Chinese Physics C

Synthesis of the superheavy elements beyond Og: extrapolating from ⁴⁸Ca to ⁵⁰Ti and ⁵⁴Cr

Yueping Fang, Long Zhu

Published:

Abstract:
Theoretical predictions on the optimal reaction energies are essential for producing superheavy elements (SHEs) beyond Og. Due to the limitation of the targets, synthesizing elements 119 and 120 will require beams of

\begin{document}$ {}^{50}{\rm{Ti}} $\end{document}

and/or

\begin{document}$ {}^{54}{\rm{Cr}} $\end{document}

ions. However, is it reliable to theoretically extrapolate from the well-investigated

\begin{document}$ {}^{48}{\rm{Ca}} $\end{document}

induced reactions to those with heavier projectiles? In this work, we answer this question from two perspectives: radial and mass asymmetry degrees of freedom. The Smoluchowski diffusion equation is employed in the mass asymmetry degree of freedom for the first time, in which by fitting the calculations to experimental evaporation residue cross sections (ERCS) for the reactions of

\begin{document}$ {}^{48}{\rm{Ca}} $\end{document}

as projectiles with the actinide targets, a strong linear correlation between the contact distance (

\begin{document}$ D_{\rm{cont}} $\end{document}

) and center-of-mass energy excess above the Coulomb barrier (

\begin{document}$ E_{\rm{c.m.}}-B_0 $\end{document}

) is found and a parametrization formula is introduced. The calculations based on the fitted formula satisfactorily reproduce the available experimental data of the ERCS. Furthermore, thanks to the recent experimental data, we extrapolate the calculation in the reactions

\begin{document}$ {}^{50}{\rm{Ti}}+{}^{242}{\rm{Pu}} $\end{document}

,

\begin{document}$ {}^{50}{\rm{Ti}}+{}^{244}{\rm{Pu}} $\end{document}

, and

\begin{document}$ {}^{54}{\rm{Cr}}+{}^{238}{\rm{U}} $\end{document}

. The calculations reproduce the experimental data rather well within the experimental errors in both perspectives. Our results demonstrate that theoretically extrapolating the projectile from

\begin{document}$ ^{48}{\rm{Ca}} $\end{document}

to

\begin{document}$ ^{50}{\rm{Ti}} $\end{document}

and

\begin{document}$ ^{54}{\rm{Cr}} $\end{document}

for synthesizing SHEs beyond Og is relatively reliable.

Correlation between diffuseness and EMC effect of nuclei with A≥ 12

Yanzhao Wang, Wenhao Zhang, Yunyun Sun, Hongmin Wang, Yonghao Gao, Jianzhong Gu

Published: , doi: 10.1088/1674-1137/ae6ed4

Abstract:
Within the double

\begin{document}$ Q^{2} $\end{document}

-rescaling model and the T. D. Lee's soliton bag model, by taking into account the local nucleon density distribution, the EMC effect of the nuclei with

\begin{document}$ A \geq 12 $\end{document}

influenced by the nuclear diffuseness is explored. It is shown that the slope of EMC ratio for each nucleus is weakened with the increase of the diffuseness parameter. It implies that the weaker the surface binding in a nucleus, the less pronounced its EMC effect. Furthermore, we find that it is not enough to only adjust the diffusion parameter to reproduce the experimental EMC ratios and the corresponding slopes simultaneously, which indicates that other nuclear medium effects should be taken into account. Then, with the experimental EMC ratios, the relatively optimal diffusion parameter of each nucleus is determined. It is found that the determined diffusion parameter of each nucleus is larger than the commonly used value (0.54 fm) except for ¹²C. To test the accuracy of the determined diffusion parameters of these nuclei, the corresponding average binding energies are extracted. We find that the extracted binding energies of most nuclei are in good agreement with the corresponding experimental data. Finally, the correlation between the EMC effect of ²⁰⁸Pb and its neutron skin thickness is discussed briefly.

Microscopic Calculations of the First 2⁺ State: Influence of Skyrme Functional Details and nucleon Pairing Interaction

A. Nasr, W. M. Seif, A. R. Abdulghany

Published: , doi: 10.1088/1674-1137/ae6b2d

Abstract:
Theoretical predictions of collective rotation are characterized by significant model-dependent uncertainties, limiting their reliability in interpreting rotational structure across the nuclear chart. To address this, we systematically examine how details of the Skyrme effective nucleon-nucleon interaction and neutron and proton pairing correlations affect the microscopic description of the first

\begin{document}$ 2^+ $\end{document}

rotational state in even-even nuclei. We employ the Hartree-Fock-Bogoliubov (HFB) method with Skyrme forces and a regularized, density-dependent, zero-range pairing interaction to compute

\begin{document}$ E(2^+) $\end{document}

excitation energies along isotopic and isotonic chains of even-even nuclei from Sr to Rf, extending to

\begin{document}$ N=156 $\end{document}

. Ten Skyrme parameterizations are analyzed, spanning diverse effective masses and nuclear-matter properties. Results are benchmarked against available experimental data. Optimal predictions for the first

\begin{document}$ 2^+ $\end{document}

state energy are obtained with EDFs having an exchange parameter

\begin{document}$ x_0 $\end{document}

between 0.42 and 0.63 and an effective nucleon mass of 0.61–0.72 times the free nucleon mass. Underestimation of

\begin{document}$ E(2^+) $\end{document}

arises from a low effective mass, a high symmetry-energy slope, or a large negative value of the

\begin{document}$ t_0/t_3 $\end{document}

parameter ratio, and the predictions deteriorate further as the spin-orbit strength falls below

\begin{document}$ W_0 \approx 120 $\end{document}

MeV fm⁵. An overestimation of the calculated

\begin{document}$ E(2^{+}) $\end{document}

indicates that either the pairing strength is excessive, or the volume-surface mixing parameter should be increased to enhance surface-peaked pairing correlations in the low-density surface region.

Naive parton picture for kaon color transparency in A(e, e′K⁺)

Kook-Jin Kong, Tae Keun Choi, Byung-Geel Yu

Published: , doi: 10.1088/1674-1137/ae6b20

Abstract:
Nuclear transparency in the electronuclear reaction

\begin{document}$ A(e,e'K^+) $\end{document}

is investigated in parallel with our previous study of pion transparency in Phys. Rev. C 111, 064608 (2025). Based on an extended Glauber framework that incorporates shadowing from the initial-state two-step process, kaon color transparency (CT) is analyzed to show that the steeper

\begin{document}$ Q^2 $\end{document}

dependence observed for kaon CT, compared with the pion case, is more naturally described by the naive parton model (NPM) than by the quantum diffusion model (QDM). The inclusion of initial-state shadowing further reduces the transparency and improves the agreement with the experimental data. The

\begin{document}$ Q^2 $\end{document}

and A dependences of the kaon transparency are presented up to

\begin{document}$ Q^2=10 $\end{document}

GeV

\begin{document}$ ^2/c^2 $\end{document}

, together with the corresponding

\begin{document}$ \alpha(Q^2) $\end{document}

and the supplementary ratio

\begin{document}$ T_A/T_C $\end{document}

, for comparison with the Jefferson Lab (JLab) data obtained with the 6-GeV electron beam on ¹²C, ⁶³Cu, and ¹⁹⁷Au nuclei.

LHC Shines on Positivity

Zhen Liu, Kun-Feng Lyu, Tong Arthur Wu

Published:

Abstract:
We show that hadron colliders have an excellent reach for positivity tests on a class of diphoton operators. Due to the helicity selection rules, the relevant dimension-6 operators either do not contribute or are highly constrained by other experimental observables. We demonstrate, for the first time, that the LHC can probe the positivity of the dimension-8 operators involving colored particles. The kinematic differential distributions of the diphoton final states are utilized to perform the

\begin{document}$ \chi^2$\end{document}

analysis. Through a global fit, the effective scale for these operators can be inclusively probed up to around 2 TeV at HL-LHC and over 5 TeV at future 100 TeV FCC-hh at 95% C.L., providing a powerful test of the positivity bounds up to the multi-TeV scale.

Polarized image of an equatorial emitting ring around a Konoplya-Zhidenko rotating non-Kerr black hole

Xin Qin, Fen Long, Songbai Chen, Jiliang Jing

Published: , doi: 10.1088/1674-1137/ae740c

Abstract:
We investigate the polarized images of an equatorial emitting ring around a rotating Konoplya-Zhidenko non-Kerr black hole, which incorporates an additional deformation parameter. This deformation parameter, η, permits the spin parameter to exceed the upper bound imposed by the standard Kerr black hole. Our results indicate that the polarized images depend not only on the magnetic field configuration, fluid velocity, and observer inclination angle, but also on the spin and deformation parameters. As the deformation parameter increases, the polarization intensity decreases monotonically. Conversely, the magnitude of the Electric Vector Position Angle (EVPA) increases with η. Furthermore, we observe that η may induce subtle yet discernible azimuthal separation features, potentially distinguishing its effects from those of the spin parameter and the magnetic field orientation angle. Nevertheless, these features remain difficult to resolve under current observational conditions and will require verification by future high-resolution facilities such as the next-generation Event Horizon Telescope (ngEHT).

Analysis of the strong decays of the Y (4660) in tetraquark scenario via the QCD sum rules

Xiao-Song Yang, Zhi-Gang Wang

Published: , doi: 10.1088/1674-1137/ae71a6

Abstract:
Motivated by the enigmatic vector charmonium-like states, we investigate the strong decay behaviors of four types of vector tetraquark states, which are possible candidates for the

\begin{document}$Y(4660)$\end{document}

, within the framework of three-point QCD sum rules based on rigorous quark-hadron duality. We take into account vacuum condensates up to dimension 5 on the QCD side and obtain the hadronic coupling constants and hence the partial decay widths of these states. The predicted total width,

\begin{document}$61.5\pm7.3\,{\rm{MeV}}$\end{document}

, is in excellent agreement with the experimental data for the

\begin{document}$Y(4660)$\end{document}

, supporting its interpretation as a

\begin{document}$[sc][\bar{s}\bar{c}]$\end{document}

tetraquark state with

\begin{document}$J^{PC}=1^{--}$\end{document}

.

Measurement of Isoscalar Pair Correlation in ¹²⁰Sn Using (α, ⁶Li) Probe

Jia-Wei Cai, Shinsuke Ota, Masanori Dozono, Satoshi Adachi, Shutaro Hanai, Yuto Hijikata, Genki Hosoya, Nobu Imai, Masatoshi Itoh, Noritaka Kitamura, Shin'ichiro Michimasa, Takeshi Y. Saito, Xiao-Dong Tang, Shumpei Yamazaki, Shohei Yonekura

Published: , doi: 10.1088/1674-1137/ae740a

Abstract:
Nucleon-pair correlations play a fundamental role in shaping nuclear structure. Two-nucleon transfer reactions provide a unique probe for investigating pair correlations in nuclei. A recent theoretical study has predicted significant proton-neutron (

\begin{document}$pn$\end{document}

) pair correlations in the unconventional

\begin{document}$N>Z$\end{document}

region. To investigate isoscalar

\begin{document}$pn$\end{document}

pair correlations, we measured the ¹²⁰Sn(α, ⁶Li)¹¹⁸In reaction in the laboratory angular range from

\begin{document}$9^\circ$\end{document}

to

\begin{document}$19^\circ$\end{document}

. Owing to the limited experimental energy resolution, no distinct peak corresponding to the ground state of ¹¹⁸In was observed. By evaluating the low-excitation-energy region, an upper limit of the cross section for populating ¹¹⁸In(g.s.) was extracted, yielding an integrated cross section of

\begin{document}$\sigma=0.42 \pm 0.02$\end{document}

μb. The DWBA calculations for the transfer of a

\begin{document}$\pi g_{9/2}\otimes\nu g_{7/2}$\end{document}

pair using an assumed value of the two-nucleon amplitude (TNA) are consistent with the experimental cross section. The competition between simultaneous and sequential transfer in this heavy system was investigated. A comparison with the ¹²⁰Sn(α, ⁶He)¹¹⁸Sn reaction indicates that the

\begin{document}$pn$\end{document}

pair-correlation strength is far weaker than that for neutron-neutron pair condensation.

Resolving diffusion signatures in distant pulsar halos with current and future experiments

Yong-Jian Wei, En-Sheng Chen, Kun Fang, Xiao-Jun Bi

Published:

Abstract:
γ-ray pulsar halos are produced by electron-positron pairs that diffuse away from the pulsar and scatter off background photons. Their morphology serves as an ideal probe for studying cosmic-ray propagation on scales of several tens of parsecs. However, the number of firmly identified pulsar halos remains limited, primarily because current γ-ray experiments, constrained by angular resolution, struggle to resolve the diffusion signatures of distant candidates (

\begin{document}$>1$\end{document}

kpc). In this work, we investigate the prospects for identifying pulsar halo candidates through morphological discrimination using simulations of two advanced γ-ray experiments: the Kilometer Square Array of the Large High Altitude Air Shower Observatory (LHAASO-KM2A) and the Cherenkov Telescope Array (CTA, under construction). Using mock observations with realistic instrumental responses, we quantitatively assess the ability of each experiment to distinguish diffusion-based halo morphologies from alternative spatial models. Our analysis indicates that if the angular resolution of LHAASO-KM2A could be improved by 40%, it would be capable of resolving several prominent pulsar halo candidates, namely the halos around pulsars J1831-0952, J0248+6021, and J0359+5414. CTA holds an advantage in resolving the morphology of sources beyond

\begin{document}$\approx1.5$\end{document}

kpc owing to its superb angular resolution. By extending exposure times to hundreds of hours, CTA is expected to achieve morphological identification for all known pulsar halo candidates.

A novel realization of linear seesaw model in a non-invertible selection rule with the assistance of $\mathbb{Z}_3$ symmetry

Hiroshi Okada, Yutaro Shoji

Published: , doi: 10.1088/1674-1137/ae6ed2

Abstract:
We propose a novel realization of the linear seesaw model with a non-invertible selection rule, assisted by

\begin{document}$\mathbb{Z}_3$\end{document}

symmetry. In our framework, Dirac mass matrices are generated at the one-loop level, breaking the non-invertible symmetry, while the symmetry remains intact at tree level. In addition to active neutrino masses, the model exhibits rich and testable phenomenology, including non-unitarity constraints, lepton flavor violation, lepton anomalous magnetic moments, and a dark matter candidate. After describing our model, we carry out a numerical analysis and present results for our physical parameters.

Atmospheric Neutrino Charged-Current Interactions at Large Liquid-Scintillator Detectors: I. Physics of Neutrino-Antineutrino Discrimination

Xinhai He, Gao-song Li, Yu-Feng Li, Wuming Luo, Liang-jian Wen

Published: , doi: 10.1088/1674-1137/ae68ef

Abstract:
In this work, we present a systematic study of the event characteristics and underlying physics relevant to neutrino-antineutrino discrimination in atmospheric neutrino charged-current interactions in large liquid scintillator detectors. This study encompasses the primary neutrino interactions, the subsequent secondary interactions of final-state particles, and the ensuing neutron captures. We investigate in detail the properties of final-state charged leptons and hadrons, deriving distinct distributions of inelasticity and neutron-capture multiplicity for both neutrino and antineutrino interactions. These distributions are used to quantify the performance of neutrino-antineutrino discrimination. Our findings lay the groundwork for atmospheric neutrino oscillation studies in large liquid scintillator detectors, particularly for determining the neutrino mass ordering.

Thermodynamic phase structure and topological charge of Hayward–AdS black holes under phase space constraints

Qi-Hang Xia, Hui-Hua Zhao, Meng-Sen Ma

Published:

Abstract:
We investigate the thermodynamic behavior of the Hayward-AdS black hole and compare it with its singular counterpart, from which it is constructed by imposing an additional constraint. The singular black hole displays a rich phase structure, including reentrant phase transitions reminiscent of those observed in higher-dimensional Kerr-AdS spacetimes. After the constraint is imposed, the resulting Hayward-AdS black hole continues to exhibit Van der Waals–type

\begin{document}$P-V$\end{document}

criticality. However, its Gibbs free energy profile differs qualitatively from that of standard RN-AdS black holes. Additionally, we extend the analysis by employing thermodynamic topology to characterize the global structure of the phase space. We find that the topological charge of the singular black hole is

\begin{document}$-1$\end{document}

, whereas that of the Hayward-AdS black hole is

\begin{document}$+1$\end{document}

. This change in topological charge indicates that the constraint not only regularizes the geometry but also induces a qualitative transformation in the thermodynamic configuration space.

An analysis of nuclear parton distribution function based on relative entropy

Shu-Man Hu, Ao-Sheng Xiong, Ji Xu, Fu-Sheng Yu, Ji-Xin Yu

Published: , doi: 10.1088/1674-1137/ae6da1

Abstract:
In this work, we propose a method for quantifying the difference between nuclear parton distribution functions in different nuclei and parton distribution functions in free nucleons using relative entropy (also known as the Kullback-Leibler divergence), a measure widely employed in quantum information theory. By introducing certain constraints and the “minimum relative entropy” hypothesis, we can determine the shape of the structure function in the intermediate-x region, which is closely connected to the renowned EMC effect. For quark structure functions, our results are consistent with the latest global fits to experimental data. This agreement suggests that the relative entropy-based methodology may provide novel insights into nucleon structure, particularly in cases where experimental data and theoretical QCD constraints are limited, such as those relevant to gluon nPDFs. Therefore, we apply this methodology to gluon nPDFs, analyzing the results from two commonly used global fitting groups, EPPS21 and nNNPDF3.0. Our analysis suggests that the central values of EPPS21 align more closely with the “minimum relative entropy” hypothesis. This finding underscores the utility of the proposed method and provides a valuable reference for future global fits of nPDFs.

Acoustic Black Hole in Hayward Spacetime: Shadow, Quasinormal Modes and Analogue Hawking Radiation

Zhong-Yi Hui, Yu-Ye Cheng, Jia-Rui Sun

Published: , doi: 10.1088/1674-1137/ae7282

Abstract:
In this paper, we study an acoustic black hole in Hayward spacetime within the framework of relativistic Gross-Pitaevskii theory. By examining the critical null geodesics, we sketch the shadow of the acoustic horizon. The quasinormal mode (QNM) frequencies of the acoustic Hayward black hole are then computed numerically using the WKB method. The results show that these modes are more stable than those of the Hayward black hole, and that variations in the QNM frequencies are correlated with the behavior of the effective potential. We also verify the relationship between QNMs and the acoustic sphere (and the acoustic shadow) in the eikonal limit. Moreover, the WKB method is employed to calculate the grey-body factor and energy emission rate of the analogue Hawking radiation. It is shown that, as the tuning parameter increases, both the grey-body factor and the energy emission rate are enhanced, which can likewise be attributed to changes in the effective potential. In addition, the acoustic shadow radius also increases with the tuning parameter. Our work extends the acoustic black hole model to regular black hole spacetime, and the findings provide a potential application for distinguishing regular black holes from black holes with singularities in astrophysical environments via acoustic black hole effects.

Frame Dependence in Generalized Chiral Kinetic Theory

Shu-Xiang Ma, Jian-Hua Gao

Published: , doi: 10.1088/1674-1137/ae740d

Abstract:
We investigate the frame dependence of distribution functions within the framework of generalized chiral kinetic theory. Based on the derived transformation rules governing the choice of frame, we analytically obtain the global equilibrium solutions in the presence of vorticity and electromagnetic fields. Our results show that, under the assumption of varying electromagnetic fields, these equilibrium solutions can be uniquely determined.

Interpretation of Ω(2012) as a Ξ(1530)${\bar{\boldsymbol K}}$ molecular state

Xiang Yu, Jin-Peng Zhang, Xu-Liang Chen, Ding-Kun Lian, Qi-Nan Wang, Wei Chen

Published: , doi: 10.1088/1674-1137/ae6da4

Abstract:
We investigate the mass and strong decay properties of the

\begin{document}$\Omega(2012)$\end{document}

resonance using QCD sum rules, assuming it to be an S-wave

\begin{document}$\Xi(1530)\bar{K}$\end{document}

molecular pentaquark state with

\begin{document}$I(J^{P})= 0(\dfrac{3}{2}^{-})$\end{document}

. A unified interpolating current is constructed, and the two-point and three-point correlation functions are calculated up to dimension-13 and dimension-10 condensate terms in the OPE series, respectively. The negative-parity contribution is isolated by employing parity-projected sum rules. The two-body strong decays into

\begin{document}$\Xi^0 K^-$\end{document}

and

\begin{document}$\Xi^- \bar{K}^0$\end{document}

are studied using the corresponding three-point correlation functions. Our analysis yields a mass of

\begin{document}$2.02 \pm 0.12~\mathrm{GeV}$\end{document}

and a total two-body decay width of

\begin{document}$\Gamma = 0.96^{+0.79}_{-0.41}~\mathrm{MeV}$\end{document}

for the

\begin{document}$\Xi(1530)\bar{K}$\end{document}

molecular state. The ratio of the two-body decay branching fractions is obtained as

\begin{document}$\mathcal{R}^{\Xi^- \bar{K}^0}_{\Xi^0 K^-} = 0.85$\end{document}

. These results are compatible with the experimental data for the

\begin{document}$\Omega(2012)$\end{document}

within uncertainties and support its interpretation as a

\begin{document}$\Xi(1530)\bar{K}$\end{document}

molecular pentaquark state.

Measurement of neutron capture cross sections of copper from 1 eV to 700 keV at CSNS Back-n.

Yubing Li, Zhendong An, Wei Jiang, Yu-gang Ma, Cheng Li, Jie Ren, Xichao Ruan, Jingyu Tang, Ruirui Fan, Di Sun, Liu Li, Jingyi Zhang, Ruoran Bai, Shaokun Liu, Chenchen Guo, Hao Liang, Junheng Hu, Ting Liu, Hongwei Wang, Yi Sui, Xiankai Li, Xinxiang Li, Wen Luo, Yaju Chen, Wen Xie, Zhouji Liao, Xinrong Hu, Chunwang Ma, Han Yi, Yonghao Chen, Qiang Li, Zhixin Tan, Hantao Jing

Published: , doi: 10.1088/1674-1137/ae71a5

Abstract:
The neutron capture cross sections of copper play a crucial role in the s process of stellar nucleosynthesis, the production of the medical isotope

\begin{document}$^{64}{\rm{Cu}}$\end{document}

for PET imaging and radiotherapy, and Neutron Resonance Capture Analysis for determining the elemental and isotopic compositions of archaeological and cultural heritage materials. The

\begin{document}${}{\rm{Cu}}({\rm{n}},\gamma)$\end{document}

cross section was measured from 1 eV to 700 keV at the Back-n facility of the Chinese Spallation Neutron Source using the time-of-flight (TOF) method. Prompt γ-rays were detected by four

\begin{document}${{\rm{C}}_{6}{\rm{D}}_{6}}$\end{document}

liquid scintillator detectors, and the data were analyzed using the pulse height weighting technique. The results are generally consistent with the evaluated data in the major library; however, some discrepancies were observed, offering valuable insights into the differences between five prominent evaluated data libraries. The R-matrix SAMMY code was used to extract the resonance parameters for

\begin{document}$^{63,65}{\rm{Cu}}$\end{document}

in the resolved resonance region. Maxwellian-averaged cross sections were calculated within the temperature range relevant to the s process nucleosynthesis model, spanning

\begin{document}$kT=5\rm{-}100$\end{document}

keV, based on the averaged cross sections in the unresolved resonance region. At

\begin{document}$kT=30$\end{document}

keV, the MACSs values for

\begin{document}$^{63}{\rm{Cu}}$\end{document}

(88.1±8.8 mb) and

\begin{document}$^{65}{\rm{Cu}}$\end{document}

(42.1±4.2 mb) were higher than the corresponding recommendations in the Karlsruhe Astrophysical Database of Nucleosynthesis in Stars.

Superhorizon fluctuations and the cosmic dipole problem

Ge Chen, Chengcheng Han, Linwei Qiu

Published: , doi: 10.1088/1674-1137/ae6b2e

Abstract:
Recent observations have identified a significant 4.9σ tension between the cosmic dipole inferred from galaxy number counts and that derived from the Cosmic Microwave Background (CMB), suggesting a potential deviation from the cosmological principle. This work investigates whether superhorizon isocurvature perturbations in cold dark matter (CDM) can account for this discrepancy. We demonstrate that, unlike adiabatic modes, which cancel at leading order, superhorizon isocurvature modes can generate an intrinsic CMB dipole without significantly affecting galaxy number counts, thereby explaining the observed mismatch. We explore both single-mode and continuous-spectrum cases, focusing on two concrete models: a nearly scale-invariant power-law spectrum with a UV cutoff and axion-induced isocurvature perturbations. For the axion scenario, we show that if the radial mode evolves during inflation, the resulting perturbations can match the required amplitude while evading current CMB constraints. Our analysis constrains the self-coupling of the axion potential to the range

\begin{document}$10^{-9} \lt \lambda \lt 4 \times 10^{-9}$\end{document}

. These findings offer a viable solution to the dipole tension and may serve as indirect evidence for axion dark matter.

Relativistic mean-field study of the neutron star inner crust using the asymmetric finite difference method

Jinzhe Zhang, Hong Shen, Ying Zhang, Jinniu Hu

Published: , doi: 10.1088/1674-1137/ae6b30

Abstract:
The ground-state properties of neutron-rich nuclear clusters in the inner crust of neutron stars are investigated within the Wigner–Seitz approximation using a relativistic mean-field framework. The radial Dirac equations are solved using an asymmetric finite-difference scheme that preserves hermiticity and eliminates spurious states. Calculations are performed for representative Wigner–Seitz cells using TM1-based interactions with different symmetry-energy slope parameters L, as well as a parametrization with a larger effective nucleon mass. It is found that the binding energy per nucleon decreases systematically with increasing L, while a larger effective nucleon mass produces a further decrease, particularly at higher densities. Quantum shell effects, which are absent in the Thomas–Fermi approximation, give rise to oscillatory density distributions and modify neutron properties. Within the Wigner–Seitz cell, the resulting neutron root-mean-square radius and chemical potential are sensitive to both L and the effective nucleon mass, underscoring their important roles in determining the microscopic structure of the neutron-star inner crust.

Systematic study of entrance channel effects in incomplete fusion dynamics

Anuj Kumar Jashwal, Avinash Agarwal, Munish Kumar, Harsh Vardhan, Satyam Gangwar, Vibhuti Sinha, Mohd. Faizan Khan, K. Kumar, S. Ali, S. Dutt, I. A. Rizvi, A. K. Chaubey

Published: , doi: 10.1088/1674-1137/ae6b1f

Abstract:
We perform a comprehensive analysis of the complete and incomplete fusion cross sections of the reaction residues produced for the

\begin{document}$ {^{16}} {\rm{O}}$\end{document}

+

\begin{document}$ {^{93}} {\rm{N}}{\rm{b}}$\end{document}

system at energies above the barrier, with a novel interpretation in terms of entrance channel parameters. The measured excitation functions of the residues have been compared with the predictions of the statistical model code PACE4 to understand the reaction mechanisms associated with the energy region of interest. The experimental cross sections of

\begin{document}$ {^{106}} {\rm{In}}$\end{document}

,

\begin{document}$ {^{105}} {\rm{C}}{\rm{d}}$\end{document}

, and

\begin{document}$ {^{104}} {\rm{C}}{\rm{d}}$\end{document}

residues measured at varying projectile energies are populated to a large extent through the complete fusion processes. However, a noticeable cross-section enhancement in the α-emitting channels has been observed compared to statistical model predictions. The observed enhancement may be attributed to the involvement of breakup fusion processes. To shed light on the onset and strength of incomplete fusion, the incomplete fusion fraction has been derived as a function of various entrance channel parameters. Further, the total fusion cross sections of three systems,

\begin{document}$ {^{18}} {\rm{O}}$\end{document}

+

\begin{document}$ {^{93}} {\rm{N}}{\rm{b}}$\end{document}

,

\begin{document}$ {^{16}} {\rm{O}}$\end{document}

+

\begin{document}$ {^{93}} {\rm{N}}{\rm{b}}$\end{document}

(present work), and

\begin{document}$ {^{13}} {\rm{C}}$\end{document}

+

\begin{document}$ {^{93}} {\rm{N}}{\rm{b}}$\end{document}

, have been reduced using standard reduction procedures, which show that the incomplete fusion fraction for reactions induced by projectile

\begin{document}$ {^{16}} {\rm{O}}$\end{document}

has a lower value compared to reactions induced by

\begin{document}$ {^{18}} {\rm{O}}$\end{document}

and a larger value when compared to reactions induced by

\begin{document}$ {^{13}} {\rm{C}}$\end{document}

. This reduction method undeniably reveals the projectile type dependency of incomplete fusion reactions, and the results may be explained by considering the projectile

\begin{document}$ {\rm{Q}}_{\alpha} $\end{document}

value. In addition, the dependence of incomplete fusion dynamics on the total asymmetry parameter, system parameter, fissility parameter, nuclear potential parameters, and target deformation is extensively investigated. Suppression in the fusion cross section is found when compared to the universal fusion function.

Significance of tensor coupling effect on shell evolutions and relativistic symmetries in calcium isotopes

Xin-Xing Shi, Quan Liu, Shou-Wan Chen, Dong-Peng Li

Published: , doi: 10.1088/1674-1137/ae6a7f

Abstract:
Based on the similarity renormalization group (SRG) method with the relativistic mean field (RMF) theory, we diagonalize the Hamiltonian incorporating the tensor coupling effect to explore pseudospin and spin symmetries and their evolutions in Ca isotopes. The restoration of pseudospin symmetry is governed by the competition between

\begin{document}$H_{T}^{sl}$\end{document}

(the coupling of tensor and spin-orbit term) and

\begin{document}$H_{T}^{dw}$\end{document}

(the coupling of tensor and Darwin term) via the SRG method. The tensor coupling effect breaks the spin symmetry, primarily driven by

\begin{document}$H_{T}^{sl}$\end{document}

. It is worth noting that the decrease (increase) of single-particle energy in

\begin{document}$\kappa <0$\end{document}

(

\begin{document}$\kappa>0$\end{document}

) states is caused by the

\begin{document}$H_{T}^{sl}$\end{document}

term in the pseudospin and spin symmetries. The tensor coupling effect drives pseudo(spin) splittings, which highlights the necessity of relativistic approaches with exchange interactions. Compared with the experimental and theoretical results, the tensor coupling effect (fitting the tensor parameters

\begin{document}$f(t)=3.1$\end{document}

) induces shell effects at

\begin{document}$N = 32, 34$\end{document}

, which renders these nuclei more magic than predictions by the traditional RMF model. Meanwhile, a more diffuse potential leads to the preservation of PSS in exotic nuclei, as supported by analysis of the mean field potential Σ and its derivative

\begin{document}$\Sigma'(r)$\end{document}

.

Symmetry-Breaking Effects on Form Factors and Observables in B → K₀^*(1430)μ⁺μ^- Decay

Saba Ayub, Saba Shafaq, Arslan Sikandar, M. Jamil Aslam

Published: , doi: 10.1088/1674-1137/ae6b23

Abstract:
In the heavy-quark and large-energy limits, symmetry relations reduce the number of independent form factors governing heavy-to-light B-meson decays. Exploiting these relations, the form factors can be parametrized while systematically incorporating symmetry-breaking corrections from perturbative QCD. Using vertex renormalization together with light-cone distribution amplitudes, we compute the vertex and hard-spectator contributions for the

\begin{document}$B \to K_0^{*}(1430)$\end{document}

transition. We then analyze the impact of these form factors on physical observables, including the branching ratio and lepton polarization asymmetries

\begin{document}$(P_L, P_N)$\end{document}

, in

\begin{document}$B \to K_0^{*}(1430)\mu^+\mu^-$\end{document}

. Our results indicate that perturbative corrections induce modest shifts of ~ 3% in both the branching ratio and the normal lepton polarization asymmetry. Consequently, any significant deviation observed experimentally from these predictions would provide a clear signal of potential New Physics effects.

Mini-review of charmonium weak decays at BESIII

Xu-Ze Li, Kai-Xin Fan, Zheng-Yun You, Yu Zhang, Minggang Zhao

Published: , doi: 10.1088/1674-1137/ae6a80

Abstract:
The weak decays of charmonium states such as

\begin{document}$ J/\psi $\end{document}

and

\begin{document}$ \psi(2S) $\end{document}

are instrumental in probing both nonperturbative QCD dynamics and the flavor structure of the Standard Model (SM). The extreme rarity of charmonium weak decays renders them highly sensitive to physics beyond the SM, particularly in channels that are heavily suppressed in the SM, such as flavor-changing neutral-current (FCNC) decays. This review highlights the critical role of the BESIII experiment, which leverages an unprecedented data sample of over

\begin{document}$ 10^{10} $\end{document}

\begin{document}$ J/\psi $\end{document}

and

\begin{document}$ 2.7\times10^{9} $\end{document}

\begin{document}$ \psi(2S) $\end{document}

events to achieve leading sensitivity in searches for charmonium weak decays. We present the latest and most stringent upper limits established by BESIII on various semileptonic, nonleptonic, and FCNC charmonium weak decay channels.

Investigating ground-state properties of neutron-rich nuclei with Z = 98 - 104 in the reflection-asymmetric relativistic mean-field theory

Yu-Ting Qiu, Jian-You Guo

Published: , doi: 10.1088/1674-1137/ae6a83

Abstract:
A systematic microscopic analysis of the ground-state properties for the neutron-rich even-even nuclei with

\begin{document}$ Z = 98 - 104 $\end{document}

and

\begin{document}$ N = 170 - 210 $\end{document}

is performed using the reflection-asymmetric relativistic mean-field theory with the NL3, NL3*, and PK1 effective interactions. The pairing effect is taken into account via the BCS approximation with a constant pairing gap. It is found that the octupole deformation significantly influences the physical properties of Cf, Fm, No, and Rf isotopes. Particularly, incorporating the reflection-asymmetric degree of freedom enhances the binding energies, quadrupole deformations, and neutron, proton, and charge radii for nuclei near

\begin{document}$ N = 184 $\end{document}

and

\begin{document}$ N = 196 $\end{document}

. The possible candidates,

\begin{document}$ N \approx 184 $\end{document}

and

\begin{document}$ N \approx 196 $\end{document}

, for the new neutron octupole magic number are predicted in the present calculations. The effect of the size of the pairing correlations on the octupole deformation of nuclei is examined by varying the pairing gap. It is found that the octupole deformation decreases as the pairing gap increases. This reduction underscores the critical role of precise treatment of the pairing correlations in achieving a reliable prediction of the octupole deformation of nuclei. Additionally, we further investigate the sensitivity of the nuclear properties to the Coulomb interaction. The results show that the inclusion of the Coulomb interaction increases quadrupole and octupole deformations as well as neutron, proton, and charge radii but leads to a marked reduction in binding energies. These conclusions remain consistent across the calculations employing the NL3, NL3*, and PK1 parameter sets. To more broadly validate the robustness of the present findings, further investigation based on other types of effective interactions and pairing forces is worthwhile.

Investigation of the production of neutron-rich isotopes in the multinucleon transfer reaction ¹⁹⁷Au + ²³⁸U

Dong-Hong Zhang, Da-Long Jiang

Published: , doi: 10.1088/1674-1137/ae6a84

Abstract:
The production mechanisms and cross sections for neutron-rich actinide nuclides formed in multinucleon transfer reactions with ²³⁸U targets are systematically investigated using the dinuclear system (DNS) model coupled with the GEMINI++ de-excitation code. The tip-to-tip configurations for the ⁴⁸Ca+²⁴⁸Cm and ²³⁸U+²³⁸U reactions are in good agreement with experimental data. Calculations of the potential energy surfaces and driving potentials for the three systems ¹⁹⁷Au+²³⁸U, ¹⁸⁶W+²³⁸U, and ²³²Th+²³⁸U indicate that the first two systems exhibit pronounced "inverse" quasifission characteristics due to shell effects. The final isotopic production cross sections of target-like fragments with Z=93-101 for the three systems are calculated at

\begin{document}$ E_{c.m.} $\end{document}

=1.10

\begin{document}$ V_{B} $\end{document}

. The results show that the production cross sections for the ¹⁹⁷Au+²³⁸U system are significantly higher than those for the other two systems, with a particularly pronounced advantage in the Z=93-98 region. Further analysis of the ¹⁹⁷Au+²³⁸U reaction at different incident energies reveals that higher incident energies are favorable in the Z=93-98 region, whereas lower energies are more advantageous in the Z=99-101 region. Calculations of the interaction time show that higher incident energies lead to longer contact times between the nuclei. Production cross sections are predicted for 61 previously unobserved neutron-rich nuclides with values greater than 1 pb, providing a theoretical basis for experimental synthesis.

Exploring new resonances with direct top flavor changing interactions

Min Huang, Yandong Liu, Hao Zhang

Published: , doi: 10.1088/1674-1137/ae662b

Abstract:
In this work, we investigate three representative new-physics resonances that couple to Standard Model (SM) quarks through flavor-changing interactions involving the top quark. We identify the possible SMEFT operators at the electroweak scale and analyze their phenomenology.

Warm Hybrid Axion Inflation in α-Attractor Models Constrained by ACT and Future Plan experiments

Waqas Ahmed, Waqar Ahmad, Ahsan Illahi, M. Junaid

Published: , doi: 10.1088/1674-1137/ae6a7e

Abstract:
We present a comprehensive study of warm hybrid inflation within the framework of α-attractor models, where an axionic inflaton is coupled to a waterfall field in the presence of thermal dissipation. The model is analyzed for both linear (

\begin{document}$ \Upsilon \propto T $\end{document}

) and cubic (

\begin{document}$ \Upsilon \propto T^{3} $\end{document}

) dissipation regimes. Confronting the theoretical predictions with the latest observational data from Planck+BICEP/Keck, P-ACT-LB-BK18, and SPT, we find that in the weak dissipative regime (

\begin{document}$ Q_{*} \lesssim 10^{-5} $\end{document}

), the scalar spectral index

\begin{document}$ n_{s} \simeq 0.965 $\end{document}

lies at the boundary of the combined P-ACT-LB-BK18 constraints, while the tensor-to-scalar ratio r remains within observable ranges. For stronger dissipation (

\begin{document}$ Q_{*} \gtrsim 10^{-2} $\end{document}

), the model predicts values of

\begin{document}$ n_{s} $\end{document}

well within the

\begin{document}$ 1-2\sigma $\end{document}

confidence region of all datasets, with tensor modes remaining fully observable in both dissipation scenarios. These results indicate that forthcoming CMB polarization experiments may be capable of detecting primordial gravitational waves, thereby providing a robust observational test of warm hybrid inflation across different dissipative regimes.

Direct CP violation in ${ {\boldsymbol D}^{\bf\pm }\to {\boldsymbol\pi}^{\bf\pm} {\boldsymbol\pi}^{\bf +} {\boldsymbol\pi}^{\bf -}} $ with ${{\boldsymbol a}_{\bf 0}^{\bf 0}{\bf (980)-}{\boldsymbol f}_{\bf 0}{\bf (980)}} $ mixing

Shi-Ji Cao, Jing-Juan Qi, Yi-Fan Zhao, Chao Wang, Zhen-Yang Wang, Xin-Heng Guo

Published: , doi: 10.1088/1674-1137/ae6b1e

Abstract:
We investigate the direct

\begin{document}$ CP $\end{document}

violation in the decay

\begin{document}$ D^\pm \to \pi^\pm \pi^+ \pi^- $\end{document}

incorporating the

\begin{document}$ a_0^0(980) $\end{document}

-

\begin{document}$ f_0(980) $\end{document}

mixing mechanism. The integrated mixing intensities

\begin{document}$ \overline \xi_{fa} $\end{document}

and

\begin{document}$ \overline \xi_{af} $\end{document}

are calculated using meson masses and coupling constants extracted from various theoretical models and experimental data, yielding values of appreciable magnitude. We find that when the invariant mass of the

\begin{document}$ \pi^+\pi^- $\end{document}

pair lies near the

\begin{document}$ f_0(980) $\end{document}

resonance, this isospin-breaking mechanism can enhance the

\begin{document}$ CP $\end{document}

asymmetry. The enhancement is particularly pronounced when the

\begin{document}$ f_0(980) $\end{document}

carries a significant

\begin{document}$ n\bar{n} $\end{document}

quark component and the

\begin{document}$ f_0(980) $\end{document}

and

\begin{document}$ \sigma(600) $\end{document}

mixing angle is approximately

\begin{document}$ 26^\circ $\end{document}

. After accounting for non-factorizable effects, we find these corrections tend to partially cancel the leading-order contributions, resulting in a suppression of the

\begin{document}$ CP $\end{document}

violations relative to the naive factorization predictions. It is emphasized that the

\begin{document}$ a_0^0(980) $\end{document}

-

\begin{document}$ f_0(980) $\end{document}

mixing mechanism should be taken into account in both theoretical and experimental studies of

\begin{document}$ CP $\end{document}

violation in B or D meson decays.

Production of muonic kaon atoms at high-energy colliders

Xiaofeng Wang, Zebo Tang, Zhangbu Xu, Chi Yang, Wangmei Zha, Yifei Zhang

Published: , doi: 10.1088/1674-1137/ae662f

Abstract:
We develop a framework for the formation of exotic muonic kaon atoms (

\begin{document}$ K\mu $\end{document}

) in semileptonic

\begin{document}$ D^{0} $\end{document}

decays, using the effective weak Hamiltonian, a helicity-based treatment of the leptonic current, and a nonrelativistic bound-state projection. The resulting branching ratio,

\begin{document}$ \mathrm{BR}(D^{0} \to(K\mu )\nu_{\mu})=2.29\times10^{-10} $\end{document}

, is implemented in a ROOT-based code to estimate yields at RHIC, LHC, and STCF. We show quantitatively that

\begin{document}$ K\mu $\end{document}

atoms—also produced through coalescence in the quark–gluon plasma (QGP)—provide a sensitive probe of low-momentum primordial muons and early-time electromagnetic radiation, offering complementary constraints in an otherwise unexplored phase space for thermal dilepton and photon emission. Newly estimated dissociation cross sections in detector material indicate that secondary-vertex reconstruction should be experimentally feasible, allowing clean experimental identification of the atoms. Projected yields from QGP coalescence in LHC and RHIC heavy-ion collisions, and from

\begin{document}$ D^{0} $\end{document}

decays in LHC high-luminosity

\begin{document}$ p+p $\end{document}

collisions indicate that the first observation of

\begin{document}$ K\mu $\end{document}

atoms is within reach.

Mean first passage time and the Kramers escape rate of phase transitions for the Bardeen-AdS-class black hole

Chen Ma, Bin Wu, Zhen-Ming Xu

Published: , doi: 10.1088/1674-1137/ae66d3

Abstract:
In this study, by utilizing the constructed generalized free energy alongside the Mean First-Passage Time and the Kramers escape rate from stochastic dynamics, we have obtained a comprehensive landscape of the phase transitions for the Bardeen-AdS-class black hole. This black hole model admits two distinct categories of solutions. Type I black holes feature a regular black hole solution, while Type II black holes possess a vacuum state solution. In the phase transition between the small black hole and the large black hole for Type I, the process may pass through a stable, metastable, or unstable regular black hole as an intermediate state. In contrast, for Type II black holes, the phase transition occurs exclusively between the vacuum state and the small black hole, and the transition process does not involve any regular black hole intermediate states.

Systematic study of the strong decays of the P_c states and their possible isospin cousins via the QCD sum rules

Xiu-Wu Wang, Xin Li, Zhi-Gang Wang

Published: , doi: 10.1088/1674-1137/ae66d1

Abstract:
In the present work, the strong decays of the discovered

\begin{document}$ P_c(4380) $\end{document}

,

\begin{document}$ P_c(4440) $\end{document}

,

\begin{document}$ P_c(4457) $\end{document}

and their possible isospin cousins are systematically studied via the assignment that they are meson-baryon molecular states. In detail, the strong decay constants and partial decay widths of their decay channels are calculated under the framework of QCD sum rules. The decay widths of the discovered

\begin{document}$ P_c(4380) $\end{document}

,

\begin{document}$ P_c(4440) $\end{document}

, and

\begin{document}$ P_c(4457) $\end{document}

are in good agreement with the experiments. The predictions of the decays of these three related possible isospin cousins are presented, which would shed light on their findings in experiments. In return, this may testify to the assignments of the discovered

\begin{document}$ P_c $\end{document}

states.

Origin of Quasi-Periodic Oscillations and Accretion Process in X-Ray Binaries around Quantum Lee-Wick Black Hole

Orhan Donmez, G. Mustafa, M. Yousaf, Faisal Javed, Ikhtiyor Saidov, Farruh Atamurotov

Published: , doi: 10.1088/1674-1137/ae6632

Abstract:
In this study, we investigate the accretion dynamics and test particle motion around a non-rotating, spherically symmetric Lee-Wick black hole (BH) to reveal how the model parameters affect orbital stability and the quasi-periodic oscillations (QPOs) observed in X-ray binary systems. In this work, we deliberately explore parameter values both within the admissible region defined by

\begin{document}$ S_2 \gt 0 $\end{document}

and

\begin{document}$ -2\sqrt{S_2} \lt S_1 \lt 2\sqrt{S_2} $\end{document}

and beyond this constraint to investigate the effect of Lee-Wick gravity. The spacetime geometry, characterized by the BH mass and the coupling parameters

\begin{document}$ S_1 $\end{document}

and

\begin{document}$ S_2 $\end{document}

, includes exponential and oscillatory corrections arising from the Lee-Wick terms. Using the effective potential approach, we derive specific energy, angular momentum, epicyclic frequencies, and the locations of the innermost stable circular orbits (ISCOs) of test particles. In addition to the analytical analysis, we explore the effects of the Lee-Wick spacetime parameters on the shock-cone morphology produced by Bondi-Hoyle-Lyttleton (BHL) accretion. To this end, we perform general relativistic hydrodynamic simulations in two characteristic regimes: Block-1 (weak Lee-Wick regime) and Block-2 (strong Lee-Wick regime). The results show that Block-1 solutions closely resemble the Schwarzschild case, while Block-2 models develop denser and asymmetric shock cones accompanied by stronger QPO activity, shifting from low-frequency to high-frequency QPOs. These variations yield distinct observational signatures that may be detectable in high-resolution X-ray timing data. Our analytical and numerical findings demonstrate that the Lee-Wick parameters

\begin{document}$ S_1 $\end{document}

and

\begin{document}$ S_2 $\end{document}

cause measurable changes in the morphology of the accretion flow and in the frequency ratios near the BH. This suggests that future multi-wavelength observations could provide an important avenue to test higher-derivative gravity theories.

Measurement of the neutron capture cross section using C₆D₆ detectors at the milli-barn scale: a case study of ²⁰⁹Bi

Jing Liu, Song Feng, Wei Jiang, Xinxiang Li, Min Xiao, Pinjing Cheng, Jieming Xue, Baoqian Li, Jirong Zhao, Luyan Tao, Peng Luan, Wenxin Huang, Youchun Xiao, Sijia Han, Cunzhi Deng, Shiqi Tang, Yixi Chen, Mengyan Wang, Shiqing Yuan, Bo Zheng

Published: , doi: 10.1088/1674-1137/ae5ef9

Abstract:
Accurate neutron capture cross section data are essential for validating nuclear models, understanding the origin of heavy elements, and improving reactor safety assessments. Measuring weakly absorbing nuclides at the milli-barn scale is challenging due to low-intensity signals, high-level environmental background, and sensitivity to target impurities. To investigate the capability of milli-barn scale neutron capture cross section measurement using the

\begin{document}$\text{C}_6\text{D}_6$\end{document}

detectors on the Back-n white neutron facility of the China Spallation Neutron Source (CSNS), an experiment on

\begin{document}$^{209}$\end{document}

Bi

\begin{document}$(n, \gamma)$\end{document}

was performed. The data were processed using the time-of-flight (TOF) method and the pulse height weighting technique (PHWT). Due to the very small capture cross section of

\begin{document}$^{209}$\end{document}

Bi and the complex background, the experimental consequence showed strong statistical fluctuations, making it difficult to identify resonance structures. To address this, the average capture cross section was determined by optimizing the energy binning. The reasons for the obscured resonance structures resulted by the background were analyzed, and possible solutions were proposed. This study provides useful experience for measuring low cross section nuclides using the

\begin{document}$\text{C}_6\text{D}_6$\end{document}

detectors.

Prospects for discovering strongly decaying doubly heavy T_bc tetraquark states at LHCb

Mingjie Feng, Yiming Li, Hua-Sheng Shao

Published: , doi: 10.1088/1674-1137/ae5a87

Abstract:
We investigate the discovery potential of the

\begin{document}$T_{bc}$\end{document}

state with

\begin{document}$J^P = 0^+$\end{document}

in proton-proton (

\begin{document}$pp$\end{document}

) collisions at LHCb at a center-of-mass energy of

\begin{document}$\sqrt{s} = 13~{\rm{TeV}}$\end{document}

. The study focuses on the decay channel

\begin{document}$T_{bc} \to B^- D^+$\end{document}

. A phenomenological approach is employed to construct the background model based on the associated production of B and D mesons, incorporating previously published LHCb results. Background processes are simulated using

\begin{document}${\mathtt{MadGraph5\_aMC@NLO}}$\end{document}

and

\begin{document}${\mathtt{Pythia8.3}}$\end{document}

. We explore the parameter space of the

\begin{document}$T_{bc}$\end{document}

mass, width, production cross section, and the effective double-parton scattering cross section (

\begin{document}$\sigma_{{\rm{eff}}}$\end{document}

) relevant for the

\begin{document}$B D$\end{document}

meson background. The integrated luminosity required for a

\begin{document}$5\sigma$\end{document}

discovery at LHCb is evaluated under various assumptions. In particular, we consider three representative

\begin{document}$T_{bc}$\end{document}

production cross section scenarios: an optimistic estimate of

\begin{document}$103~{\rm{nb}}$\end{document}

, an intermediate value of

\begin{document}$18~{\rm{nb}}$\end{document}

obtained by scaling from the

\begin{document}$T_{cc}^+$\end{document}

production cross section, and a conservative lower bound of

\begin{document}$0.3~{\rm{nb}}$\end{document}

. We find that a

\begin{document}$5\sigma$\end{document}

observation is achievable for a production cross section of

\begin{document}$103~{\rm{nb}}$\end{document}

, which is expected to be within reach during Run~4. In contrast, the more realistic cross section estimate of

\begin{document}$18~{\rm{nb}}$\end{document}

requires the full Run~5 dataset (

\begin{document}$300~{\rm{fb}}^{-1}$\end{document}

) under the most favorable parameter choices. For the conservative scenario, no significant signal would be observable even with

\begin{document}$300~{\rm{fb}}^{-1}$\end{document}

. In addition, we estimate the minimum observable

\begin{document}$\sigma(T_{bc}) \times {\cal{B}}(T_{bc} \to B^- D^+)$\end{document}

for a

\begin{document}$5\sigma$\end{document}

discovery under different luminosity scenarios, providing guidance for future experimental searches at LHCb.

Revisiting critical orbits of test particles traveling in a black hole background

Ping Li, Jun Cheng, Jiang-he Yang

Published: , doi: 10.1088/1674-1137/ae5d29

Abstract:
This paper systematically revisits the critical orbits of test particles in various black hole backgrounds, including Schwarzschild, Reissner–Nordströom, Kerr, and Kerr–Newman spacetimes. We identify the critical orbits directly from the root structure of the radial equation, and we provide explicit expressions that relate the relevant parameters—energy, angular momentum, and charge-to-mass ratio—to the critical radius, as well as explicit formulas for the critical orbits in each case. Special attention is given to the relationships among the photon spheres, black hole shadows, and critical null geodesics. We also present extensive numerical results.

Testing a Linear Relation: Short-Range Correlations and the EMC Effect for Gluons and Quarks in Nuclei

Xiao Liang, Chun-Yuan Li, Bin-Peng Shang, Zong-Guo Si, Hong-Xin Wang, Xing-Hua Yang, Dai-Xing Zhang

Published: , doi: 10.1088/1674-1137/ae76fa

Abstract:
A dark photon is an Abelian gauge boson arising from a new

\begin{document}$ U(1)_D $\end{document}

gauge symmetry, coupled to the Standard Model through kinetic mixing. The mixing parameter ϵ induces an effective coupling to the electromagnetic current, while

\begin{document}$ g_\chi $\end{document}

couples the dark photon to a stable dark matter particle χ. We study

\begin{document}$ J/\psi $\end{document}

two-body and four-body decays mediated by a light dark photon (

\begin{document}$ m_U \lt 3.0 $\end{document}

GeV) within the non-relativistic QCD (NRQCD) framework, considering both visible decays of the dark photon into SM fermions and invisible decays into dark sector particles. We investigate the detection sensitivity of BESIII and STCF experiments to the dark photon mass

\begin{document}$ m_U $\end{document}

and kinetic mixing parameter ϵ. Our results show that, for two-body final states with

\begin{document}$ m_U<2m_\chi $\end{document}

, BESIII sets ϵ upper limits of

\begin{document}$ 9.3\times10^{-4} $\end{document}

and

\begin{document}$ 7.6\times10^{-4} $\end{document}

for lepton-pair and hadronic signals, respectively, while STCF yields

\begin{document}$ 3.7\times10^{-4} $\end{document}

and

\begin{document}$ 3.1\times10^{-4} $\end{document}

. For invisible decays (

\begin{document}$ m_U\ge 2m_\chi $\end{document}

), BESIII achieves an ϵ limit of

\begin{document}$ 1.4\times10^{-3} $\end{document}

in the mass range

\begin{document}$ 0.3\sim0.8 $\end{document}

GeV, and STCF reaches

\begin{document}$ 2.3\times10^{-4} $\end{document}

in

\begin{document}$ 0.3\sim1.9 $\end{document}

GeV; no signals are expected in other mass regions, and visible decays are severely suppressed throughout. For four-body decay channels, BESIII yields an ϵ upper limit of

\begin{document}$ 7.6\times10^{-5} $\end{document}

for

\begin{document}$ m_U<2.2 $\end{document}

GeV, whereas STCF achieves

\begin{document}$ 1.2\times10^{-5} $\end{document}

over the full mass range. When

\begin{document}$ m_U\ge 2m_\chi $\end{document}

, visible modes are nearly excluded; BESIII and STCF set ϵ limits from invisible decays of

\begin{document}$ 8.8\times10^{-5} $\end{document}

for

\begin{document}$ m_U \lt 2.4 $\end{document}

GeV and

\begin{document}$ 1.4\times10^{-5} $\end{document}

for

\begin{document}$ m_U \lt 2.8 $\end{document}

GeV, respectively, with no detectable signals at higher masses. Except for the limit of

\begin{document}$ 9.3\times10^{-4} $\end{document}

, all the above ϵ bounds lie in regions that are not currently excluded by collider experiments. Compared with the constraints from two-body final state processes, the limits derived from four-body decay channels lie well below existing experimental bounds, providing supportive references for constraining this parameter in BESIII and STCF experiments. Numerical results for the decay ratios

\begin{document}$ \Gamma/\Gamma_{J/\psi} $\end{document}

, expected event numbers, significance

\begin{document}$ S/\sqrt{B} $\end{document}

, and

\begin{document}$ p_T $\end{document}

distributions are presented where applicable.

Quasinormal modes of an electrically charged Kalb-Ramond black hole

Yun-Tao Gu, Wen-Di Guo, Yu-Xiao Liu

Published: , doi: 10.1088/1674-1137/ae6ed3

Abstract:
Lorentz violation serves as a significant feature in many modified theories of gravity. In particular, spontaneous Lorentz violation induced by the Kalb-Ramond field has attracted considerable attention. Recently, an electrically charged black hole solution within the Kalb-Ramond framework was proposed. In this study, we investigate the odd-parity quasinormal modes of the resulting non-decouplable system of the gravitational and electromagnetic perturbations using both the matrix-valued continued fraction method and the matrix-valued direct integration method. Additionally, we develop a new approach to distinguish between different modes in such non-decouplable systems. An error analysis is performed, and the influence of Lorentz violation on the fundamental quasinormal modes is systematically analyzed within a suitable parameter range.

Periodic orbits and observational accretion disk around a Schwarzschild-like black hole surrounded by dark matter halo

Javokhir Sharipov, Tursunali Xamidov, Qiang Wu, Sanjar Shaymatov, Tao Zhu

Published: , doi: 10.1088/1674-1137/ae6b2f

Abstract:
In this work, we investigate the dynamics of periodic orbits and the properties of accretion disks around a Schwarzschild-like black hole (BH) immersed in a King-type dark matter (DM) halo. Our analysis focuses on how the presence of the King DM halo influences both the behavior of periodic orbits and the radiative characteristics of the accretion disk. We begin by examining time-like periodic geodesic orbits for various configurations characterized by different energy and angular momentum values, represented by the integers

\begin{document}$ (z, w, v) $\end{document}

. Furthermore, we explore the effects of the King DM halo on time-like periodic geodesics, marginally bound orbits, and innermost stable circular orbits, thereby providing a deeper understanding of how the DM halo environment modifies the behavior of these stable orbits and timelike particle geodesics. Finally, we analyze the null geodesics and the accretion disk properties by studying their direct and secondary images, redshift distributions, and radiation fluxes as observed at infinity for a range of inclination angles. This approach allows us to gain valuable insights into the spacetime geometry of a Schwarzschild-like BH within the King-type DM halo, its physical and radiative properties in the accretion disk, and the corresponding observational implications.

Influence of nonlinear electrodynamics on time-dependent accretion dynamics around Kalb-Ramond black hole

Rana Muhammad Zulqarnain, Orhan Donmez, G. Mustafa, Abdelmalek Bouzenada, Ertan Güdekli, Shukhrat Mardonov

Published: , doi: 10.1088/1674-1137/ae66d0

Abstract:
In this paper, we analyze the dynamics of test particles in a Kalb-Ramond black hole (BH) spacetime coupled to nonlinear electrodynamics. After explicitly constructing the corresponding BH metric, including the nonlinear electromagnetic contributions to the geometry, we study the geodesic equations, focusing on the effective potential, the innermost stable circular orbits (ISCOs), and test-particle trajectories. This provides a quantitative description of orbital motion under the combined gravitational, Kalb-Ramond, and nonlinear electromagnetic effects. We then examine small perturbations of circular geodesics and derive the associated epicyclic frequencies for local and distant observers. These results show how the Kalb-Ramond field and nonlinear electrodynamics influence orbital stability, quasi-periodic oscillations (QPOs), and possible high-energy astrophysical signatures. Next, we numerically model Bondi-Hoyle-Lyttleton (BHL) accretion onto Kalb-Ramond BHs to assess how spacetime parameters affect flow morphology and dynamics. As the deformation parameters increase, the shock cone becomes more collimated, the stagnation point moves closer to the event horizon, and the matter density inside the cone decreases. For small deformations, QPO frequencies exhibit systematic shifts with enhanced oscillation amplitudes, whereas strong deformations damp the oscillations and produce a smooth, quasi-steady accretion rate. In this way, we illustrate a direct connection between spacetime geometry, shock-cone structure, and accretion variability, demonstrating that accretion dynamics serve as a sensitive probe of Kalb-Ramond BH spacetimes.

The resonance effect for the CP asymmetry associated with the process ${\boldsymbol\omega{\bf\to}{\boldsymbol\pi}^+{\boldsymbol\pi}^-{\boldsymbol\pi}^{\bf 0} }$

Xi-Liang Yuan, Gang Lü, Na Wang, Chao Wang

Published: , doi: 10.1088/1674-1137/ad8ec2

Abstract:
The direct CP asymmetry in the weak decay process of hadrons is commonly attributed to the weak phase of the CKM matrix and the indeterminate strong phase. We propose a method to generate a significant phase difference through the interference between ρ and ω mesons, taking into account the G-parity allowed decay process of

\begin{document}$\omega \rightarrow \pi^{+}\pi^{-}\pi^{0}$\end{document}

and the G-parity-suppressed decay process of

\begin{document}$\rho^{0} \rightarrow \pi^{+}\pi^{-}\pi^{0}$\end{document}

in B meson decays. This interference can lead to notable changes in the CP asymmetry within the interference region. Additionally, we calculate the integral results for different phase space regions of the four-body decay process. We hope that our work provides valuable theoretical guidance for future experimental investigations on CP asymmetry in these decays.

Just Accepted