The European Physical Journal A最新文献

The (^{12})C((alpha ),(gamma ))(^{16})O reaction rate is crucial in determining the carbon-to-oxygen abundance ratio in stellar nucleosynthesis. Measuring this reaction’s cross section at stellar energies is challenging due to its extremely small value, approximately 10(^{-17}) barn at E(_{mathrm {c.m.}}) = 300 keV. To address this, R-matrix calculations are employed to extrapolate data to lower energies, requiring a comprehensive understanding of each contribution to the cross section. The dominant contributions to the cross section at stellar energies arise from electric dipole (E1) and electric quadrupole (E2) transitions to the ground state of (^{16})O, along with a significant cascade contribution. Traditionally, these contributions have been separated using the (gamma )-ray angular distribution. In this work, we propose a novel technique using the energy distribution of the (^{16})O recoils at the focal plane. This method involves a neural network trained on detailed Monte Carlo simulations of the energy distribution of recoils transported through the recoil mass separator ERNA. This approach enables the simultaneous determination of all three contributions with errors around 10% in the energy range E(_{mathrm {c.m.}}) = 1.0–2.2 MeV. By employing this new technique, we aim to significantly improve the accuracy of determining the cross section of the (^{12})C((alpha ),(gamma ))(^{16})O reaction at astrophysical energies.

The photonuclear reaction cross section of ⁵⁸Co((gamma ,)xp) reaction has been measured for the first time by employing the surrogate reaction technique. The cross section of the photonuclear reaction is obtained in the energy region 27–32 MeV. The compound nucleus ⁵⁸(hbox {Co}^{*}) was populated using the transfer reaction ⁵⁶Fe(⁶Li,(alpha )) at (hbox {E}_{lab}=) 35.9 MeV. To calculate the surrogate ratio, ⁶¹Ni((gamma ),xp) was selected as the reference reaction and the corresponding compound nucleus ⁶¹(hbox {Ni}^{*}) was populated using the transfer reaction ⁵⁹Co(⁶Li,(alpha )) at (hbox {E}_{lab}=) 40.5 MeV. Reference data taken from the recommended IAEA photonuclear database, which adopted the KAERI data in this case, have been used to determine the desired cross section. Compound nuclear cross section calculations have been done using the statistical nuclear reaction code TALYS 1.96.

In this paper, a new type of hybrid state, which consists of two valence quarks and two valence antiquarks together with a valence gluon, the gluonic tetraquark states, are investigated. Twenty-four currents of the the gluonic hidden-charm tetraquark states in ([bar{3}_c]_{c q}otimes [8_c]_{G}otimes [3_c]_{bar{c} bar{q^prime }}) configuration are constructed, and their mass spectrum are evaluated in the framework of QCD sum rules with quantum numbers of (J^P=0^{+}), (0^{-}), (1^{-}), and (1^{+}). The nonperturbative contributions up to dimension 8 are taken into account. The results indicate that there may be exist 14 gluonic hidden-charm tetraquark states, and their corresponding hidden-bottom partners are also evaluated. The possible production and decay modes of the gluonic tetraquark states are analyzed, which are hopefully measurable in BESIII, BELLEII, PANDA, Super-B, and LHCb experiments.

We systematically explore their electromagnetic characteristics to improve our understanding of the quark-gluon dynamics underlying the complex and controversial nature of multiquark systems. In this study, the magnetic dipole moments of ( D Sigma _c), ( D Sigma _c^{*}) and ( D^{*} Sigma _c) doubly-charmed pentaquarks are extracted, which are directly related to the inner organization of the relevant states. The magnetic dipole moments of these pentaquarks are evaluated employing the QCD light-cone sum rules technique with isospin spin-parity (mathrm{I(J^P)} = frac{1}{2}(frac{1}{2}^-)), (mathrm{I(J^P)} = frac{1}{2}(frac{3}{2}^-)) and (mathrm{I(J^P)} = frac{1}{2}(frac{3}{2}^-)), for ( D Sigma _c), ( D Sigma _c^{*}) and ( D^{*} Sigma _c) doubly-charmed pentaquarks, respectively. Our predictions for the magnetic dipole moment (mu _{DSigma _c} = 2.98^{+0.76}_{-0.54}~mu _N) for the ( D Sigma _c) pentaquark, (mu _{DSigma _c^*} = 1.65^{+0.45}_{-0.34}~mu _N) for the (DSigma _c^*) pentaquark, and (mu _{D^*Sigma _c} = -3.63^{+0.79}_{-0.60}~mu _N) for the (D^*Sigma _c) pentaquark. Furthermore, we have also extracted the electric quadrupole and the magnetic octupole moments of the ( D Sigma _c^{*}) and ( D^{*} Sigma _c) doubly-charmed pentaquarks. These values show a non-spherical charge distribution. As a by-product, the magnetic dipole moments of the isospin-(frac{3}{2}) partners associated with these doubly-charmed pentaquarks have also been determined. The magnetic dipole moments are calculated as follows: (mu _{DSigma _c} = 3.78^{+0.94}_{-0.70}~mu _N), ( mu _{DSigma _c^*} = 2.08^{+0.57}_{-0.43}~mu _N), (mu _{D^*Sigma _c} = -4.59^{+0.99}_{-0.76}~mu _N) for the isospin-(frac{3}{2}) partners ( D Sigma _c), ( D Sigma _c^{*}) and ( D^{*} Sigma _c) doubly-charmed pentaquarks, respectively. We hope that our predictions of the magnetic dipole moments of the doubly-charmed pentaquarks, in conjunction with the results of other theoretical investigations of the spectroscopic parameters and decay widths of these intriguing pentaquarks, will prove valuable in the search for these states in future experiments and in elucidating the internal structure of these pentaquarks.

This review article presents historical developments and recent advances in our understanding on the three-body forces and Efimov physics, from an interdisciplinary viewpoint encompassing nuclear physics and cold atoms. Theoretical attempts to elucidate the three-body force with the chiral effective field theory are explained, followed by an overview of experiments aimed at observing signatures of the nuclear three-body force. Some recent experimental and theoretical works in the field of cold atoms devoted to measuring and engineering three-body forces among atoms are also presented. As a phenomenon arising from the three-body effect, Efimov physics in both cold atoms and nuclear systems is reviewed.

This work studies the two-neutron pickup transfer in the reaction (^{12})C(p,t)(^{10})C at 43 and 80 MeV in the laboratory frame. Finite-range coupled reaction channel calculations were performed to analyze the experimental angular distributions for direct and sequential two-neutron transfer mechanisms. Shell-model calculations were carried out to derive the spectroscopic amplitudes for the target overlaps. We show that the results of the both mechanisms present the same order of magnitude of the experimental data, thus there is a competition between the direct and sequential mechanisms for both energies studied. The data, in general, are well-described for the coherent sum of the direct and sequential transfers without any normalization factor.

In the present paper, we use the parameterization of the proton structure function to derive an analytical solution for the nuclear gluon density at small x. The behavior of nuclear parton distribution functions (nPDFs) in the next-to-leading-order (NLO) approximation at small x is defined numerically in a semi-analytical study using the Gribov–Levin–Ryskin and Mueller–Qiu (GLR-MQ) approach. We observe that the gluon distribution increases with increasing (Q^2), increasing atomic number A, and decreasing x. The results of the nonlinear GLR-MQ evolution equation are comparable to the Rausch–Guzey–Klasen (RGK) nuclear gluon distributions. The longitudinal structure function is considered according to the nonlinear effects of the gluon density behavior at small x. These results show that the nonlinear effects are important in (F^A_L (x,Q^2)) for heavy nuclei.

Isomers produced by spontaneous fission of ( ^{252})Cf were measured with the VESPA setup, composed of (hbox {LaBr}_3)(Ce) detectors for fast (gamma )-ray spectroscopy and an ionization chamber for detecting fission fragments. Identification of the isomers was derived from fission fragment-(gamma )-(gamma ) coincidences. This paper presents the half-lives of 41 isomeric states measured with this setup, from less than a nanosecond up to tens of microseconds. Short-lived isomers in ( ^{94})Rb, ( ^{108})Tc, and ( ^{147})Ce are reported for the first time. In addition to this half-life analysis, the isomers are used to develop and test a nuclear charge calibration of the ionization chamber.

The low-energy ¹⁹F(p,(alpha ))¹⁶O reaction has significant implications for nuclear astrophysics. The ¹⁹F(p, (alpha ))¹⁶O reaction occurs via three channels: (p,(alpha _0)), (p,(alpha _pi )), and (p,(alpha _gamma )). At lower temperatures, below 0.15 GK, the (p,(alpha _0)) channel is the dominant contributor of the reaction. The ¹⁹F(p,(alpha _{0}))¹⁶O reaction cross section in the energy range of 400–900 keV was studied in this work. Recent data in the literature reveals a roughly 1.4 increase compared to prior findings reported in the NACRE (Nuclear Astrophysics Compilation of REactions) compilation. Therefore, we present new additional result of the study published in EPJA [22] employing a silicon strip detector array (LHASA - Large High-resolution Array of Silicon for Astrophysics). The anguar distributions, the reaction cross sections and the astrophysical S-factors of the (p,(alpha _0)) channel were obtained through this experiment. Our findings resolve the discrepancies that exist between the two previously available data sets in the literature.