillators read out by Silicon Photomultipliers. The system performed its first successful test run within the apparatus with a helium-4 target in 2022. The efficiency of the Veto-2 was determined and found to be 0.62 ± 0.01. The Veto-2 improved the signal-to-background ratio for the kaonic helium-4 Lα measurement by ∼ 16%, which is crucial due to the low expected X-ray yield of kaonic deuterium.

Potentialities of CdZnTe Quasi-Hemispherical Detectors for Hard X-ray Spectroscopy of Kaonic Atoms at the DAΦNE Collider.

Kaonic atom X-ray spectroscopy is a consolidated technique for investigations on the physics of strong kaon-nucleus/nucleon interaction. Several experiments have been conducted regarding the measurement of soft X-ray emission (<20 keV) from light kaonic atoms (hydrogen, deuterium, and helium). Currently, there have been new research activities within the framework of the SIDDHARTA-2 experiment and EXCALIBUR proposal focusing on performing precise and accurate measurements of hard X-rays (>20 keV) from intermediate kaonic atoms (carbon, aluminum, and sulfur). In this context, we investigated cadmium-zinc-telluride (CdZnTe or CZT) detectors, which have recently demonstrated high-resolution capabilities for hard X-ray and gamma-ray detection. A demonstrator prototype based on a new cadmium-zinc-telluride quasi-hemispherical detector and custom digital pulse processing electronics was developed. The detector covered a detection area of 1 cm2 with a single readout channel and interesting room-temperature performance with energy resolution of 4.4% (2.6 keV), 3% (3.7 keV), and 1.4% (9.3 keV) FWHM at 59.5, 122.1, and 662 keV, respectively. The results from X-ray measurements at the DAΦNE collider at the INFN National Laboratories of Frascati (Italy) are also presented with particular attention to the effects and rejection of electromagnetic and hadronic background.

New opportunities for kaonic atoms measurements from CdZnTe detectors

We present the tests performed by the SIDDHARTA-2 collaboration at the $$\textrm{DA}\Phi \textrm{NE}$$ 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 $$^{241}\textrm{Am}$$ 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 $$\simeq 10^{5-6}$$ , opens the possibility to plan for future kaonic atom measurements with CdZnTe detectors.

Measurements of high-n transitions in intermediate mass kaonic atoms by SIDDHARTA-2 at DA$$\mathrm {\Phi }$$NE

Measurements of high-n transitions in intermediate mass kaonic atoms by SIDDHARTA-2 at DA$$\mathrm {\Phi }$$NE

Investigating the E2 nuclear resonance effect in kaonic atoms

The nuclear E2 resonance effect occurs when an atomic de-excitation energy is closely matched by a nuclear excitation energy. It produces an attenuation of some of the atomic X-ray lines in the resonant isotope target. Investigating the nuclear E2 resonance effect in kaonic atoms, important information about kaon-nucleus strong interaction can be provided. The only nuclear resonance effect was measured by G. L. Goldfrey, G- K. Lum and C. E. Wiegand at Lawrence Berkeley Laboratory, in 1975. The nuclear E2 resonance effect was observed in 25 hours of data taking, not enough to provide a conclusive result. In four kaonic Molybdenum isotopes (, , and ), the nuclear E2 resonance effect is expected at the same transition, with similar energy values. The KAMEO (Kaonic Atoms Measuring nuclear resonance Effects Observables) experiment plans to study the E2 nuclear resonance effect in kaonic Molybdenum isotopes at the DAΦNE e+e− collider, during the SIDDHARTA-2 experiment. The experimental strategy consists of exposing four solid strip targets, each enriched with one Molybdenum isotope, to negatively charged kaons, using a germanium detector for X-ray transition measurements. A further exposure of a non-resonant isotope solid strip target will be used as reference for standard non-resonant transitions.

Kaonic atoms measurements with SIDDHARTA-2

The SIDDHARTA-2 collaboration is aiming to perform the challenging measurement of kaonic deuterium X-ray transitions to the ground state. This will allow to extract the isospin-dependent antikaon-nucleon scattering lengths, providing input to the theory of Quantum Chromodynamics (QCD) in the non-perturbative regime with strangeness. This work describes the SIDDHARTA-2 experimental apparatus and presents the results obtained during the commissioning phase realized with kaonic helium measurements. In particular, the first observation of the kaonic helium transitions to the 3s level (M-lines), reported in this work, represents a new source of information to study the kaonic helium cascade process and demonstrates the potential of the SIDDHARTA-2 apparatus, in the view of the ambitious kaonic deuterium measurement.

SIDDHARTA-2 veto system design and performance for kaonic atoms studies at DAΦNE

Light kaonic atoms spectroscopy provides a unique approach to study the low-energy strong interaction in the strangeness sector. Precise measurements of X-ray emission from light kaonic atoms provide valuable information on kaon-nucleus interaction at threshold without the need for extrapolation as required in scattering experiments. The SIDDHARTA-2 experiment at the DAΦNE collider of INFN-LNF is now poised to perform the challenging measurements of the K−- d 2p → 1s transition to extract the isospin-dependent antikaonnucleon scattering lengths. To achieve this goal, the background reduction is a crucial factor. This paper provides an overview of the SIDDHARTA-2 Veto-1 system, which uses scintillators outside the vacuum chamber to detect charged particles produced by K− absorption by the nucleus. The arrival time of these particles is correlated with the position where the kaonic atom has been created inside the setup, allowing for the rejection of kaons stopped outside the target cell, which is a critical component for reducing the background and improve the accuracy of the measurement.

Investigating the E2 Nuclear Resonance Effects in Kaonic Atoms: The KAMEO Proposal

The E2 nuclear resonance effect in kaonic atoms occurs when the energy of atomic de-excitation closely matches the energy of nuclear excitation, leading to the attenuation of some X-ray lines in the resonant isotope target. This phenomenon provides crucial information on the strong interaction between kaons and nuclei. The only nuclear E2 resonance effect observed so far was in the K− −9842Mo isotope, measured by G. L. Goldfrey, G-K. Lum, and C. E. Wiegand at Lawrence Berkeley Laboratory in 1975. However, the 25 hours of data taking were not sufficient to yield conclusive results. In four kaonic Molybdenum isotopes (9442Mo, 9642Mo, 9842and Mo, and 10042Mo), the nuclear E2 resonance effect is expected to occur at the same transition with similar energy values. To investigate this, the KAMEO (Kaonic Atoms Measuring Nuclear Resonance Effects Observables) experiment plans to conduct research on kaonic Molybdenum isotopes at the DAΦNE e+e− collider during the SIDDHARTA-2 experiment. The experimental strategy involves exposing four solid strip targets, each enriched with one Molybdenum isotope, to negatively charged kaons and using a germanium detector to measure X-ray transitions. In addition, a non-resonant 9242Mo isotope solid strip target will be used as a reference for standard non-resonant transitions.

First application of a microscopic K−NN absorption model in calculations of kaonic atoms

Strong interaction energy shifts and widths in kaonic atoms are calculated for the first time using microscopic $K^- N$ + $K^- NN$ potentials derived from $K^- N$ scattering amplitudes constructed within SU(3) chiral coupled-channels models of meson-baryon interactions. The in-medium modifications of the free-space amplitudes due to the Pauli correlations are taken into account. The $K^-N+K^-NN$ potentials evaluated for 23 nuclear species are confronted with kaonic atoms data. The description of the data significantly improves when the $K^-NN$ absorption is included. To get $\chi^2$ as low as for the $K^-N+$phenomenological multi-nucleon potential an additional phenomenological term, accounting for $K^{-}-3N(4N)$ processes, is still needed. However, density dependence of this phenomenological term points out some deficiencies in the microscopic potentials and further improvements of the applied model are thus desirable. The calculated branching ratios for $K^-N$ and $K^-NN$ absorption channels in the $^{12}$C$+K^-$ atom are in reasonable agreement with the old bubble chamber data, as well as with the latest data from the AMADEUS Collaboration.

New measurements of kaonic helium-4 L-series X-rays yields in gas with the SIDDHARTINO setup

The L-series X-rays transitions of the kaonic helium-4 exotic atom were measured by SIDDHARTINO, the reduced configuration of the SIDDHARTA-2 experiment, at the DAΦNE collider of INFN-LNF, with gaseous 4He targets at densities of 1.90 g/l and 0.82 g/l, corresponding to 1.5% and 0.66%, respectively, of the liquid helium-4 density. The absolute yields for the Lα transition are determined to be 0.15 ±0.03 and 0.12 ±0.03, for the two target densities. The yields for the Lβ and Lγ transitions are presented relatively to that of the Lα transition. These results are compatible with the yields measured by the SIDDHARTA experiment at the densities of 1.65 g/l and 2.15 g/l and contribute to refine the cascade models describing the de-excitation of kaonic atoms as function of density.

The SIDDHARTA-2 calibration method for high precision kaonic atoms x-ray spectroscopy measurements

The SIDDHARTA-2 experiment at the DAΦNE 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 DAΦNE 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.