## 2022 Vol. 46, No. 9

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2022, 46(9): 093001. doi: 10.1088/1674-1137/ac74a9
Abstract:
A search for the dimuon decay of the Standard Model Higgs boson is performed using Monte Carlo simulated events to mimic data corresponding to an integrated luminosity of 5.6 ab\begin{document}$^{-1}$\end{document} collected with the Circular Electron-Positron Collider detector in \begin{document}$e^{+}e^{-}$\end{document} collisions at \begin{document}$\sqrt{s}=240$\end{document} GeV. This study investigates the \begin{document}$e^{+}e^{-}\to ZH,\,$\end{document}\begin{document}$Z\to q\bar{q},\,H\to {{\mu^+\mu^-}}$\end{document} process, and the expected significance considering only the statistical uncertainty in the data for a background-only hypothesis for a Higgs boson with a mass of 125 GeV is found to be 6.1\begin{document}$\sigma$\end{document}, corresponding to a precision of 19%. The systematic impacts from the background Monte Carlo statistical fluctuations are estimated to be negligible. Moreover, the dependence of the measurement accuracy on the muon momentum resolution of the CEPC detector is investigated. It is found that the muon momentum resolution must be better than 204 MeV to discover the \begin{document}$H\to\mu\mu$\end{document} process at the nominal integrated luminosity. If the resolution is 100% worse than the designed parameter, the integrated luminosity must be greater than 7.2 ab\begin{document}$^{-1}$\end{document} to reach 5\begin{document}$\sigma$\end{document} significance.
2022, 46(9): 093101. doi: 10.1088/1674-1137/ac6daa
Abstract:
Exclusive vector meson production is an excellent probe for describing the structure of protons. In this study, based on the dipole model, the differential cross sections, total cross sections, and ratios of the longitudinal to transverse cross section of the \begin{document}$J/\psi$\end{document} and \begin{document}$\rho^0$\end{document} productions are calculated with the analytical solution of the Balitsky-Kovchegov (BK) equation. In addition, we consider the influences of two meson wave function models on the results. Our predictions, which are slightly sensitive to meson wave functions, agree with the experimental data. The analytical solution of the BK equation is reliable for description of exclusive vector meson productions in a certain range of \begin{document}$Q^2$\end{document}.
2022, 46(9): 093102. doi: 10.1088/1674-1137/ac6dc6
Abstract:
Recently, scientists have achieved significant progress in experiments searching for excited \begin{document}$\Xi_{b}$\end{document} and \begin{document}$\Lambda_{b}$\end{document} baryons such as \begin{document}$\Lambda_{b}(6072)$\end{document}, \begin{document}$\Lambda_{b}(6146)$\end{document}, \begin{document}$\Lambda_{b}(6152)$\end{document}, \begin{document}$\Xi_{b}(6227)$\end{document}, \begin{document}$\Xi_{b}(6100)$\end{document}, \begin{document}$\Xi_{b}(6327)$\end{document}, and \begin{document}$\Xi_{b}(6333)$\end{document}. Motivated by these achievements, we systematically analyze the \begin{document}$1D$\end{document} and \begin{document}$2D$\end{document} states of \begin{document}$\Xi_{b}$\end{document} and \begin{document}$\Lambda_{b}$\end{document} baryons using the method of quantum chromodynamics sum rules. By constructing three types of interpolating currents, we calculate the masses and pole residues of these heavy baryons with different excitation modes: \begin{document}$(L_{\rho},L_{\lambda})=(0,2)$\end{document}, \begin{document}$(2,0)$\end{document}, and \begin{document}$(1,1)$\end{document}. Subsequently, we decode the inner structures of \begin{document}$\Lambda_{b}(6146)$\end{document}, \begin{document}$\Lambda_{b}(6152)$\end{document}, \begin{document}$\Xi_{b}(6327)$\end{document}, and \begin{document}$\Xi_{b}(6333)$\end{document} and favor assigning these states as the \begin{document}$1D$\end{document} baryons with the quantum numbers \begin{document}$(L_{\rho},L_{\lambda})=(0,2)$\end{document} and \begin{document}${3}/{2}^{+}$\end{document}, \begin{document}${5}/{2}^{+}$\end{document}, \begin{document}${3}/{2}^{+}$\end{document}, and \begin{document}${5}/{2}^{+}$\end{document}, respectively. In addition, the predictions for the masses and pole residues of the other \begin{document}$1D$\end{document} and \begin{document}$2D ~\Xi_{b}$\end{document} and \begin{document}$\Lambda_{b}$\end{document} baryons in this paper will be useful for studying D-wave bottom baryons in the future.
2022, 46(9): 093103. doi: 10.1088/1674-1137/ac6e35
Abstract:
The minimal supersymmetric extension of the standard model (MSSM) is extended to the \begin{document}$U(1)_X$\end{document}SSM, whose local gauge group is \begin{document}$S U(3)_C \times S U(2)_L \times U(1)_Y \times U(1)_X$\end{document}. To obtain the \begin{document}$U(1)_X$\end{document}SSM, we add new superfields to the MSSM, namely, three Higgs singlets \begin{document}$\hat{\eta},\; \hat{\bar{\eta}},\; \hat{S}$\end{document} and right-handed neutrinos \begin{document}$\hat{\nu}_i$\end{document}. The charge conjugate and parity (CP) violating effects are considered to study the lepton electric dipole moment (EDM) in the \begin{document}$U(1)_X$\end{document}SSM. There are more CP violating phases in the \begin{document}$U(1)_X$\end{document}SSM than in the standard model (SM). In this model, several new parameters \begin{document}$(\theta_S, \theta_{BB^{\prime}}, \theta_{BL})$\end{document} are considered as CP violating phases; hence, there are new contributions to lepton EDMs. This is conducive to exploring the source of CP violation and probing new physics beyond the SM.
2022, 46(9): 093104. doi: 10.1088/1674-1137/ac6e37
Abstract:
In this paper, we present the universal structure of the alphabet of one-loop Feynman integrals. The letters in the alphabet are calculated using the Baikov representation with cuts. We consider both convergent and divergent cut integrals and observe that letters in the divergent cases can be easily obtained from convergent cases by applying certain limits. The letters are written as simple expressions in terms of various Gram determinants. The knowledge of the alphabet enables us to easily construct the canonical differential equations of the \begin{document}$d\log$\end{document} form and aids in bootstrapping the symbols of the solutions.
2022, 46(9): 093105. doi: 10.1088/1674-1137/ac6ed2
Abstract:
There may be seven \begin{document}$\bar D^{(*)} \Sigma_c^{(*)}$\end{document} hadronic molecular states. We construct their corresponding interpolating currents and calculate their masses and decay constants using QCD sum rules. Based on these results, we calculate their relative production rates in \begin{document}$\Lambda_b^0$\end{document} decays using current algebra, that is, \begin{document}${\cal{B}}(\Lambda_b^0 \to P_c K^-):{\cal{B}}(\Lambda_b^0 \to P_c^\prime K^-)$\end{document}, where \begin{document}$P_c$\end{document} and \begin{document}$P_c^\prime$\end{document} are two different states. We also study their decay properties via Fierz rearrangement and further calculate these ratios in the \begin{document}$J/\psi p$\end{document} mass spectrum, that is, \begin{document}${\cal{B}}(\Lambda_b^0 \to P_c K^- \to J/\psi p K^-):{\cal{B}}(\Lambda_b^0 \to P_c^\prime K^- \to J/\psi p K^-)$\end{document}. Our results suggest that the \begin{document}$\bar D^{*} \Sigma_c^{*}$\end{document} molecular states of \begin{document}$J^P = 1/2^-$\end{document} and \begin{document}$3/2^-$\end{document} may be observed in future experiments.
2022, 46(9): 093106. doi: 10.1088/1674-1137/ac7041
Abstract:
Using the Bethe-Salpeter equation (BSE), we investigate the forward-backward asymmetries \begin{document}$(A _{\rm FB})$\end{document} in \begin{document}$\Lambda_b \rightarrow \Lambda l^+ l^-(l=e,\mu,\tau)$\end{document} in the quark-diquark model. This approach provides precise form factors that are different from those of quantum chromodynamics (QCD) sum rules. We calculate the rare decay form factors for \begin{document}$\Lambda_b \rightarrow \Lambda l^+ l^-$\end{document}b and investigate the (integrated) forward-backward asymmetries in these decay channels. We observe the integrated \begin{document}$A^l_{\rm FB}$\end{document}, \begin{document}$\bar{A}^l_{\rm FB}(\Lambda_b \rightarrow$\end{document}\begin{document}$\Lambda e^+ e^-) \simeq -0.1371$\end{document}, \begin{document}$\bar{A}^l_{\rm FB}(\Lambda_b \rightarrow \Lambda \mu^+ \mu^-) \simeq -0.1376$\end{document}, and \begin{document}$\bar{A}^l_{\rm FB}(\Lambda_b \rightarrow \Lambda \tau^+ \tau^-) \simeq$\end{document}\begin{document}$-0.1053$\end{document}; the hadron side asymmetries \begin{document}$\bar{A}^h_{\rm FB}(\Lambda_b \rightarrow \Lambda \mu^+ \mu^-)\simeq -0.2315$\end{document}; the lepton-hadron side asymmetries \begin{document}$\bar{A}^{lh}_{\rm FB}(\Lambda_b \rightarrow \Lambda \mu^+ \mu^-)\simeq 0.0827$\end{document}; and the longitudinal polarization fractions \begin{document}$\bar{F}_L(\Lambda_b \rightarrow \Lambda \mu^+ \mu^-)\simeq 0.5681$\end{document}.
2022, 46(9): 093107. doi: 10.1088/1674-1137/ac71a6
Abstract:
Recently, the Muon g-2 experiment at Fermilab measured the muon anomalous magnetic dipole moment (MDM), \begin{document}$a_\mu=(g_\mu-2)/2$\end{document}, and reported that the new experimental average increases the difference between the experiment and the standard model (SM) prediction to 4.2σ. In this work, we reanalyze the muon anomalous MDM at the two-loop level in the μ from the ν Supersymmetric Standard Model ( \begin{document}$\mu\nu$\end{document}SSM) combined with the updated experimental average. The \begin{document}$\mu\nu$\end{document}SSM can explain the current difference between the experimental measurement and the SM theoretical prediction for the muon anomalous MDM, constrained by the 125 GeV Higgs boson mass and decays, the rare decay \begin{document}$\bar{B}\rightarrow X_s\gamma$\end{document}, and so on. We also investigate the anomalous MDM of the electron and tau lepton, \begin{document}$a_e=(g_e-2)/2$\end{document} and \begin{document}$a_\tau=(g_\tau-2)/2$\end{document}, at the two-loop level in the \begin{document}$\mu\nu$\end{document}SSM. In addition, the decaying of the 125 GeV Higgs boson into a pair of charged leptons in the \begin{document}$\mu\nu$\end{document}SSM is analyzed.
2022, 46(9): 093108. doi: 10.1088/1674-1137/ac7200
Abstract:
If two annihilation products of dark matter (DM) particles are non-relativistic and couple to a light force mediator, their plane wave functions are modified due to multiple exchanges of the force mediator. This gives rise to the final state Sommerfeld (FSS) effect. It is also possible that the final state particles form a bound state. Both the FSS effect and final bound-state (FBS) effect need to be considered in the calculation of the DM relic abundance. The annihilation products can be non-relativistic if their masses are comparable to those of the annihilating DM particles. We study the FSS and FBS effects in the mass-degenerate region using two specific models. Both models serve to illustrate different partial-wave contributions in the calculations of the FSS and FBS effects. We find that the FBS effect can be comparable to the FSS effect when the annihilation products couple strongly with a light force mediator. Those effects significantly modify the DM relic abundance.
2022, 46(9): 093109. doi: 10.1088/1674-1137/ac7299
Abstract:
The two-photon radiative decay process \begin{document}$J/\psi \to 2\gamma+hadrons$\end{document} was studied, and the main contribution processes, \begin{document}$J/\psi \to 2\gamma + g g g$\end{document} and \begin{document}$J/\psi \to 2\gamma + q \bar{q}$\end{document}, were calculated. With the specific conditions at the BESIII, this rare decay process and the main background process \begin{document}$e^{+} e^{-} \to \gamma \gamma + hadrons (q \bar{q})$\end{document}were investigated. The results show that the ratio of signal to background can reach 1.24 with optimized selection criteria at the BESIII. In addition, distributions of the signal and background are presented. All the results show that the signal is large enough to be experimentally measured.
2022, 46(9): 093110. doi: 10.1088/1674-1137/ac7317
Abstract:
The influence of the isospin-breaking \begin{document}$\pi^0 - \eta - \eta'$\end{document} mixing effect on the \begin{document}$CP$\end{document}-asymmetries of \begin{document}$B\to K\pi$\end{document} processes is examined for the first time. It is found that this mixing effect presents significant uncertainty for both the \begin{document}$CP$\end{document}-asymmetry sum rule of \begin{document}$B\to K\pi$\end{document} processes and the \begin{document}$CP$\end{document}-asymmetry difference of \begin{document}$B^+\to K^+\pi^0$\end{document} and \begin{document}$B^0\to K^+\pi^-$\end{document}, potentially obscuring the significance of the \begin{document}$K\pi$\end{document}-puzzle. As the correction caused by the \begin{document}$\pi^0 - \eta - \eta'$\end{document} mixing effect is highly dependent on four strong non-perturbative phases, a definitive conclusion is currently unavailable.
2022, 46(9): 093111. doi: 10.1088/1674-1137/ac745a
Abstract:
We study the application of BCFW recursion relations to the QED process \begin{document}$0 \to e^- e^+ n \gamma$\end{document}. Based on 6-point amplitudes (both MHVA and NMHVA) computed from Feynman diagrams in the Berends-Giele gauge, we conduct a comprehensive study on different shifts. Subsequently, we propose a new shift (LLYZ shift), which can lead to the full amplitudes of these processes and have several realistic computational advantages. We compare the number of terms and independent amplitudes of this novel shift with those of a few typical shifts.
2022, 46(9): 093112. doi: 10.1088/1674-1137/ac7547
Abstract:
New physics could be explored through loop effects using the precision measurements at the Circular Electron Positron Collider (CEPC) owing to its clean collision environment and high luminosity. In this paper, we focus on two dark matter models that involve additional electroweak fermionic multiplets. We calculate their one-loop corrections in five processes, i.e., \begin{document}$e^+e^- \to \mu^+\mu^-, \; Zh, \; W^+W^-, \; ZZ$\end{document}, and \begin{document}$Z\gamma$\end{document}, and investigate the corresponding signatures at the CEPC with the projected sensitivity. We observe that the detectable parameter regions of these processes are complementary. The combined analysis shows that the mass of dark matter \begin{document}$m_{\chi^0_1}$\end{document} in these two models can be probed up to \begin{document}$\sim 150\; {\rm{GeV}}$\end{document} and \begin{document}$\sim 450$\end{document} GeV, respectively, at a 95% confidence level.
2022, 46(9): 094001. doi: 10.1088/1674-1137/ac6dab
Abstract:
The positive-parity signature partner bands in 103,105Pd and 109Cd nuclei are investigated using the classical particle-rotor model. Based on the systematic study of neighbouring nuclei, the signature partner bands of 105Pd are assigned to the \begin{document}$\pi(g_{9/2}^{-4}) \otimes \nu(g_{7/2}h_{11/2}^{2})$\end{document} configuration, and this assignment is also supported by the present calculations. Furthermore, the calculated \begin{document}$B(E2)$\end{document} values of such bands of 105Pd reproduce the experimental values well and exhibit a decrease with increasing angular momentum, suggesting that these two bands may originate from antimagnetic rotation. Similar signature partner bands are also found in the neighboring 103Pd and 109Cd nuclei. The properties of both bands are in general agreement with the fingerprints of antimagnetic rotation, and thus the signature partner bands of 103Pd and 109Cd are suggested to be candidates for the multiple antimagnetic rotational bands of 105Pd. In addition, the evolution of the two-shears-like mechanism for possible multiple antimagnetic rotational bands in 103,105Pd and 109Cd nuclei is examined by investigating the orientation of the angular momenta.
2022, 46(9): 094002. doi: 10.1088/1674-1137/ac6f4f
Abstract:
Excited states of 119Sn have been studied using an in-beam γ-ray spectroscopic technique following the incomplete fusion of 7Li on a 116Cd target at a beam energy of 42 MeV. A new bandlike structure is proposed to result from deformed two-particle-two-hole (2p-2h) proton excitations across the Z = 50 closed shell based on the systematics of odd-A Sn isotopes and configuration-fixed constrained triaxial relativistic mean-field calculations. This observation extends the boundaries of the deformed 2p-2h collective band to A = 119 in Sn isotopes.
2022, 46(9): 094003. doi: 10.1088/1674-1137/ac73e8
Abstract:
This study measured the yields of the radionuclides 82Sr, 83(m+g)Sr, 85mSr, 85gSr, 87mSr, 81(g+0.976m)Rb, 82mRb, 83gRb, 84(m+g)Rb, and 86(m+g)Rb produced in natSr(γ, xnyp) multiparticle reactions with bremsstrahlung end-point energies of 55, 60, and 65 MeV. The bremsstrahlung radiation was generated using the 100-MeV electron linear accelerator at the Pohang Accelerator Laboratory, Korea, and the reaction yields were derived from the induced activitiesmeasured using off-line γ-ray spectrometry. To obtain accurate experimental results, we performed the necessary γ-rayinterference corrections. The experimental results were compared with the theoretical predictions obtained usingthe TALYS-1.95 statistical nuclear model code. The calculations were performed using six different level-density models to ascertain which model best fitted the experimental results. The dependence of the reaction yield on the incident bremsstrahlung energy and on the number of nucleons emitted by the photonuclear reactions was also investigated.
2022, 46(9): 094101. doi: 10.1088/1674-1137/ac6dac
Abstract:
The collinearly-improved Balitsky-Kovchegov (ciBK) equation evolved unintegrated gluon distribution (UGD) is used for the first time to study hadron production in high energy proton-proton collisions in order to improve the predictive power of the Color Glass Condensate effective theory. We show that the ciBK equation evolved UGD provides a relatively better description of LHC data on the transverse momentum and integrated multiplicity distributions of charged hadron and neutral pion production for several collision energies compared with the running coupling Balitsky-Kovchegov (rcBK) equation evolved UGD. This is because the ciBK evolved UGD has a sharper transverse momentum distribution than the rcBK UGD. The impact of running coupling prescriptions on hadron production is studied, and it is found that the parent dipole and smallest dipole running coupling prescriptions provide similar depictions of the data. Moreover, the scale dependence of the fragmentation function is investigated by taking three typical values of scale. We find that the differences resulting from the scale dependence of the fragmentation function can be fully absorbed into the normalization factor, which lumps higher order corrections.
2022, 46(9): 094102. doi: 10.1088/1674-1137/ac6ed3
Abstract:
Multinucleon transfer reactions near the Coulomb barrier are investigated based on the improved dinuclear system (DNS) model, and the deexcitation process of primary fragments are described using the statistical model GEMINI++. The production cross sections of \begin{document}$^{40,48}$\end{document}Ca+\begin{document}$^{124}$\end{document}Sn and \begin{document}$^{64}$\end{document}Ni+\begin{document}$^{130}$\end{document}Te based on the DNS model+GEMINI++ are calculated and compared with experimental data. The calculated results reproduce experimental data. The cross sections of fusion-evaporation, fragmentation, and multinucleon transfer reactions in the \begin{document}$40 \leq Z \leq 60$\end{document} region are also provided in this paper. The results show that in the \begin{document}$40 \leq Z \leq 60$\end{document} region, fusion-evaporation and fragmentation reactions have good results in the relatively proton-rich region, but in the extreme proton-deficient region, the MNT reaction is still promising for synthesizing proton-rich nuclei.
2022, 46(9): 094103. doi: 10.1088/1674-1137/ac6f4e
Abstract:
Based on the current measurement of the neutron distribution radius (\begin{document}$R_n$\end{document}) of 208Pb from the PREX-2 data, we revisited the recently developed G3 and IOPB-I force parameters by fine-tuning some specific couplings within the relativistic mean-field (RMF) model. The ω–ρ-mesons coupling \begin{document}$\Lambda_{\omega}$\end{document} and the ρ-meson coupling \begin{document}$g_{\rho}$\end{document} are constrained to the experimental neutron radius of 208Pb without compromising the bulk properties of finite nuclei and infinite nuclear matter observables. The modified parameter sets are applied to calculate the gross properties of finite nuclei such as binding energies, charge distributions, nuclear radii, pairing gaps, and single-particle energies. The root-mean-square deviations in binding energy and charge radius are estimated with respect to the available experimental data for 195 even–even nuclei, and the results compare favourably with the well-calibrated effective interactions of Skyrme, Gogny and other relativistic mean-field parametrizations. The pairing gap estimations for modified G3 and IOPB-I for Sn isotopes are also compared with the Hartree–Fock–Bogoliubov calculation with the Gogny (D1S) interaction. The isotopic shift and single-particle energy spacing are also calculated and compared with the experimental data for both original and modified versions of the G3 and IOPB-I parameter sets. Subsequently, both the modified parameter sets are used to obtain the various infinite nuclear matter observables at saturation. In addition to these, the force parameters are adopted to calculate the properties of a high isospin asymmetry dense system such as neutron star matter and tested for validation using the constraint from GW170817 binary neutron star merger events. The tuned forces predict relatively good results for finite and infinite nuclear matter systems and the current limitation on the neutron radius from PREX-2. A systematic analysis using these two refitted parameter sets over the nuclear chart will be communicated shortly.
2022, 46(9): 094104. doi: 10.1088/1674-1137/ac6fc8
Abstract:
Charmonium dissociation is an important probe of the quark–gluon plasma medium in heavy-ion collisions. The magnetic field produced in non-central collisions can affect the charmonia and their dissociation. We study the \begin{document}$c\bar{c}$\end{document} bound state in magnetic field and at finite temperature using the Schrödinger equation. We find that below the dissociation temperature, both the magnetic field and momentum of the charmonia affect the formation or dissociation of the bound state, forming a non-trivial structure.
2022, 46(9): 094105. doi: 10.1088/1674-1137/ac7201
Abstract:
Light mesons \begin{document}$(\sigma, \pi^0, \pi^\pm)$\end{document} are investigated in \begin{document}$\mu_B-T-eB$\end{document} and \begin{document}$\mu_I-T-eB$\end{document} spaces using a two-flavor NJL model and used to determine chiral symmetry restoration and the pion superfluid phase transition. In \begin{document}$\mu_B-T-eB$\end{document} space, during the chiral symmetry restoration process, the mass of the pseudo-Goldstone mode \begin{document}$\pi^0$\end{document} increases, with sudden jumps. At the critical end point, the \begin{document}$\pi^0$\end{document} meson exhibits a sharp but continuous mass increase, with a sudden mass jump at the Mott transition. In the nearby first order chiral phase transition region, we observe two \begin{document}$\pi^0$\end{document} mass jumps, one induced by the Mott transition and the other by the quark mass jump. The mass of the Higgs mode σ first decreases and then increases with chiral symmetry restoration, only showing a jump at the first order chiral phase transition. We plot a chiral phase diagram in terms of the change in quark mass, the Mott transition of the pseudo-Goldstone mode \begin{document}$\pi^0$\end{document}, and the minimum mass of the Higgs mode σ. Owing to explicit breaking of chiral symmetry in the physical case, the chiral restoration phase boundaries on the \begin{document}$\mu_B-T$\end{document} plane from the order parameter side and meson side are different. The \begin{document}$\pi^0$\end{document} and σ mass jumps will be helpful to the experimental search for the chiral phase diagram and critical end point. On the \begin{document}$\mu_I-T$\end{document} plane, the competition between the pion superfluid phase transition and chiral symmetry restoration under magnetic fields is studied in terms of the Goldstone mode \begin{document}$\pi^+$\end{document} and pseudo-Goldstone mode \begin{document}$\pi^0$\end{document}. In contrast to the two mass jumps of \begin{document}$\pi^0$\end{document} in the first order chiral phase transition region, the \begin{document}$\pi^+$\end{document} meson displays several mass jumps in the chiral crossover region. At the critical end point, \begin{document}$\pi^+$\end{document} also has sharp but continuous mass change, with a mass jump at the Mott transition. The isospin symmetry is strict, and the pion superfluid phase transition is uniquely determined by the massless Goldstone mode \begin{document}$\pi^+$\end{document}. The separation of chiral restoration and the pion superfluid phase boundaries is enhanced by the external magnetic field.
2022, 46(9): 095101. doi: 10.1088/1674-1137/ac6dc8
Abstract:
The dependence of the black hole (BH) shadow and thermodynamics may be structured in regular spacetime. Taking a regular Bardeen-AdS BH as an example, the relationship between the shadow radius and event horizon radius is derived. It is found that these two radii display a positive correlation, implying that the BH temperature can be rewritten as a function of shadow radius in regular spacetime. By analyzing the phase transition curves under the shadow context, we find that the shadow radius can replace the event horizon radius to present the BH phase transition process, and the phase transition grade can also be revealed by the shadow radius, indicating that the shadow radius may serve as a probe for phase structure in regular spacetime. Utilizing the temperature-shadow radius function, the thermal profile of the Bardeen-AdS BH is established. Moreover, the temperature exhibits an N-type change trend in the \begin{document}$P<P_{\rm{c}}$\end{document} situation. These results suggest that the phase transition process of a regular AdS BH can be completely presented in the thermal profile, and the relationship between the BH shadow and thermodynamics can also be established in regular spacetime.
2022, 46(9): 095102. doi: 10.1088/1674-1137/ac6ed4
Abstract:
One of the fundamental challenges in cosmic ray physics is to explain the nature of cosmic ray acceleration and propagation mechanisms. Owing to the precise cosmic ray data measured by recent space experiments, we can investigate cosmic ray acceleration and propagation models more comprehensively and reliably. In this paper, we combine the secondary-to-primary ratios and primary spectra measured by PAMELA, AMS02, ACE-CRIS, and Voyager-1 to constrain the cosmic ray source and transport parameters. The study shows that the \begin{document}$Z>2$\end{document} data yield a medium-energy diffusion slope \begin{document}$\delta_{2}\sim\left(0.42, 0.48\right)$\end{document} and a high-energy slope \begin{document}$\delta_{3}\sim\left(0.22, 0.34\right)$\end{document}. The \begin{document}$Z\leq2$\end{document} species place a looser constraint on \begin{document}$\delta_{2}\sim\left(0.38, 0.47\right)$\end{document} but a tighter constraint on \begin{document}$\delta_{3}\sim\left(0.21, 0.30\right)$\end{document}. The overlaps imply that heavy and light particles can provide compatible results at medium to high energies. Moreover, both the light and heavy nuclei indicate a consistent diffusion slope variation \begin{document}$\Delta\delta_{H}$\end{document} at \begin{document}$200\sim300$\end{document} GV. At low energies, significant disagreements exist between heavy and light elements. The boron-to-carbon ratio requires a much larger diffusion slope shift \begin{document}$\Delta\delta_{L}$\end{document} at approximately 4 GV or a stronger Alfvén velocity \begin{document}$v_{A}$\end{document} than the low-mass data. This indicates that the heavy and light particles may suffer different low-energy transport behaviors in the galaxy. However, a better understanding of the consistency/inconsistency between the heavy and light cosmic rays relies on more precise cross-sections, better constraints on correlations in systematic errors of data, a more accurate estimation of the galaxy halo size, and a more robust description of solar modulation during the reversal period of the heliospheric magnetic field.
We study the linear instability and nonlinear dynamical evolution of the Reissner-Nordström (RN) black hole in the Einstein-Maxwell-scalar theory in asymptotic flat spacetime. We focus on the coupling function \begin{document}$f(\phi)={\rm e}^{-b\phi^2}$\end{document}, which facilitates both scalar-free RN and scalarized black hole solutions. We first present the evolution of system parameters during dynamic scalarization. For parameter regions in which spontaneous scalarization occurs, we observe that the evolution of the scalar field at the horizon is dominated by the fundamental unstable mode from linear analysis at early times. At late times, the nonlinear evolution can be considered to be the perturbation of scalarized black holes.
This paper examines traversable wormhole models in the \begin{document}$f(R)$\end{document} theories of gravity by applying the Karmarkar condition. For this purpose, we consider spherically symmetric space-time to examine the structure of wormholes. First, we investigate wormholes and their geometry using the redshift function under various conditions. Subsequently, we discuss the embedding diagram of the upper and lower universe using radial coordinates in two and three-dimensional Euclidean affine space. Three exclusive models are considered for the \begin{document}$f(R)$\end{document} theories of gravity, and the radial and tangential pressures are observed. Furthermore, by taking a definite shape function, we observe the behavior of energy conditions. We determine that energy conditions are violated, and their violation is generic and represents the presence of exotic matter. According to Einstein's field theory, the existence of wormholes is predicated on the occurrence of rare material. Hence, we conclude that our study is more realistic and stable.