Kaonic 4He Research Articles

Trigger rejection factor in the first kaonic helium run with the complete SIDDHARTA-2 setup

The SIDDHARTA-2 experiment aims to perform the first measurement of the kaonic deuterium 2p → 1s x-ray transition energy. Such measurement, together with the measurement of kaonic hydrogen 2p → 1s x-ray energy transition performed by the SIDDHARTA experiment in 2011, allows the determination of kaon proton and kaon neutron scattering lengths and represents a fundamental input for the low energies QCD in the strangeness sector theory. The SIDDHARTA-2 experiment is presently installed at the DAΦNE electronpositron collider at the National Laboratories of Frascati, in Italy. In May 2022, the kaonic 4He x-ray transitions measurement was performed by the complete SIDDHARTA-2 setup, by using a gaseous target. The result of this measurement is presented in this paper, with a specific focus on the background rejection performed by the kaon trigger system.

L-series X-ray yields of kaonic 3He and 4He atoms in gaseous targets

The SIDDHARTA experiment measured X-rays from kaonic helium atoms using, for the first time, gaseous 3He and 4He targets. Clear patterns of the L-series X-rays of kaonic 3He and 4He atoms were observed. By using accurate Monte Carlo simulations, the absolute yields of these X-ray transitions were determined to be Y(3d → 2p) = 25.0 −5.8 +6.7 % for 3He (0.96 g/l), Y(3d → 2p) = 23.1 −4.2 +6.0 % for 4He (1.65 g/l), and Y(3d → 2p) = 17.2 −9.5 +2.6 % for 4He (2.15g/l). In addition, the yields Y (nd → 2p), with n > 3 were also determined. The measured yields provide valuable information for understanding the cascade processes of kaonic helium atoms as a function of the target density.

Strong-interaction shifts and widths of kaonic helium isotopes

The kaonic 3He and 4He transitions in gaseous targets were observed by the SIDDHARTA experiment. The X-ray energies of these transitions were measured with large-area silicon-drift detectors using the timing information of the pairs produced by the DAΦNE collider. The strong-interaction shifts and widths both of the kaonic 3He and 4He 2p states were determined, which are much smaller than the results obtained by the previous experiments. The “kaonic helium puzzle” (a discrepancy between theory and experiment) was now resolved.

Measurements of the strong-interaction widths of the kaonic 3He and 4He 2p levels

The kaonic 3He and 4He X-rays emitted in the 3d→2p transitions were measured in the SIDDHARTA experiment. The widths of the kaonic 3He and 4He 2p states were determined to be Γ2p(He3)=6±6(stat.)±7 (syst.) eV, and Γ2p(He4)=14±8 (stat.)±5 (syst.) eV, respectively. Both results are consistent with the theoretical predictions. The width of kaonic 4He is much smaller than the value of 55±34 eV determined by the experiments performed in the 70ʼs and 80ʼs, while the width of kaonic 3He was determined for the first time.

Kaonic 3He and 4He X-ray measurements in SIDDHARTA

The strong-interaction shift of kaonic 3He and 4He 2p states was measured using gaseous targets for the first time in the SIDDHARTA experiment. The determined shift of kaonic 4He is much smaller than the values obtained in the experiments performed in 70's and 80's. Thus, the problems in kaonic helium (the "kaonic helium puzzle") was definitely solved by our measurements. The first observation of the kaonic 3He X-rays was also achieved. The shift both of kaonic 3He and 4He was found to be as small as a few eV.

Calculation of cascade processes rates and simulation of the transitions in Kaonic 4He atom

Interactions of K − in a 4He target and the cascade processes rates in K4He atoms are investigated by a full-quantum mechanical approach. Then the cascade processes and x-ray yields of kaonic helium atoms in liquid helium are simulated by Monte-Carlo method. For this purpose the rates of scattering, capturing and internal Auger effect are calculated, after that the initial distribution of n, l states in Kα + ion are determined, then the cascade processes rates in Kα + ion are calculated by quantum mechanical methods. The relative x-ray L series are compared with the experimental results.

Precision Spectroscopy of Kaonic Helium-3 X-rays at J-PARC

We will measure the x-rays from kaonic 3He 3d → 2p transition with a precision below 2 eV. It can provide crucial information on the K−–nucleus strong interaction. The experiment (J-PARC E17) will be performed as Day-1, which is one of the first experiments in the J-PARC hadron facility in the year 2011. An overview and the present status of the J-PARC E17 experiment are described.

First measurement of kaonic helium-3 X-rays

The first observation of the kaonic 3He 3d→2p transition was made, using slow K− mesons stopped in a gaseous 3He target. The kaonic atom X-rays were detected with large-area silicon drift detectors using the timing information of the K+K− pairs of ϕ-meson decays produced by the DAΦNE e+e− collider. The strong interaction shift of the kaonic 3He 2p state was determined to be −2±2(stat)±4(syst) eV.

Performance of silicon-drift detectors in kaonic atom X-ray measurements

Large-area silicon drift detectors (SDDs) were used for the first time in the background condition of a collider for precision spectroscopy of the kaonic atom X-rays in the SIDDHARTA experiment for the study of the strong interaction in a low-energy regime. The measurements were performed at the DA Φ NE electron–positron collider (LNF, Italy), using gas targets of hydrogen, deuterium, helium-3, and helium-4. A test measurement using the kaonic 4He X-rays showed an excellent performance of the SDD devices under the beam conditions, and a good background suppression capability using the time correlation between the kaonic atom X-rays and the back-to-back correlated K +K − pairs produced by φ decays.

Kaonic helium-4 X-ray measurement in SIDDHARTA

The kaonic helium-4 3d→2p X-ray transition was measured in a gaseous target, where Compton scattering in helium is negligible. The X-rays were detected with large-area Silicon Drift Detectors (SDDs) using the timing information of the K+K− pairs produced by ϕ decays at the DAΦNE e+e− collider. A new value of the strong interaction shift of the kaonic 4He 2p state was determined to be 0±6 (stat)±2 (syst) eV, which confirms the recently obtained result by the KEK-PS E570 group.

Kaonic helium atoms

The KEK experiment E570 has measured the Balmer-series x-rays of kaonic 4He atoms using large-area silicon drift x-ray detectors (SDDs) in order to study the low-energy K ¯ -nucleus strong interaction. The energy of the 3 d → 2 p transition was determined to be 6467 ± 3 (stat) ± 2 (syst) eV . The resulting strong-interaction energy-level shift is in agreement with theoretical calculations, thus eliminating a long-standing discrepancy between theory and experiment. Using a similar setup, the E17 experiment at J-PARC, the first experiment to be carried out in the hadron hall of J-PARC, will measure the 3 d → 2 p x-rays of kaonic 3He.

Precision measurement of the [formula omitted] x-ray energy in kaonic 4He

We have measured the Balmer-series x-rays of kaonic 4He atoms using novel large-area silicon drift x-ray detectors in order to study the low-energy K¯-nucleus strong interaction. The energy of the 3d→2p transition was determined to be 6467±3(stat)±2(syst) eV. The resulting strong-interaction energy-level shift is in agreement with theoretical calculations, thus eliminating a long-standing discrepancy between theory and experiment.

Coupled channels approach to kaonic atoms

A method based on coupled channels is presented which allows to study the role of the Λ′ (1405) in kaonic atoms in a nonstatic way. Levels of kaonic 4He, 12C and 16O have been calculated and compared with one of the existing energy-averaging prescriptions. We conclude that the closure approximation is quite successful as far as the gross features of kaonic levels are concerned, but can hardly be used to study such details as, for instance, the dynamical modifications of the Λ′ in nuclei.

624. Study of the process of heat and mass transfer during the evaporation of a liquid with a free surface in a rarefied gas medium: VI Balakhonova, Rep NASA-TT-F-11151, July 1967, 8 pages ( Sci Tech Aerospace Reps, 5 (19), 3555, N67-33864)

Large-area silicon drift detectors (SDDs) were used for the first time in the background condition of a collider for precision spectroscopy of the kaonic atom X-rays in the SIDDHARTA experiment for the study of the strong interaction in a low-energy regime. The measurements were performed at the DAΦNE electron–positron collider (LNF, Italy), using gas targets of hydrogen, deuterium, helium-3, and helium-4. A test measurement using the kaonic 4He X-rays showed an excellent performance of the SDD devices under the beam conditions, and a good background suppression capability using the time correlation between the kaonic atom X-rays and the back-to-back correlated K+K− pairs produced by φ decays.