Chinese Physics C

Universality of thermodynamic relation with corrections in Einstein-Bel-Robinson gravity black holes

Hai-Long Zhen, Huai-Fan Li, Yu-Bo Ma

2025, 49(11): 111001. doi: 10.1088/1674-1137/ade6d3

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Abstract:
The generalized thermodynamic extremum relation, as proposed by Goon and Penco, establishes a novel theoretical framework for studying spacetime thermodynamics. However, previous investigations generally assumed that the black hole state parameter is solely a first-order function of the perturbation parameter when exploring the Goon-Penco relation in diverse spacetime contexts. An analytic expression for the perturbation parameter as a function of the black hole entropy can be expressed by treating the black hole mass as constant. The present study addresses this limitation and provides insight into the universal Goon-Penco relation when multiple thermodynamic state parameters behave as higher order functions of the perturbation parameters. Notably, we have not only established a universal relational formula for multiple state variables, but more importantly, we have proposed an innovative conjecture that reveals the existence of a universal relation between displaced thermodynamic quantities in spacetime in the context of an arbitrary black hole. These theoretical breakthroughs are expected to enable new exploration directions for quantum gravity research.

Possible explanations of the observed Λ_c resonances

Yu-Bin Zhang, Li-Ye Xiao, Xian-Hui Zhong

2025, 49(11): 112001. doi: 10.1088/1674-1137/aded00

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Abstract:
Inspired by the latest experimental progress, we systematically study the Okubo-Zweig-Iizuka (OZI)-allowed two-body strong decay properties of 1P-, 1D-, 2S-, and 2P-wave

\begin{document}$ \Lambda_c $\end{document}

baryons within the j-j coupling scheme in the framework of the quark pair creation model. The calculations indicate the following. (i) Taking the observed states

\begin{document}$ \Lambda_c(2595)^+ $\end{document}

and

\begin{document}$ \Lambda_c(2625)^+ $\end{document}

as the 1P-wave λ-mode states

\begin{document}$ \Lambda_c|J^P=1/2^-,1\rangle_{\lambda} $\end{document}

and

\begin{document}$ \Lambda_c|J^P=3/2^-,1\rangle_{\lambda} $\end{document}

, respectively, we can reproduce the experimental data well in theory. (ii) Combined with the measured mass and decay properties of

\begin{document}$ \Lambda_c(2860)^+ $\end{document}

, this excited state can be explained as the 1D-wave λ-mode state

\begin{document}$ \Lambda_c|J^P=3/2^+,1\rangle_{\lambda\lambda} $\end{document}

. (iii) The newly observed state

\begin{document}$ \Lambda_c(2910)^+ $\end{document}

may be assigned as one of the 1P-wave ρ-mode states

\begin{document}$ \Lambda_c|J^P=3/2^-,2\rangle_{\rho} $\end{document}

or

\begin{document}$ \Lambda_c|J^P=5/2^-,2\rangle_{\rho} $\end{document}

. Meanwhile, we notice that the partial decay width ratio between

\begin{document}$ \Sigma_c\pi $\end{document}

and

\begin{document}$ \Sigma_c^*\pi $\end{document}

for the two candidates is significantly different. Hence, experimental progress in this ratio measurement may elucidate the nature of

\begin{document}$ \Lambda_c(2910)^+ $\end{document}

. (iv) According to the properties of

\begin{document}$ \Lambda_c(2765)^+ $\end{document}

, we find that the 2S-wave λ-mode state

\begin{document}$ \Lambda_{c1}|J^P=1/2^+,0\rangle_{\lambda} $\end{document}

is a potential candidate. (v) The 2P-wave λ-mode state

\begin{document}$ \Lambda_{c1}|J^P=3/2^-,1\rangle_{\lambda} $\end{document}

is most likely to be a good assignment of the controversial state

\begin{document}$ \Lambda_c(2940)^+ $\end{document}

. Both the total decay width and partial decay ratio between

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

and

\begin{document}$ \Sigma_c\pi $\end{document}

are in good agreement with observations. (vi) In addition, for the missing

\begin{document}$ \Lambda_c $\end{document}

excitations, we obtain their strong decay properties and hope these are useful for future experimental exploration.

Search for heavy vector-like B quark via pair production in fully hadronic channels at CLIC

Shuo Yang, Yi-Hang Wang, Peng-Bo Zhao, Ji-Long Ma

2025, 49(11): 113101. doi: 10.1088/1674-1137/adf183

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Abstract:
Vector-like quarks (VLQs) feature in new physics models beyond the standard model (SM) to address certain problems it faces. In this study, we investigate the pair production of TeV-scale vector-like B quark (VLQ-B) at the proposed 3 TeV compact linear collider (CLIC) using a simplified effective lagrangian framework. We consider the decay modes of

\begin{document}$ B\rightarrow bZ $\end{document}

and

\begin{document}$ B\rightarrow bh $\end{document}

, coupled with the hadronic decay of Z and h bosons. The large mass of VLQ-B results in highly boosted Z or h bosons, which tend to form fat-jets. Using detector simulation of the signal and background events, along with jet clustering employing a large radius R, we conduct signal-background analyses. Exclusion limits at the 95% confidence level and 5

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

discovery prospects are obtained assuming an integrated luminosity of 5 ab⁻¹.

Study of excited D and D_s mesons in a relativized quark model

Saba Noor, Faisal Akram, Bilal Masud

2025, 49(11): 113102. doi: 10.1088/1674-1137/adec50

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Abstract:
We use a modified relativistic quark model to study the properties of excited charmed and charmed strange mesons. We calculate the masses and wave functions of conventional charmed and charmed strange mesons incorporating both spin and S-D mixing effects and fit parameters of the potential model with known experimental states using differential evolution techniques. Using leading Born-Oppenheimer expansion, we compute the spectrum and wave functions of the first gluonic excited state of charmed and charmed strange mesons. We examine the effects of gluonic excitation on the spectrum of the resulting hybrid mesons. Using our calculated spectrum and wave functions, we determine the radiative transitions of the conventional and hybrid open charm mesons. We compare our calculations with experimental data and other works. We expect our results will be beneficial in the detection of charmed and charmed strange conventional and hybrid mesons.

Role and contribution of the resonance effect for the decay process of ${ \bar {\boldsymbol B}^{\bf 0}_{\boldsymbol s} \boldsymbol\rightarrow \boldsymbol\pi^{+}\boldsymbol\pi^{-}{\boldsymbol P}}$

Xi-Liang Yuan, Chao Wang, Zhuang-Dong Bai, Gang Lü

2025, 49(11): 113103. doi: 10.1088/1674-1137/ade6d8

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Abstract:
The magnitude of the direct CP asymmetry generated during the weak decay of hadrons is attributed to the weak phase and certain strong phases. The weak phase originates from the CKM matrix, while a strong phase may result from the resonance effect produced by the mixing of vector mesons

\begin{document}$ V\left\{\rho^{0}(770),\,\omega(782),\,\phi(1020)\right\} $\end{document}

to

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

meson pairs.

\begin{document}$ \rho^{0}(770) $\end{document}

can decay directly into

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

meson pairs; both

\begin{document}$ \omega(782) $\end{document}

and

\begin{document}$ \phi(1020) $\end{document}

can also decay into

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

meson pairs, with a small contribution from isospin symmetry breaking. The main contribution for the middle state vector meson

\begin{document}$ \rho^{0}(770)-\omega(782)-\phi(1020) $\end{document}

interference is the mix of

\begin{document}$ \rho^{0}(770) $\end{document}

,

\begin{document}$ \omega(782)-\rho^{0}(770) $\end{document}

, and

\begin{document}$ \phi(1020)-\rho^{0}(770) $\end{document}

. We calculated the CP asymmetry and decay branching ratio for

\begin{document}$ \bar{B}^0_{s} \rightarrow \pi^+ \pi^- \pi^0 (\bar K ^{0}) $\end{document}

within the framework of QCD factorization and compared them with previous studies. We also analyzed the

\begin{document}$ \bar{B}^0_{s} \rightarrow \pi^+ \pi^- \eta(\eta^{(')}) $\end{document}

decay process. The results show that the CP asymmetry of these four decay processes is significantly enhanced, especially for the

\begin{document}$ \bar{B}^0_{s} \rightarrow \pi^+ \pi^- \bar K ^{0} $\end{document}

decay process. Moreover, the decay branching ratio also changes under the resonance effect. These results might provide support for the experimental analysis of the

\begin{document}$ \bar B^{0}_s $\end{document}

meson.

Probing the ATOMKI X17 vector boson using Dalitz decays V → Pe⁺e⁻

C. T. Tran, M. A. Ivanov, A. T. T. Nguyen

2025, 49(11): 113105. doi: 10.1088/1674-1137/adf1f7

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Recent anomalies observed in

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

nuclear transitions of

\begin{document}$ ^8 {{\rm{Be}}} $\end{document}

,

\begin{document}$ ^4 {\rm{He}} $\end{document}

, and

\begin{document}$ ^{12} {\rm{C}} $\end{document}

by the ATOMKI collaboration may hint at the existence of a vector boson with a mass around 17 MeV, which is referred to as X17. If it exists, this boson would affect similar processes in particle physics, including the Dalitz decays of vector mesons. Recently, the BESIII collaboration measured the Dalitz decay

\begin{document}$ D^{*0}\to D^0e^+e^- $\end{document}

for the first time and reported a

\begin{document}$ 3.5\sigma $\end{document}

excess over the theoretical prediction based on the vector meson dominance (VMD) model. This excess may be another signal of X17. In this study, we investigate the possible effects of X17 on the Dalitz decays

\begin{document}$ D^*_{(s)}\to D_{(s)}e^+e^- $\end{document}

,

\begin{document}$ B^*_{(s)}\to B_{(s)}e^+e^- $\end{document}

, and

\begin{document}$ J/\psi\to \eta_ce^+e^- $\end{document}

. The required hadronic form factors are calculated within the framework of our covariant confined quark model without relying on heavy quark effective theory or the VMD model. We present predictions for the Dalitz decay widths and the ratios

\begin{document}$ R_{ee}(V)\equiv \Gamma(V\to Pe^+e^-)/\Gamma(V\to P\gamma) $\end{document}

within the standard model and in several new physics scenarios involving modifications attributed to X17. Our results are compared with other theoretical calculations.

Effect of neutrino electromagnetic properties on quasielastic neutral-current neutrino-nucleus scattering

K. S. Kim, P. T. P. Hutauruk, Seung-il Nam, Chang Ho Hyun

2025, 49(11): 113106. doi: 10.1088/1674-1137/adf1f2

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Abstract:
In the quasielastic region, we investigate the impact of neutrino electromagnetic properties—constrained by recent experimental data—on the electroweak neutral current reaction process

\begin{document}$ ^{12}{\rm{C}}(\nu,\nu') $\end{document}

. To describe nuclear dynamics relativistically, we employ the quantum hadrodynamics model, which can reliably reproduce experimental results in this kinematic regime. In this study, we explore physics beyond the Standard Model by incorporating the neutrino’s magnetic and electric dipole form factors, as well as its charge radius, into the electroweak interaction framework within ¹²C. Specifically, we use experimentally derived values for the neutrino charge radius and magnetic moment at zero four-momentum transfer (

\begin{document}$ Q^2 = 0 $\end{document}

) to compute the differential cross section of ν-¹²C scattering. Our results indicate that the contributions from the charge radius and electric dipole form factor are negligible. However, the magnetic moment exhibits a pronounced dependence on

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

, and its effect becomes significant at low momentum transfers.

Study of ${\boldsymbol\tau\rightarrow {\boldsymbol e M^+ M^-}}$ decays in N-B-LSSM

Rong-Zhi Sun, Shu-Min Zhao, Shuang Di, Xing-Xing Dong

2025, 49(11): 113110. doi: 10.1088/1674-1137/adec4c

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Abstract:
Within the framework of the next-to-minimal supersymmetric (SUSY) extension of the Standard Model (SM) with a local B-L gauge symmetry (N-B-LSSM), we study lepton flavor violating (LFV)

\begin{document}$ \tau\rightarrow e M^+ M^- $\end{document}

decays:

\begin{document}$ \tau \rightarrow e \pi^+\pi^- $\end{document}

,

\begin{document}$ \tau \rightarrow e \pi^+K^- $\end{document}

, and

\begin{document}$ \tau \rightarrow e K^+K^- $\end{document}

. Based on the latest experimental data, the influence of different sensitive parameters on the branching ratios is considered. It can be seen from the numerical analysis that the main sensitive parameters and LFV sources are non-diagonal elements corresponding to the initial and final leptons. This work can provide a basis for discovering the existence of new physics (NP).

Present and future of the Rare-RI Ring Facility at RIBF

T. Yamaguchi, Y. Yamaguchi

2025, 49(11): 114003. doi: 10.1088/1674-1137/adf1f5

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Abstract:
An overview of the storage ring facility called Rare-RI Ring (R3) at the RI Beam Factory (RIBF), RIKEN is provided herein. The primary objective is obtaining precision atomic masses to understand astrophysical nucleosynthesis. The R3 is located downstream of the fragment separator BigRIPS in the OEDO-SHARAQ branch. Randomly produced radioactive ions are individually identified using auxiliary detectors at BigRIPS. Only a single ion of interest is injected into the R3 using the dedicated fast kicker system and ejected after thousands of revolutions in an event-by-event scheme. Revolution times under the isochronous ion-optical condition provide the mass-to-charge ratios of stored ions. Several commissioning campaigns, physics programs, and technical upgrades are summarized. In addition to mass measurements of exotic nuclei, future perspectives of new experimental opportunities are addressed.

Double-folding analysis of elastic and inelastic ³He-nucleus scattering at 60 MeV

2025, 49(11): 114101. doi: 10.1088/1674-1137/ade1cb

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Abstract:
This study investigated the elastic and inelastic scattering of ³He particles from ¹²C, ¹⁶O, ²⁴Mg, and ²⁸Si nuclei at 60 MeV using a double-folding approach with four newly derived effective nucleon-nucleon (NN) interactions (R3Y(HS), R3Y(L1), R3Y(W), and R3Y(Z)) derived from the relativistic mean-field theory. The four derived effective NN interactions exhibited strong sensitivity to the choice of exchange potential. Regularizing the NN interactions improved the agreement between calculated folded potentials and experimental data. Normalization constants for the R3Y(HS) interaction suggested its superiority over the R3Y(L1) and R3Y(W) interactions within the double-folding framework. Transition potentials based on two models, deformed potential and double folding potential, were used to describe inelastic scattering. Physically consistent deformation parameters were obtained. The deformed potential model yielded better results for ¹²C and ¹⁶O, whereas the double folding model performed better for ²⁴Mg and ²⁸Si, suggesting that the advantage of the double folding model is limited to lighter targets. The Bohr-Mottelson transition density effectively described 2⁺ states; however, it was less suitable for the 3⁻ state of ¹⁶O, for which a Tassie-like transition density provided improved agreement.

Squeezing effect on three-dimensional Hanbury Brown-Twiss radii

2025, 49(11): 114102. doi: 10.1088/1674-1137/ade4a8

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Abstract:
This study examines the impact of the squeezing effect caused by the in-medium mass modification of particles on the three-dimensional Hanbury Brown-Twiss (HBT) radii. An analysis is conducted on how the squeezing effect impacts the three-dimensional HBT radii of

\begin{document}$ \phi\phi $\end{document}

,

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

, and

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

. The squeezing effect suppresses the impact of transverse flow on the transverse source distribution and broadens the space-time rapidity distribution of the particle-emitting source, leading to an increase in the HBT radii, particularly in the out and longitudinal directions. This phenomenon becomes more significant for higher transverse pair momentum, resulting in a non-monotonic decrease in the HBT radii with increasing transverse pair momentum. The impact of the squeezing effect on the HBT radii is more pronounced for

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

than for

\begin{document}$ \phi\phi $\end{document}

. Furthermore, this effect is also more significant for ϕϕ than for

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

. The findings presented in this paper could offer fresh perspectives on investigating the squeezing effect.

Improvement of nuclear semi-empirical mass formula by including shell effect

Qing Wu, Wei-Feng Li, Zhong-Ming Niu, Hao-Zhao Liang, Min Shi

2025, 49(11): 114103. doi: 10.1088/1674-1137/ade954

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Shell effect plays an important role in nuclear mass predictions, especially for the nuclei around the magic numbers. In this study, a new semi-empirical shell correction term is constructed to improve the mass description of the Bethe-Weizsäcker (BW) formula. For nuclei with

\begin{document}$ Z,~N \geqslant 8$\end{document}

, the root mean square (rms) deviation of the newly proposed formula with respect to the latest nuclear mass evaluation dataset AME2020 is 0.887 MeV, inducing a 72.23% reduction compared to the rms deviation of 3.194 MeV for the BW formula. The deviations between the theoretical predictions and experimental data are within 1.5 MeV for 91.90% of the nuclei. In addition, the new mass formula significantly improves the predictions of the binding energies for magic nuclei. The rms deviation of our formula for the binding energy of magic nuclei is only 1.065 MeV, which is a 80.08% reduction compared with that of the BW formula.

Thermodynamic phase transition and Joule-Thomson expansion of a quantum corrected black hole in AdS spacetime

Rui-Bo Wang, Lei You, Shi-Jie Ma, Jian-Bo Deng, Xian-Ru Hu

2025, 49(11): 115102. doi: 10.1088/1674-1137/ade4a9

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Abstract:
The thermodynamics in the extended phase space of a quantum corrected black hole (BH) proposed recently is presented in this paper. Our study shows that the phase transition behavior of the BH is analogous to that of a conventional Schwarzschild BH in anti-de Sitter (AdS) space; however, a critical temperature exists such that, when the BH temperature exceeds this critical value, the small and large BH phases become separated, and no phase transition occurs. Owing to the introduction of the quantum parameter ξ, the BH equation of state splits into two branches. One branch reduces to the Schwarzschild-AdS case as

\begin{document}$ \xi\to0$\end{document}

, with its phase transition pressure lower than the critical pressure; the phase transition pressure in the other branch is greater than the critical pressure. This study shows that the

\begin{document}$ T-r_{+}$\end{document}

phase transition and heat capacity of the recently proposed BH are similar to those of the Schwarzschild-AdS BH. The Joule-Thomson expansion is divided into two stages: in the earlier stage, the BH pressure increases until it reaches a maximum; in the later stage, the pressure gradually decreases. In each stage, the BH may undergo an inversion point, resulting in an inversion curve with two branches. In addition, each stage has a minimum inversion mass, below which any BH (in each respective stage) has no inversion point.

Formation of regular black hole from baryonic matter

Vitalii Vertogradov, Ali Övgün, Daniil Shatov

2025, 49(11): 115103. doi: 10.1088/1674-1137/ade95c

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We present a family of exact, singularity-free solutions describing the collapse of baryonic matter characterized by a barotropic equation of state whose coefficient

\begin{document}$ \alpha(r,v) $\end{document}

varies in both radius and time. By matching these interior solutions to the Husain exterior metric, we obtain a self-consistent, dynamical spacetime representing a regular black hole. Although the pressure profile of our models grows with the radius and eventually violates the dominant energy condition beyond a critical surface, it necessitates an external junction for ensuring a globally well-defined spacetime, and the interior solution remains non-singular throughout the collapse. We further analyze the optical properties of these regular black holes and find that both the photon sphere radius and corresponding shadow radius increase monotonically as the local equation of state parameter α is raised. Moreover, the matching interface between the interior and exterior metrics naturally suggests a phase transition in the collapsing fluid, which can postpone the formation of an apparent horizon. Taken together, our results not only highlight novel physical features of horizon formation in regular collapse models but also identify characteristic shadow signatures that can be tested by future observations.

Constraining polymerized black holes with quasi-circular extreme mass-ratio inspirals

Sen Yang, Yu-Peng Zhang, Tao Zhu, Li Zhao, Yu-Xiao Liu

2025, 49(11): 115107. doi: 10.1088/1674-1137/adef1a

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In this study, we focus on the gravitational waves emitted by a stellar-mass object in a quasi-circular inspiral orbit around a central supermassive polymerized black hole in loop quantum gravity. Treating the stellar-mass object as a massive test particle, we derive its equations of motion and the corresponding radial effective potential. We find that the peak of the radial effective potential decreases with the quantum parameter

\begin{document}$ \hat{k} $\end{document}

. We also examine the impact of quantum corrections on the properties of stable circular orbits (SCOs) around the polymerized black hole. We model the smaller object's trajectory as an adiabatic evolution along SCOs using a semi-relativistic approach. In this method, the motion of the object is described by relativistic geodesics, and changes in the object's energy and orbital angular momentum due to gravitational radiation are calculated using the mass quadrupole formula. The corresponding gravitational waveforms are generated using the numerical kludge method, revealing that quantum corrections cause phase advances in the gravitational waveforms. We further analyze the potential constraints on the quantum parameter

\begin{document}$ \hat{k} $\end{document}

from future space-based gravitational wave observations, concluding that the constraints on

\begin{document}$ \hat{k} $\end{document}

imposed by these observations will likely be stronger than those imposed by black hole shadow measurements.

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