## 2022 Vol. 46, No. 8

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2022, 46(8): 081001. doi: 10.1088/1674-1137/ac68d7
Abstract:
The recently proposed \begin{document}$N^*(890)$\end{document} \begin{document}$1/2^-$\end{document} baryon is studied in a flavor \begin{document}$S U(3)$\end{document} scheme with K-matrix unitarization, by fitting to low-energy cross section and phase shift data. It is found that \begin{document}$N^*(890)$\end{document} co-exists with low-lying poles in other channels, which have been extensively discussed in the literature, though they belong to different octets in the \begin{document}$S U(3)$\end{document} limit. Hence, the existence of \begin{document}$N^*(890)$\end{document} is further verified.
2022, 46(8): 083101. doi: 10.1088/1674-1137/ac6666
Abstract:
Analytical formulae for the phase space factors and three-momenta of three- and four-body final states are derived for all sets of independent kinematic variables containing invariant mass variables. These formulae will help experimental physicists to perform data analysis. As an example, we show how to use these formulae to distinguish the different mechanisms of the \begin{document}$e+p\to e+J/\psi+ p$\end{document} process when searching the signals of \begin{document}$P_c$\end{document} states in the energy region of the Electron–Ion collider at China (EicC).
2022, 46(8): 083102. doi: 10.1088/1674-1137/ac67d0
Abstract:
We consider a simple scalar dark matter model within the frame of gauged \begin{document}$L_{\mu}-L_{\tau}$\end{document} symmetry. A new gauge boson \begin{document}$Z'$\end{document}, as well as two scalar fields S and Φ, are introduced to the Standard Model (SM), where S and Φ are SM singlets but both carry \begin{document}$U(1)_{L_{\mu}-L_{\tau}}$\end{document} charge. The real component and imaginary component of S can acquire different masses after spontaneously breaking symmetry, and the lighter one can play the role of dark matter, which is stabilized by an extra \begin{document}$Z_2$\end{document} symmetry. We consider the possibility of light dark matter as well as the co-annihilation case in our model and present the current \begin{document}$(g-2)_{\mu}$\end{document} anomaly, Higgs invisible decay, dark matter relic density, and direct detection constraints on the parameter space. Direct detection gives the most stringent restriction on the model, and we found that although most of the parameter space is excluded, a mass region of a few GeV is still allowed where the co-annihilation process is also permitted in the model.
2022, 46(8): 083103. doi: 10.1088/1674-1137/ac6573
Abstract:
Considering the B mesonic wave function \begin{document}${\phi}_{B2}$\end{document}, \begin{document}$B {\to} PV$\end{document} decays are restudied in the leading order for three scenarios using the perturbative QCD approach within the standard model, where \begin{document}$P = {\pi}$\end{document} and K, and V denotes the ground \begin{document}$S U(3)$\end{document} vector mesons. It is found that contributions from \begin{document}${\phi}_{B2}$\end{document} can enhance most branching ratios and are helpful for improving the overall consistency of branching ratios between the updated calculations and available data, although there are still several discrepancies between the experimental and theoretical results.
2022, 46(8): 083104. doi: 10.1088/1674-1137/ac6a4e
Abstract:
A new approach for tree-level amplitudes with multiple fermion lines is presented. It primarily focuses on the simplification of fermion lines. By calculating two vectors recursively without any matrix multiplications, the result of a fermion line is reduced to a very compact form depending only on the two vectors. Comparisons with other packages are presented, and the results show that our package FDC provides a very good performance in the processes of multiple fermion lines with this new approach and some other improvements. A further comparison with WHIZARD shows that this new approach has a competitive efficiency in computing pure amplitude squares without phase space integration.
2022, 46(8): 083105. doi: 10.1088/1674-1137/ac6a4f
Abstract:
In this paper, we present some results on the behavior of the total cross section and ρ-parameter at asymptotic energies in proton–proton (\begin{document}$pp$\end{document}) and antiproton–proton (\begin{document}$\bar{p}p$\end{document}) collisions. Hence, we consider three of the main theoretical results in high energy physics: the crossing property, derivative dispersion relation, and optical theorem. The use of such machinery facilitates the derivation of analytic formulas for a wide set of the measured global scattering parameters and some important relations between them. The suggested parameterizations approximate the energy dependence for the total cross section and ρ-parameter for \begin{document}$pp$\end{document} and \begin{document}$\bar{p}p$\end{document} with a statistically acceptable quality in the multi-TeV region. Additionally, the qualitative description is obtained for important interrelations, namely difference, sum, and ratio of the antiparticle–particle and particle–particle total cross sections. Despite the reduced number of experimental data for the total cross section and ρ-parameter at the TeV-scale, which complicates any prediction for the beginning of the asymptotic domain, the fitting procedures indicates that asymptotia occur in the energy range 25.5–130 TeV. Moreover, in the asymptotic regime, we obtain \begin{document}$\alpha_{\mathbb{P}}=1$\end{document}. A detailed quantitative study of the energy behavior of the measured scattering parameters and their combinations in the ultra–high energy domain indicates that the scenario with the generalized formulation of the Pomeranchuk theorem is more favorable with respect to the original formulation of this theorem.
2022, 46(8): 083106. doi: 10.1088/1674-1137/ac6b92
Abstract:
We investigate the in-medium masses of open charm mesons (D(\begin{document}$D^0$\end{document}, \begin{document}$D^+$\end{document}), \begin{document}$\bar{D}$\end{document}(\begin{document}$\bar{D^0}$\end{document}, \begin{document}$D^-$\end{document}), \begin{document}$D_s$\end{document}(\begin{document}${D_{s}}^+$\end{document}, \begin{document}${D_{s}}^-$\end{document})) and charmonium states (\begin{document}$J/\psi$\end{document}, \begin{document}$\psi(3686)$\end{document}, \begin{document}$\psi(3770)$\end{document}, \begin{document}$\chi_{c0}$\end{document}, \begin{document}$\chi_{c2}$\end{document}) in strongly magnetized isospin asymmetric strange hadronic matter using a chiral effective model. In the presence of a magnetic field, the number and scalar densities of charged baryons have contributions from Landau energy levels. The mass modifications of open charm mesons result from their interactions with nucleons, hyperons, and the scalar fields (the non-strange field σ, strange field ζ, and isovector field δ) in the presence of a magnetic field. The mass modifications of the charmonium states result from the modification of gluon condensates in a medium simulated by the variation in the dilaton field (χ) in the chiral effective model. The effects of finite quark masses are also incorporated in the trace of the energy-momentum tensor in quantum chromodynamics to investigate the mass shifts of charmonium states. The in-medium masses of open charm mesons and charmonia are observed to decrease with an increase in baryon density. The charged \begin{document}$D^+$\end{document}, \begin{document}$D^-$\end{document}, \begin{document}${D_{s}}^+$\end{document}, and \begin{document}${D_{s}}^-$\end{document} mesons have additional positive mass shifts due to Landau quantization in the presence of a magnetic field. The effects of the strangeness fraction are observed to be more dominant for \begin{document}$\bar{D}$\end{document} mesons compared with D mesons. The mass shifts of charmonia are observed to be larger in hyperonic media compared with nuclear media when the effect of the finite quark mass term is neglected. These medium mass modifications can have observable consequences on the production of the open charm mesons and charmonia in high-energy asymmetric heavy-ion collision experiments.
2022, 46(8): 083107. doi: 10.1088/1674-1137/ac6cd3
Abstract:
Many researches from both theoretical and experimental perspectives have been performed to search for a new Higgs Boson that is lighter than the 125 \begin{document}${\rm GeV}$\end{document} Higgs boson, which was discovered at the LHC in 2012. In this study, we explore the possibility of constraining a lighter neutral custodial fiveplet scalar \begin{document}$H_{5}^{0}$\end{document} in the Georgi-Machacek (GM) model using the latest results of the search for a lighter Higgs boson decaying into two photons from LHC data. The custodial-singlet mass eigenstate h or H is considered to be the LHC observed 125 \begin{document}${\rm GeV}$\end{document} Higgs boson. A new set of constrained parameters that is favoured by low-mass \begin{document}$H_{5}^{0}$\end{document} is proposed to generate events efficiently. The production of \begin{document}$H_{5}^{0}$\end{document} from a scan based on the constrained parameters is compared to the latest results of the search for a lighter Higgs boson decaying into two photons by the CMS Collaboration after applying theoretical constraints from the GM model and constraints from all existing relevant experimental measurements, including the recent results of the Higgs boson searches by the LHC. Numerical analyses of the surviving GM parameter space are performed. The tendencies and correlations of the GM input parameters from phenomenological studies are summarized. In addition, the discovery potential of the other interesting decay channels of this low-mass neutral custodial fiveplet scalar are discussed.
2022, 46(8): 083108. doi: 10.1088/1674-1137/ac6cd5
Abstract:
We study the \begin{document}$\bar B_s^0 \to J/\psi f_0(980)$\end{document} and \begin{document}$\bar B_s^0 \to J/\psi a_0(980)$\end{document} reactions, and pay attention to the different sources of isospin violation and mixing of \begin{document}$f_0(980)$\end{document} and \begin{document}$a_0(980)$\end{document} resonances where these resonances are dynamically generated from meson–meson interactions. We find that the main cause of isospin violation is isospin breaking in the meson–meson transition T matrices, and the other source is that the loops involving kaons in the production mechanism do not cancel due to the different masses of charged and neutral kaons. We obtain a branching ratio for \begin{document}$a_0(980)$\end{document} production of the order of \begin{document}$5 \times 10^{-6}$\end{document}. Future experiments can address this problem, and the production rate and shape of the \begin{document}$\pi^0 \eta$\end{document} mass distribution will definitely help to better understand the nature of scalar resonances.
2022, 46(8): 083109. doi: 10.1088/1674-1137/ac6cd8
Abstract:
We study the dynamical chiral symmetry breaking/restoration for various numbers of light quarks flavors \begin{document}$N_f$\end{document} and colors \begin{document}$N_c$\end{document} using the Nambu-Jona-Lasinio (NJL) model of quarks in the Schwinger-Dyson equation framework, dressed with a color-flavor dependence of effective coupling. For fixed \begin{document}$N_f = 2$\end{document} and varying \begin{document}$N_c$\end{document}, we observe that the dynamical chiral symmetry is broken when \begin{document}$N_c$\end{document} exceeds its critical value \begin{document}$N^{c}_{c}\approx2.2$\end{document}. For a fixed \begin{document}$N_c = 3$\end{document} and varying \begin{document}$N_f$\end{document}, we observe that the dynamical chiral symmetry is restored when \begin{document}$N_f$\end{document} reaches its critical value \begin{document}$N^{c}_{f}\approx8$\end{document}. Strong interplay is observed between \begin{document}$N_c$\end{document} and \begin{document}$N_f$\end{document}, i.e., larger values of \begin{document}$N_c$\end{document} tend to strengthen the dynamical generated quark mass and quark-antiquark condensate, while higher values of \begin{document}$N_f$\end{document} suppress both parameters. We further sketch the quantum chromodynamics (QCD) phase diagram at a finite temperature T and quark chemical potential μ for various \begin{document}$N_c$\end{document} and \begin{document}$N_f$\end{document}. At finite T and μ, we observe that the critical number of colors \begin{document}$N^{c}_c$\end{document} is enhanced, whereas the critical number of flavors \begin{document}$N^{c}_f$\end{document} is suppressed as T and μ increase. Consequently, the critical temperature \begin{document}$T_c$\end{document}, \begin{document}$\mu_c$\end{document}, and co-ordinates of the critical endpoint \begin{document}$(T^{E}_c,\mu^{E}_c)$\end{document} in the QCD phase diagram are enhanced as \begin{document}$N_c$\end{document} increases and suppressed when \begin{document}$N_f$\end{document} increases. Our findings agree with the lattice QCD and Schwinger-Dyson equations predictions.
2022, 46(8): 083110. doi: 10.1088/1674-1137/ac6d4e
Abstract:
In the framework of the QCD factorization approach, we study the localized \begin{document}$CP$\end{document} violations of the \begin{document}$B^-\rightarrow K^- \pi^+\pi^-$\end{document} decay with and without the \begin{document}$a_0^0(980)-f_0(980)$\end{document} mixing mechanism and observe that the localized \begin{document}$CP$\end{document} violation can be enhanced by this mixing effect when the mass of the \begin{document}$\pi^+\pi^-$\end{document} pair is in the vicinity of the \begin{document}$f_0(980)$\end{document} resonance. The corresponding theoretical prediction results are \begin{document}${\cal{A}}_{CP}(B^-\rightarrow K f_0 \rightarrow K^-\pi^+\pi^-)= [0.126,\ 0.338]$\end{document} (\begin{document}$0.232\pm0.106$\end{document} with the central value form) and \begin{document}${\cal{A}}_{CP}(B^-\rightarrow K^- f_0(a_0) \rightarrow K^-\pi^+\pi^-)=[0.230, 0.615]$\end{document} (\begin{document}$0.423\pm0.193$\end{document} with the central value form), respectively. Meanwhile, we also calculate the branching fraction of the \begin{document}$B^-\rightarrow K^-f_0(980)\rightarrow K^-\pi^+\pi^-$\end{document} decay, which is consistent with the experimental results. We suggest that the \begin{document}$a_0^0(980)-f_0(980)$\end{document} mixing mechanism should be considered when theoretically and experimentally studying the \begin{document}$CP$\end{document} violation of the B or D meson decays.
2022, 46(8): 083111. doi: 10.1088/1674-1137/ac6d51
Abstract:
The XENON1T excess of keV electron recoil events may be induced by the scattering of electrons and long-lived particles with an MeV mass and high speed. We consider a tangible model composed of two scalar MeV dark matter (DM) particles, \begin{document}$S_A$\end{document} and \begin{document}$S_B$\end{document}, to interpret the XENON1T keV excess via boosted \begin{document}$S_B$\end{document}. A small mass splitting \begin{document}$m_{S_A}-m_{S_B}>0$\end{document} is introduced, and the boosted \begin{document}$S_B$\end{document} can be produced using the dark annihilation process of \begin{document}$S_A S_A^\dagger \to \phi \to S_B S_B^\dagger$\end{document} via a resonant scalar ϕ. \begin{document}$S_B-$\end{document}electron scattering is intermediated by a vector boson X. Although the constraints from Big Bang nucleosynthesis, cosmic microwave background (CMB), and low-energy experiments set the \begin{document}$X-$\end{document}mediated \begin{document}$S_B-$\end{document}electron scattering cross section to be \begin{document}$\lesssim 10^{-35} \mathrm{cm}^2$\end{document}, the MeV scale DM with a resonance enhanced dark annihilation today can still provide sufficient boosted \begin{document}$S_B$\end{document} and induce the XENON1T keV excess. The relic density of \begin{document}$S_B$\end{document} is significantly reduced by the s-wave process \begin{document}$S_B S_B^\dagger \to X X$\end{document}, which is permitted by the constraints from CMB and 21-cm absorption. A very small relic fraction of \begin{document}$S_B$\end{document} is compatible with the stringent bounds on un-boosted \begin{document}$S_B$\end{document}-electron scattering in DM direct detection, and the \begin{document}$S_A$\end{document}-electron scattering is also allowed.
2022, 46(8): 084101. doi: 10.1088/1674-1137/ac67cf
Abstract:
Density-dependent nuclear symmetry energy is directly related to isospin asymmetry for finite and infinite nuclear systems. It is critical to determine the coefficients of symmetry energy and their related observables because they hold great importance in different areas of nuclear physics, such as the analysis of the structure of ground state exotic nuclei and neutron star studies. The ground state bulk properties of Scandium (Z = 21) and Titanium (Z = 22) nuclei are calculated, such as their nuclear binding energy (\begin{document}$B.E.$\end{document}), quadrupole deformation (\begin{document}$\beta_2$\end{document}), two-neutron separation energy (\begin{document}$S_{ {2n}}$\end{document}), differential variation in the two-neutron separation energy (\begin{document}${\rm d}S_{ {2n}}$\end{document}), and root-mean-square charge radius (\begin{document}$r_{\rm ch}$\end{document}). The isospin properties, namely the coefficient of nuclear symmetry energy and its components, such as the surface and volume symmetry energy of a finite isotopic chain, from the corresponding quantities of infinite nuclear matter, are also estimated. Finally, we correlate the neutron-skin thickness with the coefficient of symmetry energy and the related observables corresponding to the isotopic chains of these nuclei. The coherent density fluctuation model (CDFM) is used to estimate the isospin-dependent properties of finite nuclei, such as symmetry energy, surface symmetry energy, and volume symmetry energy, from their corresponding component in infinite nuclear matter. The relativistic mean-field (RMF) formalism with non-linear NL3 and relativistic-Hartree-Bogoliubov theory with density-dependent DD-ME2 interaction parameters are employed in the analysis. The weight function \begin{document}$\vert {\cal{F}}(x) \vert^{2}$\end{document} is estimated using the total density of each nucleus, which in turn is used with the nuclear matter quantities to obtain the effective symmetry energy and its components in finite nuclei. We calculate the ground state bulk properties, such as nuclear binding energy, quadrupole deformation, two-neutron separation energy, differential variation in the two-neutron separation energy, and root-mean-square charge radius, for the Sc- and Ti- isotopic chains using the non-linear NL3 and density-dependent DD-ME2 parameter sets. Furthermore, the ground state density distributions are used within the CDFM to obtain the effective surface properties, such as symmetry energy and its components, namely volume and surface symmetry energy, for both the parameter sets. The calculated quantities are used to understand the isospin dependent structural properties of finite nuclei near and beyond the drip line, which broadens the scope of discovering new magicity along the isotopic chains. A shape transition is observed from spherical to prolate near \begin{document}$N \geq$\end{document} 44 and \begin{document}$N \geq$\end{document} 40 for the Sc- and Ti- isotopic chains, respectively. Notable signatures of shell and/or sub-shell closures are found for the magic neutron numbers N = 20 and 28 for both isotopic chains using the nuclear bulk and isospin quantities. In addition to these, a few shell/sub-shell closure signatures are observed near the drip-line region at N = 34 and 50 by following the surface/isospin dependent observables, namely symmetry energy and its component, for both the isotopic chain of odd-A Sc- and even-even Ti- nuclei.
2022, 46(8): 084102. doi: 10.1088/1674-1137/ac6abc
Abstract:
A reasonable prediction of photofission observables plays a paramount role in understanding the photofission process and guiding various photofission-induced applications, such as short-lived isotope production, nuclear waste disposal, and nuclear safeguards. However, the available experimental data for photofission observables are limited, and the existing models and programs have mainly been developed for neutron-induced fission processes. In this study, a general framework is proposed for characterizing the photofission observables of actinides, including the mass yield distributions (MYD) and isobaric charge distributions (ICD) of fission fragments and the multiplicity and energy distributions of prompt neutrons (np) and prompt γ rays (γp). The framework encompasses various systematic neutron models and empirical models considering the Bohr hypothesis and does not rely on the experimental data as input. These models are then validated individually against experimental data at an average excitation energy below 30 MeV, which shows the reliability and robustness of the general framework. Finally, we employ this framework to predict the characteristics of photofission fragments and the emissions of prompt particles for typical actinides including 232Th, 235, 238U and 240Pu. It is found that the 238U(γ, f) reaction is more suitable for producing neutron-rich nuclei compared to the 232Th(γ, f) reaction. In addition, the average multiplicity number of both np and γp increases with the average excitation energy.
2022, 46(8): 084103. doi: 10.1088/1674-1137/ac6cd6
Abstract:
Recent experiments show that \begin{document}$\Delta\gamma$\end{document}, an observable designed to detect the chiral magnetic effect (CME), in small collision systems (\begin{document}$p+A$\end{document}) is similar to that in heavy ion collisions (\begin{document}$A+A$\end{document}). This introduces a challenge to the existence of the CME because it is believed that no azimuthal correlation exists between the orientation of the magnetic field (\begin{document}$\Phi_B$\end{document}) and participant plane (\begin{document}$\Phi_2$\end{document}) in small collision systems. In this work, we introduce three charge density models to describe the inner charge distributions of protons and neutrons and calculate the electric and magnetic fields produced in small \begin{document}$p+A$\end{document} collisions at both RHIC and LHC energies. Our results show that the contribution of the single projectile proton is the main contributor to the magnetic field after averaging over all participants. The azimuthal correlation between \begin{document}$\Phi_B$\end{document} and \begin{document}$\Phi_2$\end{document} is small but not vanished. Additionally, owing to the large fluctuation in field strength, the magnetic-field contribution to \begin{document}$\Delta\gamma$\end{document} may be large.
2022, 46(8): 084104. doi: 10.1088/1674-1137/ac6cd7
Abstract:
The binding and proton separation energies of nuclides with \begin{document}$Z, N = 30-50$\end{document} are investigated based on the shell model, with an uncertainty analysis via statistical methods. Several formulas are used to obtain the binding and proton separation energies according to shell-model calculations. The non-parametric bootstrap method is applied to establish an uncertainty decomposition and recomposition framework. Moreover, this is used to estimate the stability of proton(s) emission for each nuclide. Two formulas for calculating the binding energies with a systematic uncertainty of \begin{document}$\sim0.3$\end{document} MeV are proposed, and a reliable extrapolation ability is examined. These binding energy formulas deduce similar forms for their respective \begin{document}$S_ {p}$\end{document} and \begin{document}$S_ {2p}$\end{document} energies, which predict the extension of the nuclear boundary of this region. A good description of the binding and proton separation energies is provided. The one- and two-proton separation energies and partial half-lives of proton emission are predicted, thus revealing a new dripline. Furthermore, there are 30 unstable nuclides predicted to be bound against proton(s)-emission. These nuclear properties will be useful in nuclear astrophysics.
2022, 46(8): 085001. doi: 10.1088/1674-1137/ac66cc
Abstract:
Solar, terrestrial, and supernova neutrino experiments are subject to muon-induced radioactive background. The China Jinping Underground Laboratory (CJPL), with its unique advantage of a 2400 m rock coverage and long distance from nuclear power plants, is ideal for MeV-scale neutrino experiments. Using a 1-ton prototype detector of the Jinping Neutrino Experiment (JNE), we detected 343 high-energy cosmic-ray muons and (7.86\begin{document}$\pm$\end{document}3.97) muon-induced neutrons from an 820.28-day dataset at the first phase of CJPL (CJPL-I). Based on the muon-induced neutrons, we measured the corresponding muon-induced neutron yield in a liquid scintillator to be \begin{document}$(3.44 \pm 1.86_{\rm stat.}\pm$\end{document}\begin{document}$0.76_{\rm syst.})\times 10^{-4}$\end{document} μ−1g−1cm2 at an average muon energy of 340 GeV. We provided the first study for such neutron background at CJPL. A global fit including this measurement shows a power-law coefficient of (0.75\begin{document}$\pm$\end{document}0.02) for the dependence of the neutron yield at the liquid scintillator on muon energy.
2022, 46(8): 085101. doi: 10.1088/1674-1137/ac6665
Abstract:
In recent years, the study of quantum effects near the event horizon of a black hole (BH) has attracted extensive attention. It has become one of the important methods to explore BH quantum properties using the related properties of a quantum deformed BH. In this work, we study the effect of a quantum deformed BH on the BH shadow in two-dimensional Dilaton gravity. In this model, quantum effects are reflected by the quantum correction parameter m. By calculation, we find that: (1) the shape of the shadow boundary of a rotating BH is determined by the BH spin a, the quantum correction parameter m, and the BH type parameter n; (2) when the spin \begin{document}$a=0$\end{document}, the shape of the BH shadow is a perfect circle; when \begin{document}$a\neq 0$\end{document}, the shape is distorted; if the quantum correction parameter \begin{document}$m=0$\end{document}, their shapes reduce to the cases of a Schwarzschild BH and Kerr BH, respectively; (3) the degree of distortion of the BH shadow is different for various quantum correction parameters m; with an increase in the parameter m, the boundary of the BH shadow expands; (4) the size of the BH shadow varies greatly with respect to various quantum deformed BHs (n), and the change in BH shadow shape caused by parameter n is similar to that caused by parameter m, which indicates that there is a "degenerate phenomenon" between the two parameters. Because the value of m in actual physics should be very small, the current observations of the event horizon telescope (EHT) cannot distinguish quantum effects from the BH shadow. In future BH shadow measurements, it will be possible to distinguish quantum deformed BHs, which will help to better understand the quantum effects of BHs.
2022, 46(8): 085102. doi: 10.1088/1674-1137/ac67ce
Abstract:
In order to clearly understand the gravitational theory through the thermal properties of the black hole, it is important to further investigate the first-order phase transition of black holes. In this paper, we adopt different conjugate variables (\begin{document}$P\sim V$\end{document}, \begin{document}$T\sim S$\end{document}, \begin{document}$C_1\sim c_1$\end{document}, and \begin{document}$C_2\sim c_2$\end{document}) and apply Maxwell's equal-area law to study the phase equilibrium of a topological black hole in massive gravity. The condition and latent heat of phase transition are displayed as well as the coexistent curve of \begin{document}$P-T$\end{document}. The result shows that the phase transition of this system is the high/low electric potentials one, not only the large/small black holes one. We also analyze the effect of the model's parameters on phase transition. Furthermore we introduce a new order parameter to probe the microstructure of this system. This work will provide the theoretical basis to study the phase structure of topological black holes in massive gravity and to further explore the gravitational theory.
2022, 46(8): 085103. doi: 10.1088/1674-1137/ac68da
Abstract:
Dark matter (DM) direct detection experiments have been setting strong limits on the DM–nucleon scattering cross section at the DM mass above a few GeV, but leave large parameter spaces unexplored in the low mass region. DM is likely to be scattered and boosted by relativistic cosmic rays in the expanding universe if it can generate nuclear recoils in direct detection experiments to offer observable signals. Since low energy threshold detectors using Germanium have provided good constraints on ordinary halo GeV-scale DM, it is necessary to re-analyze 102.8 kg\begin{document}$\times$\end{document}day data in the CDEX-10 experiment assuming that DM is boosted by cosmic rays. For the DM mass range 1 keV \begin{document}$<m_\chi <$\end{document} 1 MeV and the effective distance within 1 kpc, we reach an almost flat floor limit at \begin{document}$8.32\times10^{-30}$\end{document} cm2 for the spin-independent DM–nucleon scattering cross section, at a 90% confidence level. The CDEX-10 result is able to close the gap unambiguously in the parameter space between the MiniBooNE and XENON1T constraints, which were partially hindered by the Earth attenuation effect. We also quantitatively calculate the expected neutrino floor on searching for CRBDM in future direct detection experiments using Germanium.
2022, 46(8): 085104. doi: 10.1088/1674-1137/ac69ba
Abstract:
In this paper, we show using several examples that the bulk geometry of asymptotically AdS\begin{document}$_3$\end{document}spacetimes can be effectively reconstructed using an intuitive and visual method called the surface growth scheme. This new approach for bulk reconstruction was originally proposed in a recent paper, along with its explicit realization using the one-shot entanglement distillation tensor network and the surface/state correspondence. In this paper, we directly analyze the growth of the bulk minimal surfaces to implement this scheme. Our study provides further support for the surface growth approach in entanglement wedge reconstruction.
2022, 46(8): 085105. doi: 10.1088/1674-1137/ac6d4f
Abstract:
In this study, we explore the axion-like particle (ALP)-photon oscillation effect in the γ-ray spectra of the blazars Markarian 421 (Mrk 421) and PG 1553+113, which are measured by the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) and Fermi Large Area Telescope (Fermi-LAT) with high precision. The Mrk 421 and PG 1553+113 observations of 15 and five phases are used in the analysis, respectively. We find that the combined analysis with all the 15 phases improves the limits of the Mrk 421 observations. For the selected blazar jet magnetic field and extragalactic background light models, the combined limit set by the Mrk 421 observations excludes the ALP parameter region with the ALP-photon coupling of \begin{document}$g_{a\gamma} \gtrsim 2 \times 10^{-11} \; {\rm GeV}^{-1}$\end{document} for the ALP mass of \begin{document}$\sim 8\times 10^{-9} \lesssim m_a \lesssim 2\times 10^{-7}\rm \; eV$\end{document} at 95% confidence level. The main uncertainties of the analysis originate from the blazar jet magnetic field model. We also find that the ALP hypothesis can slightly improve the fit to the PG 1553+113 results in several parameter regions. We do not set the limit in this case.
2022, 46(8): 085106. doi: 10.1088/1674-1137/ac67fe
Abstract:
In this paper, by exploring photon motion in the region near a Bardeen black hole, we studied the shadow and observed properties of the black hole surrounded by various accretion models. We analyzed the changes in shadow imaging and observed luminosity when the relevant physical parameters are changed. For the different spherical accretion backgrounds, we find that the radius of shadow and the position of the photon sphere do not change, but the observed intensity of shadow in the infalling accretion model is significantly lower than that in the static case. We also studied the contribution of the photon rings, lensing rings and direct emission to the total observed flux when the black hole is surrounded by an optically thin disk accretion. Under the different forms of the emission modes, the results show that the observed brightness is mainly determined by direct emission, while the lensing rings will provide a small part of the observed flux, and the flux provided by the photon ring is negligible. By comparing our results with the Schwarzschild spacetime, we find that the existence or change of relevant status parameters will greatly affect the shape and observed intensity of the black hole shadow. These results support the theory that the change of state parameter will affect the spacetime structure, thus affecting the observed features of black hole shadows.
2022, 46(8): 085107. doi: 10.1088/1674-1137/ac6574
Abstract:
The prospect of using gravitational wave detections via the quasinormal modes (QNMs) to test modified gravity theories is exciting area of current research. Gravitational waves (GWs) emitted by a perturbed black hole (BH) will decay as a superposition of their QNMs of oscillations at the ringdown phase. In this work, we investigate the QNMs of the Einstein-Euler-Heisenberg (EEH) BH for both axial and polar gravitational perturbations. We obtain master equations with the tetrad formalism, and the quasinormal frequencies of the EEH BH are calculated in the 6th order Wentzel-Kramers-Brillöuin approximation. It is interesting to note that the QNMs of the EEH BH would differ from those of the Reissner-Nordström BH under the EH parameter, which indicates the EH parameter would affect the gravitational perturbations for the EEH BH.