## 2020 Vol. 44, No. 7

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2020, 44(7): 071001. doi: 10.1088/1674-1137/44/7/071001
Abstract:
We present a model for tail wavelets, a phenomenon known as “echo” in the literature. The tail wavelet may appear in signal reconnaissances in the merger of binary compact objects, including black holes and neutron stars. We show that the dark matter surrounding the compact objects lead to a speculated tail wavelet following the main gravitational wave (GW). We demonstrate that the radiation pressure of the main wave is fully capable of pushing away the surrounding matter to some altitude, and splashing down of the matter excites the tail wavelet after ringing down of the main wave. We illustrate this concept in a simplified model, where numerical estimations are conducted on the specific distribution of dark matter outside the black hole horizon and the threshold values in accordance with observations. We study the full back reaction of the surrounding dark matter to the metric and find that the effect on to the tail wavelets is insignificant. We reveal the fine difference between the tail wavelets of a dressed and a bare black hole. We demonstrate that the tail wavelet can appear as a natural phenomenon in the frame of general relativity, without invoking modified gravities or quantum effects.
2020, 44(7): 071002. doi: 10.1088/1674-1137/44/7/071002
Abstract:
Pion-mass-dependent nucleon-nucleon (NN) potentials are obtained in terms of the one-pion exchange and contact terms from the latest lattice QCD simulations of the two-nucleon system. They assume the forms of the leading order (LO) NN potential from the chiral effective field theory and thus are referred to as the LO chiral potential in this study. We extract the coefficients of contact terms and cut-off momenta in these potentials, for the first time, by fitting the phase shifts of \begin{document}$^1S_0$\end{document} and \begin{document}$^3S_1$\end{document} channels obtained from the HALQCD collaboration with various pion masses from 468.6 to 1170.9 MeV. The low-energy constants in the \begin{document}$^1S_0$\end{document} and \begin{document}$^3S_1$\end{document} channels become weaker and approach each other for larger pion masses. These LO chiral potentials are applied to symmetric nuclear and pure neutron matter within the Brueckner-Hartree-Fock method. Presently, however, we do not yet have the information of the P-wave NN interaction to be provided by the lattice QCD simulations for a complete description of nuclear matter. Our results enhance understanding of the development of nuclear structure and nuclear matter by controlling the contribution of the pionic effect and elucidate the role of chiral symmetry of the strong interaction in complex systems.
2020, 44(7): 073101. doi: 10.1088/1674-1137/44/7/073101
Abstract:
In light of the recently obtained LHC Higgs data, we examine the parameter space of the type II two-Higgs-doublet model, in which the 125 GeV Higgs bosons exhibit wrong sign Yukawa couplings. Combining the relevant theoretical and experimental limits, we find that the LHC Higgs data exclude most of the parameter space of the wrong sign Yukawa coupling. For \begin{document}$m_H=$\end{document} 600 GeV, the allowed samples are mainly distributed across several corners and narrow bands of \begin{document}$m_A<20$\end{document} GeV, 30 \begin{document}$<m_A<120$\end{document} GeV, 240 GeV \begin{document}$<m_A<300$\end{document} GeV, 380 GeV \begin{document}$<m_A<430$\end{document} GeV, and 480 GeV \begin{document}$<m_A<550$\end{document} GeV. For \begin{document}$m_A=$\end{document} 600 GeV, \begin{document}$m_H$\end{document} is required to be lower than 470 GeV. The light pseudo-scalar with a mass of 20 GeV is still permitted in the case of the wrong sign Yukawa coupling of 125 GeV Higgs bosons.
2020, 44(7): 073102. doi: 10.1088/1674-1137/44/7/073102
Abstract:
We study the quasi-two-body decays \begin{document}$B_{(s)} \to \psi [K^*(892), K^*(1410),$\end{document} \begin{document}$K^*(1680)] \to \psi K\pi$\end{document} by employing the perturbative QCD (PQCD) factorization approach, where the charmonia \begin{document}$\psi$\end{document} represents \begin{document}$J/\psi$\end{document} and \begin{document}$\psi(2S)$\end{document}. The corresponding decay channels are studied by constructing the kaon-pion distribution amplitude (DA) \begin{document}$\Phi_{K \pi}^{\rm{P}}$\end{document}, which comprises important final state interactions between the kaon and pion in the resonant region. Relativistic Breit-Wigner formulas are adopted to parameterize the time-like form factor \begin{document}$F_{K\pi}$\end{document} appearing in the kaon-pion DAs. The SU(3) flavor symmetry breaking effect resulting from the mass difference between the kaon and pion is taken into account, which makes significant contributions to the longitudinal polarizations. The observed branching ratios and the polarization fractions of \begin{document}$B_{(s)} \to \psi K^*(892) \to \psi K\pi$\end{document} are accommodated by tuning hadronic parameters for the kaon-pion DAs. The PQCD predictions for \begin{document}$B_{(s)} \to \psi [K^*(1410), K^*(1680)] \to \psi K\pi$\end{document} modes from the same set of parameters can be tested by precise data obtained in the future from LHCb and Belle II experiments.
2020, 44(7): 073103. doi: 10.1088/1674-1137/44/7/073103
Abstract:
We present an improved calculation of the strong coupling constants \begin{document}$g_{D^*D\rho}$\end{document} and \begin{document}$g_{B^*B\rho}$\end{document} in light-cone sum rules, including one-loop QCD corrections of leading power with \begin{document}$\rho$\end{document} meson distribution amplitudes. We further compute subleading-power corrections from two-particle and three-particle higher-twist contributions at leading order up to twist-4 accuracy. The next-to-leading order corrections to the leading power contribution numerically offset the subleading-power corrections to a certain extent, and our numerical results are consistent with those of previous studies on sum rules. A comparison between our results and existing model-dependent estimations is also made.
2020, 44(7): 073104. doi: 10.1088/1674-1137/44/7/073104
Abstract:
We construct holographic Janus solutions, which describe a conformal interface in the theory of M2-branes, in four-dimensional gauged supergravities using a perturbative method. In particular, we study three Einstein-scalar systems and their BPS equations, which are derived by Bobev, Pilch, and Warner (2014). The actions of our interest are all consistent truncations of \begin{document}$D = 11$\end{document} supergravity, chosen to be invariant under \begin{document}$SO(4)\times SO(4)$\end{document}, \begin{document}$SU(3)\times U(1)\times U(1)$\end{document}, and \begin{document}$G_2$\end{document} symmetry subgroups of \begin{document}$SO(8)$\end{document}. The utility of our semi-analytic result is illustrated by the calculation of minimal area surface and the associated holographic entanglement entropy.
2020, 44(7): 073105. doi: 10.1088/1674-1137/44/7/073105
Abstract:
We derive the transverse Ward-Takahashi identities (WTI) of N-dimensional quantum electrodynamics by means of the canonical quantization method and the path integration method, and subsequently attempt to prove that QED3 is solvable based on the transverse and longitudinal WTI, indicating that the full vector and tensor vertices functions can be expressed in terms of the fermion propagators in QED3. Further, we discuss the effect of different γ matrix representations on the full vertex function.
2020, 44(7): 073106. doi: 10.1088/1674-1137/44/7/073106
Abstract:
We analyze different decay observables of semileptonic decays \begin{document}${B}_{c}\to \left({D}_{s,d}^{\left(*\right)}\right){\mu }^{+}{\mu }^{-}$\end{document}, such as the branching ratio, forward-backward asymmetry, polarization fraction, and lepton polarization asymmetry in the non-universal \begin{document}$Z'$\end{document} model. We further study the dependence of the branching fraction to the new model parameters and find that the values of different decay parameters increase in the \begin{document}$Z'$\end{document} model, which indicates a possible approach for the search of new physics as well as for the unknown phenomena of the charm B meson.
2020, 44(7): 074001. doi: 10.1088/1674-1137/44/7/074001
Abstract:
The radionuclide 22Na generates the emission of a characteristic 1.275 MeV \begin{document}$\gamma$\end{document}-ray. This is a potential astronomical observable, whose occurrence is suspected in classical novae. The \begin{document}$^{22}{{\rm{Mg}}}(p,\,\gamma)^{23}{{\rm{Al}}}$\end{document} reaction is relevant to the nucleosynthesis of 22Na in Ne-rich novae. In this study, employing the adiabatic distorted wave approximation and continuum discretized coupled channel methods, the squared neutron asymptotic normalization coefficients (ANCs) for the virtual decay of \begin{document}$^{23}{{\rm{Ne}}}$\end{document} \begin{document}$\to$\end{document} \begin{document}$^{22}{{\rm{Ne}}}$\end{document} + n were extracted, and determined as \begin{document}$(0.483\pm0.060)$\end{document} fm−1 and \begin{document}$(9.7\pm2.3)$\end{document} fm−1 for the ground state and the first excited state from the experimental angular distributions of \begin{document}${}^{22}{{\rm{Ne}}}(d,\,p){}^{23}{{\rm{Ne}}}$\end{document} populating the ground state and the first excited state of \begin{document}$^{23}{{\rm{Ne}}}$\end{document}, respectively. Then, the squared proton ANC of \begin{document}${}^{23}{{\rm{Al}}}_{\rm{g.s.}}$\end{document} was obtained as \begin{document}$C_{d5/2}^{2}({}^{23}{{\rm{Al}}})=(2.65\pm0.33)\times10^{3}$\end{document} fm−1 according to the charge symmetry of the strong interaction. The astrophysical S-factors and reaction rates for the direct capture contribution in \begin{document}${}^{22}{{\rm{Mg}}}(p,\,\gamma){}^{23}{{\rm{Al}}}$\end{document} were also presented. Furthermore, the proton width of the first excited state of \begin{document}$^{23}{{\rm{Al}}}$\end{document} was derived to be \begin{document}$(57\pm14)$\end{document} eV from the neutron ANC of its mirror state in \begin{document}$^{23}{{\rm{Ne}}}$\end{document} and used to compute the contribution from the first resonance of \begin{document}$^{23}{{\rm{Al}}}$\end{document}. This result demonstrates that the direct capture dominates the \begin{document}$^{22}{{\rm{Mg}}}(p,\,\gamma)^{23}{{\rm{Al}}}$\end{document} reaction at most temperatures of astrophysical relevance for \begin{document}$0.33 < T_9<0.64$\end{document}.
2020, 44(7): 074101. doi: 10.1088/1674-1137/44/7/074101
Abstract:
A recent experimental breakthrough identified the last bound neutron-rich nuclei in fluorine and neon isotopes. Based on this finding, we perform a theoretical study of Z = 9, 10, 11, 12 isotopes in the relativistic mean field (RMF) model. The mean field parameters are assumed from the PK1 parameterization, and the pairing correlation is described by the particle number conservation BCS (FBCS) method recently formulated in the RMF model. We show that the FBCS approach plays an essential role in reproducing experimental results of fluorine and neon isotopes. Furthermore, we predict 39Na and 40Mg to be the last bound neutron-rich nuclei in sodium and magnesium isotopes.
2020, 44(7): 074102. doi: 10.1088/1674-1137/44/7/074102
Abstract:
Positive-parity doublet bands were reported in 120I. Based on these, we discuss the corresponding experimental characteristics, including rotational alignment, and re-examine the corresponding configuration assignment. The self-consistent tilted axis cranking relativistic mean-field calculations indicate that the doublet bands are built on the configuration \begin{document}$\pi h _{11/2}\otimes \nu h ^{-1}_{11/2}$\end{document}. By adopting the two quasiparticles coupled with a triaxial rotor model, the excitation energies, energy staggering parameter S(I), \begin{document}$B(M1)/B(E2)$\end{document}, effective angles, and K plots are discussed and compared with available data. The obtained results support the interpretation of chiral doublet bands for the positive-parity doublet bands in 120I, and hence identify this nucleus as the border of the A ≈ 130 island of chiral candidates.
2020, 44(7): 074103. doi: 10.1088/1674-1137/44/7/074103
Abstract:
By incorporating an isospin-dependent form of the momentum-dependent potential in the ultra-relativistic quantum molecular dynamics (UrQMD) model, we systematically investigate effects of the neutron-proton effective mass splitting \begin{document}$m_{n-p}^{*}$\end{document}=\begin{document}$\frac{m_{n}^{*}-m_{p}^{*}}{m}$\end{document} and the density-dependent nuclear symmetry energy \begin{document}$E_{\rm{sym}}(\rho)$\end{document} on the elliptic flow \begin{document}$v_2$\end{document} in \begin{document}$^{197}{{\rm{Au}}}$\end{document} + \begin{document}$^{197}{{\rm{Au}}}$\end{document} collisions at beam energies from 0.09 to 1.5 GeV/nucleon. It is found that at higher beam energies (\begin{document}$\geqslant$\end{document} 0.25 GeV\begin{document}$/$\end{document}nucleon) with the approximately 75 MeV difference in slopes of the two different \begin{document}$E_{\rm{sym}}(\rho)$\end{document}, and the variation of \begin{document}$m_{n-p}^{*}$\end{document} ranging from –0.03 to 0.03 at saturation density with isospin asymmetry \begin{document}$\delta=(\rho_{n}-\rho_{p})/\rho=0.2$\end{document}, the \begin{document}$E_{\rm{sym}}(\rho)$\end{document} has a stronger influence on the difference in \begin{document}$v_{2}$\end{document} between neutrons and protons, i.e., \begin{document}$v_{2}^{n}-v_{2}^{p}$\end{document}, than \begin{document}$m_{n-p}^{*}$\end{document} has. Meanwhile, at lower beam energies (\begin{document}$\leqslant$\end{document} 0.25 GeV\begin{document}$/$\end{document}nucleon), \begin{document}$v_{2}^{n}-v_{2}^{p}$\end{document} is sensitive to both the \begin{document}$E_{\rm{sym}}(\rho)$\end{document} and the \begin{document}$m_{n-p}^{*}$\end{document}. Moreover, the influence of \begin{document}$m_{n-p}^{*}$\end{document} on \begin{document}$v_{2}^{n}-v_{2}^{p}$\end{document} is more evident with the parameters of this study when using the soft, rather than stiff, symmetry energy.
2020, 44(7): 074104. doi: 10.1088/1674-1137/44/7/074104
Abstract:
In this study, we apply a self-consistent mean field approximation of the three-flavor Nambu–Jona-Lasinio (NJL) model and compare it with the two-flavor NJL model. The self-consistent mean field approximation introduces a new parameter, \begin{document}$\alpha$\end{document}, that cannot be fixed in advance by the mean field approach itself. Due to the lack of experimental data, the parameter, \begin{document}$\alpha$\end{document}, is undetermined. Hence, it is regarded as a free parameter and its influence on the chiral phase transition of strong interaction matter is studied based on this self-consistent mean field approximation. \begin{document}$\alpha$\end{document} affects numerous properties of the chiral phase transitions, such as the position of the phase transition point and the order of phase transition. Additionally, increasing \begin{document}$\alpha$\end{document} will decrease the number densities of different quarks and increase the chemical potential at which the number density of the strange quark is non-zero. Finally, we observed that \begin{document}$\alpha$\end{document} affects the equation of state (EOS) of the quark matter, and the sound velocity can be calculated to determine the stiffness of the EOS, which provides a good basis for studying the neutron star mass-radius relationship.
2020, 44(7): 074105. doi: 10.1088/1674-1137/44/7/074105
Abstract:
We investigate the formation distance (R0) from the center of the radioactive parent nucleus at which the emitted cluster is most probably formed. The calculations are performed microscopically starting with the solution to the time-independent Schrödinger wave equation for the cluster-core system, using nuclear potentials based on the Skyrme-SLy4 nucleon-nucleon interactions and folding Coulomb potential, to determine the incident and transmitted wave functions of the system. Our results show that the emitted cluster is mostly formed in the pre-surface region of the nucleus, under the effect of Pauli blocking from the saturated core density. The deeper α-formation distance inside the nucleus allows less preformation probability and indicates a more stable nucleus for a longer half-life. Furthermore, the α-particle tends to be formed at a slightly deeper region inside the nuclei, with larger isospin asymmetry, and in the closed shell nuclei. Regarding the heavy clusters, we observed that the formation distance of the emitted clusters heavier than α-particle increased via increasing the isospin asymmetry of the formed cluster rather than by increasing its mass number. The partial half-life of a certain cluster-decay mode increased with increase of either the mass number or the isospin asymmetry of the emitted cluster.
2020, 44(7): 074106. doi: 10.1088/1674-1137/44/7/074106
Abstract:
The chiral magnetic effect is concisely derived by employing the Wigner function approach in the chiral fermion system. Subsequently, the chiral magnetic effect is derived by solving the Landau levels of chiral fermions in detail. The second quantization and ensemble average leads to the equation of the chiral magnetic effect for righthand and lefthand fermion systems. The chiral magnetic effect arises uniquely from the contribution of the lowest Landau level. We carefully analyze the lowest Landau level and find that all righthand (chirality is +1) fermions move along the direction of the magnetic field, whereas all lefthand (chirality is −1) fermions move in the opposite direction of the magnetic field. Hence, the chiral magnetic effect can be explained clearly using a microscopic approach.
2020, 44(7): 074107. doi: 10.1088/1674-1137/44/7/074107
Abstract:
The relativistic mean field (RMF) model has achieved great success in describing various nuclear phenomena. However, several serious defects are common. For instance, the pseudo-spin symmetry of high-l orbits is distinctly violated in general, leading to spurious shell closures \begin{document}$N/Z = 58$\end{document} and \begin{document}$92$\end{document}. This leads to problems in describing structure properties, including shell structures, nuclear masses, etc. Guided by the pseudo-spin symmetry restoration [Geng et al., Phys. Rev. C, 100: 051301 (2019)], a new RMF Lagrangian DD-LZ1 is developed by considering the density-dependent meson-nucleon coupling strengths. With the newly obtained RMF Lagrangian DD-LZ1, satisfactory descriptions can be obtained for the bulk properties of nuclear matter and finite nuclei. In particular, significant improvements on describing the single-particle spectra are achieved by DD-LZ1. In particular, the spurious shell closures \begin{document}$Z = 58$\end{document} and \begin{document}$92$\end{document}, commonly found in previous RMF calculations, are eliminated by the new effective interaction DD-LZ1, and consistently the pseudo-spin symmetry (PSS) around the Fermi levels is reasonably restored for both low-l and high-l orbits. Moreover, the description of nuclear masses is also notably improved by DD-LZ1, as compared to the other RMF Lagrangians.
2020, 44(7): 074108. doi: 10.1088/1674-1137/44/7/074108
Abstract:
In this study, the multi-quasiparticle triaxial projected shell model (TPSM) is applied to investigate \begin{document}$\gamma$\end{document}-vibrational bands in transitional nuclei of \begin{document}$^{118-128}{\rm{Xe}}$\end{document}. We report that each triaxial intrinsic state has a \begin{document}$\gamma$\end{document}-band built on it. The TPSM approach is evaluated by the comparison of TPSM results with available experimental data, which shows a satisfactory agreement. The energy ratios, B(E2) transition rates, and signature splitting of the \begin{document}$\gamma$\end{document}-vibrational band are calculated.
2020, 44(7): 074109. doi: 10.1088/1674-1137/44/7/074109
Abstract:
We study the structure of nonstrange baryons by analytically calculating the electromagnetic transition helicity amplitudes of the nucleon and Δ resonances. We employ an improved hypercentral constituent quark model and obtain the corresponding eigenenergies and eigenfunctions in closed forms. Then, we calculate the transverse and longitudinal helicity amplitudes for nucleon and Δ resonances. The comparison of evaluated observables and experimental data indicates good agreement between the proposed model and available data.
2020, 44(7): 074110. doi: 10.1088/1674-1137/44/7/074110
Abstract:
The exclusive photoproduction of vector mesons (\begin{document}$J/\psi$\end{document} and \begin{document}$\phi$\end{document}) is investigated by considering the next-to-leading order corrections in the framework of the color glass condensate. We compare the next-to-leading order modified dipole amplitude with the HERA data, finding a good agreement. Our studies show that the \begin{document}$\chi^2/d.o.f$\end{document} from the leading order, running coupling, and collinearly improved next-to-leading order dipole amplitudes are 2.159, 1.097, and 0.932 for the elastic cross-section, and 2.056, 1.449, and 1.357 for the differential cross-section, respectively. The results indicate that the higher-order corrections contribute significantly to the vector meson productions, and the description of the experimental data is dramatically improved once the higher order corrections are included. We extend the next-to-leading order exclusive vector meson production model to LHC energies using the same parameters obtained from HERA. We find that our model provides a rather good description of the \begin{document}$J/\psi$\end{document} and \begin{document}$\phi$\end{document} data in proton-proton collisions at 7 TeV and 13 TeV in LHCb experiments.
2020, 44(7): 075101. doi: 10.1088/1674-1137/44/7/075101
Abstract:
We propose a new method to test the cosmic distance duality relation using the strongly lensed gravitational waves. The simultaneous observation of the image positions, relative time delay between different images, redshift measurements of the lens and the source, together with the mass modelling of the lens galaxy, provide the angular diameter distance to the gravitational wave source. On the other hand, the luminosity distance to the source can be obtained from the observation of the gravitational wave signals. To our knowledge this is the first time a method is proposed to simultaneously measure the angular diameter distance and the luminosity distance from the same source. Hence, the strongly lensed gravitational waves provide a unique method to test the cosmic distance duality relation. With the construction of the third generation gravitational detectors such as the Einstein Telescope, it will be possible to test the cosmic distance duality relation with an accuracy of a few percent.
2020, 44(7): 075102. doi: 10.1088/1674-1137/44/7/075102
Abstract:
The Ryu-Takayanagi (RT) formula plays a large role in the current theory of gauge-gravity duality and emergent geometry phenomena. The recent reinterpretation of this formula in terms of a set of “bit threads” is an interesting effort in understanding holography. In this study, we investigate a quantum generalization of the “bit threads” based on a tensor network, with particular focus on the multi-scale entanglement renormalization ansatz (MERA). We demonstrate that, in the large c limit, isometries of the MERA can be regarded as “sources” (or “sinks”) of the information flow, which extensively modifies the original picture of bit threads by introducing a new variable ρ: density of the isometries. In this modified picture of information flow, the isometries can be viewed as generators of the flow. The strong subadditivity and related properties of the entanglement entropy are also obtained in this new picture. The large c limit implies that classical gravity can emerge from the information flow.
2020, 44(7): 075103. doi: 10.1088/1674-1137/44/7/075103
Abstract:
We construct an alternative uniformly accelerated reference frame based on a 3+1 formalism in adapted coordinates. In this frame, a time-dependent redshift drift exists between co-moving observers, which differs from that in Rindler coordinates. This phenomenon can be tested in a laboratory and improve our understanding of non-inertial frames.