2019 Vol. 43, No. 1

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Fermion bound states in geometrically deformed backgrounds
D. Bazeia, A. Mohammadi, D. C. Moreira
2019, 43(1): 013101. doi: 10.1088/1674-1137/43/1/013101
This work deals with the behavior of fermions in the background of kinklike structures in the two-dimensional spacetime. The kinklike structures appear from bosonic scalar field models that engender distinct profiles and interact with the fermion fields via the standard Yukawa coupling. We first consider two models that engender parity symmetry, one leading to the exclusion of fermion bound states, and the other to the inclusion of bound states, when the parameter that controls the bosonic structure varies from zero to unity. We then investigate a third model where the kinklike solution explicitly breaks parity symmetry, leading to fermion bound states that are spatially asymmetric.
Probing anomalous top-Higgs couplings at the HL-LHC via HWW* decay channels
Yao-Bei Liu, Stefano Moretti
2019, 43(1): 013102. doi: 10.1088/1674-1137/43/1/013102
We study the prospects of probing the anomalous tHq (q=u, c) couplings via SS2L or 3L signatures at the High Luminosity (HL-LHC) run of the 14 TeV CERN collider. We focus on signals of the tH associated production followed by the decay modes tb\begin{document}$\ell$\end{document}+ν\begin{document}$\ell$\end{document} and HWW*, and tt production followed by the decay modes tb\begin{document}$\ell$\end{document}+ν\begin{document}$\ell$\end{document} and tH(→WW*)q, where \begin{document}$\ell$\end{document}=e, μ. Based on two types of HWW* decay topologies, one assuming the semileptonic decay mode HWW*\begin{document}$\ell$\end{document}+νjj and the other the fully leptonic decay mode HWW*\begin{document}$\ell$\end{document}+ν\begin{document}$\ell$\end{document}-ν, we perform a full simulation for signals and backgrounds. It is shown that, at the future HL-LHC, the branching ratio Br(tuh) (Br(tch)) can be probed to 1.17 (1.56)×10-3 for the same-sign di-lepton channel, and to 7.1×10-4 (1.39×10-3) for the 3L channel at 3σ sensitivity.
Doubly-charged scalar in four-body decays of neutral flavored mesons
Tian-Hong Wang, Geng Li, Yue Jiang, Guo-Li Wang
2019, 43(1): 013103. doi: 10.1088/1674-1137/43/1/013103
We study the four-body decays of neutral flavored mesons, including K0, D0, B0, and Bs0. These processes, which could be induced by a hypothetical doubly-charged scalar particle, do not conserve the lepton number. Assuming, as an example, that the mass of the doubly-charged particle is 1000 GeV, and using the upper bounds of the couplings, we calculate the branching ratios of different channels. For K0h1+h2+e-e-, D0h1-h2-e+e+, and Bd, s0h1+h2+e-e-, it is of the order of 10-30, 10-32-10-29, and 10-33-10-28, respectively. Based on the experimental results for the D0h1-h2-l1+l2+ channels, we also find the upper limit for the quantity \begin{document}$\frac{{{s_\Delta }{h_{ij}}}}{{M_\Delta ^2}}$\end{document}.
A discussion on vacuum polarization correction to the cross-section of e+e-γ*/ψμ+μ-
Hong-Dou Jin, Li-Peng Zhou, Bing-Xin Zhang, Hai-Ming Hu
2019, 43(1): 013104. doi: 10.1088/1674-1137/43/1/013104
Vacuum polarization is a part of the initial-state radiative correction for the cross-section of e+e- annihilation processes. In the energy region in the vicinity of narrow resonances J/ψ and ψ(3686), the vacuum polarization contribution from the resonant component has a significant effect on the line-shape of the lepton pair production cross-section. This paper discusses some basic concepts and describes an analytical calculation of the cross-section of e+e-γ*/ψμ+μ- considering the single and double vacuum polarization effect of the virtual photon propagator. Moreover, it presents some numerical comparisons with the traditional treatments.
A non-relativistic model for the [cc] [cc] tetraquark
V.R. Debastiani, F.S. Navarra
2019, 43(1): 013105. doi: 10.1088/1674-1137/43/1/013105
We use a non-relativistic model to study the spectroscopy of a tetraquark composed of [cc] [cc] in a diquark-antidiquark configuration. By numerically solving the Schrödinger equation with a Cornell-inspired potential, we separate the four-body problem into three two-body problems. Spin-dependent terms (spin-spin, spin-orbit and tensor) are used to describe the splitting structure of the cc spectrum and are also extended to the interaction between diquarks. Recent experimental data on charmonium states are used to fix the parameters of the model and a satisfactory description of the spectrum is obtained. We find that the spin-dependent interaction is sizable in the diquark-antidiquark system, despite the heavy diquark mass, and also that the diquark has a finite size if treated in the same way as the cc systems. We find that the lowest S-wave T4c tetraquarks might be below their thresholds of spontaneous dissociation into low-lying charmonium pairs, while orbital and radial excitations would be mostly above the corresponding charmonium pair thresholds. Finally, we repeat the calculations without the confining part of the potential and obtain bound diquarks and bound tetraquarks. This might be relevant to the study of exotic charmonium in the quark-gluon plasma. The T4c states could be investigated in the forthcoming experiments at the LHC and Belle Ⅱ.
Entanglement in simple spin networks with a boundary
Yi Ling, Meng-He Wu, Yikang Xiao
2019, 43(1): 013106. doi: 10.1088/1674-1137/43/1/013106
We investigate the bipartite entanglement for the boundary states in a simple type of spin networks with dangling edges, in which the two complementary parts are linked by two or more edges. Firstly, the spin entanglement is considered in the absence of the intertwiner entanglement. By virtue of numerical simulations, we find that the entanglement entropy usually depends on the group elements. More importantly, when the intertwiner entanglement is taken into account, we find that it is in general impossible to separate the total entanglement entropy into the contribution from spins on edges and the contribution from intertwiners at vertices. These situations are in contrast to the case when the two vertices are linked by a single edge.
Sonic velocity in holographic fluids and its applications
Yapeng Hu, Yu Tian, Xiaoning Wu, Huaifan Li, Hongsheng Zhang
2019, 43(1): 013107. doi: 10.1088/1674-1137/43/1/013107
Gravity/fluid correspondence acts as an important tool in investigating the strongly correlated fluids. We carefully investigate the holographic fluids at the finite cutoff surface by considering different boundary conditions in the scenario of gravity/fluid correspondence. We find that the sonic velocity of the boundary fluids at the finite cutoff surface is critical in clarifying the superficial similarity between the bulk viscosity and perturbation of the pressure for the holographic fluid, where we set a special boundary condition at the finite cutoff surface to explicitly express this superficial similarity. Moreover, we further take the sonic velocity into account to investigate a case with a more general boundary condition. In this more genaral case, although two parameters in the first order stress tensor of holographic fluid cannot be fixed, one can still extract the information about the transport coefficients by considering the sonic velocity seriously.
Mixed electroweak-QCD corrections to e+e-μ+μ-H at CEPC with finite-width effect
Wen Chen, Feng Feng, Yu Jia, Wen-Long Sang
2019, 43(1): 013108. doi: 10.1088/1674-1137/43/1/013108
The associated production of Higgs boson with a muon pair, e+eμ+μ-H, is one of the golden channels to pin down the properties of the Higgs boson in the prospective Higgs factories exemplified by CEPC. The projected accuracy of the corresponding cross section measurement is about per cent level at CEPC. In this work, we investigate both \begin{document}${\mathcal{O}}(\alpha )$\end{document} weak correction and the \begin{document}${\mathcal{O}}(\alpha {\alpha }_{s})$\end{document} mixed electroweak-QCD corrections for this channel, appropriately taking into account the effect of finite Z0 width. The μ+μ- invariant mass spectrum is also predicted. The mixed electroweak-QCD correction turns out to reach 1.5% of the Born-order result, and thereby must be included in future confrontation with the data. We also observe that, after including higher-order corrections, the simplified prediction for the integrated cross section employing the narrow-width-approximation may deviate from our full result by a few per cents.
Near horizon OTT black hole asymptotic symmetries and soft hair
B. Cvetković, D. Simić
2019, 43(1): 013109. doi: 10.1088/1674-1137/43/1/013109
We study the near horizon geometry of both static and stationary extremal Oliva Tempo Troncoso (OTT) black holes. For each of these cases, a set of consistent asymptotic conditions is introduced. The canonical generator for the static configuration is shown to be regular. For the rotating OTT black hole, the asymptotic symmetry is described by the time reparametrization, the chiral Virasoro and centrally extended u(1) Kac-Moody algebras.
A simple description of the temperature dependence of the width of the fission-fragment mass yield in 197Au and 209Bi at intermediate energies
V. Yu. Denisov, O. A. Belyanovska, V. P. Khomenkov, I. Yu. Sedykh, K. M. Sukhyy
2019, 43(1): 014101. doi: 10.1088/1674-1137/43/1/014101
A simple approach is proposed to describe the experimental data for the widths of the fission-fragment mass yields in 197Au and 209Bi at low and intermediate energies. The approach is based on the expressions for the temperature dependence of the width of the fission-fragment mass yield and the mass of the most probable fragment. The expression for the width of the fission-fragment mass yield depends on the mass of the most probable fragment, the surface terms of the energy level density parameter, the temperature and the stiffness parameter of the potential related to mass-asymmetric degree of freedom. It is shown that the contribution of the surface term of the energy level density parameter is important for describing the experimental data in a wide range of energies.
Double heavy tri-hadron bound state via delocalized π bond
Li Ma(马力), Qian Wang(王倩), Ulf-G. Meißner
2019, 43(1): 014102. doi: 10.1088/1674-1137/43/1/014102
The number of exotic candidates that are beyond the conventional quark model has increased dramatically over recent decades. Some of these can be viewed as analogues of the deuteron. Similarly, the existence of the triton indicates that bound states formed by three hadrons could also exist. To illustrate this possibility, we study the DD*K and \begin{document}$B{B}^{* }\bar{K}$\end{document} systems using the Born-Oppenheimer approximation. To leading order, only one-pion exchange potentials are considered. This means that the three constituents share one virtual pion. This is similar to the role of the delocalized π bond for the formation of benzene in chemistry. After solving the Schrödinger equation, we find two three-body DD*K and \begin{document}$B{B}^{* }\bar{K}$\end{document} bound states with masses \begin{document}${4317.92}_{-4.32}^{+3.66}\, {\rm{MeV}}$\end{document} and \begin{document}${11013.65}_{-8.84}^{+8.49}\, {\rm{MeV}}$\end{document}, respectively. The masses of their \begin{document}$D{\bar{D}}^{* }K$\end{document} and \begin{document}$B{\bar{B}}^{* }\bar{K}$\end{document} analogues are \begin{document}${4317.92}_{-6.55}^{+6.13}\, {\rm{MeV}}$\end{document} and \begin{document}${11013.65}_{-9.02}^{+8.68}\, {\rm{MeV}}$\end{document}, respectively. From the experimental side, the \begin{document}$D{\bar{D}}^{* }K$\end{document} bound state could be found by analyzing the current world data on the \begin{document}$B\to J/\psi \pi \pi K$\end{document} process, by focusing on the J/ψπK channel.
Alternative methods for measurement of the global polarization of Λ hyperons
Irfan Siddique, Zuo-tang Liang, Michael Annan Lisa, Qun Wang, Zhang-bu Xu
2019, 43(1): 014103. doi: 10.1088/1674-1137/43/1/014103
We propose alternative methods for measurement of the global polarization of Λ hyperons. These methods involve event averages of proton and Λ momenta in the laboratory frame. We carry out simulations using these methods and show that all of them work equally well in obtaining the global polarization of Λ hyperons.
Empirical pairing gaps and neutron-proton correlations
B. S. Ishkhanov, S. V. Sidorov, T. Yu. Tretyakova, E. V. Vladimirova
2019, 43(1): 014104. doi: 10.1088/1674-1137/43/1/014104
Analysis of various mass formulas related to neutron-proton correlations in atomic nuclei is carried out. Using the example of the N=Z chain it is shown that for self-adjoint nuclei various formulas proposed in literature for estimating the np pairing energy lead to similar results. Significant differences between the calculation methods arise when nuclei with NZ are considered, which allows to reveal the complexity of neutron-proton correlations in different types of atomic nuclei and to make assumptions on the correspondence of the mass relation to the real effect of np pairing. The Shell Model parametrization of the binding energy makes it possible to draw additional conclusions on the structure of mass formulas and their relationship.