2026 Vol. 50, No. 6

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2026-6 Contents
2026, 50(6): 1-3.
Abstract:
REVIEW
Structure of the β-decay strength function
I.N. Izosimov
2026, 50(6): 062001. doi: 10.1088/1674-1137/ae4e15
Abstract:
An analysis of experimental data on measurements of the resonant and fine structure of the β-decay strength function \begin{document}$S_{\beta}(E)$\end{document} in spherical, transitional, deformed, and halo nuclei has been conducted. Modern nuclear spectroscopy methods have revealed peak splitting in \begin{document}$S_{\beta}(E)$\end{document} for Gamow–Teller (GT) type β-transitions, caused by nuclear deformation. The resonant structure of \begin{document}$S_{\beta}(E)$\end{document} for first-forbidden (FF) β-transitions has been experimentally confirmed in both spherical and deformed nuclei. It is shown that at certain nuclear excitation energies, FF β-transitions can reach intensities comparable to those of GT β-transitions. An analysis of the evolution of the energy difference (\begin{document}$E_{\text {GTR}}{-}E_{\text {IAR}})$\end{document} between the GT resonance (GTR) and isobaric analog resonance (IAR) with increasing neutron excess in nuclei has been performed. A region exhibiting Wigner spin–isospin \begin{document}$SU(4)$\end{document} symmetry has been predicted.
PARTICLES AND FIELDS
Bayesian extraction of HQET parameters from the inclusive semi-leptonic decay of the $ {\Lambda_c^+} $ baryon
Dong Xiao, Kangkang Shao
2026, 50(6): 063001. doi: 10.1088/1674-1137/ae4a09
Abstract:
We extract the non-perturbative heavy quark effective theory (HQET) parameters from the inclusive semi-leptonic decay \begin{document}$ \Lambda_c^+ \to X e^+ \nu_e $\end{document}. Unlike charmed mesons produced near the threshold, \begin{document}$ \Lambda_c^+ $\end{document} baryons produced in \begin{document}$ e^+e^- $\end{document} annihilation exhibit a complex momentum distribution, which makes the transformation of the electron energy spectrum from the laboratory frame to the \begin{document}$ \Lambda_c^+ $\end{document} rest-frame non-trivial. To address this issue, we develop a novel Bayesian inference method to reconstruct the electron energy moments in the \begin{document}$ \Lambda_c^+ $\end{document} rest-frame. We determine the HQET parameters \begin{document}$ \mu_\pi^2(\Lambda_c^+) $\end{document} and \begin{document}$ \rho_D^3(\Lambda_c^+) $\end{document} for the first time using a purely data-driven approach by performing a global fit of theoretical predictions in the 1S mass scheme to these extracted moments.
Update analysis of $ {\psi(3686)\to p\bar{p}}$
Zhi Gao, Rong-Gang Ping, Minggang Zhao
2026, 50(6): 063002. doi: 10.1088/1674-1137/ae4a0c
Abstract:
We have performed an updated analysis of the angular distribution of the \begin{document}$ \psi(3686) \to p\bar{p} $\end{document} decay by considering transverse beam polarization to investigate potential sources of forward-backward asymmetry and azimuthal modulation beyond the simple \begin{document}$ 1+\alpha\cos^2\theta $\end{document} form. We focus on the interference between the \begin{document}$ \psi(3686) $\end{document} resonance and two-photon exchange continuum process, as well as on the background from initial-state–final-state radiation (ISR–FSR) interference. A maximum-likelihood fit to the \begin{document}$ \cos\theta $\end{document} distribution of \begin{document}$ \psi(3686)\to p\bar{p} $\end{document} yields \begin{document}$ \alpha = 1.00 \pm 0.03 $\end{document}, which is consistent with previous results. Our model predicts a significant \begin{document}$ \sin(2\phi) $\end{document} modulation in the azimuthal angle, indicating the influence of transverse beam polarization. Based on these findings, two-dimensional angular analyses can be conducted in the future to fully disentangle the polarization and interference dynamics in charmonium decays to baryon pairs.
Prospects for geoneutrino detection with JUNO
Thomas Adam, Shakeel Ahmad, Rizwan Ahmed, Fengpeng An, João Pedro Athayde Marcondes de André, Costas Andreopoulos, Giuseppe Andronico, Nikolay Anfimov, Vito Antonelli, Tatiana Antoshkina, Didier Auguste, Marcel Büchner, Weidong Bai, Nikita Balashov, Andrea Barresi, Davide Basilico, Eric Baussan, Marco Beretta, Antonio Bergnoli, Nikita Bessonov, Daniel Bick, Lukas Bieger, Svetlana Biktemerova, Thilo Birkenfeld, Simon Blyth, Manuel Boehles, Anastasia Bolshakova, Mathieu Bongrand, Matteo Borghesi, Dominique Breton, Augusto Brigatti, Riccardo Brugnera, Riccardo Bruno, Antonio Budano, Jose Busto, Anatael Cabrera, Barbara Caccianiga, Hao Cai, Xiao Cai, Stéphane Callier, Steven Calvez, Antonio Cammi, Guofu Cao, Jun Cao, Yaoqi Cao, Rossella Caruso, Cédric Cerna, Vanessa Cerrone, Jinfan Chang, Yun Chang, Tim Charisse, Auttakit Chatrabhuti, Chao Chen, Haotian Chen, Jiahui Chen, Jian Chen, Jing Chen, Junyou Chen, Pingping Chen, Shaomin Chen, Shiqiang Chen, Yixue Chen, Yu Chen, Ze Chen, Zhangming Chen, Zhiyuan Chen
2026, 50(6): 063003. doi: 10.1088/1674-1137/ae457d
Abstract:
Geoneutrinos—antineutrinos emitted during the decay of long-lived radioactive elements inside the Earth—serve as a unique tool for studying our planet's composition and heat budget. The Jiangmen Underground Neutrino Observatory (JUNO) experiment in China, which has recently completed construction, is expected to collect a sample comparable in size to the entire existing world geoneutrino dataset in less than a year. This paper presents an updated estimation of JUNO's sensitivity to geoneutrinos using the best knowledge available to date about the experimental site, the surrounding nuclear reactors, the detector response uncertainties, and the knowledge of the reactor antineutrino flux. To facilitate comparison with present and future geological models, our results cover a wide range of predicted signal strengths. Despite the significant background from reactor antineutrinos, the primary channel JUNO will use to determine the neutrino mass ordering, the experiment will measure the total geoneutrino flux with a precision comparable to that of existing experiments within its first few years, ultimately achieving a world-leading precision of about 8% over ten years. JUNO's large statistics will also allow separation of the Uranium-238 and Thorium-232 contributions with unprecedented precision, providing crucial constraints on models of Earth’s formation and composition. Observation of the mantle signal above the lithospheric flux will be possible but challenging. For models with the highest predicted mantle concentrations of heat-producing elements, a ~\begin{document}$3\sigma$\end{document} detection over six years requires knowledge of the lithospheric flux to within 15%. Together with complementary measurements from other locations, JUNO’s geoneutrino results will offer cutting-edge, high-precision insights into the Earth’s interior, of fundamental importance to both the geoscience and neutrino physics communities.
Lepton flavor of four-fermion operator and fermion portal dark matter
Yuxuan He, Gang Li, Jia Liu, Xiao-Ping Wang, Xiang Zhao
2026, 50(6): 063101. doi: 10.1088/1674-1137/ae4a08
Abstract:
This study investigates the ultraviolet realization of semileptonic four-fermion operator \begin{document}$ O_{ledq}^{\alpha \beta 11} $\end{document} that incorporates Majorana dark matter (DM) in both lepton-flavor-conserving (LFC) and lepton-flavor-violating (LFV) scenarios at the one-loop level via box diagram, thereby effectively alleviating the lower bounds on the new physics scale. In addition, we investigate the interplay between model-independent constraints on the Wilson coefficients and DM direct detection, relic density, and collider searches in the context of fermion portal DM model with two mediators. We found that both the projected future constraint on the LFC Wilson coefficient \begin{document}$ C_{ledq}^{2211}/\Lambda^2< $\end{document}\begin{document}$ (12.3\; \text{TeV})^{-2} $\end{document} from the measurements of neutrino non-standard interaction in the next-generation neutrino oscillation experiments, and the LFV constraint \begin{document}$ C_{ledq}^{1211}/\Lambda^2< \left(2.2\times 10^3\; \text{TeV} \right)^{-2} $\end{document} from ongoing charged-lepton-flavor-violation searches, provide a complementary exploration of the parameter space encompassing the DM and scalar masses. With a colored mediator mass of approximately \begin{document}$ 2\; \text{TeV} $\end{document}, the sensitivity of the indirect constraints on the four-fermion operator can surpass those of collider searches and DM direct detection, in scenarios where the masses of the DM and scalar are close. By ensuring the correct DM relic density, however, we find that the collider searches and DM direct detection are more sensitive to the electroweak-scale DM and scalar than indirect constraints.
Higgs decays to Zγ and γγ in the flavor-gauged two Higgs doublet model
Feng-Zhi Chen, Qiaoyi Wen, Fanrong Xu
2026, 50(6): 063102. doi: 10.1088/1674-1137/ae4a07
Abstract:
This study examines the \begin{document}$ h\to Z\gamma $\end{document} and \begin{document}$ h\to\gamma\gamma $\end{document} decays in the flavor-gauged two Higgs doublet model (FG2HDM), which augments the Standard Model (SM) with an additional scalar doublet, a singlet, and a \begin{document}$ U(1)' $\end{document} flavor gauge symmetry. Beyond the SM spectrum, FG2HDM predicts five additional physical scalars and a new neutral gauge boson, \begin{document}$ Z' $\end{document}. We demonstrate that while both decay channels are sensitive to charged Higgs loops, \begin{document}$ h \to Z\gamma $\end{document} is uniquely modified by fermion-antifermion-Z (\begin{document}$ f\bar{f}Z $\end{document}) vertex corrections. These vertex corrections further impact top-quark observables and the flavor-changing neutral current (FCNC) process \begin{document}$ b\to s\ell^+\ell^- $\end{document}. Our analysis identifies a viable parameter space (\begin{document}$ m_{H^\pm}>200 $\end{document} GeV and \begin{document}$ \lambda_{hH^+H^-}<0 $\end{document}) consistent with current \begin{document}$ 1\sigma $\end{document} experimental limits, where the signal strength \begin{document}$ \mu_{\gamma\gamma} $\end{document} remains the primary constraint on scalar sector parameters. Regarding the \begin{document}$ f\bar{f}Z $\end{document} couplings, we delineate the allowed regions in the \begin{document}$ \mathcal{Q}_{tL} $\end{document}-\begin{document}$ \mathcal{Q}_{tR} $\end{document} plane by evaluating the leading top-quark contributions, revealing that \begin{document}$ b\to s\ell^+\ell^- $\end{document} imposes the most stringent bounds. Finally, we highlight that the \begin{document}$ 14\% $\end{document} projected precision for \begin{document}$ \mu_{Z\gamma} $\end{document} at the High-Luminosity LHC (HL-LHC) will significantly enhance sensitivity to the FG2HDM.
Study of atomic effects on electron spectrum in bound-muon decay process
M. Y. Kaygorodov, Y. S. Kozhedub, A. V. Malyshev, A. O. Davydov, Y. Wu, S. B. Zhang
2026, 50(6): 063103. doi: 10.1088/1674-1137/ae4328
Abstract:
The process in which a muon bound to the nuclear potential decays into an unbound electron, a muon neutrino, and an electron antineutrino is considered. The study examines atomic effects on the differential transition rate relative to the energy of the emitted electron, specifically the electron spectrum, near its high-energy boundary, within the framework of Fermi effective theory. The analysis takes into account corrections due to finite-nuclear-size, nuclear-deformation, electron-screening, and vacuum-polarization effects, all of which are incorporated self-consistently into the Dirac equation. Furthermore, the nuclear-recoil correction to the muon binding energy is included. Calculations are carried out for the isotopes of C, Al, and Si, which are particularly important for forthcoming experiments aimed at search for the charged-lepton flavor-violating process of muon-to-electron conversion in a nuclear field.
Role of Σ(1660) in the K pπ0π0Σ0 reaction
Xing-Yi Ji, Si-Wei Liu, Wen-Tao Lyu, De-Min Li, En Wang, Ju-Jun Xie
2026, 50(6): 063104. doi: 10.1088/1674-1137/ae551e
Abstract:
The processes of \begin{document}$ K^-p \to \pi^0 \pi^0 \Sigma^0 $\end{document} and \begin{document}$ K^- p \to \pi^0 \Lambda(1405) $\end{document} are studied within the effective Lagrangian approach. In addition to the “background” contribution from the u-channel nucleon pole term, the contribution from the \begin{document}$ \Sigma(1660) $\end{document} resonance with spin-parity \begin{document}$ J^P=1/2^+ $\end{document} is also considered. For the \begin{document}$ K^-p \to \pi^0 \pi^0 \Sigma^0 $\end{document} reaction, we perform a calculation for the total and differential cross sections by considering the contribution from the \begin{document}$ \Sigma(1660) $\end{document} intermediate resonance decaying into \begin{document}$ \pi^0 \Lambda(1405) $\end{document} with \begin{document}$ \Lambda(1405) $\end{document} decaying into \begin{document}$ \pi^0 \Sigma^0 $\end{document}. With our model parameters, the available experimental data on both the \begin{document}$ K^-p \to \pi^0 \pi^0 \Sigma^0 $\end{document} and \begin{document}$ K^- p \to \pi^0 \Lambda(1405) $\end{document} reactions can be fairly well reproduced. It is shown that the contribution from the \begin{document}$ \Sigma(1660) $\end{document} resonance is necessary, and that these experimental measurements could be used to determine some properties of the \begin{document}$ \Sigma(1660) $\end{document} resonance.
NLO QCD sum rules analysis of 1− + tetraquark states
Wei-Yang Lai, Hong-Ying Jin
2026, 50(6): 063105. doi: 10.1088/1674-1137/ae4baa
Abstract:
We have performed a next-to-leading-order (NLO) QCD sum rules analysis of the \begin{document}$1^{-+}$\end{document} light tetraquark states. By investigating various compact and molecular tetraquark currents, we extracted the mass spectra of the corresponding states, all of which lie above \begin{document}$1.7\,\text{GeV}$\end{document}. We have identified multiple \begin{document}$1^{-+}$\end{document} states around \begin{document}$2.0\,\text{GeV}$\end{document} matching well with \begin{document}$\pi_{1}(2015)$\end{document}, confirming that \begin{document}$\pi_{1}(2015)$\end{document} is an excellent tetraquark candidate. By contrast, our calculations exclude the possibility that the \begin{document}$\pi_{1}(1400)$\end{document} is a tetraquark or hybrid–tetraquark mixture. This result suggests that it may not exist, which is consistent with recent experimental results.
Exploring muonphilic dark matter with the Z2-even mediator at muon colliders
Wanyun Chen, Haoqi Li, Chih-Ting Lu, Qiulei Wang
2026, 50(6): 063106. doi: 10.1088/1674-1137/ae5044
Abstract:
The Galactic Center GeV Excess (GCE) remains a compelling but enigmatic signal from the inner regions of our galaxy. Muonphilic dark matter (DM), which couples exclusively to muons via a new mediator, provides a viable explanation for the GCE and relic density while naturally evading constraints from direct detection, collider searches, and other multimessenger observations. Based on the viable nonresonant parameter space identified in previous global fits, we perform a comprehensive study on the prospects for discovering such muonphilic DM in the context of a future 3 TeV muon collider, focusing on simplified models with a \begin{document}$Z_2$\end{document}-even mediator. Four distinct search strategies are investigated: visible on-shell mediator decays (\begin{document}$\mu^{+}\mu^{-}\gamma$\end{document} final state), invisible on-shell mediator decays (mono-photon plus missing energy), mono-photon production via off-shell mediators, and vector boson fusion production. Through a detailed signal-background analysis using cut-and-count methods, we project the exclusion limits at \begin{document}$ 95 $\end{document}% confidence level for seven representative models across a wide range of mediator masses. Our results demonstrate that the projected limits cover a significant portion of viable parameter space that explains the GCE, establishing a muon collider as a decisive machine for testing the muonphilic DM hypothesis.
Discovery prospects for photophobic axion-like particles in the WWjj final state at the High-Luminosity LHC
Jiaojiao Feng, Ying-nan Mao, Kechen Wang
2026, 50(6): 063107. doi: 10.1088/1674-1137/ae5048
Abstract:
We evaluate discovery prospects for photophobic axion-like particles (ALPs) in the WWjj final state at the High-Luminosity LHC (HL-LHC; \begin{document}$\sqrt{s}=14\ {\rm{TeV}}$\end{document}, \begin{document}${\cal{L}}=3\ {\rm{ab}}^{-1}$\end{document}). In the photophobic limit (\begin{document}$g_{a\gamma\gamma}=0$\end{document}), ALPs couple to electroweak gauge bosons and are produced in association with two jets (\begin{document}$ pp\to jj\ a $\end{document}) via both s-channel electroweak exchange and vector boson fusion (VBF)–like topologies, followed by \begin{document}$a\to W^+W^-$\end{document} decay. We target the different-flavour dilepton mode \begin{document}$W^+W^- \to e^\pm\mu^\mp\nu \bar{\nu}$\end{document} with two jets and moderate missing transverse momentum. The analysis employs a two-step strategy: initial preselection that defines the signal-like final state, followed by a multivariate analysis (MVA) trained on dijet and dileptonic-WW kinematics from both the s-channel and VBF-like production mechanisms to separate signal from background; the MVA threshold is optimized independently at each \begin{document}$m_a$\end{document}. We present 2σ and 5σ discovery sensitivities for the ALP–W coupling \begin{document}$g_{aWW}$\end{document} across the 170–4000 GeV mass range. For \begin{document}$260\ {\rm{GeV}}\le m_a\le1500\ {\rm{GeV}}$\end{document}, the 2σ (5σ) sensitivity is approximately flat around \begin{document}$ 0.61(0.76)\ {\rm{TeV}}^{-1}$\end{document}. At large masses/couplings, the mapping between an experimental rate and a single EFT parameter \begin{document}$g_{aWW}$\end{document} can become UV sensitive, and we treat the extreme high-mass/high-coupling corner as an extrapolation; therefore, we also report model-independent discovery thresholds for the fiducial quantity \begin{document}$ \sigma(pp\to jj\ a)\times\rm{Br}(a\to W^+W^-) $\end{document} over the same mass range to enable reinterpretation for other models. These results indicate that the \begin{document}$WWjj$\end{document} topology offers competitive and complementary sensitivity to heavy photophobic ALPs at the HL-LHC.
Pseudopotential of hybrid mesons in a holographic anisotropic plasma
Jing Zhou, Saiwen Zhang
2026, 50(6): 063108. doi: 10.1088/1674-1137/ae5a88
Abstract:
We investigate the pseudopotential of hybrid mesons in a holographic anisotropic background within the AdS/CFT correspondence. Hybrid states are modeled by introducing a defect, and we analyze the associated force-balance condition in the string configuration. From this setup, we derive the balance equation and compute key physical quantities, including the separation distance, pseudopotential, and binding energy of the hybrid mesons. We find that increasing the anisotropy parameter a decreases the separation distance for both ground and excited states. However, while the ground-state potential decreases, the pseudopotential of the hybrid state increases. Additionally, the pseudopotential of hybrid mesons exhibits significant sensitivity to variations in the angular parameter α.
S, T, U parameters in the B-LSSM
Sheng-Kai Cui, Ke-Sheng Sun, Yu-Li Yan, Jin-Lei Yang, Tai-Fu Feng
2026, 50(6): 063109. doi: 10.1088/1674-1137/ae5590
Abstract:
Using the pinch technique, we determine the one-loop vertices of weak interactions in the B-LSSM and incorporate their pinch contributions into the gauge boson self-energies. Compared to the definitions of the S, T, and U parameters in the Standard Model based on the \begin{document}$S U(2)_L \otimes U(1)_Y$\end{document} group, the corresponding parameters in the local B-L gauge symmetry (B-LSSM) are modified. We present these redefined S, T, and U parameters and demonstrate the convergence of the results. In the framework of the low-energy effective Lagrangian for weak interactions, the S, T, and U parameters can be expressed as functions of specific parameters in the B-LSSM. The updated experimental and fitting results strongly constrain the parameter space of the B-LSSM.
NUCLEAR PHYSICS
Multinucleon transfer products in 48Ca, 54Cr+243Am and 54Cr+238U reactions
G. Xie, Z. Y. Zhang, J. G. Wang, L. Ma, M. H. Huang, C. L. Yang, X. L. Wu, Z. G. Gan, H. B. Yang, M. M. Zhang, Y. L. Tian, Y. S. Wang, J. Y. Wang, Y. H. Qiang, L. Zhu, X. Y. Huang, S. Y. Xu, Z. Zhao, Z. C. Li, X. Zhang, H. Zhou, J. H. Zheng, L. C. Sun, F. Guan, W. X. Huang, Z. Qin, Y. Wang, X. J. Yin, Y. F. Cui, Y. He, L. T. Sun, Z. Z. Ren, S. G. Zhou, V. K. Utyonkov, A. A. Voinov, Yu. S. Tsyganov, A. N. Polyakov, D. I. Solovyev, D. Ibadullayev, M. V. Shumeiko
2026, 50(6): 064001. doi: 10.1088/1674-1137/ae4bab
Abstract:
Experiments with 48Ca and 54Cr induced reactions were performed at the gas-filled recoil separator named Spectrometer for Heavy Atoms and Nuclear Structure-2 (SHANS2) of the China Accelerator Facility for superheavy Elements (CAFE2). The isotopic distributions of nuclei produced in the reactions of 48Ca+243Am, 54Cr+243Am, and 54Cr+238U were investigated. Bombardments were conducted at energies near the respective Coulomb barriers, with the SHANS2 magnetic rigidities set to collect fusion-evaporation residues. α-decay spectroscopy was employed to identify products, revealing 58 different isotopes in these experiments. The analysis indicates that the distribution of nuclides produced in different reactions exhibits clear systematic trends. Based on their mass distributions, these nuclei were attributed to the products from the quasi-fission (QF) process. Additionally, several short-lived fission events were identified and attributed to the fission isomers near the target.
Photoneutron cross section measurements on 65Cu: toward understanding (n, γ) cross sections relevant to weak s-process nucleosynthesis
Yu-Long Shen, Zi-Rui Hao, Qian-kun Sun, Hong-Wei Wang, Long-Xiang Liu, Hang-Hua Xu, Yue Zhang, Sheng Jin, Kai-Jie Chen, Meng-Die Zhou, Zhen-Wei Wang, Meng-Ke Xu, Xiang-Fei Wang, Chang Yang, Pu Jiao, Chun-Wang Ma, Gong-Tao Fan, Zhi-Cai Li, Wen Luo
2026, 50(6): 064002. doi: 10.1088/1674-1137/ae5a18
Abstract:
A new measurement of the 65Cu(γ, n)64Cu photoneutron cross section is performed using quasi-monoenergetic, tunable γ-ray beams produced at the Shanghai Laser Electron Gamma Source (SLEGS). The energy spectrum of the SLEGS γ-ray beams incident on the isotopically enriched 65Cu target is monitored using a BGO detector, while the photoneutron yields are determined with a moderated 3He detection array with high and flat efficiency. Within the energy range of \begin{document}$10.1 \le E_\gamma \le 17.6$\end{document} MeV, the measured \begin{document}$\sigma(E_\gamma)$\end{document} data have an uncertainty of \begin{document}$\lesssim 4$\end{document}%, and a pronounced giant-dipole peak is observed at \begin{document}$E_\gamma \simeq 16.65$\end{document} MeV with a maximal cross section of \begin{document}$\sigma_{\text{max}} \simeq 137$\end{document} mb. These photoneutron data are compared with previous experimental results and are employed to extract the γ-ray strength function of 65Cu above the neutron threshold. Furthermore, we calculate the radiative neutron capture cross sections and astrophysical reaction rates for 64Cu, which is a short-lived intermediate nucleus whose reaction rate controls the local abundance distribution in the weak s-process. It is found that the calculated 64Cu(n, γ)65Cu data have an overall agreement with ENDF/B-VIII.0, JEFF-3.3, and TENDL-2023 evaluations, and the corresponding astrophysical reaction rates are consistent with those reported in the JINA REACLIB database.
Photonuclear reactions on stable isotopes of cadmium and tellurium at bremsstrahlung end-point energies of 10−23 MeV
F. A. Rasulova, A. A. Kuznetsov, V. O. Nesterenko, J. H. Khushvaktov, S. I. Alekseev, N.Yu. Fursova, A. S. Madumarov, I. Chuprakov, S. S. Belyshev, N. V. Aksenov
2026, 50(6): 064003. doi: 10.1088/1674-1137/ae551d
Abstract:
In this study, the γ-activation approach was used to conduct tests at the bremsstrahlung end-point energies of 10−23 MeV by utilizing the MT-25 microtron beam. The experimental values of the relative yields and cross sections per equivalent quantum of photonuclear reactions on the stable isotopes of cadmium and tellurium were compared with the theoretical calculation results obtained from TALYS-2.0 using the default parameters and the combined model of photonucleon reactions (CMPR). The inclusion of isospin splitting in the CMPR allows for the definition of experimental data on the proton escape reactions with energies ranging from 17 to 23 MeV. Therefore, isospin splitting must be considered to accurately describe the decay of the giant dipole resonance. For Cd isotopes, essential discrepancies of yet unclear origin between theory (TALYS 2.0 and CMPR) and experimental data are found in the neutron channel.
Exploring toroidal α-cluster configurations in 28Si within the 7α cluster model
Su-Yu Zhou, Bo Zhou
2026, 50(6): 064101. doi: 10.1088/1674-1137/ae4578
Abstract:
Two 7α cluster configurations in 28Si are investigated within the framework of the generator coordinate method (GCM) with Brink-Bloch 7α wave functions by taking the edge length as the generator coordinate, including a uniform toroidal configuration and a disk-like configuration. Within the framework of the 7α cluster model with imposed geometric symmetry, we observe that a uniform toroidal configuration may emerge at approximately 40 MeV above the 7α threshold. This provides a cluster-model perspective that complements some mean-field descriptions of toroidal structure in 28Si.
Predictions of neutron-capture reaction cross sections using a Bayesian neural network approach combined with a physically motivated empirical formula
H. B. Li, W. F. Li, Q. Wu, Z. M. Niu
2026, 50(6): 064102. doi: 10.1088/1674-1137/ae50e6
Abstract:
Neutron-capture reaction cross sections are studied using the Bayesian neural network (BNN) approach in combination with a recently proposed empirical formula for the cross sections. In addition to the proton and neutron numbers, four physical quantities are found to be important for improving the predictive performance of the BNN approach: the pairing effect-related variable δ, shell effect-related variables \begin{document}$ \nu_{n} $\end{document} and \begin{document}$ \nu_{p} $\end{document}, and theoretical neutron-capture reaction cross sections. The BNN approach more effectively describes the Maxwellian-averaged (\begin{document}$ n,\gamma $\end{document}) cross sections (MACS) at \begin{document}$ kT $\end{document} = 30 keV than the TENDL-astro 2023 theoretical library calculated using TALYS code based on the Hauser–Feshbach statistical model. The root-mean-square deviation of the BNN approach with respect to the natural logarithm of the experimental MACS data from the Karlsruhe Astrophysical Database of Nucleosynthesis in Stars is reduced to 0.1373, compared with the value of 0.2545 for TENDL-astro 2023. The BNN predictions align well with MACS trends predicted by TENDL-astro 2023 when extrapolated to the unknown region, though there are quantitative deviations between them.
Decomposition of angular momentum projected nuclear wave function
Wen Chen, Zhan-Jiang Lian, Xue-Wei Li, Xin-Yang Xia, Zi-Yang He, Ke-Zheng Ruan, Zao-Chun Gao
2026, 50(6): 064103. doi: 10.1088/1674-1137/ae5efa
Abstract:
Angular momentum projection is a fundamental technique for constructing nuclear wave functions with definite angular momentum. Traditionally, a projected nuclear wave function is expanded in basis states obtained by performing angular momentum projection directly on reference states of the entire nuclear system. Alternatively, one can construct nuclear wave functions using another kind of projected bases, called the coupled projected bases, which are generated by first performing angular momentum projection on the reference states for neutrons and protons, respectively, and then coupling the projected neutron states with the projected proton ones via Clebsch–Gordon coefficients. In the present work, we derive a new identity that provides a decomposition of the conventional angular-momentum-projected nuclear wave function in terms of the coupled projected bases. This decomposition offers direct insight into the underlying structure of nuclear states. To illustrate this point, we present decompositions of variation-after-projection shell-model (VAPSM) wave functions for the ground states of several sd-shell nuclei. Notably, even for the ground states of even-even nuclei, the nucleons are not fully paired. Finally, we demonstrate that the VAPSM wave function can be further improved by employing the coupled projected bases.
PARTICLE AND NUCLEAR ASTROPHYSICS AND COSMOLOGY
Quantum gravitational corrections to Reissner-Nordström black hole thermodynamics and their implications for the weak gravity conjecture
Yong Xiao, Qiang Wang, Aonan Zhang
2026, 50(6): 065101. doi: 10.1088/1674-1137/ae457a
Abstract:
In this paper, we investigate the quantum gravitational corrections to the thermodynamical quantities of Reissner-Nordström black holes within the framework of effective field theory. The effective action originates from integrating out massless particles, including gravitons, at the one-loop level. We perform a complete thermodynamic analysis for both non-extremal and extremal black holes and are mainly concerned with the shift in the charge-to-mass ratio \begin{document}$ q/M$\end{document}, which plays an important role in analyzing the weak gravity conjecture. For non-extremal black holes, we identify a relationship between the shift in the charge-to-mass ratio and the thermodynamic stability of the black holes. For extremal black holes, we show that quantum gravity effects naturally lead to the super-extremality \begin{document}$ q/M>1$\end{document} of charged black holes.
On the perturbation solutions to the Blandford-Znajek mechanism in the Kerr-Sen black hole
Haiyuan Feng, Ziqiang Cai, Rong-Jia Yang, Jinjun Zhang
2026, 50(6): 065103. doi: 10.1088/1674-1137/ae4327
Abstract:
We investigated the steady, axisymmetric, force-free magnetosphere of the Kerr–Sen black hole (BH) within the framework of the Einstein–Maxwell–dilaton–axion (EMDA) theory. By perturbatively solving the nonlinear Grad–Shafranov (GS) equation, we determined the magnetic field configuration and quantified the influence of the dilaton parameter r2 on the energy extraction rate and radiative efficiency. Our results show that both the energy extraction power and radiative efficiency increase with r2, exceeding the values of the standard Kerr BH; meanwhile, the extraction efficiency remains consistent with the Kerr case. In addition, we performed χ2 statistical analysis using observational data from six binary BH systems. The results indicate that the Kerr BH currently provides a better fit for bulk Lorentz factors Γ = 2 and 5.
Analytical study of fundamental oscillation frequencies around black holes in nonlocal gravity
Rana Muhammad Zulqarnain, Phongpichit Channuie, Abdelmalek Bouzenada, Asifa Ashraf, Farruh Atamurotov, Ikhtiyor Saidov
2026, 50(6): 065104. doi: 10.1088/1674-1137/ae432c
Abstract:
In this study, we investigate the dynamics of test particles in the spacetime of a static, spherically symmetric black hole (BH) illustrated within nonlocal gravity models. After presenting the BH geometries and horizon structures, we examine the motion of particles by analyzing the effective potential, innermost stable circular orbits, and corresponding effective force. We then extend the study to small perturbations of circular orbits, exploring harmonic oscillations characterized by frequencies measured by both local and distant observers, as well as the periastron precession effects. Particular attention is given to the interplay between the nonlocal gravity corrections and the stability properties of geodesics. We analyze the center-of-mass energy of colliding particles near the event horizon and show the influence of BH parameters on energy extraction processes. The results show the mechanism of influnece of nonlocal modifications of gravity on the standard predictions of the BH structure, orbital stability, and high-energy particle dynamics, with possible implications for astrophysical observations and theoretical models of strong gravity. This study examines the differences between the inverse electrodynamics of BHs and the Schwarzschild BH configuration, demonstrating the influnece of additional parameters on the dynamics and stability of test particles.
ModMax charged black holes in PFDM: Electric Penrose and particle collisions
Nuriddin Kurbonov, Mukhabbat Kurbanova, Javlon Rayimbaev, Yunus Turaev, Sulton Usanov, Saidmuhammad Ahmedov
2026, 50(6): 065106. doi: 10.1088/1674-1137/ae5b56
Abstract:
In this study, we investigate the influence of the parameters of ModMax nonlinear electrodynamics and perfect-fluid dark matter (PFDM) on the geometry and physical properties of charged black holes. A static, spherically symmetric solution to the Einstein field equations describing a charged ModMax black hole immersed in a PFDM background is obtained. The motion of charged test particles in this spacetime is analyzed in detail, including the effective potential, the conditions for stable and unstable circular orbits, and the radius of the innermost stable circular orbit (ISCO). It is shown that the ModMax parameter γ shifts the orbits outward for repulsive Coulomb interactions and inward for attractive forces, while increasing PFDM enhances gravitational attraction, shifting the ISCO inward. Furthermore, the interactions and collisions of charged particles near the event horizon are examined. The center-of-mass energy \begin{document}${\cal{E}}_{\rm cm}$\end{document} exhibits the characteristic behavior in charged-particle collisions, rapidly increasing as the particles approach the horizon. The parameter γ amplifies the BSW acceleration mechanism, while α suppresses it. The electric Penrose process for charged particles is also examined, revealing that the efficiency of energy extraction increases with the black hole charge and is strongly influenced by the interaction parameter γ, which plays a dominant role in enhancing the efficiency, whereas the effect of α remains comparatively negligible.
Reconciling the ACT preference in f(T) gravity: inflation and reheating constraints
Feng-Yi Zhang, Rongrong Zhai, Li-Yang Chen
2026, 50(6): 065107. doi: 10.1088/1674-1137/ae5806
Abstract:
Compared with the results of Planck-only analyses, recent measurements from the Atacama Cosmology Telescope (ACT) indicate a preference for a slightly bluer scalar spectral index, placing canonical inflationary models in General Relativity (GR) under mild pressure. We demonstrate that f(T) gravity systematically accommodates these dataset-dependent preferences by suppressing the tensor-to-scalar ratio in monomial and hilltop potentials and by shifting the spectral index of E-models toward the ACT-favored region. Incorporating Big Bang Nucleosynthesis bounds, we break the degeneracy between the inflationary e-folding number and the post-inflationary thermal history. A direct side-by-side comparison reveals that reconciling models such as the Starobinsky potential with ACT data in GR strictly necessitates a non-standard, stiff (kinetic-dominated) reheating phase. In contrast, torsional corrections in f(T) gravity significantly enlarge the viable parameter space, relaxing these stringent phenomenological requirements and establishing a coherent framework that jointly constrains CMB observables and reheating dynamics.
Thermodynamic GUP correction for black hole within quintessence matter
Riasat Ali, Tiecheng Xia, Rimsha Babar
2026, 50(6): 065109. doi: 10.1088/1674-1137/ae5049
Abstract:
We examine the black hole geometry in general relativity using Einstein's equations to modify the geometry in quintessence matter. In quintessence matter, we incorporate black hole geometry into the standard formula to assess the Hawking temperature. We implement the Hamilton-Jacobi semi-classical technique to examine the Hawking temperature of a four-dimensional black hole spacetime. The boson particles are tunnelled into the horizon under the action of the generalized uncertainty principle (GUP) by implementing the relativistic field equation and WKB strategy. The Hawking temperature is investigated under the influence of the GUP parameter, particle properties, and black hole geometry parameters. Entropy and emission energy corrections are also examined using the Hawking temperature.
Observational constraints on dissipative Chaplygin gas cosmology in the framework of coincident f(Q) gravity
Sayantan Ghosh, Raja Solanki, P. K. Sahoo
2026, 50(6): 065110. doi: 10.1088/1674-1137/ae50e5
Abstract:
In this study, we shed light on the unified approach to dark energy and dark matter via the generalized Chaplygin gas model in symmetric teleparallel gravity (STGR). We employ the equation of state provided by generalized Chaplygin gas, which naturally arises in string theory, tachyonic field theory, and Randall-Sundrum-type brane world solutions. Such a generalized Chaplygin gas not only provides a viable candidate for dark energy but also for dark matter via Bose-Einstein condensation (BEC). We also consider the interaction between dark matter and dark energy to provide a more realistic perspective. Moreover, we perform Markov Chain Monte Carlo (MCMC) analysis with the combined Hubble and Pantheon datasets, conduct Om diagnostics, and construct \begin{document}$ r-s $\end{document} plots to comment on the late behavior of our model. Through Om diagnostics, we find values located in phantom regions, as expected, owing to several physical reasons. Finally, we outline our future research directions.