Production of the X(4014)as the Spin-2 Partner of X(3872)in e^(+)e^(-)Collisions

In 2021,the Belle collaboration reported the first observation of a new structure in theψ(2S)γfinal state produced in the two-photon fusion process.In the hadronic molecule picture,this new structure can be associatedwith the shallow isoscalar D*D* bound state and as such is an excellent candidate for the spin-2 partner of the X(3872)with the quantum numbers J^(PC)=2^(++)conventionally named X_(2).

Precision Tests of the Nonlinear Mode Coupling of Anisotropic Flow via High-Energy Collisions of Isobars

Valuable information on dynamics of expanding fluids can be inferred from the response of such systems to perturbations in their initial geometry.We apply this technique in high-energy^(96)Ru+^(96)Ru and^(96)Zr+^(96)Zr collisions to scrutinize the expansion dynamics of the quark-gluon plasma,where the initial geometry perturbations are sourced by the differences in deformations and radial profiles between^(96)Ru and^(96)Zr,and the collective response is captured by the change in anisotropic flow Vn between the two collision systems.Using a transport model,we analyze how the nonlinear coupling between lower-order flow harmonics V_(2)and V_(3)to the higher-order flow harmonics V_(4)and V_(5),expected to scale as V_(4)NL= χ_(4)V_(2)2and V_(5)NL= χ_(5)V_(2)V_(3),gets modified as one moves from^(96)Ru+^(96)Ru to^(96)Zr+^(96)Zr systems.We find that these scaling relations are valid to high precision:variations of order 20% in V_(4)NLand V_(5)NLdue to differences in quadrupole deformation,octupole deformation,and nuclear skin modify χ_(4)and χ_(5)by about 1–2%.Percent-level deviations are however larger than the expected experimental uncertainties and could be measured.Therefore,collisions of isobars with different nuclear structures are a unique tool to isolate subtle nonlinear effects in the expansion of the quark-gluon plasma that would be otherwise impossible to access in a single collision system.

Bistability in Coupled Oscillators Exhibiting Synchronized Dynamics

We report some new results associated with the synchronization behavior of two coupled double-well Duffing oscillators （DDOs）. Some sufficient algebraic criteria for global chaos synchronization of the drive and response DDOs via linear state error feedback control are obtained by means of Lyapunov stability theory. The synchronization is achieved through a bistable state in which a periodic attractor co-exists with a chaotic attractor. Using the linear perturbation analysis, the prevalence of attractors in parameter space and the associated bifurcations are examined. Subcritical and supercritical Hopf bifurcations and abundance of Arnold tongues -- a signature of mode locking phenomenon are found.

Electron-Helium Scattering in a Bichromatic Laser Field in the Second-Order Born Approximation

The elastic scattering of electrons in atomic helium assisted by a bichromatic laser field is investigated in the second order Born approximation. The target atom is approximated by a simple screening potential. The dependence of the differential cross section on the relative phase between the two laser components is calculated, and compared with the recent results of first order Born approximation [Sun J F, Liang M C and Zhu Z L 2007 Chin. Phys. Lett. 24 2572].

Pressure and Spectral Density of Fermions at Finite Temperature

The pressure of a fermion system is expressed as a mass integral over the full two-point spectral densities within the real time formalism by use of the Keldysh representation for the propagators.This simpliSes the calculation significantly and allows a Dyson resummation.The expression is used to demonstrate that potential infrared divergences are rendered harmless.We apply it to check the pressures of an ideal fermion gas and of a chemically non-equilibrated quantum chromodynamics plasma.

A Note on Similarity Reductions of Barotropic and Quasi-geostrophic Potential Vorticity Equation

Applying the classical Lie symmetry approach to the barotropic and quasi-geostrophic potential vorticity equation without forcing and dissipation on a β-plane channel, we find a new symmetry, which is not presented in a previous work [F. Huang, Commun. Theor. Phys. （Beijing, China） 42 （2004） 903]. A general finite transformation group is obtained based on the full Lie point symmetry, Furthermore, two new types of similarity reduction solutions are obtained.

Dust-Acoustic Waves in Strongly Coupled Dusty Plasmas Containing Variable-Charge Impurities

A relatively self-consistent theory of dust-acoustic waves in the strongly coupled dusty plasmas containing variable-charge impurities is given.Relevant physical processes such as dust elastic relaxation and dust charge relaxation are taken into account.It is shown that the negative dispersion of dust-acoustic waves due to the strong correlation of dusts is enhanced in the presence of dust-neutral collisions.

Relativistic Chiral Description of the 1S0 Nucleon-Nucleon Scattering

Recently,a relativistic chiral nucleon-nucleon interaction was formulated up to leading order,which provides a good description of the phase shifts of J≤1 partial waves[Chin.Phys.C 42(2018)014103].Nevertheless,a separable regulator function that is not manifestly covariant was used in solving the relativistic scattering equation.In the present work,we first explore a covariant and separable form factor to regularize the kernel potential and then apply it to study the simplest but most challenging ^(1)S_(0) channel which features several lowenergy scales.In addition to being self-consistent,we show that the resulting relativistic potential can describe quite well the unique features of the ^(1)S_(0) channel at leading order,in particular the pole position of the virtual bound state and the zero amplitude at the scattering momentum ~340 MeV,indicating that the relativistic formulation may be more natural from the viewpoint of effective field theories.

Analysis of the Low-Energy π^±p Elastic-Scattering Data

We report the results of a phase-shift analysis (PSA) of the low-energy π±p elastic-scattering data. Following the method which we had set forth in our previous PSA [1], we first investigate the self-consistency of the low-energy π±p elastic-scattering databases, via two separate analyses of (first) the π+p and (subsequently) the π-p elastic-scattering data. There are two main differences to our previous PSA: 1) we now perform only one test for the acceptance of each data set (based on its contribution to the overall 2) and 2) we adopt a more stringent acceptance criterion in the statistical tests. We show that it is possible to obtain self-consistent databases after removing a very small amount of the data (4.57% of the initial database). We subsequently fit the ETH model [38] to the truncatedπ±p elastic-scattering databases. The model-parameter values show reasonable stability when subjected to different criteria for the rejection of single data points and entire data sets. Our result for the pseudovector πNN coupling constant is 0.0726±0.0014. We extract the scattering lengths and volumes, as well as the s- and p-wave hadronic phase shifts up to T = 100 MeV. Large differences in the s-wave part of the interaction can be seen when comparing our hadronic phase shifts with the current SAID solution (WI08);there is general agreement in the p waves, save for the ~1/21- hadronic phase shift.

Electron Acceleration in the Bubble Regime with Dense-Plasma Wall Driven by an Ultraintense Laser Pulse

An optimizing scheme for electron acceleration in the wake bubble with dense-plasma wall driven by an ultraintense laser pulse is presented and investigated by particle-in-cell simulation. The wall has an inner diameter matching the expected lateral bubble size. The bubble shape can be transversely controlled and longitudinally shrunk. The accelerated electrons as a bunch have a high quality because the electrons almost stay close to the bottom of the bubble and are accelerated to much high energy with narrow energy spread.

Enhanced Correlation of Electron-Positron Pair in Two and Three Dimensions

Early time electron-positron correlation in vacuum pair-production in an external field is investigated. The entangled electron and positron wave functions are obtained analytically in the configuration and momentum spaces. It is shown that, relative to that of the one-dimensional theory, two- and three-dimensional calculations yield enhanced spatial correlation and broadened momentum spectra. In fact, at early times the electron and positron almost coincide spatially. The correlation also depends on the direction of the applied field. For the spatial correlation, the transverse correlation is stronger than the longitudinal correlation.

Effects of a phase transition on two-pion interferometry in heavy ion collisions at √SNN=2.4-7.7 GeV

Hanbury-Brown-Twiss(HBT) correlations for charged pions in central Au+Au collisions at √SNN=2.4-7.7 GeV(corresponding to beam kinetic energies in the fixed target frame from Elab=1.23 to 30 GeV/nucleon) are calculated using the ultra-relativistic quantum molecular dynamics model with different equations of state(EoSs).The effects of a phase transition at high baryon densities are clearly observed in the explored HBT parameters.The results show that the available data on the HBT radii,RO/RSand R^(2)_(O)-R^(2)_(S),in the investigated energy region favor a relatively stiff EoS at low beam energies,which then turns into a soft EoS at high collision energies consistent with astrophysical constraints on the high-density EoS of quantum chromodynamics(QCD).The specific effects of two different phase transition scenarios on RO/RSand R^(2)_(O)-R^(2)_(S)are investigated.A phase transition with a significant softening of the EoS below four times the nuclear saturation density can be excluded using HBT data.Our results highlight that the pion’s RO/RSand R^(2)_(O)-R^(2)_(S)are sensitive to the stiffness of the EoS and can be used to constrain and understand the QCD EoS in a high baryon density region.

大入射能量范围内重离子输运过程的动力学性质研究

基于一个改进的微观动力学输运模型——极端相对论量子分子动力学(UrQMD),较为系统地研究了从SIS能区到AGS和SPS能区,再到RHIC能区,入射能量跨5个数量级的重离子核反应及多个人们感兴趣的实验观测量,如粒子产额、集体流、核阻止以及两粒子HBT关联等。研究表明,不论单粒子观测量,还是两粒子关联观测量,都能自洽地由同一个输运模型加以描述。

Stability of the linear chain structure for 12C in covariant density functional theory on a 3D lattice

The stability of the linear chain structure of three α clusters for 12C against the bending and fission is investigated in the cranking covariant density functional theory, in which the equation of motion is solved on a 3D lattice with the inverse Hamiltonian and the Fourier spectral methods. Starting from a twisted three α initial configuration, it is found that the linear chain structure is stable when the rotational frequency is within the range of ~2.0-~2.5 MeV. Beyond this range, the final states are not stable against fission. By examining the density distributions and the occupation of single-particle levels, however, these fissions are found to arise from the occupation of unphysical continuum with large angular momenta. To properly remove these unphysical continuum, a damping function for the cranking term is introduced. Eventually, the stable linear chain structure could survive up to the rotational frequency ~3.5 MeV, but the fission still occurs when the rotational frequency approaches ~4.0 MeV.

Quantum anomalous energy effects on the nucleon mass

Apart from the quark and gluon kinetic and potential energies, the nucleon mass includes a novel energy of pure quantum origin resulting from anomalous breaking of scale symmetry. We demonstrate the effects of this quantum anomalous energy(QAE) in QED, as well as in a toy 1+1 dimensional non-linear sigma model where it contributes non-perturbatively, in a way resembling the Higgs mechanism for the masses of matter particles in electro-weak theory. The QAE contribution to the nucleon mass can be explained using a similar mechanism, in terms of a dynamical response of the gluonic scalar field through Higgs-like couplings between the nucleon and scalar resonances. In addition, the QAE sets the scale for other energies in the nucleon through a relativistic virial theorem, and contributes a negative pressure to confine the colored quarks.

Non-Markovian discrete qubit dynamics

The study of open quantum systems is important for fundamental issues of quantum physics as well as for technological applications such as quantum information processing. The interaction of a quantum system with its environment is usually detrimental for the quantum properties of the system and leads to decoherence. However,sometimes a quantum control can lead to a coherent partial exchange of information between the system and the dynamics of the open system might become non-Markovian. In this article, we study experimentally discrete nonMarkovian open quantum system dynamics. We implement a local control protocol using linear optics for controlling the information flow between the open system and the environment. We show how the transition from Markovian to non-Markovian dynamics can be controlled using only local operations for the open system.

Exploring novel target structures for manipulating relativistic laser–plasma interaction

The improved laser-to-pedestal contrast ratio enabled by current high-power laser pulse cleaning techniques allows the fine features of the target survive before the main laser pulse arrives. We propose to introduce the nano-fabrication technologies into laser–plasma interaction to explore the novel effects of micro-structures. We found out that not only laser-driven particle sources but also the laser pulse itself can be manipulated by specifically designed micro-cylinder and-tube targets, respectively. The proposal was supported by full-3D particle-in-cell simulations and successful proofof-principle experiments for the first time. We believe this would open a way to manipulate relativistic laser–plasma interaction at the micro-size level.

Different types of spin currents in the comprehensive materials database of nonmagnetic spin Hall effect

Spin Hall effect(SHE)has its special position in spintronics.To gain new insight into SHE and to identify materials with substantial spin Hall conductivity(SHC),we performed high-precision high-throughput ab initio calculations of the intrinsic SHC for over 20,000 nonmagnetic crystals.The calculations revealed a strong relationship between the magnitude of the SHC and the crystalline symmetry,where a large SHC is typically associated with mirror symmetry-protected nodal line band structures.This database includes 11 materials with an SHC comparable to or even larger than that of Pt.Materials with different types of spin currents were additionally identified.Furthermore,we found that different types of spin current can be obtained by rotating applied electrical fields.This improves our understanding and is expected to facilitate the design of new types of spin-orbitronic devices.

Nuclear Dynamics at the Particle Threshold

Recently, new low-energy modes of excitation called pygmy resonances have been observed.Their distinct feature is the close connection to nuclear skin oscillations. A successful description of the pygmy resonances could be achieved in a microscopic theoretical approach which incorporates the density functional theory and QRPA formalism extended with multi-phonon degrees of freedom. The latter is found of crucial importance for the understanding of the fine structure of nuclear electric and magnetic excitations at low energies. Corresponding microscopic multi-phonon response functions are implemented in the studies of s-process of nucleosynthesis.