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2025 No.4
2025, 49(4): 044107. doi: 10.1088/1674-1137/ada5c9
Abstract:
In this study, the energy bands of quadrupole and octupole excited states are investigated. This is achieved by employing the Bohr Hamiltonian, incorporating quadrupole and octupole deformations whose variables are accurately separated. Subsequently, the Woods-Saxon potential is added to the problem. Because this problem cannot yield suitable solutions using conventional approximations, we solve it numerically using machine learning. A detailed description is given of how wave functions and their associated energies are obtained. Throughout this procedure, we demonstrate how machine learning aids us in easily accomplishing our objective. We examine and analyze the energy spectrum and possible multipole transitions for candidate isotopes$ ^{226} $ Ra and $ ^{226} $ Th.
In this study, the energy bands of quadrupole and octupole excited states are investigated. This is achieved by employing the Bohr Hamiltonian, incorporating quadrupole and octupole deformations whose variables are accurately separated. Subsequently, the Woods-Saxon potential is added to the problem. Because this problem cannot yield suitable solutions using conventional approximations, we solve it numerically using machine learning. A detailed description is given of how wave functions and their associated energies are obtained. Throughout this procedure, we demonstrate how machine learning aids us in easily accomplishing our objective. We examine and analyze the energy spectrum and possible multipole transitions for candidate isotopes
2025, 49(4): 044108. doi: 10.1088/1674-1137/ada7cf
Abstract:
When an energetic parton traverses the hot QCD medium, it may suffer from multiple scattering and lose its energy. The medium-induced gluon radiation for a massive quark will be suppressed relative to that of a light quark due to the dead-cone effect. The development of new declustering techniques of jet evolution makes a direct study of the dead-cone effect in the QCD medium possible for the first time. In this work, we compute the emission angle distribution of the charm-quark-initiated splittings in D0 meson tagged jet and that of the light parton-initiated splittings in an inclusive jet in p+p and Pb+Pb at 5.02 TeV by utilizing the declustering techniques of jet evolution. The heavy quark propagation and induced energy loss in the QCD medium are simulated with the SHELL model based on the Langevin equation. By directly comparing the emission angle distributions of charm-quark-initiated splittings with those of light parton-initiated splittings at the same energy intervals of the initial parton, we provide insights into the fundamental splitting structure in A+A collisions, thereby exploring the possible observation of the dead-cone effect in medium-induced radiation. We further investigate the case of the emission angle distributions normalized to the number of splittings and find the dead-cone effect will broaden the emission angle of the splitting and reduce the possibility for such splitting to occur, leading the massive parton to lose less energy. We also find that the collisional energy loss mechanism has a negligible impact on the medium modification to the emission angle distribution of the charm-quark-initiated splittings for D0 meson-tagged jets.
When an energetic parton traverses the hot QCD medium, it may suffer from multiple scattering and lose its energy. The medium-induced gluon radiation for a massive quark will be suppressed relative to that of a light quark due to the dead-cone effect. The development of new declustering techniques of jet evolution makes a direct study of the dead-cone effect in the QCD medium possible for the first time. In this work, we compute the emission angle distribution of the charm-quark-initiated splittings in D0 meson tagged jet and that of the light parton-initiated splittings in an inclusive jet in p+p and Pb+Pb at 5.02 TeV by utilizing the declustering techniques of jet evolution. The heavy quark propagation and induced energy loss in the QCD medium are simulated with the SHELL model based on the Langevin equation. By directly comparing the emission angle distributions of charm-quark-initiated splittings with those of light parton-initiated splittings at the same energy intervals of the initial parton, we provide insights into the fundamental splitting structure in A+A collisions, thereby exploring the possible observation of the dead-cone effect in medium-induced radiation. We further investigate the case of the emission angle distributions normalized to the number of splittings and find the dead-cone effect will broaden the emission angle of the splitting and reduce the possibility for such splitting to occur, leading the massive parton to lose less energy. We also find that the collisional energy loss mechanism has a negligible impact on the medium modification to the emission angle distribution of the charm-quark-initiated splittings for D0 meson-tagged jets.
2025, 49(4): 044106. doi: 10.1088/1674-1137/ada7ce
Abstract:
In this work, we study the$K^- p \to \gamma \Lambda$ reaction in an effective Lagrangian approach and isobar model. Compared to previous studies using a Regge-plus-resonance model, we consider the contributions of the t-channel (K and $K^*$ ) and u-channel (proton) exchanges explicitly as the background contribution. To restore the gauge invariance of the amplitude violated by introducing the phenomenological form factors, we employ two different methods from the literature. Then, we discuss the roles of possible resonance contributions in this reaction and present predictions of Λ polarization based on various models. We find that the contribution of the background terms plays an important role in the present reaction. Meanwhile, the $\Lambda(1520)$ , $\Sigma(1660)$ , and $\Sigma(1670)$ resonances may also contribute to this reaction. Due to the uncertainties of the present data and relatively small contributions of the hyperon resonances, we cannot identify the roles of various hyperon resonances in the present work. However, we show that the measurement of the spin polarization of the final Λ will be helpful to verify various models.
In this work, we study the
2025, 49(4): 044105. doi: 10.1088/1674-1137/ada377
Abstract:
Bremsstrahlung photons emitted during nucleon-nucleus reactions in compact stars are investigated. The influence of stellar medium density on emission intensity is studied from a quantum perspective for the first time. A bremsstrahlung model is generalized, where a new term describing the influence of the stellar medium is added to interactions between nucleons and nuclei (in the framework of a nuclear model of deformed oscillatoric shells). Polytropic EOS, Chandrasekar EOS, and Harrison-Wheeler EOS are employed for calculation. Haensel and Potekhin's unified EOS of neutron-star matter based on FPS and SLy EOSs are used for tests. Bremsstrahlung calculations are tested on existing measurements of bremsstrahlung in the scattering of protons off 197Au nuclei at a proton beam energy of$E_{ p}=190$ MeV. Many properties of bremsstrahlung emitted from nuclear processes in the stellar medium of compact stars are studied for the first time. In particular, the spectra of photons in the scattering of protons and neutrons off 4He, 8Be, 12C, 16O, 24Mg, 40Ca, 56Fe are estimated based on stellar medium density. The medium of white dwarfs has a small influence on the bremsstrahlung emission from nuclear processes, while bremsstrahlung emission is intensive in neutron stars and it is changed in dependence on stellar medium and structure.
Bremsstrahlung photons emitted during nucleon-nucleus reactions in compact stars are investigated. The influence of stellar medium density on emission intensity is studied from a quantum perspective for the first time. A bremsstrahlung model is generalized, where a new term describing the influence of the stellar medium is added to interactions between nucleons and nuclei (in the framework of a nuclear model of deformed oscillatoric shells). Polytropic EOS, Chandrasekar EOS, and Harrison-Wheeler EOS are employed for calculation. Haensel and Potekhin's unified EOS of neutron-star matter based on FPS and SLy EOSs are used for tests. Bremsstrahlung calculations are tested on existing measurements of bremsstrahlung in the scattering of protons off 197Au nuclei at a proton beam energy of
2025, 49(4): 044001. doi: 10.1088/1674-1137/adacc3
Abstract:
Stimulated by a keen interest in possible collective behavior in high-energy proton-proton and proton-nucleus collisions, we study two-particle angular correlations in pseudorapidity and azimuthal differences in simulated p + p interactions using the Pythia 8 event generator. Multi-parton interactions and color connection are included in these simulations, which have been perceived to produce collectivity in final-state particles. Meanwhile, contributions from genuine few-body nonflow correlations, not of collective flow behavior, are known to be severe in these small-system collisions. We present our Pythia correlation studies pedagogically and report azimuthal harmonic anisotropies analyzed using several methods. We observe anisotropies in these Pythia simulated events qualitatively and semi-quantitatively, similar to experimental data. Our findings highlight the delicate nature of azimuthal anisotropies in small-system collisions and provide a benchmark that can aid in improving data analysis and interpreting experimental measurements in small-system collisions.
Stimulated by a keen interest in possible collective behavior in high-energy proton-proton and proton-nucleus collisions, we study two-particle angular correlations in pseudorapidity and azimuthal differences in simulated p + p interactions using the Pythia 8 event generator. Multi-parton interactions and color connection are included in these simulations, which have been perceived to produce collectivity in final-state particles. Meanwhile, contributions from genuine few-body nonflow correlations, not of collective flow behavior, are known to be severe in these small-system collisions. We present our Pythia correlation studies pedagogically and report azimuthal harmonic anisotropies analyzed using several methods. We observe anisotropies in these Pythia simulated events qualitatively and semi-quantitatively, similar to experimental data. Our findings highlight the delicate nature of azimuthal anisotropies in small-system collisions and provide a benchmark that can aid in improving data analysis and interpreting experimental measurements in small-system collisions.
2025, 49(4): 044103. doi: 10.1088/1674-1137/ada7d1
Abstract:
We study the transverse momentum ($p_T$ ) differential anisotropic flow and flow fluctuation in Pb+Pb collisions at $\sqrt{s_{_{NN}}}$ =5.02 TeV at the LHC. A (3+1)-dimensional CLVisc hydrodynamics framework with fluctuating TRENTO (or AMPT) initial conditions is utilized to simulate the space-time evolution of the quark-gluon plasma (QGP) medium. The effects of shear viscosity and the sub-nucleon structure on anisotropic flow and flow fluctuation are analyzed. Our result shows that shear viscosity tends to suppress both flow coefficients (${v_2\{2}\}$ , ${v_2\{4\}}$ , and ${\langle v_2\rangle}$ ) and flow fluctuation (${\sigma_{v_2}}$ ) owing to its smearing effect on local density fluctuation. The flow coefficients appear to be insensitive to the sub-nucleon structure, whereas the flow fluctuation ${\sigma_{v_2}}$ tends to be suppressed by the sub-nucleon structure in central collisions but enhanced in peripheral collisions. After taking into account the sub-nucleon structure effect, our numerical result can qualitatively describe the relative flow fluctuations (${v_2\{4\}/v_2\{2\}}$ , $F({v_2})$ ) measured by the ALICE Collaboration at the LHC. We further investigate the effects of shear viscosity, sub-nucleon structure, and initial condition model on the flow angle and flow magnitude decorrelations (${A_2^f}$ , ${M_2^f}$ ) using the four-particle correlation method. We find that the flow decorrelation effect is typically stronger in central collisions than in peripheral collisions. The flow angle decorrelation is found to be insensitive to the shear viscosity and sub-nucleon structure, whereas the flow magnitude decorrelation shows quite different behaviors when using the TRENTO and AMPT initial condition models. Our study sheds light on the anisotropic flow, transport properties, and initial structure of the QGP created in high-energy nuclear collisions.
We study the transverse momentum (
2025, 49(4): 044101. doi: 10.1088/1674-1137/ad9a8c
Abstract:
By combining the Skyrme-Hartree-Fock method with complex momentum representation (CMR), the resonant states of$ {}^{17}_\Lambda $ O, $ {}^{41}_{\Lambda} $ Ca, $ {}^{49}_{\Lambda} $ Ca, and $ {}^{57}_\Lambda $ Ni were investigated. The phase shifts for hyperon-nucleus elastic scattering were determined with continuum level density (CLD), and the scattering length as well as the resonance energy were obtained by utilizing the effective range expansion. Our method, abbreviated as CMR-CLD, exhibits good consistency with traditional approaches and provides ground work for investigating scattering and resonance problems in deformed and multi-hyperon hypernuclei.
By combining the Skyrme-Hartree-Fock method with complex momentum representation (CMR), the resonant states of
2025, 49(4): 045104. doi: 10.1088/1674-1137/ad9f44
Abstract:
In this study, we investigate the optical properties of a quantum-corrected black hole (BH) in loop quantum gravity surrounded by a plasma medium. First, we determine the photon and shadow radii resulting from quantum corrections and the plasma medium in the environment surrounding a quantum-corrected BH. Our findings indicate that the photon sphere and BH shadow radii decrease owing to the quantum correction parameter α, which acts as a repulsive gravitational charge. Further, we investigate the gravitational weak lensing by applying the general formalism used to model the deflection angle of the light traveling around the quantum-corrected BH within the plasma medium. We show, in conjunction with the fact that the combined effects of the quantum correction and non-uniform plasma frequency parameter can decrease the deflection angle, that the light traveling through the uniform plasma can be strongly deflected than the non-uniform plasma environment surrounding the quantum-corrected BH. Finally, we examine the magnification of the lensed image brightness under the effect of the quantum correction parameter α, including the uniform and non-uniform plasma effects.
In this study, we investigate the optical properties of a quantum-corrected black hole (BH) in loop quantum gravity surrounded by a plasma medium. First, we determine the photon and shadow radii resulting from quantum corrections and the plasma medium in the environment surrounding a quantum-corrected BH. Our findings indicate that the photon sphere and BH shadow radii decrease owing to the quantum correction parameter α, which acts as a repulsive gravitational charge. Further, we investigate the gravitational weak lensing by applying the general formalism used to model the deflection angle of the light traveling around the quantum-corrected BH within the plasma medium. We show, in conjunction with the fact that the combined effects of the quantum correction and non-uniform plasma frequency parameter can decrease the deflection angle, that the light traveling through the uniform plasma can be strongly deflected than the non-uniform plasma environment surrounding the quantum-corrected BH. Finally, we examine the magnification of the lensed image brightness under the effect of the quantum correction parameter α, including the uniform and non-uniform plasma effects.
2025, 49(4): 045103. doi: 10.1088/1674-1137/ada378
Abstract:
We investigate the critical collapse of spherically symmetric scalar fields in asymptotically anti-de Sitter spacetime, focusing on two scenarios: real and complex scalar fields with potentials. By fine-tuning the amplitude of the initial scalar field under different cosmological constants, we find a linear relationship between the critical amplitude of the first collapse and the cosmological constant in both scenarios. Furthermore, we observe that the slope of this linear relationship varies linearly with coupling strength.
We investigate the critical collapse of spherically symmetric scalar fields in asymptotically anti-de Sitter spacetime, focusing on two scenarios: real and complex scalar fields with potentials. By fine-tuning the amplitude of the initial scalar field under different cosmological constants, we find a linear relationship between the critical amplitude of the first collapse and the cosmological constant in both scenarios. Furthermore, we observe that the slope of this linear relationship varies linearly with coupling strength.
2025, 49(4): 045101. doi: 10.1088/1674-1137/adab62
Abstract:
We investigate the linear cosmological perturbations in the context of the so-called energy-momentum squared gravity (EMSG) theory. Recent research shows that the EMSG theory can reproduce a viable background cosmological evolution comparable to ΛCDM, whereas the matter-dominated era exhibits slight distinctions. In this paper, we focus on power-law EMSG models and derive the equations for the linear cosmological perturbations. We explore the propagation of the gravitational wave (GW) and the growth of matter density perturbation at the first order, and we estimate the model parameters from the simulated GW and observed redshift space distortion data. Our analysis reveals that the model parameters should be small and positive in the$ 1\sigma $ confidence interval, which indicates that the theory agrees closely with the observational data and can be considered an alternative to the standard cosmological model.
We investigate the linear cosmological perturbations in the context of the so-called energy-momentum squared gravity (EMSG) theory. Recent research shows that the EMSG theory can reproduce a viable background cosmological evolution comparable to ΛCDM, whereas the matter-dominated era exhibits slight distinctions. In this paper, we focus on power-law EMSG models and derive the equations for the linear cosmological perturbations. We explore the propagation of the gravitational wave (GW) and the growth of matter density perturbation at the first order, and we estimate the model parameters from the simulated GW and observed redshift space distortion data. Our analysis reveals that the model parameters should be small and positive in the
2025, 49(4): 043002. doi: 10.1088/1674-1137/ada914
Abstract:
We search for nuclear recoil signals of dark matter (DM) models with a light mediator using data taken from a p-type point-contact germanium detector of the CDEX-10 experiment at the China Jinping Underground Laboratory. The 90% confidence level upper limits on the DM-nucleon interaction cross section from 205.4 kg-day exposure data are derived, excluding the new parameter space in 2−3 GeV DM mass when the mediator mass is comparable to or lower than the typical momentum transfer. We further interpret our results to constrain a specific self-interacting DM model with a light mediator coupling to the photon through kinetic mixing and set experimental limits on the model parameter region favored by astrophysical observations.
We search for nuclear recoil signals of dark matter (DM) models with a light mediator using data taken from a p-type point-contact germanium detector of the CDEX-10 experiment at the China Jinping Underground Laboratory. The 90% confidence level upper limits on the DM-nucleon interaction cross section from 205.4 kg-day exposure data are derived, excluding the new parameter space in 2−3 GeV DM mass when the mediator mass is comparable to or lower than the typical momentum transfer. We further interpret our results to constrain a specific self-interacting DM model with a light mediator coupling to the photon through kinetic mixing and set experimental limits on the model parameter region favored by astrophysical observations.
2025, 49(4): 043001. doi: 10.1088/1674-1137/ada350
Abstract:
Using an electron-positron collision data sample corresponding to$ (1.0087\pm0.0044)\times10^{10} $ $ J/\psi $ events collected using the BESIII detector at the BEPCII collider, we firstly search for the lepton number violation decay $ \phi \to \pi^+ \pi^+ e^- e^- $ via $ J/\psi\to \phi\eta $ . No obviously signals are found. The upper limit on the branching fraction of $ \phi \to \pi^+ \pi^+ e^- e^- $ is set to be $ 1.3\times10^{-5} $ at the 90% confidence level.
Using an electron-positron collision data sample corresponding to
2025, 49(4): 044102. doi: 10.1088/1674-1137/ada126
Abstract:
The preformed cluster model (PCM) is applied to investigate the heavy particle radioactivity (HPR) and spontaneous fission (SF) processes for even-Z superheavy nuclear systems. Different proximity potentials are used to calculate the decay half-lives of$Z=112-120 $ nuclei. The fragmentation potential and preformation distribution suggest that SF is the major contributor up to $Z=114 $ , and HPR starts competing for heavier nuclei. The heavy cluster emission is supported by Pb-magicity, whereas SF is reinforced owing to the deformations of fission fragments. The heavy cluster decay half-lives (log$ _{10} $ TC) are calculated using the PCM and are compared with the estimates of the analytical super asymmetric fission (ASAF) model. The calculated log$ _{10} $ TC values agree well with the ASAF measurements when using the Prox-00 and Mod Prox-00 versions of potentials. However, Prox-77, Prox-88, and Prox-BW-91 are not appropriate to address the log$ _{10} $ TC for $ Z \geq 116$ nuclei. To resolve this, we include Z-dependence in the radius parameters. Interestingly, the half-lives match the ASAF data after the inclusion of Z-dependence. The branching ratios are also calculated for superheavy nuclei and compared with the estimates of unified description (UD) formula, universal curve (UNIV), universal decay law (UDL), Horoi formula, and ASAF measurements. Furthermore, the SF half-lives ($T_{\rm SF}$ ) of $ ^{282} $ Cn, $ ^{284} $ Cn, $ ^{284} $ Fl, and $ ^{286} $ Fl superheavy nuclei are estimated through various proximity potentials. Among them, Prox-00 is appropriate for addressing the experimental data. Using this potential, the SF half-lives are estimated through the PCM for $Z=116-120 $ isotopes at different neck-length parameters. Finally, the scaled total kinetic energy (TKE) values are compared with the available data.
The preformed cluster model (PCM) is applied to investigate the heavy particle radioactivity (HPR) and spontaneous fission (SF) processes for even-Z superheavy nuclear systems. Different proximity potentials are used to calculate the decay half-lives of
2025, 49(4): 043101. doi: 10.1088/1674-1137/ada0b4
Abstract:
This study explores the production of charged Higgs particles through photon-photon collisions within the context of the Two Higgs Doublet Model, including one-loop-level scattering amplitudes of electroweak and QED radiation. The cross-section has been scanned for the plane ($m_{\phi^{0}}, \sqrt{s}$ ) to investigate the process of $\gamma\gamma \rightarrow H^{+}H^{-}$ . Three particular numerical scenarios, i.e., low-$m_{H}$ , non-alignment, and short-cascade are employed. The decay channels for charged Higgs particles are examined using $h^{0}$ for low-$m_{H^{0}}$ and $H^{0}$ for non-alignment and short-cascade scenarios incorporating the new experimental and theoretical constraints along with the analysis for cross-sections. We find that, at a low energy, the cross-section is consistently higher for all scenarios. However, as$\sqrt{s}$ increases, it reaches a peak value at 1$~$ TeV for all benchmark scenarios. The branching ratio of the decay channels indicates that for non-alignment, the mode of decay $W^{\pm} h^{0}$ takes control, and for a short cascade, the prominent decay mode remains $t\overline {b}$ , whereas in the low-$m_{H}$ scenario, the dominant decay channel is of $W^{\pm} h^{0}$ . In our research, we employ contemporary machine-learning methodologies to investigate the production of high-energy Higgs bosons within a 3.0 TeV $\gamma\gamma$ collider. We have used multivariate approaches such as Boosted Decision Trees (BDT), LikelihoodD, and Multilayer Perceptron (MLP) to show the observability of heavy-charged Higgs Bosons versus the most significant Standard Model backgrounds. The purity of the signal efficiency and background rejection are measured for each cut value.
This study explores the production of charged Higgs particles through photon-photon collisions within the context of the Two Higgs Doublet Model, including one-loop-level scattering amplitudes of electroweak and QED radiation. The cross-section has been scanned for the plane (
2025, 49(4): 045102. doi: 10.1088/1674-1137/adaa57
Abstract:
This research paper examines a cosmological model in flat space-time via$ f(R,G) $ gravity, where R and G are the Ricci scalar and Gauss-Bonnet invariant, respectively. Our model assumes that $ f(R,G) $ is an exponential function of G combined with a linear combination of R. We scrutinize the observational limitations under a power law cosmology that relies on two parameters, the Hubble constant ($ H_0 $ ) and the deceleration parameter (q) utilizing the 57-point $ H(z) $ data, 8-point BAO data, 1701-point Pantheon+ data, joint data of $ H(z) $ + Pantheon, and joint data of $ H(z) $ + BAO + Pantheon+. The outcomes for $ H_0 $ and q are realistic within observational ranges. We also address energy conditions, $ Om(z) $ analysis, and cosmographical parameters such as jerk, lerk, and snap. Our estimate of $ H_0 $ is remarkably consistent with various recent Planck Collaboration studies that utilize the ΛCDM model. According to our study, power law cosmology within the context of $ f(R,G) $ gravity provides the most comprehensive explanation of the important aspects of cosmic evolution.
This research paper examines a cosmological model in flat space-time via
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