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2024-8 Contents
2024, 48(8): 1-3.
Abstract:
LETTERS
New signature of low mass Z′ in J/ψ decays
Chao-Qiang Geng, Chia-Wei Liu, Jiabao Zhang
2024, 48(8): 081001. doi: 10.1088/1674-1137/ad53b6
Abstract:
We explored a new approach to search for a low-mass \begin{document}$ Z^{\prime} $\end{document} particle through \begin{document}$ J/\psi $\end{document} decays by identifying its existence through parity-violating phenomena in the isospin-violating final states of \begin{document}$ \Lambda\overline{\Sigma}^{0} $\end{document} and the corresponding charge conjugated states of \begin{document}$ \overline{\Lambda}\Sigma^{0} $\end{document}. Our investigation centered on a generation-independent and leptophobic \begin{document}$ Z^{\prime} $\end{document} with mass below 10 GeV. Given the present experimental conditions at Beijing Spectrometer III (BESIII) and the anticipated opportunities at the Super Tau Charm Factory (STCF), we conducted Monte-Carlo simulations to predict possible events at both facilities. Notably, we foresee a substantial enhancement in the precision of the lower limit estimation of \begin{document}$ \alpha_{\text{NP}} $\end{document} as well as a reduction in statistical uncertainty with upcoming STCF experiments. Furthermore, it is essential to highlight that a null result in the measurement of \begin{document}$ \alpha_{\text{NP}} $\end{document} would impose stringent constraints, requiring the \begin{document}$ Z^{\prime}-q-q $\end{document} couplings to be in the order of \begin{document}$ 10^{-2} $\end{document}.
PARTICLES AND FIELDS
Amplitude analysis of the decays ${\boldsymbol D^{\bf 0}\bf\to\pi^+\pi^-\pi^+\pi^-} $ and ${\boldsymbol D^{\bf 0}\bf\to\pi^+\pi^-\pi^0\pi^0} $
M. Ablikim, M. N. Achasov, P. Adlarson, O. Afedulidis, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, I. Balossino, Y. Ban, H.-R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Cetin, J. F. Chang, W. L. Chang, G. R. Che, G. Chelkov, C. Chen, C. H. Chen, Chao Chen, G. Chen, H. S. Chen, M. L. Chen, S. J. Chen, S. L. Chen, S. M. Chen, T. Chen, X. R. Chen, X. T. Chen, Y. B. Chen, Y. Q. Chen, Z. J. Chen, Z. Y. Chen, S. K. Choi, X. Chu, G. Cibinetto, F. Cossio, J. J. Cui, H. L. Dai, J. P. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, C. Q. Deng, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, F. De Mori, B. Ding, X. X. Ding, Y. Ding, J. Dong, L. Y. Dong, M. Y. Dong, X. Dong, M. C. Du, S. X. Du, Z. H. Duan, P. Egorov, Y. H. Fan, J. Fang, S. S. Fang, W. X. Fang, Y. Fang, Y. Q. Fang, R. Farinelli, L. Fava, F. Feldbauer, G. Felici, C. Q. F
2024, 48(8): 083001. doi: 10.1088/1674-1137/ad3d4d
Abstract:
Using \begin{document}$ e^+e^- $\end{document} annihilation data corresponding to an integrated luminosity of 2.93 \begin{document}$ \rm fb^{-1} $\end{document} taken at the center-of-mass energy \begin{document}$ \sqrt{s}=3.773 $\end{document} GeV with the BESIII detector, a joint amplitude analysis is performed on the decays \begin{document}$ D^0\to\pi^+\pi^-\pi^+\pi^- $\end{document} and \begin{document}$ D^0\to\pi^+\pi^-\pi^0\pi^0 $\end{document}(non-η). The fit fractions of individual components are obtained, and large interferences among the dominant components of the decays \begin{document}$ D^{0}\to a_{1}(1260)\pi $\end{document}, \begin{document}$ D^{0}\to\pi(1300)\pi $\end{document}, \begin{document}$ D^{0}\to\rho(770)\rho(770) $\end{document}, and \begin{document}$ D^{0}\to2(\pi\pi)_{S} $\end{document} are observed in both channels. With the obtained amplitude model, the \begin{document}$ CP $\end{document}-even fractions of \begin{document}$ D^0\to \pi^+\pi^-\pi^+\pi^- $\end{document} and \begin{document}$ D^0\to\pi^+\pi^-\pi^0\pi^0 $\end{document}(non-η) are determined to be \begin{document}$ (75.2\; \pm\; 1.1_{\rm stat.}\; \pm\; 1.5_{\rm syst.})\ $\end{document}% and \begin{document}$(68.9\; \pm\; 1.5_{\rm stat.}\; \pm\; 2.4_{\rm syst.})$\end{document}%, respectively. The branching fractions of \begin{document}$ D^0\to \pi^+\pi^-\pi^+\pi^- $\end{document} and \begin{document}$ D^0\to\pi^+\pi^-\pi^0\pi^0 $\end{document}(non-η) are measured to be \begin{document}$(0.688\; \pm\; 0.010_{\rm stat.}\; \pm\; 0.010_{\rm syst.})$\end{document}% and \begin{document}$(0.951\; \pm\; 0.025_{\rm stat.}\; \pm\; 0.021_{\rm syst.})$\end{document}%, respectively. The amplitude analysis provides an important model for the binning strategy in measuring the strong phase parameters of \begin{document}$ D^0 \to 4\pi $\end{document} when used to determine the CKM angle \begin{document}$ \gamma (\phi_{3}) $\end{document} via the \begin{document}$ B^{-}\to D K^{-} $\end{document} decay.
Analysis of strong decays of SU(3) partners of Ω(2012) baryon
T. M. Aliev, S. Bilmis, M. Savci
2024, 48(8): 083101. doi: 10.1088/1674-1137/ad446a
Abstract:
We estimate the coupling constants and decay widths of the \begin{document}$S U(3)$\end{document} partners of the \begin{document}$ \Omega(2012) $\end{document} hyperon, as discovered by the BELLE Collaboration, using the distribution amplitudes of the octet baryons within the light cone sum rules method. Our study includes a comparison of the obtained results for the relevant decay widths with those derived within the framework of the flavor \begin{document}$S U(3)$\end{document} analysis. We observe a good agreement between the predictions of both approaches. Moreover, our result on the decay width of \begin{document}$ \Omega \to \Xi K $\end{document} is compatible with the existing experimental result within the uncertainties of the model predictions. These results can provide helpful insights for determining the nature of the \begin{document}$S U(3)$\end{document} partners of the \begin{document}$ \Omega(2012) $\end{document} baryon.
Moving doubly heavy baryon in a strongly coupled plasma via holography
Xuan Liu, Jia-Jie Jiang, Xun Chen, Mitsutoshi Fujita, Akira Watanabe
2024, 48(8): 083102. doi: 10.1088/1674-1137/ad39cf
Abstract:
Gauge/gravity duality is used to study the properties of the doubly heavy baryon \begin{document}$ ({QQq}) $\end{document} at finite rapidity and temperature in heavy-ion collisions. We investigate the impact of rapidity on string breaking and screening of \begin{document}${QQq} $\end{document} and compare these effects with the results for \begin{document}$ Q\bar{Q} $\end{document} in detail. Computations reveal that the string-breaking distances of \begin{document}$ {QQq} $\end{document} and \begin{document}$ Q\bar{Q} $\end{document} are close in the confined state, and the effects of rapidity and temperature on the string breaking are not significant. An interesting result shows that \begin{document}${QQq} $\end{document} cannot be determined at sufficiently high temperatures and rapidities. However, \begin{document}$ Q\bar{Q} $\end{document} can exist under any conditions as long as the separation distance is sufficiently small. Furthermore, the screening distances of \begin{document}$ {QQq} $\end{document} and \begin{document}$ Q\bar{Q} $\end{document} are compared at finite rapidity and temperature. Based on the above analysis, we infer that \begin{document}$ Q\bar{Q} $\end{document} is more stable than \begin{document}$ {QQq} $\end{document} at finite rapidity and temperature.
Analysis of ${{\boldsymbol b}{\bf\rightarrow} {\boldsymbol c}{\boldsymbol\tau}\bar{\boldsymbol\nu}_{\boldsymbol\tau}}$ anomalies using weak effective Hamiltonian with complex couplings and their impact on various physical observables
Muhammad Arslan, Tahira Yasmeen, Saba Shafaq, Ishtiaq Ahmed, Muhammad Jamil Aslam
2024, 48(8): 083103. doi: 10.1088/1674-1137/ad34bc
Abstract:
Recently, the experimental measurements of the branching ratios and different polarization asymmetries for processes occurring through flavor-changing-charged current \begin{document}$ (b\rightarrow c\tau\overline{\nu}_{\tau}) $\end{document}transitions by BABAR, Belle, and LHCb have revealed some significant differences from the corresponding Standard Model (SM) predictions. This has triggered an interest to search for physics beyond the SM in the context of various new physics (NP) models and using the model-independent weak effective Hamiltonian (WEH). Assuming left-handed neutrinos, we add the dimension-six vector, (pseudo-)scalar, and tensor operators with complex Wilson coefficients (WCs) to the SM WEH. Using 60%, 30%, and 10% constraints resulting from the branching ratio of \begin{document}$ B_{c}\to\tau\bar{\nu}_{\tau} $\end{document}, we reassess the parametric space of these new physics WCs accommodating the current anomalies based on the most recent HFLAV data of \begin{document}$ R_{\tau/{\mu,e}}\left(D\right) $\end{document} and \begin{document}$ R_{\tau/{\mu,e}}\left(D^*\right) $\end{document} and Belle data of \begin{document}$ F_{L}\left(D^*\right) $\end{document} and \begin{document}$ P_{\tau}\left(D^*\right) $\end{document}. We find that the allowed parametric region of left-handed scalar couplings strongly depends on the constraints of the \begin{document}$ B_{c}\rightarrow \tau\bar{\nu}_{\tau} $\end{document} branching ratio, and the maximum pull from the SM predictions results from the <60% branching ratio limit. Also, the parametric region changes significantly if we extend the analysis by adding LHCb data of \begin{document}$ R_{\tau/\mu}\left(J/\psi\right) $\end{document} and \begin{document}$ R_{\tau/\ell}\left(\Lambda_c\right) $\end{document}. Furthermore, due to the large uncertainties in the measurements of \begin{document}$ R_{\tau/\mu}\left(J/\psi\right) $\end{document} and \begin{document}$ R_{\tau/\ell}\left(X_c\right) $\end{document}, we derive the sum rules which complement them with \begin{document}$ R_{\tau/{\mu,e}}\left(D\right) $\end{document} and \begin{document}$ R_{\tau/{\mu,e}}\left(D^*\right) $\end{document}. Using the best-fit points of the new complex WCs along with the latest measurements of \begin{document}$ R_{\tau/{\mu,e}}\left(D^{(*)}\right) $\end{document}, we predict the numerical values of the observable \begin{document}$ R_{\tau/\ell}\left(\Lambda_c\right) $\end{document}, \begin{document}$ R_{\tau/\mu}\left(J/\psi\right) $\end{document} , and \begin{document}$ R_{\tau/\ell}\left(X_c\right) $\end{document} from the sum rules. The simultaneous dependence of abovementioned physical observables on the NP WCs is established by plotting their correlation with \begin{document}$ R_{D} $\end{document} and \begin{document}$ R_{D^*} $\end{document}, which are useful to discriminate between various NP scenarios. We find that the most significant impact of NP results from the WC \begin{document}$ C_{L}^{S}=4C^{T} $\end{document}. Finally, we study the impact of these NP couplings on various angular and \begin{document}$ CP $\end{document} triple product asymmetries that could be measured in some ongoing and future experiments. The precise measurements of these observables are important to check the SM and extract the possible NP.
Féeton (B-L gauge boson) dark matter for the 511-keV gamma-ray excess and the prediction of low-energy neutrino flux
Jie Sheng, Yu Cheng, Weikang Lin, Tsutomu T. Yanagida
2024, 48(8): 083104. doi: 10.1088/1674-1137/ad4af3
Abstract:
The féeton is the gauge boson of the \begin{document}$ U(1)_{B-L} $\end{document} gauge theory. If the gauge coupling constant is extremely small, the féeton becomes a candidate for dark matter. We show that its decay to a pair of an electron and a positron explains the observed Galactic 511-keV gamma-ray excess in a consistent manner. This féeton dark matter decays mainly into pairs neutrino and anti-neutrino. Future low-energy experiments with improved directional capability will enable capturing these neutrino signals. The seesaw-motivated parameter space predicts a relatively short féeton lifetime that is comparable to the current cosmological constraint.
Masses of the conjectured H-dibaryon at different temperatures
Liang-Kai Wu, Han Tang, Ning Li, Xin-Yang Wang
2024, 48(8): 083105. doi: 10.1088/1674-1137/ad3d4c
Abstract:
We present a lattice QCD determination of masses of the conjectured H-dibaryon, denoted as \begin{document}$ m_H $\end{document}, at nine different temperatures: \begin{document}$ T/T_c = $\end{document}0.24, 0.63, 0.76, 0.84, 0.95, 1.09, 1.27, 1.52, and 1.90. The masses of baryons N, Σ, Ξ, and Λ at different temperatures were also computed. The simulations were performed on an anisotropic lattice with \begin{document}$ N_f=2+1 $\end{document} flavours of clover fermion at a quark mass corresponding to \begin{document}$m_\pi=384(4)\; {{\rm{MeV}}}$\end{document}. The thermal ensembles were provided by the FASTSUM collaboration, whereas the zero temperature ensembles were provided by the Hadspec collaboration. We also calculated the spectral density of the correlation function of those particles. The spectral density distributions show a rich peak structure at the lowest temperature; at intermediate temperatures, the mass values of those particles obtained by the extrapolation method reflect a two-peak structure. While the spectral density for the octet baryon becomes smooth at \begin{document}$ T/T_c = $\end{document} 1.27, 1.52, and 1.90, the spectral density for the H-dibaryon becomes smooth at \begin{document}$ T/T_c = 1.90 $\end{document}. At \begin{document}$ T/T_c =0.24 $\end{document}, the mass difference of the H-dibaryon and Λ pair, expressed as \begin{document}$ \Delta m = m_H - 2\,m_{\Lambda} $\end{document}, was estimated to be \begin{document}$ \Delta m = -14.6(6.2) $\end{document} MeV, which suggests the existence of a bound H-dibaryon state.
Pion-photon and kaon-photon transition distribution amplitudes in the Nambu–Jona-Lasinio model
Jin-Li Zhang, Jun Wu
2024, 48(8): 083106. doi: 10.1088/1674-1137/ad2b54
Abstract:
The Nambu–Jona-Lasinio model is utilized to investigate the pion- and kaon-photon leading-twist transition distribution amplitudes using proper time regularization. Separately, the properties of the vector and axial vector pion-photon transition distribution amplitudes are examined, and the results meet the desired properties. Our study involves sum rule and polynomiality condition. The vector and axial vector pion-photon transition form factors that are present in the \begin{document}$ \pi^+\rightarrow \gamma e^+ \nu $\end{document} process are the first Mellin moments of the pion-photon transition distribution amplitudes. The vector transition form factor originates from the internal structure of hadrons, the axial current can be coupled to a pion, this pion is virtual, and its contribution will be present independently of the external hadrons. The kaon transition form factors are similar. The vector form factor's value at zero momentum transfer is determined by the axial anomaly, while this is not the case for the axial one. The vector and axial form factors, as well as the neutral pion vector form factor \begin{document}$ F_{\pi \gamma \gamma}(t) $\end{document}, are depicted. According to our findings, the pion axial transition form factor is harder than the vector transition form factor and harder than the electromagnetic form factor. We also discuss the link between \begin{document}$ \pi - \gamma $\end{document} and \begin{document}$ \gamma - \pi $\end{document} transitions distribution amplitudes.
Next-to-leading-order relativistic and QCD corrections to prompt $ {\boldsymbol J/\boldsymbol\psi} $ pair photoproduction at future ${\boldsymbol e^{\bf +}\boldsymbol e^{\bf -}} $ colliders
Zhi-Guo He, Xiao-Bo Jin, Bernd A. Kniehl, Rong Li
2024, 48(8): 083107. doi: 10.1088/1674-1137/ad408f
Abstract:
Within the framework of nonrelativistic-QCD factorization, we calculate both the next-to-leading-order relativistic and QCD corrections to prompt \begin{document}$ J/\psi $\end{document} pair production, with feed-down from \begin{document}$ \psi(2S) $\end{document} mesons, via photon-photon collisions at future \begin{document}$ e^+e^- $\end{document} colliders, including the Future Circular Lepton Collider (FCC-ee), the Circular Electron Positron Collider (CEPC), and the Compact Linear Collider (CLIC). We present total cross sections and distributions in single \begin{document}$ J/\psi $\end{document} transverse momentum and rapidity, as well as in \begin{document}$ J/\psi $\end{document} pair invariant mass. The relativistic and QCD corrections both turn out to be large and negative. However, the production rates are large enough for useful experimental studies.
A comparative lattice analysis of SU(2) dark glueballs
Min-Huan Chu, Jun-Hui Lai, Wei Wang, Jialu Zhang, Qianteng Zhu
2024, 48(8): 083108. doi: 10.1088/1674-1137/ad4e24
Abstract:
We study the mass and scattering cross section of \begin{document}$S U(2)$\end{document} glueballs as dark matter candidates using lattice simulations. We employ both naive and improved \begin{document}$S U(2)$\end{document} gauge actions in \begin{document}$ 3+1 $\end{document} dimensions with several β values, and we adopt both the traditional Monte Carlo method and flow-based model based on machine learning techniques to generate lattice configurations. The mass of a dark scalar glueball with \begin{document}$ J^{PC}=0^{++} $\end{document} and the Nambu-Bethe-Salpeter wave function are calculated. Using a coupling constant of \begin{document}$ \beta=2.2 $\end{document} as an illustration, we compare the dark glueball mass calculated from the configurations generated from the two methods. While consistent results can be achieved, the two methods demonstrate distinct advantages. Using the Runge-Kutta method, we extract the glueball interaction potential and two-body scattering cross section. From the observational constraints, we obtain the lower bound of the mass of scalar glueballs as candidates of dark matter.
Invisible and semi-invisible decays of bottom baryons
Yong Zheng, Jian-Nan Ding, Dong-Hao Li, Lei-Yi Li, Cai-Dian Lü, Fu-Sheng Yu
2024, 48(8): 083109. doi: 10.1088/1674-1137/ad4afa
Abstract:
The similar densities of dark matter and baryons in the universe imply that they may arise from the same ultraviolet model. B-Mesogenesis, which assumes dark matter is charged under the baryon number, attempts to simultaneously explain the origin of baryon asymmetry and dark matter in the universe. In particular, B-Mesogenesis may induce bottom-baryon decays into invisible or semi-invisible final states, which provide a distinctive signal for probing this scenario. In this work, we systematically study the invisible decays of bottom baryons into dark matter and the semi-invisible decays of bottom baryons into a meson or a photon together with a dark matter particle. In particular, the fully invisible decay can reveal the stable particles in B-Mesogenesis. Some QCD-based frameworks are used to calculate the hadronic matrix elements under the B-Mesogenesis model. We estimate the constraints on the Wilson coefficients or the product of some new physics couplings with the Wilson coefficients according to the semi-invisible and invisible decays of bottom baryons detectable at future colliders.
NUCLEAR PHYSICS
Measurement of the neutron total cross section of 9Be at the Back-n white neutron source of CSNS
Jiangbo Bai, Jingyu Tang, Liqun Shi, Yonghao Chen, Han Yi, Jie Bao, Yu Bao, Ping Cao, Haolei Chen, Zhen Chen, Zengqi Cui, Ruirui Fan, Changqing Feng, Keqing Gao, Xiaolong Gao, MinHao Gu, Changcai Han, Guozhu He, Yongcheng He, Yang Hong, Yiwei Hu, Hanxiong Huang, Xiru Huang, Haoyu Jiang, Wei Jiang, Zhijie Jiang, Hantao Jing, Ling Kang, Bo Li, Chao Li, Jiawen Li, Qiang Li, Xiao Li, Yang Li, Jie Liu, Shubin Liu, Ze Long, Guangyuan Luan, Changjun Ning, Mengchen Niu, Binbin Qi, Jie Ren, Xichao Ruan, Zhaohui Song, Kang Sun, Zhijia Sun, Zhixin Tan, Xinyi Tang, Binbin Tian, Lijiao Wang, Pengcheng Wang, Zhaohui Wang, Xiaoguang Wu, Xuan Wu, Likun Xie, Xiaoyun Yang, Li Yu, Tao Yu, Yongji Yu, Guohui Zhang, Linhao Zhang, Qiwei Zhang, Xianpeng Zhang, Yuliang Zhang, Zhiyong Zhang, Luping Zhou, Zhihao Zhou, Kejun Zhu
2024, 48(8): 084001. doi: 10.1088/1674-1137/ad4c5b
Abstract:
The neutron total cross section data of 9Be are essential in the nuclear structure model research of light nuclei and nuclear power installations. The neutron total cross section of 9Be in the 0.3 eV−120 MeV energy region has been measured using time-of-flight and transmission methods with the Neutron Total Cross Sectional Spectrometer (NTOX) based on the multi-cell fast fission chamber at the China Spallation Neutron Source (CSNS)-Back-n white neutron source (Back-n). The fission count-neutron energy distributions of 235U and 238U without samples and with Be samples with three thicknesses were measured in the double-bunch operation mode for a beam power of 100 kW. The Bayesian method was used to eliminate the influence of the double-bunch problem on neutron measurement in the energy region above 10 keV. The neutron total cross section of 9Be results was consistent with ENDF/B-VIII.0 evaluation library data in the 0.3 eV−20 MeV energy region. In the energy ranges of 0.3 eV to 10 keV and 0.01 to 20 MeV, the deviations between our results and the evaluation results of ENDF/B-VIII.0 were within 2.5% and 15%, respectively. In the resonance energy region, the measured resonance energies in our experiment were 0.63, 0.82, and 2.8 MeV, respectively. The results showed that the total cross section uncertainties of three Be samples were within 2.2% in the energy region below 1 MeV. The total cross section uncertainty of 30 mm Be from 235U was the smallest and less than 5% in the energy region of 0.3 eV−120 MeV. The results of this experiment can provide technical support for further data analysis and related nuclear data evaluation.
Inclusive quasielastic neutrino-nucleus scattering with energy density functional nuclear models
K. S. Kim, Soonchul Choi, Hana Gil, Chang Ho Hyun
2024, 48(8): 084101. doi: 10.1088/1674-1137/ad4855
Abstract:
In this study, we calculated the inclusive charged-current neutrino-nucleus scattering from 40Ar in the quasielastic region. To explore the effect of uncertainties stemming from the nuclear structure, we used the KIDS (Korea-IBS-Daegu-SKKU) nuclear energy density functional and Skyrme force models, namely SLy4, SkI3, and MSk7. These models were selected to have distinct behavior in terms of the density dependence of the symmetry energy and the effective mass of the nucleon. In the charged-current neutrino scattering, the single- and double-differential cross sections were calculated for various kinematics. Total cross sections are reported as a function of the incident neutrino energy. The theoretical cross sections were compared with experimental data, and the roles of the effective mass and symmetry energy were investigated in terms of charged-current neutrino-nucleus scattering.
Calculation of the energy dependence of fission fragments yields and kinetic energy distributions for neutron-induced 235U fission
Ya-Ning Han, Zheng Wei, Yi-Xuan Wang, Dong-Ying Huo, Peng-Qi Zhang, Ming Li, Jun Ma, Kang Wu, Yong-Guang Zheng, Yuan He, Zhi-Yong Deng, Tian-Zhi Jiang, Xiang-Lin Zhuo, Jin Li, Yun Zhang, Yu Zhang, Jun-Run Wang, Xiao-Dong Su, Ze-En Yao
2024, 48(8): 084102. doi: 10.1088/1674-1137/ad485c
Abstract:
Fission fragments yields and average total kinetic energy are fundamental nuclear data for nuclear energy applications and the study of nuclear devices. Certain fission products, such as 95Zr, 99Mo, 140Ba, 144Ce, and 147Nd, serve as burnup monitors, assessing the number of fissions induced by neutrons on 235U. However, current experimental data for these fission products worldwide are inconsistent, introducing significant uncertainty into related scientific research. In this study, we employed the Potential-driving Model to calculate the independent yields of 235U and evaluate its advantages in such calculations. Additionally, we investigated the energy dependence of independent yields to select important products. Furthermore, we calculated the cumulative yields of 95Zr, 99Mo, 140Ba, 144Ce, and 147Nd, and compared them with existing literature data to explore the energy dependence of fission products for 235U. Given the lack of fission product yield data above 14.8 MeV, we extended our calculated incident neutron energy to 20 MeV, aiming to support future scientific research. The Geant4 physical model does not consider the influence of incident neutron energy on the average total kinetic energy of fission fragments; thus, we introduced the excitation function of the total kinetic energy of fission fragments recommended by Madland et al., which effectively describes the experimental data of the average total kinetic energy of fragments formed in 235U fission. In this paper, we comprehensively discuss the energy dependence of fission product yields and average total kinetic energy.
Applying deep learning technique to chiral magnetic wave search
Yuan-Sheng Zhao, Xu-Guang Huang
2024, 48(8): 084103. doi: 10.1088/1674-1137/ad4c5d
Abstract:
The chiral magnetic wave (CMW) is a collective mode in quark-gluon plasma originated from the chiral magnetic effect (CME) and chiral separation effect. Its detection in heavy-ion collisions is challenging owing to significant background contamination. In [Y. S. Zhao et al., Phys. Rev. C 106, L051901 (2022)], we constructed a neural network that accurately identifies the CME-related signal from the final-state pion spectra. In this study, we have generalized this neural network to the case of CMW search. We show that, after an updated training, the neural network effectively recognizes the CMW-related signal. Additionally, we have assessed the performance of the neural network in comparison with other known methods for CMW search.
Correlation between the charge radii difference in mirror partner nuclei and thesymmetry energy slope
Xiao-Rong Ma, Shuai Sun, Rong An, Li-Gang Cao
2024, 48(8): 084104. doi: 10.1088/1674-1137/ad47a8
Abstract:
A correlation between the charge radii difference of mirror partner nuclei \begin{document}$ \Delta{R_{\mathrm{ch}}} $\end{document} and the slope parameter L of symmetry energy has been built to ascertain the equation of state of isospin asymmetric nuclear matter. In this work, the influences of pairing correlations and isoscalar compression modulus on the \begin{document}$ \Delta{R_{\mathrm{ch}}} $\end{document} are systematically investigated based on the Skyrme energy density functional theory. The calculated results suggest that the linear correlation between \begin{document}$ \Delta{R_{\mathrm{ch}}} $\end{document} and L is decreased by the surface pairing correlations. The slope parameter deduced from the difference of charge radii of mirror-pair nuclei 32Ar-32Si, 36Ca-36S, 38Ca-38Ar, and 54Ni-54Fe falls into the range of \begin{document}$ L=42.57 $\end{document}−\begin{document}$ 50.64 $\end{document} MeV, that is, the rather soft equation of state of asymmetric nuclear matter. Besides, the range of the slope parameter can also be influenced by the effective forces classified by various isoscalar incompressibility coefficients.
Uncertainties of nuclear level density estimated using Bayesian neural networks
Xinyu Wang, Ying Cui, Yuan Tian, Kai Zhao, Yingxun Zhang
2024, 48(8): 084105. doi: 10.1088/1674-1137/ad47a7
Abstract:
Nuclear level density (NLD) is a critical parameter for understanding nuclear reactions and the structure of atomic nuclei; however, accurate estimation of NLD is challenging owing to limitations inherent in both experimental measurements and theoretical models. This paper presents a sophisticated approach using Bayesian neural networks (BNNs) to analyze NLD across a wide range of models. It uniquely incorporates the assessment of model uncertainties. The application of BNNs demonstrates remarkable success in accurately predicting NLD values when compared to recent experimental data, confirming the effectiveness of our methodology. The reliability and predictive power of the BNN approach not only validates its current application but also encourages its integration into future analyses of nuclear reaction cross sections.
Quenching and flow of charm and bottom quarks via semi-leptonic decay of D and B mesons in Pb+Pb collisions at the LHC
Shu-Qing Li, Wen-Jing Xing, Shanshan Cao, Guang-You Qin
2024, 48(8): 084106. doi: 10.1088/1674-1137/ad4c59
Abstract:
Heavy flavor particles provide important probes of the microscopic structure and thermodynamic properties of the quark-gluon plasma (QGP) produced in high-energy nucleus-nucleus collisions. We studied the energy loss and flow of charm and bottom quarks inside the QGP via the nuclear modification factor (\begin{document}$R_{AA}$\end{document}) and elliptic flow coefficient (\begin{document}$ v_2 $\end{document}) of their decayed leptons in heavy-ion collisions at the LHC. The dynamical evolution of the QGP was performed using the CLVisc (3+1)-dimensional viscous hydrodynamics model; the evolution of heavy quarks inside the QGP was simulated with our improved Langevin model that considers both collisional and radiative energy loss of heavy quarks; the hadronization of heavy quarks was simulated via our hybrid coalescence-fragmentation model; and the semi-leptonic decay of D and B mesons was simulated via PYTHIA. Using the same spatial diffusion coefficient for charm and bottom quarks, we obtained smaller \begin{document}$R_{AA}$\end{document} and larger \begin{document}$ v_2 $\end{document} of charm decayed leptons than bottom decayed leptons, indicating stronger energy loss of charm quarks than bottom quarks inside the QGP within our current model setup.
PARTICLE AND NUCLEAR ASTROPHYSICS AND COSMOLOGY
Spatial covariant gravity with two degrees of freedom in the presence of an auxiliary scalar field: Perturbation analysis
Zhi-Chao Wang, Xian Gao
2024, 48(8): 085101. doi: 10.1088/1674-1137/ad47a9
Abstract:
We investigate a class of gravity theories respecting only spatial covariance, termed spatially covariant gravity, in the presence of an auxiliary scalar field. We examine the conditions on the Lagrangian required to eliminate scalar degrees of freedom, allowing only two tensorial degrees of freedom to propagate. Instead of strict constraint analysis, in this paper, we employ the perturbation method and focus on the necessary conditions to evade the scalar mode at the linear order in perturbations around a cosmological background. Beginning with a general action and solving the auxiliary perturbation variables in terms of a would-be dynamical scalar mode, we derive the condition to remove its kinetic term, thus ensuring that no scalar mode propagates. As an application of the general condition, we study a polynomial-type Lagrangian as a concrete example, in which all monomials are spatially covariant scalars containing two derivatives. We find that the auxiliary scalar field is essential, and new terms in the Lagrangian are allowed. Our analysis provides insights into constructing gravity theories with two degrees of freedom in the extended framework of spatially covariant gravity.
Teukolsky-like equations with various spins in spherically symmetric spacetime
Ya Guo, Hiroaki Nakajima, Wenbin Lin
2024, 48(8): 085102. doi: 10.1088/1674-1137/ad2a61
Abstract:
We study wave equations with various spins on the background of a general spherically symmetric spacetime. We obtain the unified expression of the Teukolsky-like master equations and the corresponding radial equations with the general spins. We also discuss the gauge dependence in the gravitational-wave equations, which have appeared in previous studies.
Periapsis shift in spherically symmetric spacetimes and effects of electric interactions
Qianchuan Wang, Junji Jia
2024, 48(8): 085103. doi: 10.1088/1674-1137/ad4018
Abstract:
The periapsis shift of charged test particles in arbitrary static and spherically symmetric charged spacetimes are studied. Two perturbative methods, the near-circular approximation and post-Newtonian methods, are developed and shown to be very accurate when the results are determined to high orders. The near-circular approximation method is more precise when eccentricity e of the orbit is small, whereas the post-Newtonian method is more effective when orbit semilatus rectum p is large. Results from these two methods are shown to agree when both e is small and p is large. These results are then applied to the Reissner-Nordström spacetime, the Einstein-Maxwell-dilation gravity, and a charged wormhole spacetime. The effects of various parameters on the periapsis shift, particularly that of the electrostatic interaction, are carefully studied. The periapsis shift data of the solar-Mercury are then used to constrain the charges of the Sun and Mercury, and the data of the Sgr A*-S2 periapsis shift are used to determine, for the first time using this method, the constraints of the charges of Sgr A* and S2.
Imprints of a gravitational wave through the weak field deflection of photons
Reggie C. Pantig, Ali Övgün
2024, 48(8): 085104. doi: 10.1088/1674-1137/ad4e25
Abstract:
In this study, we investigate the novel phenomenon of gravitational lensing experienced by gravitational waves traveling past a Schwarzschild black hole perturbed by a specific, first-order, polar gravitational wave. We apply the Gauss-Bonnet theorem, finding a topological contribution to the deflection of light rays passing near the black hole. We demonstrate that the deflection angle can be determined by analyzing a region entirely outside the path of the light ray, leading to a calculation based solely on the parameters of the perturbing wave (Legendre polynomial order, l; frequency, σ). This approach offers a unique perspective on gravitational lensing and expands our understanding of black hole interactions with gravitational waves.
Quasi-normal modes, emission rate, and shadow of charged AdS black holes with perfect fluid dark matter
Hao Chen, Shi-Hai Dong, Sepehr Hassanabadi, Narges Heidari, Hassan Hassanabadi
2024, 48(8): 085105. doi: 10.1088/1674-1137/ad4af4
Abstract:
In this study, we comprehensively investigated charged AdS black holes surrounded by a distinct form of dark matter. In particular, we focused on key elements including the Hawking temperature, quasi-normal modes (QNMs), emission rate, and shadow. We first calculated the Hawking temperature, thereby identifying critical values such as the critical radius and maximum temperature of the black hole, essential for determining its phase transition. Further analysis focused on the QNMs of charged AdS black holes immersed in perfect fluid dark matter (PFDM) within the massless scalar field paradigm. Employing the Wentzel-Kramers-Brillouin (WKB) method, we accurately derived the frequencies of these QNMs. Additionally, we conducted a meticulous assessment of how the intensity of the PFDM parameter α influences the partial absorption cross sections of the black hole, along with a detailed study of the frequency variation of the energy emission rate. The pivotal role of geodesics in understanding astrophysical black hole characteristics is highlighted. Specifically, we examined the influence of the dark matter parameter on photon evolution by computing the shadow radius of the black hole. Our findings distinctly demonstrate the significant impact of the PFDM parameter α on the boundaries of this shadow, providing crucial insights into its features and interactions. We also provide profound insights into the intricate dynamics between a charged AdS black hole, novel dark matter, and various physical phenomena, elucidating their interplay and contributing valuable knowledge to the understanding of these cosmic entities.
Observational signatures of rotating black holes in the semiclassical gravity with trace anomaly
Zhenyu Zhang, Yehui Hou, Minyong Guo
2024, 48(8): 085106. doi: 10.1088/1674-1137/ad432b
Abstract:
In a recent work by Fernandes [Phys. Rev. D 108(6), L061502 (2023)], an exact stationary and axisymmetric solution was discovered in semiclassical gravity with type-A trace anomaly. This was identified as a quantum-corrected version of the Kerr black hole. In this study, we explore the observational signatures of this black hole solution. Our investigation reveals that prograde and retrograde light rings exist, whose radii increase monotonically with the coupling parameter α. When α is negative, the shadow area for the quantum-corrected black hole is smaller than that of the Kerr black hole, whereas when α is positive, the area is larger. For a near-extremal black hole, its high-spin feature (the NHEKline) is found to be highly susceptible to disruption by α. Furthermore, we discuss the images of the quantum-corrected black hole in the presence of a thin accretion disk and compare them to those of the Kerr black hole. Our study highlights the importance of near-horizon emission sources in detecting the effects of quantum corrections by black hole images.
Discovery potential of the Glashow resonance in an air shower neutrino telescope
Guo-Yuan Huang
2024, 48(8): 085107. doi: 10.1088/1674-1137/ad4c5c
Abstract:
The in-ice or in-water Cherenkov neutrino telescope, such as IceCube, has already proved its power in measuring the Glashow resonance by searching for the bump around \begin{document}$ E^{}_{\rm \nu} = 6.3\; {\rm PeV} $\end{document} arising from the W-boson production. There are many proposals for the next few decades for observations of cosmic tau neutrinos with extensive air showers, also known as tau neutrino telescopes. The air shower telescope is, in principle, sensitive to the Glashow resonance via the channel \begin{document}$ W \to \tau \nu^{}_{\tau} $\end{document} followed by the tau decay in the air (e.g., TAMBO, which has a geometric area of approximately \begin{document}$ 500\; {\rm km^2} $\end{document}). Using a thorough numerical analysis, we find that the discovery significance can be up to 90% with a TAMBO-like setup if PeV neutrinos primarily originate from neutron decays, considering the flux parameters measured by IceCube as the input. The presence of new physics affecting the neutrino flavor composition can also increase the significance. However, if ultrahigh-energy neutrinos are dominantly produced from meson decays, it will be statistically difficult for an advanced proposal such as TAMBO to discriminate the Glashow resonance induced by \begin{document}$ \overline{\nu}^{}_{e} $\end{document} from the intrinsic \begin{document}$ \nu^{}_{\tau}/\overline{\nu}^{}_{\tau} $\end{document} background. We have identified several limitations for such advanced telescopes, in comparison with the in-ice or in-water telescope, when measuring resonances: (i) a suppressed branching ratio of 11% for the decay \begin{document}$ W \to \tau \nu^{}_{\tau} $\end{document}; (ii) the smearing effect and reduced acceptance because the daughter neutrino takes away \begin{document}$ \langle y \rangle \sim \ $\end{document}75% of the energy from the W decay; and (iii) a large attenuation effect for Earth-skimming neutrinos with the resonance.
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