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2025-9 Contents
2025, 49(9): 1-3.
Abstract:
LETTERS
Precise measurement of the χc0 resonance parameters and branching fractions of χc0,c2 → π+π−/K+K−
M. Ablikim, M. N. Achasov, P. Adlarson, O. Afedulidis, X. C. Ai, R. Aliberti, A. Amoroso, Y. Bai, O. Bakina, I. Balossino, Y. Ban, H.-R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Cetin, X. Y. Chai, J. F. Chang, G. R. Che, Y. Z. Che, G. Chelkov, C. Chen, C. H. Chen, Chao Chen, G. Chen, H. S. Chen, H. Y. Chen, M. L. Chen, S. J. Chen, S. L. Chen, S. M. Chen, T. Chen, X. R. Chen, X. T. Chen, Y. B. Chen, Y. Q. Chen, Z. J. Chen, Z. Y. Chen, S. K. Choi, G. Cibinetto, F. Cossio, J. J. Cui, H. L. Dai, J. P. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, C. Q. Deng, Z. Y. Deng, A. Denig, I. Denisenko, M. Destefanis, F. De Mori, B. Ding, X. X. Ding, Y. Ding, J. Dong, L. Y. Dong, M. Y. Dong, X. Dong, M. C. Du, S. X. Du, Y. Y. Duan, Z. H. Duan, P. Egorov, Y. H. Fan, J. Fang, S. S. Fang, W. X. Fang, Y. Fang, Y. Q. Fang, R. Farinelli, L. Fava, F. Feldbauer
2025, 49(9): 091001. doi: 10.1088/1674-1137/ade95f
Abstract:
By analyzing a \begin{document}$\psi(3686)$\end{document} data sample containing \begin{document}$(107.7\pm0.6)\times10^{6}$\end{document} events taken with the BESIII detector at the BEPCII storage ring in 2009, the \begin{document}$\chi_{c0}$\end{document} resonance parameters are precisely measured using \begin{document}$\chi_{c0,c2} \to \pi^+\pi^-/K^+K^-$\end{document} events. The mass of \begin{document}$\chi_{c0}$\end{document} is determined to be \begin{document}$M(\chi_{c0})=(3415.63\pm0.07\pm0.07\pm0.07$\end{document}) MeV/\begin{document}$c^2$\end{document}, and its full width is \begin{document}$\Gamma(\chi_{c0})=(12.52\pm0.12\pm0.13)~{\rm{MeV}}$\end{document}, where the first uncertainty is statistical, the second systematic, and the third for mass comes from \begin{document}$\chi_{c2}$\end{document} mass uncertainty. These measurements improve the precision of \begin{document}$\chi_{c0}$\end{document} mass by a factor of four and width by one order of magnitude over the previous individual measurements, and significantly boost our knowledge about the charmonium spectrum. Together with additional \begin{document}$(345.4\pm2.6)\times10^{6}$\end{document} \begin{document}$\psi(3686)$\end{document} data events taken in 2012, the decay branching fractions of \begin{document}$\chi_{c0,c2}\to\pi^+\pi^-/K^+K^-$\end{document} are measured as well, with precision improved by a factor of three compared to previous measurements. These \begin{document}$\chi_{c0}$\end{document} decay branching fractions provide important inputs for the study of glueballs.
PARTICLES AND FIELDS
Parameterization of zero-skewness unpolarized GPDs
Hossein Vaziri, Mohammad Reza Shojaei
2025, 49(9): 093101. doi: 10.1088/1674-1137/add923
Abstract:
Recent parameterizations of parton distribution functions (PDFs) have led to the determination of the gravitational form factors pertaining to the dependence of nucleons on their generalized parton distributions (GPDs) in the limit \begin{document}$\xi \to 0 $\end{document}. This study aims to obtain the flavor division of nucleon electromagnetic and gravitational form factors using the VS24 ansatz and two PDFs at the \begin{document}$ N^3L0 $\end{document}approximation in GPDs. The PDFs and GPD formalism enable the calculation of various form factors of nucleons in different approximations, as well as the calculation of the electric radius of nucleons. The study, despite its high approximation complexity, enhances the accuracy of calculations and aligns them more closely with experimental values.
A three-body form factor at sub-leading power in the high-energy limit: planar contributions
Yishuai Guo, Zhi-Feng Liu, Mingming Lu, Tianya Xia, Li-Lin Yang
2025, 49(9): 093102. doi: 10.1088/1674-1137/addcc7
Abstract:
We analyzed two-loop planar contributions to a three-body form factor at next-to-leading power in the high-energy limit, where the masses of the external particles are much smaller than their energies. Calculations were performed by exploiting differential equations for the expansion coefficients, both to facilitate linear relations among them and to derive their analytic expressions. The results are expressed in terms of generalized polylogarithms involving a few simple symbol letters. Our method can readily be applied to calculations of non-planar contributions as well. Our results provide crucial information for establishing sub-leading factorization theorems for massive scattering amplitudes in the high-energy limit.
Probing type II seesaw leptogenesis through lepton flavor violation
Chengcheng Han, Yijun Han, Sihui Huang, Zhanhong Lei
2025, 49(9): 093103. doi: 10.1088/1674-1137/ade079
Abstract:
Lepton flavor violation (LFV) offers a powerful probe of physics beyond the Standard Model, particularly in models addressing neutrino masses and the baryon asymmetry of the universe. In this study, we investigate LFV processes within the framework of type II seesaw leptogenesis, where the Standard Model is extended by an \begin{document}$S U(2)_L$\end{document} triplet Higgs field. We focus on key LFV processes, including \begin{document}$\mu^+\to e^+\gamma$\end{document}, \begin{document}$\mu^+ \to e^+e^-e^+$\end{document}, and \begin{document}$\mu \rightarrow e$\end{document} conversion in nuclei, deriving stringent constraints on the parameter space from current experimental data. We scan the 3σ range of neutrino oscillation parameters and identify the most conservative bounds consistent with existing measurements. Our results reveal that the MEG experiment currently provides the most stringent constraints in the normal ordering (NO) scenario, while the SINDRUM experiment offers comparable sensitivity in the inverted ordering (IO) case. Future experiments, such as MEG II, Mu3e, Mu2e, and COMET, are predicted to significantly improve the sensitivity, testing larger regions of the parameter space.
Probing Ds*-meson longitudinal twist-2 LCDA
Si-Hai Zhang, Tao Zhong, Hai-Bing Fu, Ya-Xiong Wang, Wan-Bing Luo
2025, 49(9): 093104. doi: 10.1088/1674-1137/add683
Abstract:
In this study, we continue an investigation of the semileptonic decays \begin{document}$ B_s\to D_s^*\ell \bar\nu_{\ell} $\end{document}. First, we derive the moments of the \begin{document}$ D_s^* $\end{document}-meson longitudinal leading-twist light-cone distribution amplitude (LCDA) based on QCD sum rules within the background field theory framework. Considering the contributions of the vacuum condensates up to dimension-six, its first ten non-zero \begin{document}$ \xi $\end{document}-moments at the initial scale \begin{document}$ \mu_0 = 1.3\; {\rm{GeV}} $\end{document} are \begin{document}$ \langle \xi^{\|, 1}_{2; D_s^*} \rangle|_{\mu_0} = -0.302_{-0.046}^{+0.038} $\end{document}, \begin{document}$ \langle\xi^{\|, 2}_{2;D_s^*}\rangle|_{\mu_0} = +0.229_{-0.034}^{+0.039} $\end{document}, \begin{document}$ \langle\xi^{\|, 3}_{2;D_s^*}\rangle|_{\mu_0} = -0.121_{-0.019}^{+0.015} $\end{document}, \begin{document}$ \langle\xi^{\|, 4}_{2;D_s^*}\rangle|_{\mu_0} = +0.101_{-0.014}^{+0.017} $\end{document}, \begin{document}$ \langle\xi^{\|, 5}_{2; D_s^*} \rangle|_{\mu_0} = -0.066_{-0.010}^{+0.009} $\end{document}, \begin{document}$ \langle\xi^{\|, 6}_{2;D_s^*}\rangle|_{\mu_0} = +0.053_{-0.007}^{+0.009} $\end{document}, \begin{document}$ \langle\xi^{\|, 7}_{2;D_s^*}\rangle|_{\mu_0} = -0.041_{-0.007}^{+0.006} $\end{document}, \begin{document}$ \langle\xi^{\|, 8}_{2;D_s^*}\rangle|_{\mu_0} = +0.037_{-0.005}^{+0.006} $\end{document}, \begin{document}$ \langle\xi^{\|, 9}_{2; D_s^*} \rangle|_{\mu_0} = -0.026_{-0.004}^{+0.003} $\end{document}, and \begin{document}$ \langle\xi^{\|, 10}_{2;D_s^*}\rangle|_{\mu_0} = +0.025_{-0.004}^{+0.004} $\end{document}. We also construct the \begin{document}$ D_s^* $\end{document}-meson longitudinal leading-twist LCDA by using the light-cone harmonic oscillator model. Then, using the above moments, we fix the model parameters \begin{document}$ \alpha_{2;D_s^*} $\end{document} and \begin{document}$ B_1^{2;D_s^*} $\end{document} using the least squares method and apply them to calculate \begin{document}$ B_s \to D_s^* $\end{document} transition form factors \begin{document}$ A_1(q^2), A_2(q^2) $\end{document} and \begin{document}$ V(q^2) $\end{document} that are derived using the QCD light-cone sum rules. In the large recoil region, we obtain \begin{document}$ A_1(0) = 0.632_{-0.135}^{+0.228}, A_2(0) = 0.706_{-0.092}^{+0.109} $\end{document}, and \begin{document}$ V(0) = 0.647_{-0.069}^{+0.076} $\end{document}. These form factors are then extrapolated to the allowed whole physical \begin{document}$ q^2 $\end{document}-region through the simplified series expansion. Finally, we obtain the branching fractions for the two decay channels of \begin{document}$ B_s\to D_s^*\ell\bar\nu_\ell $\end{document}, \begin{document}$ {\cal{B}}(B_s^0 \to D_s^{*+}e^-\bar\nu_e) = (5.45_{-1.57}^{+2.15})\times 10^{-2} $\end{document} and \begin{document}$ {\cal{B}}(B_s^0 \to D_s^{*+}\mu^-\bar\nu_\mu) = $\end{document}\begin{document}$ (5.43_{-1.57}^{+2.14})\times 10^{-2} $\end{document}. In addition, we present the CKM matrix element \begin{document}$ |V_{cb}| $\end{document} by matching the LHCb Collaboration branching fraction, yielding a value of \begin{document}$ |V_{cb}| = (40.11_{-7.49}^{+6.54})\times 10^{-3} $\end{document}.
Rotation effect on the thermodynamics of QCD matter
Fei Sun, Shuang Li, Rui Wen, Anping Huang, Wei Xie
2025, 49(9): 093105. doi: 10.1088/1674-1137/add25e
Abstract:
In this study, we investigated the impact of rotation on the thermodynamic properties of QCD matter using the three-flavor NJL model. We examined the dependencies of key thermodynamic quantities, such as the trace anomaly, specific heat, speed of sound, angular momentum, and moment of inertia, on temperature, quark chemical potential, and angular velocity. Our main finding is that the speed of sound exhibits a nonmonotonic behavior as the angular velocity varies.
HEP ML LAB: An end-to-end framework for applying machine learning to phenomenology studies
Jing Li, Hao Sun
2025, 49(9): 093106. doi: 10.1088/1674-1137/addcc9
Abstract:
Recent years have seen the development and growth of machine learning in high-energy physics. However, additional effort is required to continue exploring the use of machine learning to its full potential. To simplify the application of the existing algorithms and neural networks and to advance the reproducibility of the analysis, we developed HEP ML LAB (\begin{document}$ \mathrm{hml}$\end{document}), a Python-based, end-to-end framework for phenomenology studies. It covers the complete workflow from event generation to performance evaluation, and provides a consistent style of use for different approaches. We propose an observable naming convention to streamline the data extraction and conversion processes. In the KERAS style, we provide the traditional cut-and-count and boosted decision trees together with neural networks. We take the \begin{document}$W^+ $\end{document} tagging as an example and evaluate all built-in approaches with the metrics of significance and background rejection. With its modular design, HEP ML LAB is easy to extend and customize, and can be used as a tool for both beginners and experienced researchers.
A unitary coupled-channel approach to J/ψ radiative decay to pseudoscalar pairs
Yang-hong Lu, Jia-jun Wu, Bei-jiang Liu, Xiao-yan Shen
2025, 49(9): 093107. doi: 10.1088/1674-1137/ade4a2
Abstract:
We present a comprehensive theoretical approach for describing the amplitude of the processes \begin{document}$ J/\psi \to \gamma ab $\end{document}, where a and b are pseudoscalar mesons. Our approach systematically incorporates final-state rescattering between the pseudoscalar pair \begin{document}$ ab $\end{document}, contributions from intermediate resonances, and coupled-channel effects via rescattering of a with an intermediate state \begin{document}$ \bar{X} $\end{document} (which subsequently decays to \begin{document}$ \gamma b $\end{document}). This formalism ensures unitarity in the two-body rescattering amplitude and dynamically dressed couplings between resonances and the pseudoscalar pair. Using a toy model, we perform numerical calculations and demonstrate that coupled-channel effects significantly influence the lineshape of the invariant mass spectrum of the final states. These findings highlight the necessity of including coupled-channel dynamics in interpretations of \begin{document}$ J/\psi $\end{document} radiative decays.
CP violations and branching ratios for Bc+→ D(s)+π+π−(K+K−) from interference of the vector mesons in Perturbative QCD
Kun Shuai Ye, Gang Lü, Na Wang, Jian Chai, Xin-Heng Guo
2025, 49(9): 093108. doi: 10.1088/1674-1137/add523
Abstract:
Within the framework of the perturbative QCD approach utilizing \begin{document}$k_T$\end{document} factorization, we investigated the CP violation and branching ratios in the decay processes of \begin{document}$B_{c}^{+}\to D_{(s)} ^{+}V(V\rightarrow\pi^{+}\pi^{-})$\end{document} and \begin{document}$B_{c}^{+}\to D_{(s)}^{+}V(V\rightarrow K^{+}K^{-})$\end{document}, where V denotes the three vector mesons \begin{document}$\rho^0$\end{document}, ω, and ϕ. During the \begin{document}$V\to \pi^+\pi^-$\end{document} and \begin{document}$V\to K^+K^-$\end{document} decay processes, we incorporated the \begin{document}$\rho^{0}-\omega-\phi$\end{document} mixing mechanism to describe the amplitudes of these quasi-two-body decays. Within the interference region of the three vector particles, we observed distinct changes in both CP violations and branching ratios. Furthermore, our study presents evidence for local CP violations and branching ratios that warrants further experimental investigation.
Searching for doubly charmed baryons from ${ \overline{\boldsymbol B}_{\boldsymbol c}}$ meson decays
Ye Xing, Ji Xu
2025, 49(9): 093109. doi: 10.1088/1674-1137/add5d1
Abstract:
In this study, we investigate the production of doubly charmed baryons from anti-bottom charmed mesons. Using the effective Lagrangian approach, we discuss triangle diagrams at the hadronic level to access the branching ratios of \begin{document}$\overline{B}_c\to {\cal{B}}_{ccq}+{\cal{B}}_{\bar c\bar q\bar q}$\end{document}. Apparently, the specific process \begin{document}$\overline {B}_c \to \Xi_{cc}^{+} \, \overline {\Xi}_{\bar c}^{'0}$\end{document} occupies the largest possibility on the order of \begin{document}$9.1\times 10^{-5}$\end{document}. In addition, although the production of undiscovered \begin{document}$\Omega_{cc}^+$\end{document} is Cabibbo suppressed in \begin{document}$\overline B_c\to \Omega_{cc}^+ \, \overline {\Xi}_{\bar c}^0$\end{document}, its branching ratio can still reach a level of \begin{document}$10^{-7}$\end{document}. These results are expected to provide valuable support for future experiments.
NUCLEAR PHYSICS
Contrasting features of parton energy loss in heavy-ion collisions at RHIC and LHC
Thomas Marshall, Philip Suh, Gang Wang, Huan Zhong Huang
2025, 49(9): 094001. doi: 10.1088/1674-1137/adcf0f
Abstract:
Energetic quarks and gluons lose energy as they traverse the hot and dense medium created in high-energy heavy-ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC). The nuclear modification factor (\begin{document}$ R_{AA} $\end{document}) of leading particles quantifies parton energy loss in such collisions, with the particle spectrum in \begin{document}$ p+p $\end{document} collisions as a reference. Previous \begin{document}$ R_{AA} $\end{document} measurements at RHIC energies have revealed an approximately constant trend at high transverse momenta (\begin{document}$ p_{T} $\end{document}), implying a scenario where parton energy loss, \begin{document}$ \Delta p_{T} $\end{document}, scales proportionally with \begin{document}$ p_{T} $\end{document}, a feature naively expected from energy loss dynamics in elastic collisions. In this study, we investigate the LHC \begin{document}$ R_{AA} $\end{document} measurements that exhibit a pronounced \begin{document}$ p_{T} $\end{document} dependence of \begin{document}$ R_{AA} $\end{document} for various particle species, and our analysis attributes this behavior to \begin{document}$ \Delta p_T $\end{document} being approximately proportional to \begin{document}$ \sqrt{p_{T}} $\end{document}. These distinct features are consistent with model calculations of dominant radiative energy loss dynamics at LHC, in contrast to the dominance of collisional energy loss at RHIC. Additionally, the linear increase of the fractional energy loss with medium density at different \begin{document}$ p_{T} $\end{document} magnitudes affirms our previous empirical observation that the magnitude of the energy loss depends more strongly on the initial entropy density than the parton's path length through the medium. Implications on the dynamical scenarios of parton energy loss and future experimental investigations are also discussed.
Development status of efficiency improvement at the Rare-RI Ring facility
Y. Yamaguchi, A. Yano, T. Ohnishi, Y. Abe, N. Chandrakumar, G. Hudson-Chang, N. Imai, Y. Kikuchi, N. Kitamura, R. Kojima, J. Li, T. Moriguchi, D. Nagae, S. Naimi, S. Nishizawa, A. Ozawa, F. Suzaki, K. Takiura, N. Tomioka, R. Tuchiya, M. Wakasugi, K. Watanabe, T. Yamaguchi, R. Yokoyama, H. Zhang
2025, 49(9): 094002. doi: 10.1088/1674-1137/add25d
Abstract:
The rare radioactive-isotope (RI) ring is an isochronous storage ring for deriving the masses of extremely short-lived rare RIs. Since the successful commissioning experiment in 2015, the time of flight mass measurement technique has been established through test experiments using unstable nuclei with well-known masses. The experiments for unknown masses were started in 2018. While conducting experiments, we continue to develop equipment to further improve the efficiency and precision of mass measurements. The upgraded kicker system can generate a magnetic field with an extractable duration equivalent to the revolution time of the ring. This is essential for extracting extremely rare events as well as shortening the measurement time compared with that in the initial experiments. New steering magnets make it possible to eliminate an uncertain vertical beam deviation that occurs upstream. As a result, we confirm that the extraction yield is increased. A new resonant Schottky pick-up is able to detect single particles in timeframes on the order of milliseconds. It will be useful not only for beam diagnostics but also for lifetime measurement experiments of extremely short-lived rare RIs planned as a future application.
Minimization method for accurate position-determination using a position-sensitive Schottky cavity doublet
G. Hudson-Chang, S. Sanjari, S. Naimi, S. Litvinov, Yu. A. Litvinov, T. Ohnishi, Z. Podolyak, A. Yano, Y. Yamaguchi, T. Yamaguchi
2025, 49(9): 094003. doi: 10.1088/1674-1137/add5d7
Abstract:
A position-sensitive Schottky Cavity Doublet (SCD) was developed to enhance the accuracy of isochronous mass measurement at the Rare Radio-Isotope Ring (R3) at RIBF-RIKEN, Japan. The aim is to increase the accuracy of position measurement, which is used to correct the momentum spread, thus reducing the uncertainty in the mass determination. The detector comprises a cylindrical reference cavity and elliptical position-sensitive cavity, which uses an offset beam-pipe to create a relation between the Schottky power and horizontal position. The uncertainty in the power response can be improved by minimizing free parameters inside the power equation, providing a second-order correction for the position determination. This requires a large dispersion and momentum spread to effectively characterize the SCD acceptance, which simulations show is achieved when using 76Zn as a reference isotope. A key parameter to minimize is uncertainty of the impedance map, which relates power to position in the elliptical cavity. We find that an uncertainty in impedance of 0.3 Ω results in a precision equal to that of the current mass measurement method. Additionally, measuring momentum with the SCD enables the removal of other detectors from the beam-line, which drastically reduces the yield of high-Z beams via charge-change interactions.
Constraining explosive nucleosynthesis by indirect reaction methods at storage rings using unstable beams in batch mode
G. de Angelis, F. Recchia, J. Glorius, J. Gerl, B. Jurado, Xiao-Lin Tu, Jian-Ling Lou, S. Carollo, C. Berthelot, N. Watwood, B. P. Kay, P. Aguilera, M. L. Avila, J. Benito Garcia, K. Bhatt, D. Brugnara, K. A. Chipps, A. Couture, A. Demerdjiev, G.D. Dimitrova, S. Dutta, A. Ertoprak, R. Escudeiro, S. J. Freeman, F. Galtarossa, E. Geleva, B. Gongora Servin, A. Gottardo, A. Hall-Smith, J. Henderson, C. Hoffman, R. O. Hughes, H. Jayatissa, M. La Commara, G. Leckenby, S. M. Lenzi, D. Mengoni, M. R. Mumpower, W. J. Ong, M. Paul, J. Pellumaj, C. Domingo-Pardo, R. M. Perez Vidal, S. Pigliapoco, A. Ratkiewicz, K. Rezynkina, S. Rocca, D. K. Sharp, Yang Sun, T. L. Tang, D. Tonev, I. A. Tolstukhin, G. Wendell Misch, M. Williams, B. Wloch, Fan-Fei Zeng
2025, 49(9): 094004. doi: 10.1088/1674-1137/add877
Abstract:
Nuclear reaction studies on unstable isotopes can strongly help in improving our understanding of nucleosynthesis in stars. Indirect approaches to determining astrophysical reaction rates are increasingly common-place and undergoing continuous refinement. Of particular interest is the use of such indirect techniques at storage rings, which, among other aspects, allow to recycle rare unstable beams. We propose to investigate the reaction rates of astrophysical interest using indirect methods (surrogate, Trojan horse, etc.) in reverse kinematics at the IMP-CAS storage ring. Long lived radioactive ion beams, produced remotely, can be accelerated, and made to interact with light targets. The proposed reactions are 85Kr(p, p’γ), 85Kr(d, pγ), constraining the neutron flux in an s-process branching point, 79Se(p, p’γ), 79Se(d, pγ), constraining the temperature in s-process nucleosyntheses, and 59Fe(d, pγ), constraining core collapse supernovae.
Constraint on symmetry energy slope using neutron skins of 48Ca, 64Ni, 124Sn, and 208Pb and its impact on neutron star radius
Yu Huang, Kai-Xuan Huang, Zu-Xing Yang, Xiao-Lin Tu, Jin-Niu Hu, Jing-Tao Zhang, Ji-Feng Han
2025, 49(9): 094005. doi: 10.1088/1674-1137/add9fd
Abstract:
We constrain the symmetry energy slope L at the saturation density using the neutron skin values of 48Ca, 64Ni, 124Sn, and 208Pb determined by various experiments. The resulting L of 50(6) MeV is consistent with the world-averaged value from different observables and methodologies. The implications of newly constrained L on the radius determinations of 1.4 solar-mass neutron stars are also discussed based on the established \begin{document}$ R_{1.4}$\end{document}-L linear relationships by the DD-ME2 and TW99 EoS families.
Fox-Wolfram moment of jet production in relativistic heavy-ion collisions
Wei-Xi Kong, Ben-Wei Zhang
2025, 49(9): 094101. doi: 10.1088/1674-1137/add5d8
Abstract:
Fox-Wolfram moments (FWMs) are a set of event shape observables that characterize the angular distribution of energy flow in high-energy collisions. In this paper, we present the first theoretical investigation of FWMs for multi-jet production in relativistic heavy-ion collisions. We computed jet productions in p+p collisions using a Monte Carlo event generator called SHERPA. In addition, we used the linear Boltzmann transport model to simulate the multiple scatterings of energetic partons in the hot and dense QCD matter. We also calculated the event-normalized distributions of the lower-order FWM, \begin{document}$H_1^T$\end{document}, in p+p and Pb+Pb collisions. We found that for events with jet number \begin{document}$n_\text{jet} = 2$\end{document}, the \begin{document}$H_1^T$\end{document} distribution in Pb+Pb collisions is suppressed for small \begin{document}$H_1^T$\end{document}regions while it is enhanced for large \begin{document}$H_1^T$\end{document} regions as compared to p+p collisions. For events with \begin{document}$n_\text{jet}>2$\end{document}, the jet-number reduction effect due to jet quenching in QGP decreases the \begin{document}$H_1^T$\end{document} distribution for large \begin{document}$H_1^T$\end{document}regions in Pb+Pb collisions relative to p+p collisions. The medium modifications of the Fox-Wolfram moment \begin{document}$H_1^T$\end{document} for events with \begin{document}$n_\text{jet}\ge 2$\end{document} are also presented. They resemble those of events with \begin{document}$n_\text{jet} = 2$\end{document}. This is demonstrated by the relative contribution fractions of events with different final-state jet numbers with respect to \begin{document}$H_1^T$\end{document}.
α-decay half-lives of superheavy nuclei within a one-parameter model
Li-Qian Qi, Hong-Min Wang, Jian-Po Cui, Yan-Zhao Wang, Jian-Zhong Gu
2025, 49(9): 094102. doi: 10.1088/1674-1137/addcc8
Abstract:
The α-decay half-lives of superheavy nuclei (SHN) with charge numbers \begin{document}$ Z \geq 104 $\end{document} are investigated by employing a phenomenological one-parameter model based on quantum-mechanical tunneling through a potential barrier, where both the centrifugal and overlapping effects have been considered. It is shown that the experimental α-decay half-lives of the 81 SHN are reproduced well. Moreover, the order of magnitude for the α-particle preformation probability inside a parent nucleus (\begin{document}$S_{ {\alpha }} $\end{document}) is found to be \begin{document}$ 10^{-2} $\end{document}. Then, within this model, the \begin{document}$S_{ {\alpha }} $\end{document} values and α-decay half-lives of Z = 118−120 isotopes are predicted by inputting the α-decay energies (\begin{document}$ Q_{\alpha } $\end{document}) extracted from the relativistic continuum Hartree-Bogoliubov (RCHB) theory, Duflo-Zuker 19 (DZ19, where 19 denotes the number of fitting parameters) model, improved Weizsacker-Skyrme (lMWS) model, and machine learning (ML) approach. By analyzing the evolutions of \begin{document}$ Q_{\alpha } $\end{document}, \begin{document}$S_{ {\alpha} }$\end{document} and α-decay half-lives of Z = 118−120 isotopes with the neutron number N of the parent nucleus, it is found that the shell effect at N = 184 is evident for all nuclear mass models. Meanwhile, for the case of the RCHB, N = 172 is determined as a submagic number. However, the submagic number at N = 172 is replaced by N = 178 for the ML approach.
Application of dynamical eikonal approximation in elastic scattering reaction within 10–60 MeV/nucleon
Xiao-Yan Yun, Dan-Yang Pang, Yi-Ping Xu
2025, 49(9): 094103. doi: 10.1088/1674-1137/ade127
Abstract:
We study the application of the dynamical eikonal approximation (DEA) to elastic scattering for Coulomb-dominated reactions at low energy. Our test case consists of elastic scattering for 8B, 9C, and 11Be on 208Pb at 21.3, 25.2 and 12.7 MeV/nucleon, respectively. We introduce an empirical correction to the DEA method to account for Coulomb deflection, which significantly improves the description of elastic scattering of weakly-bound nuclei on a heavy target. The angular distributions of elastic scattering obtained using the empirical correction show good agreement with experimental data down to approximately 10 MeV/nucleon. Furthermore, we study the the effect of relativistic kinematics corrections on the angular distributions of elastic scattering at incident energies between 20 and 60 MeV/nucleon. The results show that relativistic kinematics corrections are crucial for describing the angular distributions of elastic scattering as low as approximately 40 MeV/nucleon.
Ab initio study of shell evolution in neutron-rich Si, S, Ar, and Ca isotopes near N = 32 and 34
Qi Yuan, Liu-Yuan Shen, Meng-Ran Xie, Hong-Hui Li, Jian-Guo Li, Xing Xu, Wei Zuo
2025, 49(9): 094104. doi: 10.1088/1674-1137/add5dd
Abstract:
Shell evolution is crucial for understanding nuclear structures across the nuclear chart. In this work, we employed the ab initio valence space in-medium similarity renormalization group with chiral nucleon-nucleon and three-nucleon interactions to study neutron-rich Si, S, Ar, and Ca isotopes, particularly focusing on nuclei near \begin{document}$ N=32, 34 $\end{document}. We systematically analyzed both neutron and proton shell evolutions by examining the excitation energies of the first \begin{document}$ 2^+ $\end{document} states and the effective single-particle energies. Our calculations show that the \begin{document}$ N=32 $\end{document} sub-shell gradually weakens as protons are removed from the doubly magic nucleus \begin{document}$ ^{52} {\rm{Ca}}$\end{document}, eventually disappearing in \begin{document}$ ^{46} {\rm{Si}}$\end{document}. Conversely, the strength of the \begin{document}$ N=34 $\end{document} sub-shell is enhanced with the removal of protons from \begin{document}$ ^{54} {\rm{Ca}}$\end{document}. Furthermore, our results indicate the existence of the proton \begin{document}$ Z=14 $\end{document} sub-shell in neutron-rich Si isotopes. These findings suggest that \begin{document}$ ^{48} {\rm{Si}}$\end{document} is a doubly magic nucleus, with the excitation energy of the first \begin{document}$ 2^+ $\end{document} state around 2.49 MeV, which is approximately 400 keV higher than that of \begin{document}$ ^{54} {\rm{Ca}}$\end{document}. This value is comparable to those of other well-known exotic doubly magic nuclei, such as \begin{document}$ ^{52} {\rm{Ca}}$\end{document} and \begin{document}$ ^{78} {\rm{Ni}}$\end{document}, which is of great interest for further experiments at RIB facilities. In addition, we predicted the low-lying spectra of neutron-rich Si, S, and Ar isotopes, providing new insights for future experiments.
Effect of electron–electron interaction on pair production in supercritical collisions of highly charged ions
N. K. Dulaev, D. A. Telnov, R. V. Popov, V. M. Shabaev, Y. S. Kozhedub, X. Ma, I. A. Maltsev, A. D. Mironov, I. I. Tupitsyn
2025, 49(9): 094105. doi: 10.1088/1674-1137/ade12b
Abstract:
The effect of electron-electron interaction on positron emission in supercritical collisions of highly charged ions is studied within the monopole approximation using the time-dependent density functional theory and time-dependent Hartree–Fock–Slater methods. Positron production probabilities and energy spectra are calculated for U–U, U–Cm, and Cm–Cm collision systems, considering both bare nuclei and highly charged ions with partially filled electron shells. The results indicate that the screening of the nuclear potential by electrons as well as Pauli blocking substantially reduce positron production and suppress the characteristic signatures of spontaneous vacuum decay, previously found in collisions of bare nuclei.
Study of QCD critical point with the effect of three-nucleon correlations on light nuclei yield ratios using PYTHIA8/Angantyr
Zuman Zhang, Ning Yu, Sha Li, Shuang Li, Siyu Tang, Meimei Zhang
2025, 49(9): 094106. doi: 10.1088/1674-1137/add10f
Abstract:
This study utilizes the PYTHIA8 Angantyr model to systematically investigate the effects of three nucleons correlation \begin{document}$C_{n^2p}$\end{document} on the light nuclei yield ratio \begin{document}$N_tN_p/N_d^2$\end{document} for Au+Au collisions at \begin{document}$\sqrt{s_{\mathrm{NN}}}$\end{document} = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV. The analysis explores this property across different rapidity ranges, collision centralities, and collision energies, while also examining the roles of multi-parton interactions (MPI) and color reconnection (CR) mechanisms. The light nuclei yield ratio remains stable with changes in rapidity coverage and collision centrality but slightly increases with rising collision energy. The impact of CR on the light nuclei yield ratio depends on the presence of MPI; when MPI is turned off, CR has no effect. Additionally, the three-nucleon correlation enhances the light nuclei yield ratio for both central and peripheral collisions. However, the non-monotonic energy dependence observed in experiments, the peak at \begin{document}$\sqrt{s_{\mathrm{NN}}}=20\sim30$\end{document} GeV reported by the STAR experiment, cannot be explained by the Angantyr model owing to its lack of key mechanisms related to the quark-gluon plasma (QGP). Nevertheless, the Angantyr model serves as an important baseline for studying collision behaviors in the absence of QGP effects.
Fixing effective range parameters in elastic α-12C scattering: impact on resonant 24+ state of 16O and SE2 factor of 12C(α,γ)16O
Shung-Ichi Ando
2025, 49(9): 094107. doi: 10.1088/1674-1137/addaae
Abstract:
Elastic α-12C scattering for \begin{document}$ l=2 $\end{document} and E2 transition of radiative α capture on 12C and 12C(α,γ)16O are studied in cluster effective field theory. Owing to the problem in fixing the asymptotic normalization coefficient (ANC) of the subthreshold \begin{document}$ 2_1^+ $\end{document} state of 16O or, equivalently, the effective range parameters of the \begin{document}$ 2_1^+ $\end{document} state, from the elastic scattering data, we introduced the conditions that lead to a large value of the ANC in this study. We also introduced d-wave phase shift data of the elastic scattering up to the α energy, \begin{document}$ E_\alpha=10 $\end{document} MeV, which contain the resonant \begin{document}$ 2_4^+ $\end{document} state of 16O. Applying these conditions, the parameters of the S matrix of the elastic scattering for \begin{document}$ l=2 $\end{document} were fitted to the phase shift data, and the fitted parameters were employed in the calculation of the astrophysical \begin{document}$ S_{E2} $\end{document} factor of 12C(α,γ)16O; we extrapolated the \begin{document}$ S_{E2} $\end{document} factor to the Gamow-peak energy, \begin{document}$ E_G=0.3 $\end{document} MeV. We found that the aforementioned conditions lead to significant effects in the observables of the \begin{document}$ 2_4^+ $\end{document} state of 16O and the estimate of the \begin{document}$ S_{E2} $\end{document} factor at \begin{document}$ E_G $\end{document} and confirmed that the ANC of the \begin{document}$ 2_1^+ $\end{document} of 16O cannot be determined by the phase shift data for \begin{document}$ l=2 $\end{document}.
Influence of neutron-pair condensation on the difference in charge radii of mirror nuclei
Jing Huang, Xiang Jiang, Na Tang, Rong An
2025, 49(9): 094108. doi: 10.1088/1674-1137/add5d6
Abstract:
A highly linear correlation exists between the differences in charge radii of mirror-pair nuclei and the slope parameter of symmetry energy, as reported in literature. This study investigates the impact of neutron-proton correlations, deduced from neutron- and proton-pair condensation near the Fermi surface, on determining the symmetry energy slope parameter using Skyrme density functionals. Differential charge radii of Ni isotopes are employed to assess the validity of the proposed model. Results suggest that the modified model can reproduce the shell quenching of charge radii at the neutron number \begin{document}$ N=28 $\end{document} along the Ni isotopic chain. The shell closure effect of the charge radii can also be predicted at the neutron number \begin{document}$ N=50 $\end{document}. Correlations between the differences in charge radii of the mirror pair nuclei 32Ar-32Si and 54Ni-54Fe and the slope parameter of symmetry energy are also analyzed. Notably, the range of the symmetry energy slope is influenced by the neutron-pair condensation near the Fermi surface. Moreover, a relatively stiff equation of state can be inferred from the mirror pairs 32Ar-32Si and 54Ni-54Fe when the effect of the neutron-pair condensation is considered.
Effective decay rates of nuclei in astrophysical environments
Chao Dong, Zhi-Hong Li, Ge-Xing Li, Yun-Ju Li, Na Song, Chen Chen, Jun-Wen Tian, Jia-Ying-Hao Li, Zhi-Cheng Zhang, Hui-Ling Tian, Mei-Yue-Nan Ma
2025, 49(9): 094110. doi: 10.1088/1674-1137/adcf11
Abstract:
Nuclear β-decay plays a pivotal role at various stages of stellar evolution. However, the effective decay rates of nuclei in astrophysical environments may differ significantly from their laboratory values. This paper presents a detailed methodology for calculating nuclear half-life under the influence of temperature, electron density, ionization, and incomplete thermal equilibrium. We analyze the impact of astrophysical conditions on the β-decay of 26Al, 59Fe, 79Se, and 205Pb, revealing substantial variations in their effective half-lives within stellar environments. These changes lead to significant differences in nucleosynthetic yields, underscoring the critical importance of accounting for environmental effects when modeling nuclear decay rates.
Predictions of unknown masses using a feedforward neural network
Cheng-wei Dai, Hui Jiang, Yang Lei
2025, 49(9): 094111. doi: 10.1088/1674-1137/add10a
Abstract:
In this study, a feedforward neural network (FNN) approach is employed to optimize three local mass models (GK, GKs, and GK+J). We find that adding physical quantities related to the pairing effect in the input layer can effectively improve the prediction accuracy of local models. For the known masses in AME2012, the FNN reduces the root-mean-square deviation between theory and experiment for the three mass models by 11 keV, 32 keV, and 623 keV. Among them, the improvement effect of the light mass region with mass number between 16 and 60 is better than that of medium and heavy mass regions. The approach also has good optimization results when extrapolating AME2012 to AME2020 and the latest measured masses after AME2020. Based on the improved mass data, the separation energies for single- and two-proton (neutron) emissions and α-decay energies are obtained, which agree well with the experiment.
Nucleon-Δ elastic cross section in isospin-asymmetric nuclear medium with inclusion of scalar-isovector δ meson field
Manzi Nan, Pengcheng Li, Wei Zuo, Qingfeng Li
2025, 49(9): 094112. doi: 10.1088/1674-1137/add8fd
Abstract:
The production, dynamic evolution, and decay of \begin{document}$ \Delta $\end{document} particles play a crucial role in understanding the properties of high baryon density nuclear matter in intermediate-energy heavy-ion collisions. In this study, energy-, density-, and isospin-dependent nucleon-\begin{document}$ \Delta $\end{document} elastic cross sections (\begin{document}$ \sigma^{*}_{N \Delta} $\end{document}) were studied within the framework of the relativistic Boltzmann-Uehling-Uhlenbeck transport theory, in which the \begin{document}$ \delta $\end{document} meson field is considered in addition to the \begin{document}$ \sigma $\end{document}, \begin{document}$ \omega $\end{document}, and \begin{document}$ \rho $\end{document} meson fields. The results show that the \begin{document}$ \delta $\end{document} and \begin{document}$ \rho $\end{document} meson related exchange terms have a nonnegligible contribution to \begin{document}$ \sigma^{*}_{N \Delta} $\end{document} compared to only considering the \begin{document}$ \rho $\end{document} meson exchange terms, although there is a significant cancellation of the cross section among these meson exchange terms. In addition, owing to the different effects of the medium correction on the effective masses of neutrons, protons, and differently charged \begin{document}$ \Delta $\end{document}s, the individual \begin{document}$ \sigma^{*}_{N \Delta} $\end{document}exhibits an ordered isospin-asymmetry (\begin{document}$ \alpha $\end{document}) dependence, and \begin{document}$ \sigma^{*}_{n\Delta} $\end{document} and \begin{document}$ \sigma^{*}_{p\Delta} $\end{document} have opposite \begin{document}$ \alpha $\end{document} dependencies. Moreover, the \begin{document}$ \alpha $\end{document} dependence of the ratio \begin{document}$ R(\alpha)=\sigma^{*}(\alpha)/\sigma^{*}(\alpha=0) $\end{document} for \begin{document}$ n\Delta $\end{document} reaction channels satisfies \begin{document}$ n\Delta^{++}>n\Delta^{+}>n\Delta^{0}>n\Delta^{-} $\end{document}, while for \begin{document}$ p\Delta $\end{document}, it satisfies \begin{document}$ p\Delta^{-}>p\Delta^{0}>p\Delta^{+}>p\Delta^{++} $\end{document}. In addition, the results indicate that the isospin effect on \begin{document}$ \sigma^{*}_{N \Delta} $\end{document}, which is mostly caused by the isovector \begin{document}$ \rho $\end{document} and \begin{document}$ \delta $\end{document} meson fields, is still significant at densities up to three times the normal nuclear density. Finally, a parametrization of the energy-, density-, and isospin-dependent \begin{document}$ N\Delta $\end{document} elastic cross sections is proposed based on the microscopic calculated results. Thus, the in-medium \begin{document}$ \sigma^{*}_{N \Delta} $\end{document} in the energy range of \begin{document}$ \sqrt{s} $\end{document}=2.3~3.0 GeV can be properly described.
Relativistic corrections to energy spectrum of hydrogen due to full one-photon-exchange interaction
Zi-Wen Zhang, Hai-Qing Zhou
2025, 49(9): 094113. doi: 10.1088/1674-1137/add684
Abstract:
In this study, we present expressions for the full effective potential corresponding to the one-photon exchange interaction between two fermions within the framework of the effective Schrödinger-like equation, derived exactly from the Bethe-Salpeter equation in quantum electrodynamics. The final effective potential is expressed in terms of eight scalar functions. When these scalar functions are expanded order by order in terms of velocities, we systematically recover the non-relativistic effective potential organized in terms of velocities. By retaining the exact momentum dependence in the effective potential, we estimate its corrections to the energy spectrum of hydrogen using a highly precise numerical method. A comparison is made between our numerical results and those obtained using conventional the bound-state perturbative theory. Our calculations suggest that this method can accurately account for all relativistic contributions. It would be interesting to extend these calculations to positronium, muonic hydrogen, and scenarios involving nuclear structure and radiative corrections.
PARTICLE AND NUCLEAR ASTROPHYSICS AND COSMOLOGY
Investigating the shadows of new regular black holes with a Minkowski core: effects of spherical accretion and core type differences
Yi Xiong, Jin Pu, Yi Ling, Guo-Ping Li, Gao-Ming Deng
2025, 49(9): 095101. doi: 10.1088/1674-1137/addfce
Abstract:
We investigated the shadows and optical appearances of a new type of regular black holes (BHs) with a Minkowski core under various spherical accretion scenarios. These BHs are constructed by modifying the Newtonian potential based on the minimum observable length in the Generalized Uncertainty Principle (GUP). They correspond one-to-one with traditional regular BHs featuring a de-Sitter (dS) core (such as Bardeen/Hayward BHs), characterized by a quantum gravity effect parameter (\begin{document}$ \alpha_0 $\end{document}) and spacetime deformation factor (n). We found that the characteristic parameters give rise to some novel observable features. For these new BHs, both the shadow and photon sphere radii decrease with the increase in \begin{document}$ \alpha_0 $\end{document}, while the observed specific intensity increases. Conversely, as n increases, the shadow and photon sphere radii increase, while the observed specific intensity decreases. Under different spherical accretion scenarios, the shadows and photon sphere radii remain identical; however, the observed specific intensity is greater under static spherical accretion than under infalling spherical accretion. Additionally, we found that these regular BHs with different cores exhibit variations in shadows and optical appearances, particularly under static spherical accretion. Compared with Bardeen BH, the new BHs exhibit a lower observed specific intensity, a dimmer photon ring, and smaller shadow and photon sphere radii. Larger values of \begin{document}$ \alpha_0 $\end{document} lead to more significant differences, and a similar trend was also observed when comparing with Hayward BH. Under infalling spherical accretion, the regular BHs with different cores exhibit only slight differences in observed specific intensity, which become more evident when \begin{document}$ \alpha_0 $\end{document} is relatively large. This suggests that the unique spacetime features of these regular BHs with different cores can be distinguished through astronomical observation.
Circular motion and acceleration of charged particles around magnetized rotating black holes in scalar-tensor-vector gravity
Saeed Ullah Khan, Javlon Rayimbaev, Zhi-Min Chen, Zdeněk Stuchlík
2025, 49(9): 095102. doi: 10.1088/1674-1137/add8fc
Abstract:
One of the most critical issues in relativistic astrophysics is explaining the origin mechanisms of (ultra)high-energy charged particle components of cosmic rays. Black holes (BHs), which are vast reservoirs of (gravitational) energy, are candidates for such energetic cosmic ray sources. The main idea of this study is to investigate the effects of scalar-tensor-vector gravity (STVG) and so-called modified gravity (MOG) on charged particle acceleration by examining their dynamics and acceleration through the magnetic Penrose process (MPP) near magnetized Kerr BHs in MOG (Kerr-MOG BHs). First, we briefly study the horizon structure of the Kerr-MOG BH. Then, we derive the effective potential for the circular motion of charged particles by considering electromagnetic and MOG field interactions on the particles to gain insight into the stability of circular orbits. Our results show that the magnetic field can extend the region of stable circular orbits, whereas the STVG parameter reduces the instability of the circular orbit. Thus, from the examination of particle trajectories, we observe that, at fixed values of other parameters, the Schwarzschild BH captures the test particle; in the case of the Kerr BH, the test particle escapes to infinity or is captured by the BH, while in the Kerr-MOG BH, the test particle is trapped in some region around the BH and starts orbiting it at a smaller value of the MOG field parameter. By investigating the MPP, we found that, in stronger magnetic fields, the behavior of orbits becomes more chaotic. As a result, the particle escapes to infinity with high energies.
Analytical solutions of CPT-odd Maxwell equations in Schwarzschild spacetime
Hao Wang, Zhi Xiao, Bing Sun
2025, 49(9): 095103. doi: 10.1088/1674-1137/ade541
Abstract:
In this paper, we present the CPT-violating (CPTV) Maxwell equations in curved spacetime using the Newman-Penrose (NP) formalism. We obtain a semi-analytical solution to the Maxwell equations in Schwarzschild spacetime under the assumption that the CPT-odd \begin{document}$ \left(k_{AF}\right)^\mu $\end{document} term exhibits spherical symmetry in the Schwarzschild background. By retaining only terms up to the linear order in the \begin{document}$ \left(k_{AF}\right)^\mu $\end{document} coefficient, we obtain perturbative solutions by treating the solutions of the Lorentz-invariant Maxwell equations as the zeroth-order approximation and incorporating the \begin{document}$ \left(k_{AF}\right)^\mu $\end{document} terms jointly as an additional source term alongside the external charge current. Each resulting NP scalar field can be factorized into two components: the radial component, expressed in terms of hypergeometric functions, and the angular component, described by spin-weighted spherical harmonics.
Quasinormal modes of accelerating spacetime
Tao Zhou, Peng-Cheng Li
2025, 49(9): 095104. doi: 10.1088/1674-1137/add10d
Abstract:
We calculate the exact values of the quasinormal frequencies for massless perturbations with spin \begin{document}$ s\leq2 $\end{document} propagating in purely accelerating spacetime. Using two different methods, we transfer the perturbation equations into hypergeometric differential equations and obtain identical quasinormal frequencies. These purely imaginary spectra are shown to be independent of the spin of the perturbation and match those of the acceleration modes identified in accelerating black holes in the Minkowski limit. This implies that the acceleration modes originate from the purely accelerating spacetime and that the presence of black holes would deform the spectra. Additionally, we compute the quasinormal frequencies of scalar, electromagnetic, and gravitational perturbations in D-dimensional de Sitter spacetime and compare them with previous findings to validate our method.
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