Highlights

Sound velocity in dense stellar matter with strangeness and compact stars
2021, 45(5): 055104. doi: 10.1088/16741137/abea0dThe phase state of dense matter in the intermediate density range (
$\sim$ 110 times the nuclear saturation density) is both intriguing and unclear and can have important observable effects in the present gravitational wave era of neutron stars. As matter density increases in compact stars, the sound velocity is expected to approach the conformal limit ($c_s/c=1/\sqrt{3}$ ) at high densities and should also fulfill the causality limit ($c_s/c<1$ ). However, its detailed behavior remains a prominent topic of debate. It was suggested that the sound velocity of dense matter could be an important indicator of a deconfinement phase transition, where a particular shape might be expected for its density dependence. In this work, we explore the general properties of the sound velocity and the adiabatic index of dense matter in hybrid stars as well as in neutron stars and quark stars. Various conditions are employed for the hadronquark phase transition with varying interface tension. We find that the expected behavior of the sound velocity can also be achieved by the nonperturbative properties of the quark phase, in addition to a deconfinement phase transition. Moreover, it leads to a more compact star with a similar mass. We then propose a new class of quark star equation of states, which can be tested by future highprecision radius measurements of pulsarlike objects. 
Relative probabilities of breakup channels in reactions of ^{6,7}Li with ^{209}Bi at energies around and above the Coulomb barrier
2021, 45(5): 054104. doi: 10.1088/16741137/abe3eeCoincidence measurements of breakup fragments in reactions of
${^{6, 7}{\rm{Li}}}$ with${^{209}{\rm{Bi}}}$ at energies around and above the Coulomb barrier were carried out using a large solidangle covered detector array. Through the Q values along with the relative energies of the breakup fragments, different breakup components (prompt breakups and delayed breakups) and different breakup modes ($\alpha + t$ ,$\alpha + d$ ,$\alpha + p$ , and$\alpha + \alpha$ ) are distinguished. A new breakup mode,$\alpha + t$ , is observed in${^{6}{\rm{Li}}}$ induced reactions at energies above the Coulomb barrier. Correlations between breakup modes and breakup components as well as their variations with the incident energy are investigated. The results will help us better understand the breakup effects of weakly bound nuclei on the suppression of a complete fusion, particularly for the abovebarrier energies. 
Categorization of twoloop Feynman diagrams in the
$ {{\cal O}{\mathit{\boldsymbol{(\alpha^2)}}}} $ correction to$ {{\mathit{\boldsymbol{e^+}}}{{\mathit{\boldsymbol{e^}}}} {\mathit{\boldsymbol{\rightarrow ZH}}}} $ 2021, 45(5): 053102. doi: 10.1088/16741137/abe84dThe$ e^+e^ \rightarrow ZH $ process is the dominant process for the Higgs boson production at the future Higgs factory. In order to match the analysis on the Higgs properties with highly precise experiment data, it will be crucial to include the theoretical prediction to the full nexttonexttoleading order electroweak effect in the production rate$ \sigma(e^+e^\rightarrow ZH) $ . In this inspiring work, we categorize the twoloop Feynman diagrams of the$ {\cal O}(\alpha^2) $ correction to$ e^+e^ \rightarrow ZH $ into 6 categories according to relevant topological structures. Although 25377 diagrams contribute to the$ {\cal O}(\alpha^2) $ correction in total, the number of the most challenging diagrams with seven denominators is 2250, which contain only 312 nonplanar diagrams with 155 independent types. This categorization could be a valuable reference for the complete calculation in future.
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DiHiggs production as a probe of flavor changing neutral Yukawa couplings
Published: 20210512, doi: 10.1088/16741137/abfb50

Chiral symmetry restoration and deconfinement in the contact interaction model of quarks with a parallel electric and magnetic fields
Published: 20210512

Theoretical uncertainties on the extraction of inmedium NN cross sections by different Pauli blocking algorithms
Published: 20210507, doi: 10.1088/16741137/abfb51
In Press
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Effects of electric fields on ^{7}Be halflife
Published: 20210512, doi: 10.1088/16741137/abf6c3Show AbstractFirstprinciple calculations based on the density functional theory (DFT) method are adopted to investigate the influence of a strong electric field on the ^{7}Be halflife. Accordingly, electronic structures of Be and BeO are examined in the presence of a homogeneous electric field. The electron density at the nucleus is estimated upon the geometry optimization. Our computations for the Be metal indicate a 0.02% increase in the decay rate of the ^{7}Be nucleus, corresponding to a 0.02% decrease in the ^{7}Be halflife, both at 5.14 V/Å (0.1 a.u.). Furthermore, it is determined that the decay rate of ^{7}Be is not considerably altered up to 3.6 V/Å in the BeO structure. Our results show that the screening energy of the electron can be dependent on the applied electric field strength. Furthermore, we predict variations in the Coulomb potential at the ^{7}Be nucleus due to electric field application.

Thermodynamic instability of 3D EinsteinBornInfeld AdS black holes
Published: 20210511, doi: 10.1088/16741137/abf1dcShow AbstractSuperentropic black holes possess finitearea but noncompact event horizons and violate the reverse isoperimetric inequality. It has been conjectured that such black holes always have negative specific heat at constant volume
$ C_{V} $ or negative specific heat at constant pressure$ C_{P} $ whenever$ C_{V}>0 $ , making them unstable in extended thermodynamics. In this paper, we describe a test of this instability conjecture with a family of nonlinear electrodynamic black holes, namely 3D EinsteinBornInfeld (EBI) AdS black holes. Our results show that when nonlinear electrodynamics effects are weak, the instability conjecture is valid. However, the conjecture can be violated in some parameter region when nonlinear electrodynamics effects are strong enough. This observation thus provides a counter example to the instability conjecture, which suggests that superentropic black holes may be thermodynamically stable. 
Hydrodynamic description of D meson production in highenergy heavyion collisions
Published: 20210511, doi: 10.1088/16741137/abf645Show AbstractThe large values and constituentquarknumber scaling of the elliptic flow of low
$ p_T $ D mesons imply that charm quarks, initially produced through hard processes, might be partially thermalized through strong interactions with quarkgluon plasma (QGP) in highenergy heavyion collisions. To quantify the degree of thermalization of low$ p_T $ charm quarks, we compare the$ D^0 $ meson spectra and elliptic flow from a hydrodynamic model to experimental data as well as transport model simulations. We use an effective charm chemical potential at the freezeout temperature to account for the initial charm quark production from hard processes and assume that they are thermalized in the local comoving frame of the medium before freezeout.$ D^0 $ mesons are sampled statistically from the freezeout hypersurface of the expanding QGP as described by the eventbyevent (3+1)D viscous hydrodynamic model CLVisc. Both the hydrodynamic and transport models can describe the elliptic flow of$ D^0 $ mesons at$ p_T<3 $ GeV/c as measured in Au+Au collisions at$ \sqrt{s_{NN}} = 200 $ GeV. Though the experimental data on$ D^0 $ spectra are consistent with the hydrodynamic result at small$ p_T\sim 1 $ GeV/c, they deviate from the hydrodynamic model at high transverse momentum,$ p_T>2 $ GeV/c. The diffusion and parton energy loss mechanisms in the transport model can describe the measured spectra reasonably well within the theoretical uncertainty. Our comparative study indicates that charm quarks only approach local thermal equilibrium at small$ p_T $ , even though they acquire sizable elliptic flow comparable to lightquark hadrons at both small and intermediate$ p_T $ .
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