## 2020 Vol. 44, No. 6

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2020, 44(6): 061001. doi: 10.1088/1674-1137/44/6/061001
Abstract:
In the semi-constrained next-to minimal supersymmetric standard model (scNMSSM, or NMSSM with non-universal Higgs mass) under current constraints, we consider a scenario where \begin{document}$h_2$\end{document} is the SM-like Higgs, \begin{document}$\tilde{\chi}^0_1$\end{document} is a singlino-dominated LSP; \begin{document}$\tilde{\chi}^{\pm}_1$\end{document} and \begin{document}$\tilde{\chi}^0_{2,3}$\end{document} are mass-degenerated, light, and higgsino-dominated next-to-lightest supersymmetric particles (NLSPs). We investigate the constraints of these NLSPs by searching for supersymmetry particles at the LHC Run-I and Run-II and discuss the possibility of discovering these NLSPs in the future. We arrive at the following conclusions: (i) With all data of Run I and up to \begin{document}$36\;{\rm{fb}}^{-1}$\end{document} data of Run II at the LHC, the search results by ATLAS and CMS still cannot exclude the higgsino-dominated NLSPs of \begin{document}$100\sim200\;{\rm{GeV}}$\end{document}. (ii) When the mass difference with \begin{document}$\tilde{\chi}^0_{1}$\end{document} is smaller than \begin{document}$m_{h_2}$\end{document}, \begin{document}$\tilde{\chi}^0_{2}$\end{document} and \begin{document}$\tilde{\chi}^0_{3}$\end{document} have opposite preferences with regard to decaying to \begin{document}$Z/Z^*$\end{document} or \begin{document}$h_1$\end{document}. (iii) When the mass difference between NLSP and LSP is larger than \begin{document}$m_Z$\end{document}, most samples can be verified at the \begin{document}$5\sigma$\end{document} level with future \begin{document}$300\;{\rm{fb}}^{-1}$\end{document} data at the LHC. Meanwhile, with \begin{document}$3000\;{\rm{fb}}^{-1}$\end{document} data at high-luminosity LHC (HL-LHC), almost all of the samples can be verified at the \begin{document}$5\sigma$\end{document} level, even if the mass difference is insufficient. (iv) The \begin{document}$a_1$\end{document} funnel and the \begin{document}$h_2/Z$\end{document} funnel mechanisms for the singlino-dominated LSP annihilation cannot be distinguished by searching for NLSPs.
2020, 44(6): 063101. doi: 10.1088/1674-1137/44/6/063101
Abstract:
Using all experimentally measured charmless \begin{document}$B \to PP$\end{document}, \begin{document}$PV$\end{document} decay modes, where \begin{document}$P(V)$\end{document} denotes a light pseudoscalar (vector) meson, we extract the CKM angle \begin{document}$\gamma$\end{document} by a global fit. All hadronic parameters are determined from the experimental data, such that the approach is least model dependent. The contributions of the various decay modes are classified by the topological weak Feynman diagram amplitudes, which are determined by the global fit. To improve the precision of the approach, we consider the flavor SU(3) breaking effects of the topological diagram amplitudes of the decay modes by including the form factors and decay constants. The fit result for the CKM angle \begin{document}$\gamma$\end{document} is \begin{document}$(69.8 \pm 2.1 \pm 0.9) ^{\circ }$\end{document}. It is consistent with the current world average values but has a smaller uncertainty.
2020, 44(6): 063102. doi: 10.1088/1674-1137/44/6/063102
Abstract:
Using the latest PandaX limits on the light dark matter (DM) with a light mediator, we check their implication on the parameter space of the general singlet extension of MSSM (without Z3 symmetry), which can have a sufficient DM self-interaction to solve the small-scale structure problem. We find that the PandaX limits can tightly constrain the parameter space, depending on the coupling λ between the singlet and doublet Higgs fields. For the singlet extension of MSSM with Z3 symmetry, the so-called NMSSM, we also demonstrate the PandaX constraints on its parameter space, which gives a light DM with the correct relic density but without sufficient self-interaction to solve the small-scale structure problem. We find that in NMSSM, the GeV dark matter with a sub-GeV mediator is tightly constrained.
2020, 44(6): 063103. doi: 10.1088/1674-1137/44/6/063103
Abstract:
In a previous paper by several of the authors a number of predictions were made in a study pertaining to the anomalous production of multiple leptons at the Large Hadron Collider (LHC). Discrepancies in multi-lepton final states have become statistically compelling with the available Run 2 data. These could be connected with a heavy boson, H, which predominantly decays into a standard model Higgs boson, h, and a singlet scalar, S, where \begin{document}$m_H\approx 270$\end{document} GeV and \begin{document}$m_S\approx 150$\end{document} GeV. These can then be embedded into a scenario where a two-Higgs-doublet is considered with an additional singlet scalar, 2HDM+S. The long-standing discrepancy in the muon anomalous magnetic moment, \begin{document}$\Delta a_\mu$\end{document}, is interpreted in the context of the 2HDM+S type-II and type-X, along with additional fermionic degrees of freedom. The 2HDM+S model alone, with constraints from the LHC data, does not seem to explain the \begin{document}$\Delta a_\mu$\end{document} anomaly. However, adding fermions with mass of order \begin{document}${\cal O}(100)$\end{document} GeV can explain the discrepancy for sufficiently low values of fermion-scalar couplings.
2020, 44(6): 063104. doi: 10.1088/1674-1137/44/6/063104
Abstract:
We revisit the heavy quarkonium leptonic decays \begin{document}$\psi(nS) \to \ell^+\ell^-$\end{document} and \begin{document}$\Upsilon(nS) \to \ell^+\ell^-$\end{document} using the Bethe-Salpeter method. The emphasis is on the relativistic corrections. For the \begin{document}$\psi(1S-5S)$\end{document} decays, the relativistic effects are \begin{document}$22^{+3}_{-2}$\end{document}%, \begin{document}$34^{+5}_{-5}$\end{document}%, \begin{document}$41^{+6}_{-6}$\end{document}%, \begin{document}$52^{+11}_{-13}$\end{document}% and \begin{document}$62^{+14}_{-12}$\end{document}%, respectively. For the \begin{document}$\Upsilon(1S-5S)$\end{document} decays, the relativistic effects are \begin{document}$14^{+1}_{-2}$\end{document}%, \begin{document}$23^{+0}_{-3}$\end{document}%, \begin{document}$20^{+8}_{-2}$\end{document}%, \begin{document}$21^{+6}_{-7}$\end{document}% and \begin{document}$28^{+2}_{-7}$\end{document}%, respectively. Thus, the relativistic corrections are large and important in heavy quarkonium leptonic decays, especially for the highly excited charmonium. Our results for \begin{document}$\Upsilon(nS) \to \ell^+\ell^-$\end{document} are consistent with the experimental data.
2020, 44(6): 063105. doi: 10.1088/1674-1137/44/6/063105
Abstract:
We construct the axialvector and tensor current operators to systematically investigate the ground and first radially excited tetraquark states with quantum numbers \begin{document}$J^{PC}=1^{+-}$\end{document} using the QCD sum rules. We observe one axialvector tetraquark candidate for \begin{document}$Z_c(3900)$\end{document} and \begin{document}$Z_c(4430)$\end{document}, two axialvector tetraquark candidates for the \begin{document}$Z_c(4020)$\end{document}, and three axialvector tetraquark candidates for \begin{document}$Z_c(4600)$\end{document}.
2020, 44(6): 063106. doi: 10.1088/1674-1137/44/6/063106
Abstract:
The \begin{document}$ZZ\gamma$\end{document} triple neutral gauge couplings are absent in the Standard Model (SM) at the tree level. They receive no contributions from dimension-6 effective operators, but can arise from effective operators of dimension-8. We study the scale of new physics associated with such dimension-8 operators that can be probed by measuring the reaction \begin{document}$\,e^+e^-\to Z\gamma$\end{document} followed by \begin{document}$\,Z\to\ell\bar\ell,\nu \bar \nu$\end{document} decays, at future \begin{document}$e^+e^-$\end{document} colliders including the CEPC, FCC-ee, ILC and CLIC. We demonstrate how angular distributions of the final-state mono-photon and leptons can play a key rôle in suppressing SM backgrounds. We further demonstrate that using electron/positron beam polarizations can significantly improve the signal sensitivities. We find that the dimension-8 new physics scale can be probed up to the multi-TeV region at such lepton colliders.
2020, 44(6): 064101. doi: 10.1088/1674-1137/44/6/064101
Abstract:
Using the vector exchange interaction in the local hidden gauge approach, which in the light quark sector generates the chiral Lagrangians and has produced realistic results for \begin{document}$\Omega_c, \Xi_c, \Xi_b$\end{document} and the hidden charm pentaquark states, we study the meson-baryon interactions in the coupled channels that lead to the \begin{document}$\Xi_{bb}$\end{document} and \begin{document}$\Omega_{bbb}$\end{document} excited states of the molecular type. We obtain seven states of the \begin{document}$\Xi_{bb}$\end{document} type with energies between \begin{document}$10408$\end{document} and \begin{document}$10869$\end{document} MeV, and one \begin{document}$\Omega_{bbb}$\end{document} state at \begin{document}$15212$\end{document} MeV.
2020, 44(6): 064102. doi: 10.1088/1674-1137/44/6/064102
Abstract:
The exact solution of the U(5)-O(6) transitional description in the interacting boson model with two-particle and two-hole configuration mixing is derived based on the Bethe ansatz approach. The Bethe ansatz equations are provided to determine the model's eigenstates and corresponding eigen-energies. N = 2 and N = 4 cases are considered as examples to demonstrate the solution features. As an example of the application, some low-lying level energies and B(E2) ratios of 108Cd are fitted and compared with the corresponding experimental data.
2020, 44(6): 064103. doi: 10.1088/1674-1137/44/6/064103
Abstract:
The constraints on tidal deformability \begin{document}$\Lambda$\end{document} of neutron stars were first extracted from GW170817 by LIGO and Virgo Collaborations. However, the relationship between the radius \begin{document}$R$\end{document} and tidal deformability \begin{document}$\Lambda$\end{document} is still under debate. Using an isospin-dependent parameterized equation of state (EOS), we study the relation between \begin{document}$R$\end{document} and \begin{document}$\Lambda$\end{document} and its dependence on parameters of symmetry energy \begin{document}$E_{\rm sym}$\end{document} and EOS of symmetric nuclear matter \begin{document}$E_0$\end{document} when the mass is fixed at \begin{document}$1.4$\end{document} \begin{document}$M_\odot$\end{document}, \begin{document}$1.0$\end{document} \begin{document}$M_\odot$\end{document}, and \begin{document}$1.8$\end{document} \begin{document}$M_\odot$\end{document}. We find that, although the changes of high order parameters of \begin{document}$E_{\rm sym}$\end{document} and \begin{document}$E_0$\end{document} can shift individual values of \begin{document}$R_{1.4}$\end{document} and \begin{document}$\Lambda_{1.4}$\end{document}, the \begin{document}$R_{1.4}\sim\Lambda_{1.4}$\end{document} relation remains approximately at the same fitted curve. The slope \begin{document}$L$\end{document} of the symmetry energy plays the dominant role in determining the \begin{document}$R_{1.4}\sim\Lambda_{1.4}$\end{document} relation. By investigating the mass dependence of the \begin{document}$R\sim\Lambda$\end{document} relation, we find that the well fitted \begin{document}$R\sim\Lambda$\end{document} relation for 1.4 \begin{document}$M_\odot$\end{document} is broken for massive neutron stars.
2020, 44(6): 064104. doi: 10.1088/1674-1137/44/6/064104
Abstract:
Because of the presence of modified warp factors in metric tensors, we use deformed AdS5 spaces to apply the AdS/CFT correspondence to calculate the spectra for even and odd glueballs, scalar and vector mesons, and baryons with different spins. For the glueball cases, we derive their Regge trajectories and compare them with those related to the pomeron and the odderon. For the scalar and vector mesons, as well as baryons, the determined masses are compatible with the PDG. In particular, for these hadrons we found Regge trajectories compatible with another holographic approach as well as with the hadronic spectroscopy, which present an universal Regge slope of approximately 1.1 GeV2.
2020, 44(6): 065001. doi: 10.1088/1674-1137/44/6/065001
Abstract:
The Water Cherenkov Detector Array (WCDA) is a major component of the Large High Altitude Air Shower Array Observatory (LHAASO), a new generation cosmic-ray experiment with unprecedented sensitivity, currently under construction. WCDA is aimed at the study of TeV \begin{document}$\gamma$\end{document}-rays. In order to evaluate the prospects of searching for TeV \begin{document}$\gamma$\end{document}-ray sources with WCDA, we present a projection of the one-year sensitivity of WCDA to TeV \begin{document}$\gamma$\end{document}-ray sources from TeVCat using an all-sky approach. Out of 128 TeVCat sources observable by WCDA up to a zenith angle of \begin{document}$45^\circ$\end{document}, we estimate that 42 would be detectable in one year of observations at a median energy of 1 TeV. Most of them are Galactic sources, and the extragalactic sources are Active Galactic Nuclei (AGN).
2020, 44(6): 065002. doi: 10.1088/1674-1137/44/6/065002
Abstract:
The precise measurement of cosmic-ray (CR) knees of different primaries is essential to reveal CR acceleration and propagation mechanisms, as well as to explore new physics. However, the classification of CR components is a difficult task, especially for groups with similar atomic numbers. Given that deep learning achieved remarkable breakthroughs in numerous fields, we seek to leverage this technology to improve the classification performance of the CR Proton and Light groups in the LHAASO-KM2A experiment. In this study, we propose a fused graph neural network model for KM2A arrays, where the activated detectors are structured into graphs. We find that the signal and background are effectively discriminated in this model, and its performance outperforms both the traditional physics-based method and the convolutional neural network (CNN)-based model across the entire energy range.
2020, 44(6): 065101. doi: 10.1088/1674-1137/44/6/065101
Abstract:
We study the spin precession frequency of a test gyroscope attached to a stationary observer in the five-dimensional rotating Kaluza-Klein black hole (RKKBH). We derive the conditions under which the test gyroscope moves along a timelike trajectory in this geometry, and the regions where the spin precession frequency diverges. The magnitude of the gyroscope precession frequency around the KK black hole diverges at two spatial locations outside the event horizon. However, in the static case, the behavior of the Lense-Thirring frequency of a gyroscope around the KK black hole is similar to the ordinary Schwarzschild black hole. Since a rotating Kaluza-Klein black hole is a generalization of the Kerr-Newman black hole, we present two mass-independent schemes to distinguish these two spacetimes.
2020, 44(6): 065102. doi: 10.1088/1674-1137/44/6/065102
Abstract:
Asymptotically safe gravity is an effective approach to quantum gravity. It is important to differentiate modified gravity, which is inspired by asymptotically safe gravity. In this study, we examine particle dynamics near the improved version of a Schwarzschild black hole. We assume that in the context of an asymptotically safe gravity scenario, the ambient matter surrounding the black hole is of isothermal nature, and we investigate the spherical accretion of matter by deriving solutions at critical points. The analysis of various values of the state parameter for isothermal test fluids, viz., k = 1, 1/2, 1/3, 1/4 show the possibility of accretion onto an asymptotically safe black hole. We formulate the accretion problem as Hamiltonian dynamical system and explain its phase flow in detail, which reveals interesting results in the asymptotically safe gravity theory.
2020, 44(6): 065103. doi: 10.1088/1674-1137/44/6/065103
Abstract:
We propose a cosmological scenario that describes the evolution of the universe based on particle creation and holographic equipartition. The model attempts to solve the inflation of the early universe and the accelerated expansion of the present universe without introducing the dark energy from the thermodynamical perspective. Throughout the evolution of the universe, we assume that the universe consistently creates particles, and that the holographic equipartition is always satisfied. Further, we set the creation rate of particles proportional to \begin{document}$H^{2}$\end{document} in the early universe and to H in the present and late universe, where H depicts the Hubble parameter. Consequently, we obtain the solutions \begin{document}$a(t)\propto {\rm e}^{\alpha t/3}$\end{document} and \begin{document}$a(t)\propto t^{1/2}$\end{document} for the early universe and solutions \begin{document}$a(t)\propto t^{\delta}$\end{document} and \begin{document}$a(t)\propto {\rm e}^{Ht}$\end{document} for the present and late universe, respectively, where \begin{document}$\alpha$\end{document} and \begin{document}$\delta$\end{document} are the parameters. Finally, we obtain and analyze two important thermodynamic properties for the present model.
2020, 44(6): 065104. doi: 10.1088/1674-1137/44/6/065104
Abstract:
We study the collision property of spinning particles near a Bañados-Teitelboim-Zanelli (BTZ) black hole. Our results show that although the center-of-mass energy of two ingoing particles diverges if one of the particles possesses a critical angular momentum, the particle with critical angular momentum cannot exist outside of the horizon due to violation of the timelike constraint. Further detailed investigation indicates that only a particle with a subcritical angular momentum is allowed to exist near an extremal rotating BTZ black hole, and the corresponding collision center-of-mass energy can be arbitrarily large in a critical angular momentum limit.
2020, 44(6): 065105. doi: 10.1088/1674-1137/44/6/065105
Abstract:
We discuss the \begin{document}$P-V$\end{document} criticality and the Joule-Thomson expansion of charged AdS black holes in the Rastall gravity. We find that although the equation-of-state of a charged AdS black hole in the Rastall gravity is related to the Rastall parameter \begin{document}$\lambda$\end{document}, its reduced equation-of-state at the critical point is independent of the Rastall parameter \begin{document}$\lambda$\end{document}, as is the case in the Einstein gravity where \begin{document}$\lambda=0$\end{document}. This is the reason why the critical exponents are not related to the Rastall parameter \begin{document}$\lambda$\end{document}. We also find that the inversion temperature \begin{document}${T_{i}}$\end{document} is related to the Rastall parameter \begin{document}$\lambda$\end{document}, but that the minimum inversion temperature \begin{document}${T_{i}}^{\rm min}$\end{document} and the ratio \begin{document}$\varepsilon$\end{document} between the minimum inversion temperature and the critical temperature are both independent of the Rastall parameter \begin{document}$\lambda$\end{document}. At the critical point, the thermodynamic evolution of a charged AdS black hole in the Rastall gravity behaves as in the van der Waals fluid and charged AdS black hole in the Einstein gravity. We show the inversion curves and isenthalpic curves in the \begin{document}$T-P$\end{document} plane and analyze the effect of the Rastall constant \begin{document}$\lambda$\end{document} on the inversion curves of a charged AdS black hole during the Joule-Thomson expansion.
2020, 44(6): 065106. doi: 10.1088/1674-1137/44/6/065106
Abstract:
We study matter accretion onto Einstein-aether black holes by adopting the Hamiltonian approach. The general solution of accretion is discussed using the isothermal equation of state. Different types of fluids are considered, including ultra-relativistic, ultra-stiff, sub-relativistic, and radiation fluids, and the accretion process onto Einstein-aether black holes is analyzed. The behavior of the fluid flow and the existence of critical points is investigated for Einstein-aether black holes. We further discuss the general expression and behavior of polytropic fluid onto Einstein-aether black holes. The most important feature of this work is the investigation of the mass accretion rate of the above-mentioned fluids and the comparison of our findings with the Schwarzschild black hole, which generates particular signatures. Moreover, the maximum mass accretion rate occurs near the Killing and universal horizons, and the minimum accretion rate lies between them.
2020, 44(6): 069101. doi: 10.1088/1674-1137/44/6/069101
Abstract:
2020, 44(6): 069102. doi: 10.1088/1674-1137/44/6/069102
Abstract:
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ISSN 1674-1137 CN 11-5641/O4

Original research articles, Ietters and reviews Covering theory and experiments in the fieids of

• Particle physics
• Nuclear physics
• Particle and nuclear astrophysics
• Cosmology
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