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2024-6 Contents
2024, 48(6): 1-3.
Determination of the resonant parameters of ${ \boldsymbol\chi_{\boldsymbol c \bf 0}\bf (3915)} $ with global fit
Chunhua Li, Xijun Wang, Chen Wu
2024, 48(6): 063001. doi: 10.1088/1674-1137/ad3943
Particle \begin{document}$ \chi_{c0}(3915) $\end{document} was first observed by the Belle experiment in the \begin{document}$ \omega J/\psi $\end{document} invariant mass spectrum in the process \begin{document}$ B\to K\omega J/\psi $\end{document} and subsequently confirmed by the BaBar experiment. Both experiments reported the resonant parameters of this particle in the processes \begin{document}$ \gamma\gamma\to\omega J/\psi $\end{document} and \begin{document}$ B\to K\omega J/\psi $\end{document} assuming \begin{document}$ \chi_{c0}(3915) $\end{document} as an S-wave Breit-Wigner resonance. We performed a global fit to the distributions of invariant mass of \begin{document}$ \omega J/\psi $\end{document} measured by the Belle and BaBar experiments and additionally incorporated the measurements reported by the LHCb experiment to extract the mass and width of \begin{document}$ \chi_{c0}(3915) $\end{document}. We obtained \begin{document}$ M=3920.9\pm0.9 $\end{document} MeV/\begin{document}$ c^2 $\end{document} and \begin{document}$ \Gamma=18.2\pm2.4 $\end{document} MeV, which are consistent with the values from PDG within one standard deviation but with higher precision.
Mass suppression effect in QCD radiation and hadron angular distribution in jet
Chuan-Hui Jiang, Hai Tao Li, Shi-Yuan Li, Zong-Guo Si
2024, 48(6): 063101. doi: 10.1088/1674-1137/ad2f22
The finite mass of the heavy quark suppresses the collimated radiations; this is generally referred to as the dead cone effect. In this paper, we study the distribution of hadron multiplicity over the hadron opening angle with respect to the jet axis for various jet flavors. The corresponding measurement can be the most straightforward and simplest approach to explore the dynamical evolution of the radiations in the corresponding jet, which can expose the mass effect. We also propose a transverse energy-weighted angular distribution, which sheds light on the interplay between perturbative and non-perturbative effects in the radiation. Through Monte-Carlo simulations, our calculations show that the dead cone effect can be clearly observed by finding the ratio between the b and light-quark (inclusive) jets; this is expected to be measured at the LHC in the future.
BL model with D4 × Z4 × Z2 symmetry for fermion mass hierarchies and mixings
V. V. Vien
2024, 48(6): 063102. doi: 10.1088/1674-1137/ad2f23
We constructed a gauge \begin{document}$ B-L $\end{document} model with \begin{document}$ D_4\times Z_4\times Z_2 $\end{document} symmetry to explain the quark and lepton mass hierarchies and their mixings with realistic CP phases via the type-I seesaw mechanism. Six quark mases, three quark mixing angles, and the CP phase in the quark sector take the central values whereas Yukawa couplings in the quark sector are diluted in a range of difference of three orders of magnitude by the perturbation theory at the first order. Concerning the neutrino sector, a small neutrino mass is achieved by the type-I seesaw mechanism. Both inverted and normal neutrino mass hierarchies are consistent with the experimental data. The predicted sum of neutrino masses for normal and inverted hierarchies, the effective neutrino masses, and the Dirac CP phase are also consistent with recently reported limits.
QCD sum rule study of JP = 1± exotic states with two heavy quarks in the molecular picture
T.M. Aliev, S. Bilmis, M. Savcı
2024, 48(6): 063103. doi: 10.1088/1674-1137/ad305f
In this study, the spectroscopic parameters of exotic molecular states composed of mesons containing two heavy quarks (scalar - axial and pseudoscalar - axial meson combinations) are investigated within the QCD sum rules. Our findings reveal that molecular states containing charm quarks do not form bound states, whereas states with b-quarks can form exotic molecular states. This observation has significant implications for understanding the structure of these exotic states.
Analysis of the gluon distribution with next-to-leading order splitting function at small-x
Jingxuan Chen, Xiaopeng Wang, Yanbing Cai, Xurong Chen, Qian Wang
2024, 48(6): 063104. doi: 10.1088/1674-1137/ad305d
An approximated solution for the gluon distribution from DGLAP evolution equations with the NLO splitting function in the small-x limit is presented. We first obtain simplified forms of the LO and NLO splitting functions in the small-x limit. With these approximated splitting functions, we obtain the analytical gluon distribution using the Mellin transform. The free parameters in the boundary conditions are obtained by fitting the CJ15 gluon distribution data. We find that the asymptotic behavior of the gluon distribution is consistent with the CJ15 data; however, the NLO results considering the "ladder" structure of gluon emission are slightly better than the LO results. These results indicate that the corrections from NLO have a significant influence on the behavior of the gluon distribution in the small-x region. In addition, we investigate the DGLAP evolution of the proton structure function using the analytical solution of the gluon distribution. The differential structure function reveals that our results have a similar tendency to the CJ15 data at small-x.
Electrodynamics with violations of Lorentz and U(1) gauge symmetries and their Hamiltonian structures
Xiu-Peng Yang, Bao-Fei Li, Tao Zhu
2024, 48(6): 063105. doi: 10.1088/1674-1137/ad33be
This study aims to investigate Lorentz/U(1) gauge symmetry-breaking electrodynamics in the framework of the standard-model extension and analyze the Hamiltonian structure for the theory with a specific dimension \begin{document}$ d\leq 4 $\end{document} of Lorentz breaking operators. For this purpose, we consider a general quadratic action of the modified electrodynamics with Lorentz/gauge-breaking operators and calculate the number of independent components of the operators at different dimensions in gauge invariance and breaking. With this general action, we then analyze how Lorentz/gauge symmetry-breaking can change the Hamiltonian structure of the theories by considering Lorentz/gauge-breaking operators with dimension \begin{document}$ d\leq 4 $\end{document} as examples. We show that the Lorentz-breaking operators with gauge invariance do not change the classes of the theory constrains and the number of physical degrees of freedom of the standard Maxwell electrodynamics. When U(1) gauge symmetry-breaking operators are present, the theories generally lack a first-class constraint and have one additional physical degree of freedom compared to the standard Maxwell electrodynamics.
Exploring dark matter-gauge boson effective interactions at current and future colliders
Yu Zhang, Yi-Wei Huang, Wei-Tao Zhang, Mao Song, Ran Ding
2024, 48(6): 063106. doi: 10.1088/1674-1137/ad2362
In this study, we systematically investigate collider constraints on effective interactions between Dark Matter (DM) particles and electroweak gauge bosons. We consider the simplified models in which scalar or Dirac fermion DM candidates couple only to electroweak gauge bosons through high dimensional effective operators. Considering the induced DM-quarks and DM-gluons operators from the Renormalization Group Evolution (RGE) running effect, we present comprehensive constraints on the effective energy scale Λ and Wilson coefficients \begin{document}$ C_B(\Lambda),\,C_W(\Lambda) $\end{document} from direct detection, indirect detection, and collider searches. In particular, we present the corresponding sensitivity from the Large Hadron Electron Collider (LHeC) and Future Circular Collider in the electron-proton mode (FCC-ep) for the first time, update the mono-j and mono-γ search limits at the Large Hadron Collider (LHC), and derive the new limits at the Circular Electron Positron Collider (CEPC).
$ { \boldsymbol D^{\bf +} \boldsymbol\to \boldsymbol\pi^{\bf +} \boldsymbol\nu\bar{\boldsymbol\nu}} $ decay process within the QCDSR approach
Yu Chen, Hai-Bing Fu, Tao Zhong, Sheng-Bo Wu, Dong Huang
2024, 48(6): 063107. doi: 10.1088/1674-1137/ad30f0
In this paper, we investigate the charmed meson rare decay process \begin{document}$ D^+ \to \pi^+\nu\bar\nu $\end{document} using an approach based on QCD sum rules. First, the pion twist-2, 3 distribution amplitude (DA) moments \begin{document}$ \langle\xi_{2;\pi}^n\rangle|_\mu $\end{document} and \begin{document}$ \langle \xi_{3;\pi}^{(p,\sigma),n}\rangle|_\mu $\end{document} are calculated up to the tenth and fourth orders, respectively, in the QCD sum rules according to the background field theory. After constructing the light-cone harmonic oscillator model for the pion twist-2, 3 DAs, we obtain their behaviors by matching the calculated ξ-moments. Then, the \begin{document}$ D\to \pi $\end{document} transition form factors (TFFs) are calculated using an approach based on QCD light-cone sum rules. The vector form factor at the large recoil region is \begin{document}$ f_+^{D\to\pi}(0) = 0.627^{+0.120}_{-0.080} $\end{document}. Using the rapidly converging simplified series expansion of \begin{document}$ z(q^2,t) $\end{document}, we present the TFFs and corresponding angular coefficients in the whole squared momentum transfer physical region. Based on non-standard neutrino interactions, the \begin{document}$ D^+ \to \pi^+ \nu\bar\nu $\end{document} decay can be related to the \begin{document}$ \bar D^0 \to \pi^+ e\bar \nu_e $\end{document} decay indirectly. Thus, we first describe the semileptonic decay process \begin{document}$ \bar D^0 \to \pi^+ e\bar \nu_e $\end{document}, differential decay widths, and branching fraction with \begin{document}$ {\cal B}(\bar D^0\to\pi^+e\bar\nu_e) = 0.308^{+0.155}_{-0.066} \times 10^{2} $\end{document}. The \begin{document}$ \bar D^0\to\pi^+e\bar\nu_e $\end{document} differential/total predictions for forward-backward asymmetry, \begin{document}$ q^2 $\end{document}-differential flat terms, and lepton polarization asymmetry are also reported. The prediction for the \begin{document}$ D^+ \to \pi^+ \nu\bar\nu $\end{document} branching fraction is \begin{document}${\cal B}(D^+ \to \pi^+ {\nu }{\bar\nu}) = $\end{document}\begin{document}$ 1.85^{+0.93}_{-0.46}\times10^{-8}$\end{document}.
ρ-meson longitudinal leading-twist distribution amplitude revisited and the Dρ semileptonic decay
Tao Zhong, Ya-Hong Dai, Hai-Bing Fu
2024, 48(6): 063108. doi: 10.1088/1674-1137/ad34be
Motivated by our previous study [Phys. Rev. D 104(1), 016021 (2021)] on the pionic leading-twist distribution amplitude (DA), we revisit the ρ-meson leading-twist longitudinal DA \begin{document}$ \phi_{2;\rho}^\|(x,\mu) $\end{document} in this study. A model proposed by Chang based on the Dyson-Schwinger equations is adopted to describe the behavior of \begin{document}$ \phi_{2;\rho}^\|(x,\mu) $\end{document}. However, the ξ-moments of \begin{document}$ \phi_{2;\rho}^\|(x,\mu) $\end{document} are calculated with the QCD sum rules in the framework of the background field theory. The sum rule formulas for these moments are improved. More accurate values for the first five nonzero ξ-moments at the typical scale \begin{document}$ \mu = (1.0, 1.4, 2.0, 3.0)\; {\rm GeV} $\end{document} are given, e.g., at \begin{document}$ \mu = 1\; {\rm GeV} $\end{document}, \begin{document}$ \langle\xi^2\rangle_{2;\rho}^\| = 0.220(6) $\end{document}, \begin{document}$ \langle\xi^4\rangle_{2;\rho}^\| = 0.103(4) $\end{document}, \begin{document}$ \langle\xi^6\rangle_{2;\rho}^\| = 0.066(5) $\end{document}, \begin{document}$ \langle\xi^8\rangle_{2;\rho}^\| = 0.046(4) $\end{document} , and \begin{document}$ \langle\xi^{10}\rangle_{2;\rho}^\| = 0.035(3) $\end{document}. By fitting these values with the least squares method, the DSE model for \begin{document}$ \phi_{2;\rho}^\|(x,\mu) $\end{document} is determined. By taking the left-handed current light-cone sum rule approach, we obtain the transition form factor in the large recoil region, i.e., \begin{document}$ A_1(0) = 0.498^{+0.014}_{-0.012} $\end{document}, \begin{document}$ A_2(0)=0.460^{+0.055}_{-0.047} $\end{document}, and \begin{document}$ V(0) = 0.800^{+0.015}_{-0.014} $\end{document}, and the ratio \begin{document}$ r_2 = 0.923^{+0.133}_{-0.119} $\end{document}, \begin{document}$ r_V = 1.607^{+0.071}_{-0.071} $\end{document}. After extrapolating with a rapidly converging series based on \begin{document}$ z(t) $\end{document}-expansion, we present the \begin{document}$ |V_{cd}| $\end{document}-independent decay width for the semileptonic decays \begin{document}$ D\to\rho\ell^+\nu_\ell $\end{document}. Finally, the branching fractions are \begin{document}$ \mathcal{B}(D^0\to \rho^- e^+ \nu_e) = 1.825^{+0.170}_{-0.162}\pm 0.004 $\end{document}, \begin{document}$\mathcal{B}(D^+ \to \rho^0 e^+ \nu_e) = $\end{document}\begin{document}$ 2.299^{+0.214}_{-0.204}\pm 0.011$\end{document}, \begin{document}$ \mathcal{B}(D^0\to \rho^- \mu^+ \nu_\mu) = 1.816^{+0.168}_{-0.160}\pm 0.004 $\end{document}, and \begin{document}$\mathcal{B}(D^+ \to \rho^0 \mu^+ \nu_\mu) =2.288^{+0.212}_{-0.201} \pm 0.011$\end{document}.
X(3960), X0(4140), and other compact ${\boldsymbol c \boldsymbol s\bar{\boldsymbol c}\bar{\boldsymbol s}} $ states
Shi-Yuan Li, Yan-Rui Liu, Zi-Long Man, Zong-Guo Si, Jing Wu
2024, 48(6): 063109. doi: 10.1088/1674-1137/ad34c4
We studied the spectrum and rearrangement decays of S-wave \begin{document}$ cs\bar{c}\bar{s} $\end{document} tetraquark states in a simplified quark model. The masses and widths were estimated by assuming that \begin{document}$ X(4140) $\end{document} is the lower \begin{document}$ 1^{++} \;\; cs\bar{c}\bar{s} $\end{document} tetraquark. Comparing our results with experimental measurements, we found that \begin{document}$ X(3960) $\end{document}, recently observed by LHCb, can be considered the lowest \begin{document}$ 0^{++} \;\; cs\bar{c}\bar{s} $\end{document} tetraquark state and \begin{document}$ X_0(4140) $\end{document} could be the second lowest \begin{document}$ 0^{++} \;\; cs\bar{c}\bar{s} $\end{document} tetraquark. Predictions of ratios between partial widths for the involved tetraquarks are provided in this paper. We aim to identify more \begin{document}$ cs\bar{c}\bar{s} $\end{document} tetraquarks with \begin{document}$ J^{PC}=1^{+-} $\end{document}, \begin{document}$ 0^{++} $\end{document}, and \begin{document}$ 2^{++} $\end{document}.
TALYS calculation and a short review of the experimental status of proton capture studies on p-nuclei: A guide to future investigation
Indrani Ray, Argha Deb
2024, 48(6): 064001. doi: 10.1088/1674-1137/ad2dc3
TALYS calculations were performed to obtain the theoretical proton capture cross-sections on the p-nuclei. A short review on the status of related experimental studies was also conducted. Some basic properties such as Q-values, Coulomb barrier, Gamow peak, Gamow Window, and decay properties of the parent and daughter nuclei were studied. Various experimental parameters, e.g., beam energy, beam current, targets, and detectors, used in experimental investigations reported in the literature, were tabulated. The results of the TALYS calculations in the Gamow region were compared with the corresponding experimental values wherever available. This study is expected to facilitate the planning of future experiments.
Prompt neutron emission in 250No spontaneous fission associated with ground and isomeric state decays
R.S. Mukhin, A.V. Isaev, A.V. Andreev, M.L. Chelnokov, V.I. Chepigin, H.M. Devaraja, I.N. Izosimov, A.A. Kuznetsova, O.N. Malyshev, A.G. Popeko, Yu.A. Popov, A. Rahmatinejad, B. Sailaubekov, T.M. Shneidman, E.A. Sokol, A.I. Svirikhin, M.S. Tezekbayeva, M.A. Bychkov, A.V. Yeremin, O. Dorvaux, B. Gall, K. Kessaci, K. Hauschild, A. Lopez-Martens
2024, 48(6): 064002. doi: 10.1088/1674-1137/ad361a
The complete-fusion reaction 204Pb(48Ca,2n)250No was used to study two activities of 250No with distinct half-lives. A total of 1357 events were observed in the SFiNx neutron detection system. The average number of neutrons emitted per spontaneous fission of 250No was determined to be \begin{document}$ (4.1 \pm 0.1) $\end{document}. The unusually symmetrical shape of the prompt neutron multiplicity distribution was restored and presented for the first time. Statistical tests were performed to compare the prompt neutron multiplicity distributions associated with the ground state and K-isomer state decays.
Systematic study of cluster radioactivity within the generalized liquid drop model
Jun-Gang Deng, Jun-Hao Cheng, Xiao-Jun Bao, Hong-Fei Zhang
2024, 48(6): 064101. doi: 10.1088/1674-1137/ad30ef
Cluster radioactivity is studied within the generalized liquid drop model (GLDM), in which the shell correction energy, pairing energy, and cluster preformation factor are considered. The calculations show significant improvements and can reproduce the experimental data within a factor of 8.04 after considering these physical effects. In addition, the systematic trend of the cluster preformation factors \begin{document}$ P_c $\end{document} is discussed in terms of the \begin{document}$ N_p N_n $\end{document} scheme to study the influence of the valence proton-neutron interaction and shell effect on cluster radioactivity. It is found that \begin{document}$ \log_{10}{P_c} $\end{document} is linearly related to \begin{document}$ N_p N_n $\end{document}. This is in agreement with a recent study [L. Qi et al., Phys. Rev. C 108, 014325 (2023)], in which \begin{document}$ \log_{10}{P_c} $\end{document}, obtained using different theoretical models and treatment methods than those used in this study, also had a linear relationship with \begin{document}$ N_p N_n $\end{document}. Combined with the work by Qi et al., this study suggests that the linear relationship between \begin{document}$ \log_{10}{P_c} $\end{document} and \begin{document}$ N_p N_n $\end{document} is model-independent and both the shell effect and valence proton-neutron interaction play essential roles in cluster radioactivity. An analytical formula is proposed to calculate the cluster preformation factor based on the \begin{document}$ N_p N_n $\end{document} scheme. In addition, the cluster preformation factors and the cluster radioactivity half-lives of some heavy nuclei are predicted, which can provide a reference for future experiments.
A study of U-isotope ground state properties with covariant energy density functional
Junchen Wang, Yuan Tian, Ruirui Xu, Ying Cui, Xi Tao, Xiaodong Sun, Zhi Zhang, Yue Zhang, Yinlu Han, Zhigang Ge, Nengchuan Shu
2024, 48(6): 064102. doi: 10.1088/1674-1137/ad305c
In this study, we systematically analyzed the ground state of uranium isotopes from 225 to 240. In our calculations, we used the covariant energy density functional of density-dependent meson exchange interaction (DD-ME2) with separable pairing interaction (TMR). Using the multiple deformation constraint, we calculated the potential energy surface (PES) of the uranium isotopes for both even-even and even-odd nuclei with quadrupole and octupole deformation. Based on our calculation and upon comparing the experimental data and Hartree-Fock-Bogoliubov calculations with Gogny D1S calculation data, the ground state of uranium isotopes with reflection-asymmetric deformation was found to be preferred.
Isoscaling properties for neutron-rich fragments in highly asymmetric heavy ion collision systems
Dan Peng, Chun-Wang Ma, Chun-Yuan Qiao, Xing-Quan Liu, Hui-Ling Wei
2024, 48(6): 064103. doi: 10.1088/1674-1137/ad33bd
Traditionally, isoscaling has been interpreted and applied within the framework of the grand canonical ensemble, based on the assumption that fragment production occurs following the attainment of a statistical equilibrium state. However, the influence of the symmetry energy can lead to differences in the neutron and density distribution in neutron-rich nuclei. This in turn may impact the isoscaling parameters (usually denoted by α and β). We examine the isoscaling properties for neutron-rich fragments produced in highly asymmetric systems on inverse kinematics, namely \begin{document}$ ^{40,48} $\end{document}Ca and \begin{document}$ ^{58,64} $\end{document}Ni + \begin{document}$ ^{9} $\end{document}Be at 140 MeV per nucleon. We evaluate α and β values and sort them as a function of the neutron excess \begin{document}$ I \equiv N-Z $\end{document}. The significant differences in α extracted from fragments within different ranges of I emphasize the importance of understanding the dependence of isoscaling parameters on fragments generated in various collision regions. Furthermore, the \begin{document}$ |\beta(N)| / \alpha(Z) $\end{document} value for a specific fragment in small size and highly isospin asymmetry systems can serve as a probe to detect the variations in neutron density and proton density in different regions of the nucleus and indicate the limitations of theoretical models in investigating these issues.
Sequential decay analysis of 235U(nth, f ) reaction using fragmentation approach
Nitin Sharma, Ashutosh Kaushik, Manoj K. Sharma
2024, 48(6): 064104. doi: 10.1088/1674-1137/ad2dc1
Numerous experimental and theoretical observations have concluded that the probability of the three fragment emission (ternary fission) or binary fission increases when one proceeds towards the heavy mass region of nuclear periodic table. Many factors affect fragment emission, such as the shell effect, deformation, orientation, and fissility parameter. Binary and ternary fissions are observed for both ground and excited states of the nuclei. The collinear cluster tripartition (CCT) channel of the \begin{document}$ ^{235} $\end{document}U(n\begin{document}$^{\rm th}$\end{document}, f) reaction is studied, and we observe that the CCT may be a sequential or simultaneous emission phenomenon. To date, different approaches have been introduced to study the CCT process as a simultaneous or sequential process, but the decay dynamics of these modes have not been not fully explored. Identifying the three fragments of the sequential process and exploring their related dynamics using an excitation energy dependent approach would be of further interest. Hence, in this study, we investigate the sequential decay mechanism of the \begin{document}$ ^{235} $\end{document}U(n\begin{document}$^{\rm th}$\end{document}, f) reaction using quantum mechanical fragmentation theory (QMFT). The decay mechanism is considered in two steps, where initially, the nucleus splits into an asymmetric channel. In the second step, the heavy fragment obtained in the first step divides into two fragments. Stage I analysis is conducted by calculating the fragmentation potential and preformation probability for the spherical and deformed choices of the decaying fragments. The most probable fragment combination of stage I are identified with respect to the dips in the fragmentation structure and the corresponding maxima of the preformation probability (\begin{document}$ P_0 $\end{document}). The light fragments of the identified decay channels (obtained in step I) agree closely with the experimentally observed fragments. The excitation energy of the decay channel is calculated using an iteration process. The excitation energy is shared using an excitation energy dependent level density parameter. The obtained excitation energy of the identified heavy fragments is further used to analyze the fragmentation, and the subsequent binary fragments of the sequential process are obtained. The three identified fragments of the sequential process agree with experimental observations and are found near the neutron or proton shell closure. Finally, the kinetic energy of the observed fragments is calculated, and the middle fragment of the CCT mechanism is identified.
Implications of neutron skin measurements on Skyrme equations of state
Da Wei Guan, Jun Chen Pei, Chong Ji Jiang
2024, 48(6): 064105. doi: 10.1088/1674-1137/ad3814
The recent measurements of neutron skins via parity violation in electron scattering have extracted an abnormally thick neutron skin for \begin{document}$ ^{208} $\end{document}Pb, which has significant consequences in nuclear equation of state (EoS) and neutron star observations. In this study, we perform optimizations of extended Skyrme forces in a consistent manner by including neutron skin thicknesses from PREX-II and CREX experiments and investigate nuclear EoSs and neutron stars in the GW170817 event. By varying the fitting weights of neutron skins, several new Skyrme parameterizations are obtained. Our results show the competition in the fitting procedure to simultaneously describe neutron skins, other properties of finite nuclei, and neutron star observations. The prospects of resolving neutron skin issues are also discussed.
Transfer learning and neural networks in predicting quadrupole deformation
Yuan Lin, Jia-Xing Li, Hong-Fei Zhang
2024, 48(6): 064106. doi: 10.1088/1674-1137/ad361d
Accurately determining the quadrupole deformation parameters of atomic nuclei is crucial for understanding their structural and dynamic properties. This study introduces an innovative approach that combines transfer learning techniques with neural networks to predict the quadrupole deformation parameters of even-even nuclei. With the application of this innovative technique, the quadrupole deformation parameters of 2331 even-even nuclei are successfully predicted within the nuclear region defined by proton numbers \begin{document}$8 \leq Z \leq 134 $\end{document} and neutron numbers \begin{document}$N \geq 8$\end{document}. Additionally, we discuss the impact of nuclear quadrupole deformation parameters on the capture cross-sections in heavy-ion fusion reactions, reconstructing the capture cross-sections for the reactions \begin{document}$^{48}{\rm{Ca}} + ^{244}{\rm{Pu}}$\end{document} and \begin{document}$^{48}{\rm{Ca}} + ^{248}{\rm{Cm}}$\end{document}. This research offers new insights into the application of neural networks in nuclear physics and highlights the potential of merging advanced machine learning techniques with both theoretical and experimental data, particularly in fields where experimental data are limited.
Optimization of performance of the KM2A full array using the Crab Nebula
Zhen Cao, F. Aharonian, Q. An, Y.X. Bai, Y.W. Bao, D. Bastieri, X.J. Bi, Y.J. Bi, J.T. Cai, Q. Cao, W.Y. Cao, Zhe Cao, J. Chang, J.F. Chang, A.M. Chen, E.S. Chen, Liang Chen, Lin Chen, Long Chen, M.J. Chen, M.L. Chen, Q.H. Chen, S.H. Chen, T.L. Chen, Y. Chen, N. Cheng, Y.D. Cheng, M.Y. Cui, S.W. Cui, X.H. Cui, Y.D. Cui, B.Z. Dai, H.L. Dai, Z.G. Dai, , D. della Volpe, X.Q. Dong, K.K. Duan, J.H. Fan, Y.Z. Fan, J. Fang, K. Fang, C.F. Feng, L. Feng, S.H. Feng, X.T. Feng, Y.L. Feng, S. Gabici, B. Gao, C.D. Gao, L.Q. Gao, Q. Gao, W. Gao, W.K. Gao, M.M. Ge, L.S. Geng, G. Giacinti, G.H. Gong, Q.B. Gou, M.H. Gu, F.L. Guo, X.L. Guo, Y.Q. Guo, Y.Y. Guo, Y.A. Han, H.H. He, H.N. He, J.Y. He, X.B. He, Y. He, M. Heller, Y.K. Hor, B.W. Hou, C. Hou, X. Hou, H.B. Hu, Q. Hu, S.C. Hu, D.H. Huang, T.Q. Huang, W.J. Huang, X.T. Huang, X.Y. Huang, Y. Huang, Z.C. Huang, X.L. Ji, H.Y. Jia, K. Jia, K. Jiang, X.W. Jiang, Z.J. Jiang, M. Jin, M.M. Kang, T. Ke, D. Kuleshov, K. Kurinov, B.B. Li, Cheng Li, Cong Li, D. Li, F. Li, H.B. Li, H.C
2024, 48(6): 065001. doi: 10.1088/1674-1137/ad2e82
The full array of the Large High Altitude Air Shower Observatory (LHAASO) has been in operation since July 2021. For its kilometer-square array (KM2A), we optimized the selection criteria for very high and ultra-high energy γ-rays using data collected from August 2021 to August 2022, resulting in an improvement in significance of the detection in the Crab Nebula of approximately 15%, compared with that of previous cuts. With the implementation of these new selection criteria, the angular resolution was also significantly improved by approximately 10% at tens of TeV. Other aspects of the full KM2A array performance, such as the pointing error, were also calibrated using the Crab Nebula. The resulting energy spectrum of the Crab Nebula in the energy range of 10-1000 TeV are well fitted by a log-parabola model, which is consistent with the previous results from LHAASO and other experiments.
Critical behavior and Joule-Thomson expansion of charged AdS black holes surrounded by exotic fluid with modified Chaplygin equation of state
Meng-Yao Zhang, Hao Chen, Hassan Hassanabad, Zheng-Wen Long, Hui Yang
2024, 48(6): 065101. doi: 10.1088/1674-1137/ad32c0
By considering the concept of a unified single fluid model, referred to as modified Chaplygin gas (MCG), which amalgamates dark energy and dark matter, we explore the thermodynamic characteristics of charged anti-de Sitter (AdS) black holes existing in an unconventional fluid accompanied by MCG. To accomplish this objective, we derive the equations of state by regarding the charge \begin{document}$ Q^{2} $\end{document} as a thermodynamic variable. The effects of MCG parameters on the critical thermodynamic quantities (\begin{document}$ \psi_{c} $\end{document}, \begin{document}$ T_{c} $\end{document}, \begin{document}$ Q_{c}^{2} $\end{document}) are examined, followed by a detailed analysis of the \begin{document}$ Q^{2}-\psi $\end{document} diagram. To provide a clearer explanation of the phase transition, we present an analysis of the Gibbs free energy. It is important to note that if the Hawking temperature exceeds the critical temperature, a distinct pattern is observed known as swallowtail behavior. This indicates that the system undergoes a first-order phase transition from a smaller black hole to a larger one. The critical exponent of the system is found to be in complete agreement with that of the van der Waals fluid system. Furthermore, we investigate the impact of MCG parameters and black hole charge on Joule-Thomson (J-T) expansion in the extended phase space. The J-T coefficient is examined to pinpoint the exact region experiencing cooling or heating, and the observation reveals that the presence of negative heat capacity results in the occurrence of a cooling process. The impact of MCG on the inversion curve of charged black holes exhibits a striking resemblance to that observed in most multi-dimensional black hole systems. In addition, it is worth noting that certain parameters exert a significant influence on the ratio \begin{document}$\dfrac{T_{\min}}{T_{c}}$\end{document}. For specific values of the MCG parameters, the ratio is consistent with the charged AdS black hole. The parameters γ and β have a non-negligible effect on the isenthalpic curve.
Cosmological constraints on neutrino mass within consistent cosmological models
Ye-Huang Pang, Xue Zhang, Qing-Guo Huang
2024, 48(6): 065102. doi: 10.1088/1674-1137/ad34c0
Recently, the emergence of cosmological tension has raised doubts about the consistency of the ΛCDM model. To constrain the neutrino mass within a consistent cosmological framework, we investigate three massive neutrinos with normal hierarchy (NH) and inverted hierarchy (IH) in both the axion-like early dark energy (Axi-EDE) and AdS-EDE models. We use joint datasets including the cosmic microwave background power spectrum from Planck 2018, Pantheon of type Ia supernova, baryon acoustic oscillation, and \begin{document}$ H_0 $\end{document} data from SH0ES. For the νAxi-EDE model, we obtain \begin{document}$\sum m_{\nu,\mathrm{NH}}$\end{document} < 0.152 eV and \begin{document}$\sum m_{\nu,\mathrm{IH}}$\end{document} < 0.178 eV, whereas for the νAdS-EDE model, we find \begin{document}$\sum m_{\nu,\mathrm{NH}}$\end{document} < 0.135 eV and \begin{document}$\sum m_{\nu,\mathrm{IH}} $\end{document} < 0.167 eV. Our results exhibit a preference for NH in both the νAxi-EDE and νAdS-EDE models.
Impacts of gravitational-wave background from supermassive black hole binaries on the detection of compact binaries by LISA
Fan Huang, Yan-Chen Bi, Zhoujian Cao, Qing-Guo Huang
2024, 48(6): 065103. doi: 10.1088/1674-1137/ad34c2
In the frequency band of the Laser Interferometer Space Antenna (LISA), extensive research has been conducted on the impact of foreground confusion noise generated by galactic binaries within the Milky Way Galaxy. Additionally, recent evidence of a stochastic signal, announced by the NANOGrav, EPTA, PPTA, CPTA, and InPTA, indicates that the stochastic gravitational-wave background (SGWB) generated by supermassive black hole binaries (SMBHBs) can contribute strong background noise within the LISA band. Given the presence of such strong noise, it is expected to have significant impacts on LISA's scientific missions. In this study, we investigate the impacts of the SGWB generated by SMBHBs on the detection of individual massive black hole binaries, verified galactic binaries, and extreme mass ratio inspirals in the context of LISA. We find it essential to resolve and eliminate the excess noise from the SGWB to guarantee the success of LISA's missions.
New results on the dynamics of critical collapse
Jun-Qi Guo, Yu Hu, Pan-Pan Wang, Cheng-Gang Shao
2024, 48(6): 065104. doi: 10.1088/1674-1137/ad361c
We study the dynamics of the critical collapse of a spherically symmetric scalar field. Approximate analytic expressions for the metric functions and matter field in the large-radius region are obtained. In the central region, owing to the boundary conditions, the equation of motion for the scalar field is reduced to the flat-spacetime form.
Observational appearance and extra photon rings of an asymmetric thin-shell wormhole with a Bardeen profile
Ke-Jian He, Zhi Luo, Sen Guo, Guo-Ping Li
2024, 48(6): 065105. doi: 10.1088/1674-1137/ad34bf
In this work, the optical appearance of an asymmetric thin-shell wormhole with a Bardeen profile is studied. To initiate the process, we need to construct an asymmetric thin-shell wormhole utilizing the cut-and-paste technique proposed by Visser and subsequently ascertain its pertinent physical quantities such as the radius of the photon sphere and critical impact parameters for different values of magnetic charge g. Then, the effective potential and motion behavior of photons are also investigated within the framework of asymmetric thin-shell wormholes with a Bardeen profile. It can be found that the effective potential, ray trajectory, and azimuthal angle of the thin-shell wormhole exhibit a strong correlation with the mass ratio of black holes. By considering the accretion disk as the sole background light source, we observe additional photon rings and lensing bands in the optical appearance of the asymmetric thin-shell wormhole with a Bardeen profile compared to those exhibited by the Bardeen black hole. One can find that there is an increase in the size of the specific additional light bands with increasing magnetic charge g, which is different from the black hole case. These exceptionally luminous rings can serve as a robust criterion for the identification and characterization of the thin-shell wormhole spacetime.
Surface growth approach for bulk reconstruction in the AdS/BCFT correspondence
Xi-Hao Fang, Fang-Zhong Chen, Jia-Rui Sun
2024, 48(6): 065106. doi: 10.1088/1674-1137/ad32be
In this study, we extend the surface growth approach for bulk reconstruction into the AdS spacetime with a boundary in the AdS/BCFT correspondence. We show that the geometry in the entanglement wedge with a boundary can be constructed from the direct growth of bulk extremal surfaces layer by layer. Furthermore, we observe that the surface growth configuration in BCFT can be connected with the defect multi scale entanglement renormalization ansatz (MERA) tensor network. Additionally, we investigate the entanglement of purification within the surface growth process, which not only reveals more refined structure of entanglement entropy in the entanglement wedge but also suggests a selection rule for surface growth in the bulk reconstruction.
Constraints on axion-like particles from the observation of Galactic sources by the LHAASO
Jun Li, Xiao-Jun Bi, Lin-Qing Gao, Xiaoyuan Huang, Run-Min Yao, Peng-Fei Yin
2024, 48(6): 065107. doi: 10.1088/1674-1137/ad361e
High-energy photons may oscillate with axion-like particles (ALPs) when they propagate through the Milky Way's magnetic field, resulting in an alteration in the observed photon energy spectrum. Ultra-high energy gamma-ray spectra, measured by the Large High Altitude Air Shower Observatory (LHAASO) up to \begin{document}$ {\cal{O}}(1)\; {\rm{PeV}} $\end{document}, provide a promising opportunity to investigate the ALP-photon oscillation effect. In this study, we utilize the gamma-ray spectra of four Galactic sources measured by the LHAASO, that is, the Crab Nebula, LHAASO J2226+6057, LHAASO J1908+0621, and LHAASO J1825-1326, to explore this effect. We employ the CLs method to set constraints on the ALP parameters. Our analysis of the observations of the four sources reveals that the ALP-photon coupling \begin{document}$ g_{a\gamma} $\end{document} is constrained to be smaller than \begin{document}$ 1.4\times 10^{-10} $\end{document} \begin{document}$ {\rm GeV}^{-1} $\end{document} for an ALP mass of \begin{document}$ \sim 4\times 10^{-7} \; {\rm{eV}} $\end{document} at 95% C.L. Combining the observations of the Crab Nebula from the LHAASO and other experiments, we find that the ALP-photon coupling may be set to approximately \begin{document}$ 7.5\times 10^{-11} $\end{document} \begin{document}$ {\rm GeV}^{-1} $\end{document} for an ALP mass of \begin{document}$ \sim 4 \times 10^{-7}\; {\rm{eV}} $\end{document}, which is similar to the CAST constraint.
Constraints on real scalar inflation from preheating using LATTICEEASY
Wei Cheng, Tong Qin, Jiujiang Jiang, Ruiyu Zhou
2024, 48(6): 065108. doi: 10.1088/1674-1137/ad34bd
In this paper, we undertake a detailed study of real scalar inflation using LATTICEEASY simulations to investigate preheating phenomena. Generally, the scalar inflation potential with non-minimal coupling can be approximated using a quartic potential. We observe that the evolutionary behavior of this potential remains unaffected by the coupling coefficient. Furthermore, the theoretical predictions for the scalar spectral index (\begin{document}$n_s$\end{document}) and tensor-to-scalar power ratio (r) are independent of this coefficient. Consequently, the coefficients of this model are not constrained by Planck observations. Fortunately, the properties of preheating after inflation provide a viable approach to examining these coefficients. Through LATTICEEASY simulations, we trace the evolution of particle number density, scale factor, and energy density during the preheating process. Subsequently, we derive the parameters, such as the energy ratio (γ) and the e-folding number of preheating (\begin{document}$N_{\rm pre}$\end{document}), which facilitate further predictions of \begin{document}$n_s$\end{document} and r. We successfully validate real scalar inflation model using preheating in LATTICEEASY simulations based on the analytical relationship between preheating and inflation models.
Photon orbits and phase transition for Letelier AdS black holes immersed in perfect fluid dark matter
Ashima Sood, Md Sabir Ali, J. K. Singh, Sushant G. Ghosh
2024, 48(6): 065109. doi: 10.1088/1674-1137/ad361f
We obtain an exact solution for spherically symmetric Letelier AdS black holes immersed in perfect fluid dark matter (PFDM). Considering the cosmological constant as the positive pressure of the system and volume as its conjugate variable, we analyze the thermodynamics of our black holes in the extended phase space. Owing to the background clouds of strings parameter (a) and the parameter endowed with PFDM (β), we analyze the Hawking temperature, entropy, and specific heat. Furthermore, we investigate the relationship between the photon sphere radius and phase transition for the Letelier AdS black holes immersed in PFDM. Through the analysis, with a particular condition, non-monotonic behaviors are found between the photon sphere radius, impact parameter, PFDM parameter, temperature, and pressure. We can regard the changes in both the photon sphere radius and impact parameter before and after phase transition as the order parameter; their critical exponents near the critical point are equal to the same value, 1/2, similar to that in ordinary thermal systems. This indicates that a universal relation of gravity may exist near the critical point for a black hole thermodynamic system.