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  • Test particles and quasiperiodic oscillations around Kiselev black hole with cloud of strings
    2024, 48(4): 045109-045109-16. doi: 10.1088/1674-1137/ad2060
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    In the present work, we study the dynamics of test particles around a Schwarzschild black hole surrounded by quintessence and immersed in a scalar string cloud field. We start our study by defining the possible values of quintessence and cloud of string parameters corresponding to the existence of the black hole horizon for the fixed values of the parameter of the equation of state for dark energy. We also study the behavior of the effective potential for the circular motion of test particles, energy, and angular momentum of the particles together with innermost stable circular orbits (ISCOs). We investigate the fundamental frequencies in the particles' oscillations along stable circular orbits. We related the stability of the orbits to the Lyapunov exponent, and the chaotic behavior is studied graphically. Finally, we apply the fundamental frequencies to describe quasiperiodic oscillations (QPOs), and it is obtained that in the presence of both fields low-frequency twin-peak QPOs are not observed. Also, we obtain constraint values for the string clouds parameter and mass of the black hole candidates located in the center of the microquasars GRO J1655-40 & GRS 1915+105 and Milky Way galaxy.
  • α-particle preformation factors in heavy and superheavy nuclei
    2024, 48(4): 044105-044105-13. doi: 10.1088/1674-1137/ad21e9
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    In this study, α-particle preformation factors in heavy and superheavy nuclei from 220Th to 294Og are investigated. By combing experimental α decay energies and half-lives, the α-particle preformation factors $ P_{\alpha} $ are extracted from the ratios between theoretical α decay half-lives calculated using the Two-Potential Approach (TPA) and experimental data. We find that the α-particle preformation factors exhibit a noticeable odd-even staggering behavior, and unpaired nucleons inhibit α-particle preformation. Moreover, we find that both the α decay energy and mass number of parent nucleus exhibit considerable regularity with the extracted experimental α-particle preformation factors. After considering the major physical factors, we propose a local phenomenological formula with only five valid parameters for α-particle preformation factors $ P_{\alpha} $. This analytic expression has a clear physical meaning as well as good precision. As an application, this analytic formula is extended to estimate the α-particle preformation factors and further predict the α decay half-lives for unknown even-even nuclei with Z = 118 and 120.
  • Solar neutrino background in high-pressure gaseous 82SeF6 TPC neutrinoless double beta decay experiments
    2024, 48(4): 043003-043003-14. doi: 10.1088/1674-1137/ad2675
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    In this study, the possibility of observing a solar neutrino background in a future neutrinoless double beta decay experiment using a high-pressure gaseous 82SeF6 TPC is investigated. Various contributions are simulated, and possible features that could be used for event classification are discussed; two types of backgrounds are identified. The rate of multi-site background events is approximately 0.63 events/(ton·yr) in a 30 keV ROI window. This background could be effectively reduced to less than 0.0001 events/(ton·yr) (95% C.L.) while maintaining a high signal efficiency of 93% by applying a selection based on the number of clusters and energy of the leading cluster. The rate of the single-electron background events is approximately 0.01 events/(ton·yr) in the ROI. Assuming a reduction factor of 10 for the single-electron background events obtained via the algorithms developed for radioactive background rejection, the total background induced by the solar neutrino would be 0.001 events/(ton·yr), which is sufficiently small for conducting ton-level experiments.
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