The European Physical Journal A最新文献

We study the (D^0 rightarrow rho ^0 phi ), (omega phi ) decays which proceed in a direct mode via internal emission with equal rates. Yet, the experimental branching ratio for the (rho ^0 phi ) mode is twice as big as that for the (omega phi ) mode. We find a natural explanation based on the extra indirect mechanism where (K^{*+} K^{*-}) is produced via external emission and that channel undergoes final state interaction with other vector–vector channels to lead to the (rho ^0 phi ), (omega phi ) final states, with transition amplitudes dominated by the (a_0(1710)) resonance, recently discovered, and (f_0(1710)) respectively. The large coupling of the (a_0(1710)) to the (rho ^0 phi ) channel is mostly responsible for this large ratio of the production rates.

We present a comprehensive coupled reaction channels analysis of the (^{12})C+(^{208})Pb system over a broad range of bombarding energies, employing the parameter-free São Paulo potential for the real part of the nuclear interaction. The calculations include couplings to low-lying inelastic states and transfer channels, with no adjustable parameters. Theoretical results are compared with experimental data for elastic scattering, fusion, inelastic excitation, and transfer cross sections. The inclusion of channel couplings significantly improves the agreement with the data. These findings reaffirm the predictive power of the São Paulo potential and underscore the importance of coupled reaction channels calculations in describing heavy-ion collisions, not only near the Coulomb barrier but also at much higher energies.

Extreme Light Infrastructure - Nuclear Physics (ELI-NP) is the nuclear physics pillar of the pan-European project Extreme Light Infrastructure. Started in 2012, the project has accomplished several milestones that have placed it among the most relevant research infrastructures worldwide in nuclear photonics. Two main extreme light sources were included in the ELI-NP project, a 2 x 10 PW laser system and a high intensity gamma beam system. The high power laser system is operational since 2020 and delivers beam time to users. The gamma beam system is still under construction. Several experimental setups have been developed and commissioned for the two extreme light beams. The paper makes an overview of some of the first results obtained with the research infrastructure developed at ELI-NP.

Cross sections of the (^{16})O(n, (alpha _0))(^{13})C reaction were measured in the 6.8–11.7 MeV neutron energy region based on the HI-13 tandem accelerator of China Institute of Atomic Energy (CIAE). Two experiments were performed in 2022 and 2023 at total 21 neutron energy points. A gridded ionization chamber (GIC) was used as the charged particle detector, with working gas of 3.0 atm Kr+4.0%CO(_2) in 2022 and 4.0 atm Kr+3.0%CO(_2) in 2023. The oxygen atoms in the CO(_2) were used as the gas sample. A (^{238})U(_3)O(_8) sample inside the GIC was used to determine the neutron fluences and an EJ-309 scintillation detector was placed on the beam line to measure the neutron energy spectra to correct the events induced by the low-energy neutrons. Based on the present measurement cross sections and existing measurement data from the EXFOR library, R-matrix analysis was carried out for the (n + ^{16})O system using the RAC code. Present cross sections are compared with existing measurement data and evaluation data. In the 6.8–9.5 MeV neutron energy region our measurement results are consistent with the evaluation data in the ENDF/B-VIII.1 library. In the 9.5–11.7 MeV neutron energy region, A peak near 10.5 MeV in the excitation function in our measurement and R-matrix calculation results was obtained while the excitation functions given by the evaluations and existing measurements have a valley structure.

In this study, the excitation functions of evaporation residues produced in the (^{18})O + (^{144})Sm system have been measured through offline (gamma ) ray spectrometry. The statistical model code PACE-4, ALICE91, and EMPIRE 3.2.2 were utilized to distinguish the evaporation residues populated through the compound and non-compound nuclear fusion processes. For a comprehensive investigation of fusion suppression and its correlation with the charge of the target and the (Q_{alpha }) value of the projectile, the compound nuclear fusion cross sections of various projectile-target combinations were analyzed within the framework of the Universal Fusion Function (UFF) reduction method. The study revealed that the measured fusion functions of various systems were suppressed compared to the UFF, where the degree of suppression was dependent on the projectile’s (Q_{alpha }) value. Besides that, an exponential increase in the suppression was further observed with increasing (Q_{alpha }) values, while the target charge had a marginal effect. A generalized formula based on present study has been proposed to estimate fusion suppression of different systems as a function of (Q_{alpha }) value of the projectile. The above observations indicates that the involvement of non-compound nuclear reactions leads to a reduction in the compound nuclear fusion cross section at energies above the Coulomb barrier. This is primarily attributed to the loss of flux in the compound nuclear fusion channel, which is offset by an increased flux in non-compound fusion processes.

The enhancement in sub-barrier fusion cross-sections caused by different intrinsic degrees of freedom, such as inelastic excitations and deformations, has been well explored. However, the influence of positive Q-value neutron transfer channels and their microscopic understanding on fusion dynamics have still been far from complete. Therefore, I aim to investigate the role of multi neutron transfer channels on the dynamics of fusion reactions around the Coulomb barrier by judicially selecting 11 different (^{28,30})Si-induced systems. These reactions are chosen in such a way that they possess positive and negative Q-values for neutron transfer channels to make the comparison more apparent. For this purpose, a channel coupling approach within the framework of a semiclassical model is being used to investigate the role of multi-neutron transfer with positive Q-values on fusion phenomena. The sub-barrier fusion enhancement compared to the one-dimensional barrier penetration model (uncoupled) is investigated by considering collective excitations in colliding nuclei and multi-neutron transfer channels with Q > 0 within the channel coupling model. All the fusion excitation functions, except for a few cases, have been successfully explained by the coupled channel calculations using the channel coupling model. Slight deviation from the model calculations is observed for (^{28})Si+(^{90,92})Zr below the Coulomb barrier and (^{28})Si+(^{144})Nd in the above-barrier energy region. Only the significant effect of up to 2n pickup transfer with Q > 0 was found on sub-barrier fusion.

The full widths of the vector charmonium and bottomonium hybrid mesons (H_{ textrm{c}}) and (H_{textrm{b}}), characterized by the quantum numbers (1^{ mathrm {--}}), are determined by analyzing their dominant strong decay modes: (H_{textrm{c}} rightarrow D^{+}D^{-}), (D_{0}overline{D}_{0}), ( D_{s}^{+}D_{s}^{-} ), ( D^{*+}D^{*-} ), ( D^{*0}overline{D}^{*0}), ( D^{*+}D^{-} ), ( D^{*0}overline{D}^{0} ), (D_{s}^{*+}D_{s}^{-} ) and (H_{textrm{b}} rightarrow B^{+}B^{-}), (B_{0}overline{B}_{0}). To evaluate the partial widths of these channels, we employ the QCD three-point sum rule approach, which provides a reliable method for extracting the strong coupling constants at the relevant hybrid-meson–meson interaction vertices. Based on this analysis, the full widths of these hybrid quarkonia are found to be (Gamma _{H_{textrm{c}}} =(309.6pm 39.0)~ textrm{MeV} ) and (Gamma _{H_{textrm{b}}} =(78.8pm 15.4)~textrm{MeV} ). These results are expected to facilitate the interpretation of future experimental data concerning the spectroscopy and decay patterns of exotic charmonium- and bottomonium-like hybrid mesons.