2021 Vol. 45, No. 10

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Possible existence of bound nuclei beyond neutron drip lines driven by deformation
Xiao-Tao He, Chen Wang, Kai-Yuan Zhang, Cai-Wan Shen
2021, 45(10): 101001. doi: 10.1088/1674-1137/ac1b99
Based on the relativistic calculations of the nuclear masses in the transfermium region from No \begin{document}$ (Z = 102) $\end{document} to Ds \begin{document}$ (Z = 110) $\end{document} using the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc), the possible existence of bound nuclei beyond the neutron drip lines is studied. The two-neutron and multi-neutron emission bound nuclei beyond the primary neutron drip line of \begin{document}$ N = 258 $\end{document} are predicted in \begin{document}$ Z = 106,108 $\end{document}, and \begin{document}$ 110 $\end{document} isotopes. A detailed microscopic mechanism investigation reveals that nuclear deformation plays a vital role in the existence of bound nuclei beyond the drip line. Furthermore, not only the quadrupole deformation \begin{document}$ \beta_{2} $\end{document} but also the higher orders of deformation are indispensable in the reliable description of the phenomenon of reentrant binding.
Measurements of the center-of-mass energies of ${{\boldsymbol e^+}{\boldsymbol e^-}} $ collisions at BESIII
M. Ablikim, M. N. Achasov, P. Adlarson, S. Ahmed, M. Albrecht, R. Aliberti, A. Amoroso, M. R. An, Q. An, X. H. Bai, Y. Bai, O. Bakina, R. Baldini Ferroli, I. Balossino, Y. Ban, K. Begzsuren, N. Berger, M. Bertani, D. Bettoni, F. Bianchi, J. Bloms, A. Bortone, I. Boyko, R. A. Briere, H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Cetin, J. F. Chang, W. L. Chang, G. Chelkov, D. Y. Chen, G. Chen, H. S. Chen, M. L. Chen, S. J. Chen, X. R. Chen, Y. B. Chen, Z. J. Chen, W. S. Cheng, G. Cibinetto, F. Cossio, X. F. Cui, H. L. Dai, X. C. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, F. De Mori, Y. Ding, C. Dong, J. Dong, L. Y. Dong, M. Y. Dong, X. Dong, S. X. Du, Y. L. Fan, J. Fang, S. S. Fang, Y. Fang, R. Farinelli, L. Fava, F. Feldbauer, G. Felici, C. Q. Feng, J. H. Feng, M. Fritsch, C. D. Fu, Y. Gao, Y. G. Gao, I. Garzia, P. T. Ge, C. Geng, E. M. Gersabeck, A Gilman, K. Goetzen, L. Gong, W. X. Gong, W. Gradl, M. Greco, L. M. Gu, M. H. Gu, Y. T. Gu, C. Y Gua
2021, 45(10): 103001. doi: 10.1088/1674-1137/ac1575
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5 fb\begin{document}$ ^{-1} $\end{document} of \begin{document}$ e^+e^- $\end{document} collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process \begin{document}$e^+e^- \to $\end{document}\begin{document}$ (\gamma_{\rm ISR/FSR}) \mu^+\mu^-$\end{document}, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-collection period.
Searches for dark matter via charged Higgs pair production in the Inert Doublet Model at a γγ collider
Guo-He Yang, Mao Song, Gang Li, Yu Zhang, Jian-You Guo
2021, 45(10): 103101. doi: 10.1088/1674-1137/ac1577
The Inert Doublet Model (IDM) is one of the simplest extensions beyond the Standard Model (SM) with an extended scalar sector, which provides a scalar dark matter particle candidate. In this study, we investigated the double charged Higgs production at a \begin{document}$\gamma\gamma$\end{document} collider. By scanning the whole parameter space, we obtained the parameter points corresponding to the correct relic abundance of dark matter. After applying all theoretical and experimental constraints, the parameter space for the existence of dark matter was extremely restricted. We performed an analysis of the signal of \begin{document}$H^+H^-$\end{document} production in the IDM and the SM background, with the optimized selection conditions chosen for the kinematic variables to maximize the signal significance. Comparing the signal with the background, we obtained the parameter points that may be detected in future \begin{document}$\gamma\gamma$\end{document} collider experiments.
Some remarks on X(6900)
Qin-Fang Cao, Hao Chen, Hong-Rong Qi, Han-Qing Zheng
2021, 45(10): 103102. doi: 10.1088/1674-1137/ac0ee5
The analysis of the LHCb data on \begin{document}$X(6900)$\end{document} found in the di-\begin{document}$J/\psi$\end{document} system was performed using a momentum-dependent Flatté-like parameterization. The use of the pole counting rule and spectral density function sum rule provides consistent evidence that both confining and molecular states are possible. Alternatively, the nature of \begin{document}$X(6900)$\end{document} cannot be distinguished if only the di-\begin{document}$J/\psi$\end{document} experimental data with current statistics are available. Nevertheless, we found that the lowest state in the di-\begin{document}$J/\psi$\end{document} system likely has the same quantum numbers as \begin{document}$X(6900)$\end{document}, and \begin{document}$X(6900)$\end{document} is probably not interpreted as a \begin{document}$J/\psi-\psi(2S)$\end{document} molecular state.
Universality of entropy principle for a general diffeomorphism-covariant purely gravitational theory
Jie Jiang, Xiongjun Fang, Sijie Gao
2021, 45(10): 103103. doi: 10.1088/1674-1137/ac0f72
Thermodynamics plays an important role in gravitational theories. It is a principle that is independent of gravitational dynamics, and there is still no rigorous proof to show that it is consistent with the dynamical principle. We consider a self-gravitating perfect fluid system with the general diffeomorphism-covariant purely gravitational theory. Based on the Noether charge method proposed by Iyer and Wald, considering static off/on-shell variational configurations, which satisfy the gravitational constraint equation, we rigorously prove that the extrema of the total entropy of a perfect fluid inside a compact region for a fixed total particle number demands that the static configuration is an on-shell solution after we introduce some appropriate boundary conditions, i.e., it also satisfies the spatial gravitational equations. This means that the entropy principle of the fluid stores the same information as the gravitational equation in a static configuration. Our proof is universal and holds for any diffeomorphism-covariant purely gravitational theories, such as Einstein gravity, \begin{document}$ f(R)$\end{document} gravity, Lovelock gravity, f(Gauss-Bonnet) gravity and Einstein-Weyl gravity. Our result indicates the consistency between ordinary thermodynamics and gravitational dynamics.
Generalized Crewther relation and a novel demonstration of the scheme independence of commensurate scale relations up to all orders
Xu-Dong Huang, Xing-Gang Wu, Qing Yu, Xu-Chang Zheng, Jun Zeng, Jian-Ming Shen
2021, 45(10): 103104. doi: 10.1088/1674-1137/ac1934
In this study, we investigate in detail the generalized Crewther Relation (GCR) between the Adler function (D) and the Gross-Llewellyn Smith sum rules coefficient (\begin{document}$ C^{\rm{GLS}}$\end{document}) using the newly proposed single-scale approach of the principle of maximum conformality (PMC). The resultant GCR is scheme-independent, with the residual scale dependence due to unknown higher-order terms highly suppressed. Thus, a precise test of QCD theory without renormalization schemes and scale ambiguities can be achieved by comparing with data. Moreover, a demonstration of the scheme independence of the commensurate scale relation up to all orders is presented. Additionally, for the first time, the Pade approximation approach has been adopted for estimating the unknown \begin{document}$ 5_{\rm{th}}$\end{document}-loop contributions from the known four-loop perturbative series.
Entropic destruction of heavy quarkonium with hyperscaling violation
Ang Li, Zi-Qiang Zhang
2021, 45(10): 103105. doi: 10.1088/1674-1137/ac1ac4
We study the entropic destruction of heavy quarkonium in strongly coupled theories with an anisotropic scaling symmetry in time and a spatial direction. We consider Lifshitz and hyperscaling violation theories, which are covariant under a generalized Lifshitz scaling symmetry with the dynamical exponent z and hyperscaling violation exponent \begin{document}$ \theta$\end{document}. It is shown that the entropic force depends on the parameters of these theories. In particular, increasing z decreases the entropic force, thus reducing the quarkonium dissociation, while increasing \begin{document}$ \theta$\end{document} has the opposite effect.
Discovery potentials of double-charm tetraquarks
Qin Qin, Yin-Fa Shen, Fu-Sheng Yu
2021, 45(10): 103106. doi: 10.1088/1674-1137/ac1b97
In this study, we investigate the discovery potential of double-charm tetraquarks \begin{document}$ T^{\{cc\}}_{[\bar{q}\bar{q}']} $\end{document}. We find that their production cross sections at the LHCb with \begin{document}$ \sqrt{s} = 13 $\end{document} TeV reach \begin{document}$ \mathcal{O}(10^4) $\end{document} pb, which indicates that the LHCb has collected \begin{document}$ \mathcal{O}(10^8) $\end{document} such particles. Through the decay channels of \begin{document}$ T^{\{cc\}}_{[\bar{u}\bar{d}]}\to D^{+}K^{-}\pi^{+} $\end{document} or \begin{document}$ D^0D^+\gamma $\end{document} (if stable) or \begin{document}$ T^{\{cc\}}_{[\bar{u}\bar{d}]}\to D^0D^{*+}\to D^0D^0\pi^+ $\end{document} (if unstable), it is highly expected that they get discovered at the LHCb in the near future. We also discuss the productions and decays of the double-charm tetraquarks at future Tera-\begin{document}$ Z $\end{document} factories.
Efficiency corrections for mutually inclusive variables and particle identification effect for mixed-cumulants in heavy-ion collisions
Arghya Chatterjee, Toshihiro Nonaka, ShinIchi Esumi, Xiaofeng Luo
2021, 45(10): 104001. doi: 10.1088/1674-1137/ac1100
Mix-cumulants of conserved charge distributions are sensitive observables for probing properties of the QCD medium and phase transition in heavy-ion collisions. To perform precise measurements, efficiency correction is one of the most important step. In this study, using the binomial efficiency model, we derive efficiency correction formulas for mutually exclusive and inclusive variables. The UrQMD model is applied to verify the validity of these formulas for different types of correlations. Furthermore, we investigate the effect of the multiplicity loss and contamination emerging from the particle identifications. This study provides important steps toward future measurements of mixed-cumulants in relativistic heavy-ion collisions.
The effect of single-particle space-momentum angle distribution on two-pion HBT correlation in relativistic heavy-ion collisions using a multiphase transport model
Hang Yang, Qichun Feng, Yanyv Ren, Jingbo Zhang, Lei Huo
2021, 45(10): 104102. doi: 10.1088/1674-1137/ac1856
Using the string melting version of a multiphase transport (AMPT) model, we analyze the transverse momentum dependence of the HBT radius \begin{document}$R_{\rm s}$\end{document} and the single-pion angle distribution on the transverse plane in central Au+Au collisions at \begin{document}$\sqrt{S_{NN}}$\end{document}=19.6, 27, 39, 62.4, and 200 GeV. Additionally, a numerical connection between these two phenomena is established with a series of functions. We can estimate the single-pion angle distribution on the transverse plane from HBT analysis.
Systematic study of two-proton radioactivity with a screened electrostatic barrier
You-Tian Zou, Xiao Pan, Xiao-Hua Li, Hong-Ming Liu, Xi-Jun Wu, Biao He
2021, 45(10): 104102. doi: 10.1088/1674-1137/ac1b96
In this study, a phenomenological model is proposed based on Wentzel-Kramers-Brillouin (WKB) theory and applied to investigate the two-proton (\begin{document}$2p$\end{document}) radioactive half-lives of nuclei near or beyond the proton drip line. The total diproton-daughter nucleus interaction potential is composed of the Hulthen-type electrostatic term and the centrifugal term. The calculated \begin{document}$2p$\end{document} radioactive half-lives can accurately reproduce the existing 10 experimental datasets of five true \begin{document}$2p$\end{document} radioactive nuclei with σ = 0.736. In addition, we extend this model to predict the half-lives of possible \begin{document}$2p$\end{document} radioactive nuclei whose \begin{document}$2p$\end{document} radioactivity is energetically allowed or observed but not yet quantified in NUBASE2016. The predicted results are in agreement with those obtained using the Gamow-like model, generalized liquid drop model, Sreeja formula, and Liu formula.
The sixth order cumulant of net-proton number in Binomial distribution at $ {\sqrt{{\boldsymbol s}_{\boldsymbol{NN}}}}$ = 200 GeV
Li-Zhu Chen, Ye-Yin Zhao, Jin Wu, Zhi-Ming Li, Yuan-Fang Wu
2021, 45(10): 104103. doi: 10.1088/1674-1137/ac1b98
It is proposed that ratios of the sixth order to the second order cumulant (\begin{document}$C_6/C_2$\end{document}) of conserved quantities are sensitive to the chiral crossover transition. Recently, the negative \begin{document}$C_6/C_2$\end{document} was obtained in both theoretical Lattice QCD and experiments at \begin{document}$\sqrt{s_{NN}}$\end{document} = 200 GeV. In this study, we investigate the behavior of net-proton \begin{document}$C_6/C_2$\end{document} in statistical Binomial distribution (BD) at \begin{document}$\sqrt{s_{NN}}$\end{document} = 200 GeV in Au + Au collisions. With the BD parameters extracted from RHIC/STAR, it is found that \begin{document}$C_6/C_2$\end{document} can be negative. Furthermore, the obtained \begin{document}$C_6/C_2$\end{document} becomes smaller when applying the same magnitude of experimental statistics and calculation method to simulations. In 0-10% centrality, there is a significant difference between the simulated result and theoretical expectation. Based on the extracted parameters and experimentally collected statistics, the baseline of net-proton \begin{document}$C_6/C_2$\end{document} in BD is presented.
Kinemaitcs in spatially flat FLRW spacetimes
Ion I. Cotăescu
2021, 45(10): 105101. doi: 10.1088/1674-1137/ac1576
The kinematics on spatially flat FLRW spacetimes is presented for the first time in local charts with physical coordinates, i.e., the cosmic time and proper Cartesian space coordinates of Painlevé-type. It is shown that there exists a conserved momentum that determines the form of the covariant four-momentum on geodesics in terms of physical coordinates. Moreover, with the help of this conserved momentum, the peculiar momentum can be defined, thus separating the peculiar and recessional motions without ambiguity. It is shown that the energy and peculiar momentum satisfy the mass-shell condition of special relativity while the recessional momentum does not produce energy. In this framework, the measurements of the kinetic quantities along geodesics performed by different observers are analyzed, pointing out an energy loss of the massive particles similar to that producing the photon redshift. The examples of the kinematics on the de Sitter expanding universe and a new Milne-type spacetime are extensively analyzed.
Instability of a black hole with f (R) global monopole under extended uncertainty principle
Hongbo Cheng, Yue Zhong
2021, 45(10): 105102. doi: 10.1088/1674-1137/ac1668
We consider the evolution of a black hole involving an f(R) global monopole based on the Extended Uncertainty Principle (EUP). The black hole evolutions refer to the instability due to the Parikh-Kraus-Wilczeck tunneling radiation or fragmentation. It is found that the EUP corrections make the entropy difference larger to encourage the black hole to radiate more significantly. We also show that the appearance of the EUP effects results in the black hole's division. The influence from the global monopole and the revision of general relativity can also adjust the black hole evolution simultaneously but cannot change the final result that the black hole will not be stable because of the EUP's effects.
The possible equation of state of dark matter in low surface brightness galaxies
Xiaobo Gong, Meirong Tang, Zhaoyi Xu
2021, 45(10): 105103. doi: 10.1088/1674-1137/ac0f73
The observed rotation curves of low surface brightness (LSB) galaxies play an essential role in studying dark matter, and indicate the existence of a central constant density dark matter core. However, the cosmological N-body simulations of cold dark matter predict an inner cusped halo with a power-law mass density distribution, and cannot reproduce a central constant-density core. This phenomenon is called cusp-core problem. When dark matter is quiescent and satisfies the condition for hydrostatic equilibrium, the equation of state can be adopted to obtain the density profile in the static and spherically symmetric space-time. To address the cusp-core problem, we assume that the equation of state is independent of the scaling transformation. Its lower order approximation for this type of equation of state can naturally lead to a special case, i.e., \begin{document}$p=\zeta\rho+2\epsilon V_{\rm rot}^{2}\,\rho$\end{document}, where p and \begin{document}$\rho$\end{document} represent the pressure and density, respectively, \begin{document}$V_{\rm rot}$\end{document} depicts the rotation velocity of galaxy, and \begin{document}$\zeta$\end{document} and \begin{document}$ \epsilon$\end{document} are positive constants. It can obtain a density profile that is similar to the pseudo-isothermal halo model when \begin{document}$\epsilon$\end{document} is approximately 0.15. To obtain a more universally used model, let the equation of state include the polytropic model, i.e. \begin{document}$p= \frac{\zeta}{\rho_{0}^{s}}\rho^{1+s}+ 2\epsilon V_{\rm rot}^{2}\,\rho$\end{document}, from which we can obtain other types of density profiles, such as the profile that is nearly same as the Burkert profile, where s and \begin{document}$\rho_{0}$\end{document} are positive constants.
Constraining the cosmic ray propagation halo thickness using Fermi-LAT observations of high-latitude clouds
Yuhua Yao, Bing-Qiang Qiao, Wei Liu, Qiang Yuan, Hong-Bo Hu, Xiao-Jun Bi, Chao-Wen Yang, Yi-Qing Guo
2021, 45(10): 105104. doi: 10.1088/1674-1137/ac1064
The diffusive halo is a basic characteristic of cosmic ray (CR) propagation and can advance our understanding of many CR-related phenomena and indirect dark matter. The method used to derive the halo size often has degeneracy problems and is thus affected by large uncertainties. The diffuse \begin{document}$\rm\gamma$\end{document} rays from high-latitude clouds might shed light on the halo size independently. Because predictions using the spatially dependent propagation (SDP) model have better agreement with the observed CRs than those of the conventional propagation model, in this work, we investigated halo thickness based on the SDP model using Fermi-LAT \begin{document}$\rm\gamma$\end{document}-ray observations of high- and intermediate-velocity clouds. We found that to avoid exceeding the relative \begin{document}$\gamma$\end{document}-ray emissivity in high-latitude clouds, the halo thickness should be in the range of 3.3-9 kpc. Moreover, the spatial morphology of \begin{document}$\rm\gamma$\end{document}-rays estimated based on the SDP model for different values of the halo thickness are distinctive, which provides us with a tool to determine the halo size. This newly developed model can be tested and tuned using multi-wavelength observations in future studies.
Strong constraints on Lorentz violation using new γ-ray observations around PeV
Liang Chen, Zheng Xiong, Cong Li, SongZhan Chen, HuiHai He
2021, 45(10): 105105. doi: 10.1088/1674-1137/ac1166
The tiny modification of dispersion relation induced by Lorentz violation (LV) is an essential topic in quantum gravity (QG) theories, which can be magnified into significant effects when dealing with astrophysical observations at high energies and long propagation distances. LV would lead to photon decay at high energies; therefore, observations of high-energy photons could constrain LV or even QG theories. The Large High Altitude Air Shower Observatory (LHAASO) is the most sensitive gamma-array instrument currently operating above 100 TeV. Recently, LHAASO reported the detection of 12 sources above 100 TeV with maximum photon energy exceeding 1 PeV. According to these observations, the most stringent restriction is achieved in this study, i.e., limiting the LV energy scale to \begin{document}$1.7\times10^{33} $\end{document} eV, which is over 139,000 times that of the Planck energy, and achieving an improvement of approximately 1.9 orders of magnitude over previous limits.
Dynamic phase transition of charged dilaton black holes
Jie-Xiong Mo, Shan-Quan Lan
2021, 45(10): 105106. doi: 10.1088/1674-1137/ac125f
The dynamic phase transition of charged dilaton black holes is investigated in this paper. The Gibbs free energy landscape is introduced, and the corresponding \begin{document}$G_{\rm L}$\end{document} is calculated for the dilaton black hole. We numerically solve the Fokker-Planck equation constrained by only the reflecting boundary condition. The effects of dilaton gravity on the probabilistic evolution of dilaton black holes are explored. Firstly, the horizon radius difference between a large dilaton black hole and a small dilaton black hole increases with the parameter \begin{document}$\alpha$\end{document}. Secondly, with increasing \begin{document}$\alpha$\end{document}, the system needs much more time to achieve a stationary distribution. Finally, the values attained for \begin{document}$\rho(r_{\rm l},t)$\end{document} and \begin{document}$\rho(r_{\rm s},t)$\end{document} vary with \begin{document}$\alpha$\end{document}. Additionally, by resolving the Fokker-Planck equation constrained by both the reflecting boundary condition and absorbing boundary condition, we investigate the first passage process of dilaton black holes. The initial peak decays more slowly with increasing\begin{document}$\alpha$\end{document}, which can also be observed via the slowing decay of \begin{document}$\Sigma(t)$\end{document} (the sum of the probability of the black hole system not having completed a first passage by time t). Moreover, the time corresponding to the single peak of the first passage time distribution is found to increase with the parameter \begin{document}$\alpha$\end{document}. Considering these observations, the dilaton field is found to slow down the dynamic phase transition process between a large black hole and a small black hole.