arXiv subjects

A. Krakó

Publications and source records attributed to A. Krakó.

4 recordsLinked to original sources

arXiv2026

Negative-parity high-spin structure of 105Pd

Negative-parity medium- and high-spin structure of the nucleus 105Pd was studied through the 96Zr(13C,4n)105Pd reaction at incident energies of 51 and 58 MeV, using the EUROBALL IV gamma-ray spectrometer in conjunction with the DIAMANT charged particle array. New bands have been observed and the previously reported bands have been extended to higher energies and spins. Altogether six decoupled bands with E2 transitions and one strongly coupled band with M1 + E2 transitions have been observed. The observed energy spectra and B(M1)/B(E2) ratios are compared with results of quantum particle rotor model calculations. Based on these comparisons, quasiparticle configurations can be assigned to two newly observed decoupled bands as well as to the strongly coupled band. The previously emerged possible interpretation for the third decoupled band as a two-phonon wobbling excitation lacks support. The observations indicate possible gamma-band nature for this band. The strongly coupled band, consistently with the absence of another observed strongly coupled band in this experiment, does not exhibit chirality.

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arXiv2024

An Update on the Hypothetical X17 Particle

Recently, when examining the differential internal pair creation coefficients of $^8$Be, $^4$He and $^{12}$C nuclei, we observed peak-like anomalies in the angular correlation of the e$^+$e$^-$ pairs. This was interpreted as the creation and immediate decay of an intermediate bosonic particle with a mass of $m_{X}c^2\approx$ 17~MeV, receiving the name X17 in subsequent publications. Our results initiated a significant number of new experiments all over the world to detect the X17 particle and determine its properties. In this paper we will give an overview of the experiments the results of which are already published, and the ones closest to being published. We will also introduce our latest results obtained for the X17 particle by investigating the e$^+$e$^-$ pair correlations in the decay of the Giant Dipole Resonance (GDR) of $^{8}$Be.

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arXiv2023

Observation of the X17 anomaly in the decay of the Giant Dipole Resonance of $^8$Be

Angular correlation spectra of $e^+e^-$ pairs produced in the $^{7}$Li($p$,$γ$)$^{8}$Be nuclear reaction were studied at a proton beam energy of $E_p$~=~4.0~MeV, which corresponds to the excitation energy of the Giant Dipole Resonance (GDR) in $^8$Be. The spectra measured show a peak like anomaly at 120$^\circ$ and a broader anomaly also above 140$^\circ$. Both anomalies could consistently be described by assuming that the same hypothetical X17 particle was created both in the ground-state transition and in the transition going to the broad ($Γ$=1.5~MeV), first excited state in $^8$Be. The invariant mass of the particle, which was derived to be $m_Xc^2 = 16.95 \pm 0.48$(stat.)~MeV, agrees well with our previously published values.

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arXiv2022

New anomaly observed in $^{12}$C supports the existence and the vector character of the hypothetical X17 boson

Employing the $^{11}$B(p,$γ$)$^{12}$C nuclear reaction, the angular correlation of $e^+e^-$ pairs was investigated in the angular range of $40^\circΘ\leq 175^\circ$ for five different proton energies between E$_p$ = 1.50 - 2.50 MeV. At small angles ($Θ\leq 120^\circ$), the results can be well interpreted by the internal pair creation process of electromagnetic radiations with E1 and M1 multipolarities and by the external pair creation in the target backing. However, at angles greater than $120^\circ$, additional count excess and anomalies were observed, which could be well accounted for by the existence of the previously suggested hypotetical X17 particle. Our results show that the X17 particle was generated mainly in E1 radiation. The derived mass of the particle is $m_\mathrm{X}c^2$=17.03$\pm 0.11 (stat) \pm 0.20 (syst)$ MeV. According to the mass, and to the derived branching ratio ($B_x=3.6(3)\times10^{-6}$), this is likely the same X17 particle, which we recently suggested for describing the anomaly observed in the decay of $^8$Be and $^4$He.

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