Zhang Wei-Ning

Two-Pion Interferometry for the Granular Sources in Ultrarelativistic Heavy Ion Collisions at the RHIC and the LHC

We investigate the two-pion interferometry in ultrarelativistic heavy ion collisions in the granular source model of quark-gluon plasma droplets. The pion transverse momentum spectra and HBT radii of the granular sources agree well with the experimental data of the most central Au-Au collisions at = 200 GeV at the RHIC and Pb-Pb collisions at = 2.76 TeV at the LHC. In the granular source model the larger initial system breakup time for the LHC collisions as compared to the RHIC collisions may lead to the larger HBT radii Rout, Rside and Rlong. However, the large droplet transverse expansion and limited average relative emitting time of particles in the granular source lead to slightly smaller ratios of the transverse Hanbury-Brown-Twiss radii Rout/Rside.

Resonance Conversion as a Catalyzer of Nuclear Reactions

It is shown that resonance internal conversion offers a feasible tool for mastering nuclear processes with laser or synchrotron radiation. The physics of the process is discussed in detail in a historical aspect. Possible experimental application is shown in the case of the M1 70.6-keV transition in nuclei of 169Yb. The nuclear transition rate in hydrogen-like ions of this nuclide can be enhanced by up to four orders of magnitude.

Relativistic effects on the back-to-back correlation functions of boson-antiboson pairs in high energy heavy ion collisions*

We calculate the back-to-back correlation (BBC) functions of relativistic boson-antiboson pairs in high energy heavy ion collisions using the Monte Carlo method. The relativistic effects on the BBC functions of φφ and K + K − pairs are investigated. The investigations indicate that the relativistic effects on the BBC functions of K + K − pairs with large momenta are significant, and the effect is sensitive to the particle freeze-out temperature.

Interferometry Signatures for QCD First-Order Phase Transition in High Energy Heavy Ion Collisions

Using the technique of quantum transport of the interfering pair we examine the Hanbury–Brown–Twiss (HBT) interferometry signatures for the particle-emitting sources of pions and kaons produced in heavy ion collisions at 10–30 AGeV. The evolution of the sources is described by relativistic hydrodynamics with the first-order phase transition from quark-gluon plasma (QGP) to hadronic matter. We use quantum probability amplitudes in a path-integral formalism to calculate the two-particle correlation functions, where the effects of particle decay and multiple scattering are taken into consideration. Our model-calculated results indicate that both the HBT radii of pions and kaons increase with the system initial energy density. The HBT lifetimes of the pion and kaon sources increase significantly when the initial energy density is tuned to the phase boundary between the QGP and mixed phase. This increase of HBT lifetimes will likely appear in heavy ion collisions with an incident energy between 10–30 AGeV.Using the technique of quantum transport of the interfering pair we examine the HanburyBrown-Twiss (HBT) interferometry signatures for the particle-emitting sources of pions and kaons produced in the heavy ion collisions at GSI-FAIR energies. The evolution of the sources is described by relativistic hydrodynamics with the system equation of state of the first-order phase transition from quark-gluon plasma (QGP) to hadronic matter. We use quantum probability amplitudes in a path-integral formalism to calculate the two-particle correlation functions, where the effects of particle decay and multiple scattering are taken into consideration. We find that the HBT radii of kaons are smaller than those of pions for the same initial conditions. Both the HBT radii of pions and kaons increase with the system initial energy density. The HBT lifetimes of the pion and kaon sources are sensitive to the initial energy density. They are significantly prolonged when the initial energy density is tuned to the phase boundary between the QGP and mixed phase. This prolongations of the HBT lifetimes of pions and kaons may likely be observed in the heavy ion collisions with an incident energy in the GSI-FAIR energy range. PACS numbers: 25.75.-q, 25.75.Gz, 25.75.Nq ∗ wnzhang@dlut.edu.cn

Semiclassical Model of Quark-Gluon Plasma

A semiclassical model of a gluon—quark plasma (QGP) is provided. The spinof the quark is described by an antisymmetric tensor Sμν and color charges,and spin tensor are defined as semiclassical numbers. The transport propertiesof QGP in color space and spin space are investigated. The consistency of thesemiclassical model and the quantum models of QGP is discussed.

Source function extracted from single-event HBT correlation functions of hydrodynamical sources *

We investigate the single-event two-pion correlation functions for the hydrodynamic particle-emitting sources with the fluctuating initial conditions generated by the Heavy Ion Jet Interaction Generator (HIJING). Using a three-dimension fast Fourier transform (FFT), we further extract the source functions from the single-event correlation functions. It is found that the inhomogeneity of the hydrodynamic sources with the fluctuating initial conditions lead to event-by-event fluctuations of the correlation functions and source functions.

Two-pion interferometry for viscous hydrodynamic sources

The space-time evolution of the (1+1)-dimensional viscous hydrodynamics with an initial quarkgluon plasma (QGP) produced in ultrarelativistic heavy ion collisions is studied numerically. The particleemitting sources undergo a crossover transition from the QGP to hadronic gas. We take into account a usual shear viscosity for the strongly coupled QGP as well as the bulk viscosity which increases significantly in the crossover region. The two-pion Hanbury-Brown-Twiss (HBT) interferometry for the viscous hydrodynamic sources is performed. The HBT analyses indicate that the viscosity effect on the two-pion HBT results is small if only the shear viscosity is taken into consideration in the calculations. The bulk viscosity leads to a larger transverse freeze-out configuration of the pion-emitting sources, and thus increases the transverse HBT radii. The results of the longitudinal HBT radius for the source with Bjorken longitudinal scaling are consistent with the experimental data.The space-time evolution of the (1+1)-dimensional viscous hydrodynamics with an initial quark-gluon plasma (QGP) produced in ultrarelativistic heavy ion collisions is studied numerically. The particle-emitting sources undergo a crossover transition from the QGP to hadronic gas. We take into account a usual shear viscosity for the strongly coupled QGP as well as the bulk viscosity which increases significantly in the crossover region. The two-pion Hanbury-Brown-Twiss (HBT) interferometry for the viscous hydrodynamic sources is performed. The HBT analyses indicate that the viscosity effect on the two-pion HBT results is small if only the shear viscosity is taken into consideration in the calculations. The bulk viscosity leads to a larger transverse freeze-out configuration of the pion-emitting sources, and thus increases the transverse HBT radii. The results of the longitudinal HBT radius for the source with Bjorken longitudinal scaling are consistent with the experimental data.

Interferometry imaging for the evolving source in heavy ion collisions at HIRFL-CSR energy

Imaging analysis of two-pion interferometry is performed for an evolving particle-emitting source in heavy ion collisions at HIRFL-CSR energy. The source evolution is described by the relativistic hydrodynamics in (2+1) dimensions. The model-independent characteristic quantities of the source are investigated and compared with the interferometry results obtained by the usual Gaussian formula fit. It is found that the firstorder source function moments can describe the source sizes. The ratio of the normalized standard deviation σ to the first-order moment R, σ/R, is sensitive to the shape of the source function.

Inhomogeneous space-time structure and two-pion interferometry in NEXSPHERIO model

We examine the space-time structure of particle-emitting source and two-pion interferometry in a smoothed hydrodynamic model with fluctuating initial conditions. An equation of state with a crossover transition between quark-gluon plasma and hadronic gas is adopted in the description of the system evolution. We find that the fluctuating initial conditions lead to inhomogeneous particle-emitting sources. The interferometry results of Rs and Ro indicate that both the source size and the duration of pion emission decrease when the freeze-out temperature increases. The values of Ro/Rs obtained by our simulated two-pion interferometry are consistent with the previous results of smoothed particle hydrodynamics, and smaller than those calculated in usual hydrodynamic models.

Two-pion interferometry for a partially coherent evolution source

We give the formulas of two-pion Hanbury-Brown-Twiss (HBT) correlation function for a partially coherent evolution pion-emitting source, using quantum probability amplitudes in a path-integral formalism. The multiple scattering of the particles in the source is taken into consideration based on Glauber scattering theory. Two-pion interferometry with effects of the multiple scattering and source collective expansion is examined for a partially coherent source of hadronic gas with a finite baryon density and evolving hydrodynamically. We do not find observable effect of either the multiple scattering or the source collective expansion on HBT chaotic parameter.