Some aspects of global Lambda polarization in heavy-ion collisions

Large orbital angular momentum can be generated in non-central heavy-ion collisions, and part of it is expected to be converted into final particle's polarization due to the spin-orbit coupling. Within the framework of A Multi-Phase Transport (AMPT) model, we studied the vorticity-induced polarization of $\Lambda$ hyperons at the midrapidity region $|\eta|<1$ in Au-Au collisions at energies $\sqrt{s_{NN}}=7.7\sim200$ GeV. Our results show that the global polarization decreases with the collisional energies and is consistent with the recent STAR measurements. This behavior can be understood by less asymmetry of participant matter in the midrapidity region due to faster expansion of fireball at higher energies. As another evidence, we discuss how much the angular momentum is deposited in different rapidity region. The result supports our asymmetry argument.Comment: 6 pages, 4 figures, CPOD 2017 proceedin

The Parametric Decay Instability of Alfven waves in Turbulent Plasmas and the Applications in the Solar Wind

We perform three dimensional (3D) ideal magnetohydrodynamic (MHD) simulations to study the parametric decay instability of Alfven waves in turbulent plasmas and explore its possible applications in the solar wind. We find that, over a broad range of parameters in background turbulence amplitudes, the parametric decay instability of an Alfven wave with various amplitudes can still occur, though its growth rate in turbulent plasmas tends to be lower than both the theoretical linear theory prediction and that in the non-turbulent situations. Spatial - temporal FFT analyses of density fluctuations produced by the parametric decay instability match well with the dispersion relation of the slow MHD waves. This result may provide an explanation of the generation mechanism of slow waves in the solar wind observed at 1 AU. It further highlights the need to explore the effects of density variations in modifying the turbulence properties as well as in heating the solar wind plasmas.Comment: Accepted for publication in The Astrophysical Journa

B→SB\to S Transition Form Factors in the PQCD approach

Under two different scenarios for the light scalar mesons, we investigate the transition form factors of $B(B_s)$ mesons decay into a scalar meson in the perturbative QCD approach. In the large recoiling region, the form factors are dominated by the short-distance dynamics and can be calculated using perturbation theory. We adopt the dipole parametrization to recast the $q^2$ dependence of the form factors. Since the decay constants defined by the scalar current are large, our predictions on the $B\to S$ form factors are much larger than the $B\to P$ transitions, especially in the second scenario. Contributions from various light-cone distribution amplitudes (LCDAs) are elaborated and we find that the twist-3 LCDAs provide more than a half contributions to the form factors. The two terms of the twist-2 LCDAs give destructive contributions in the first scenario while they give constructive contributions in the second scenario. With the form factors, we also predict the decay width and branching ratios of the semileptonic $B\to Sl\bar\nu$ and $B\to Sl^+l^-$ decays. The branching ratios of $B\to Sl\bar\nu$ channels are found to have the order of $10^{-4}$ while those of $B\to Sl^+l^-$ have the order of $10^{-7}$. These predictions can be tested by the future experiments.Comment: 20 pages, 31 figure

Diagnosis and treatment of intraocular tuberculosis

Tuberculosis(TB)is a chronic infectious disease with high rate of morbidity and mortality world wide, and it is easy to relapse. TB can involve multiple organs, when it infects eye, it can cause lesions in anterior segment, posterior segment and the accessory organs of the eye. The purpose of this paper is to describe the clinical manifestation of intraocular TB, its diagnosis and treatment

Neutron Density Distributions of Neutron-Rich Nuclei Studied with the Isobaric Yield Ratio Difference

The isobaric yield ratio difference (IBD) between two reactions of similar experimental setups is found to be sensitive to nuclear density differences between projectiles. In this article, the IBD probe is used to study the density variation in neutron-rich $^{48}$Ca. By adjusting diffuseness in the neutron density distribution, three different neutron density distributions of $^{48}$Ca are obtained. The yields of fragments in the 80$A$ MeV $^{40, 48}$Ca + $^{12}$C reactions are calculated by using a modified statistical abrasion-ablation model. It is found that the IBD results obtained from the prefragments are sensitive to the density distribution of the projectile, while the IBD results from the final fragments are less sensitive to the density distribution of the projectile.Comment: 3 figure