Surface excitations, shape deformation and the long-time behavior in a stirred Bose-Einstein condensate

The surface excitations, shape deformation and the formation of persistent current for a Gaussian obstacle potential rotating in an highly oblate Bose-Einstein condensate(BEC)are investigated. Vortex dipole can be produced and trapped in the center of the stirrer even for slow motion of the stirring beam. When the barrier angular velocity is above some critical value, the condensate shape can be deformed remarkably according to the rotation frequency due to the existence of plenty of surface wave excitations. After a long enough time, a few vortices are found to be left either trapped in the condensate or pinned by the obstacle, a vortex dipole or several vortices can be trapped at the beam center, which enables the possibility of vortex manipulation.Comment: 5 pages, 4 figure

Production of heavy isotopes in transfer reactions by collisions of 238^{238}U+238^{238}U

The dynamics of transfer reactions in collisions of two very heavy nuclei $^{238}$U+$^{238}$U is studied within the dinuclear system (DNS) model. Collisions of two actinide nuclei form a super heavy composite system during a very short time, in which a large number of charge and mass transfers may take place. Such reactions have been investigated experimentally as an alternative way for the production of heavy and superheavy nuclei. The role of collision orientation in the production cross sections of heavy nuclides is analyzed systematically. Calculations show that the cross sections decrease drastically with increasing the charged numbers of heavy fragments. The transfer mechanism is favorable to synthesize heavy neutron-rich isotopes, such as nuclei around the subclosure at N=162 from No (Z=102) to Db (Z=105).Comment: 4 pages, 4 figure

QCD and Relativistic O(αsv2)O(\alpha_{s}v^2) Corrections to Hadronic Decays of Spin-Singlet Heavy Quarkonia hc,hbh_c, h_b and ηb\eta_b

We calculate the annihilation decay widths of spin-singlet heavy quarkonia $h_c, h_b$ and $\eta_b$} into light hadrons with both QCD and relativistic corrections at order $O(\alpha_{s}v^{2})$ in nonrelativistic QCD. With appropriate estimates for the long-distance matrix elements by using the potential model and operator evolution method, we find that our predictions of these decay widths are consistent with recent experimental measurements. We also find that the $O(\alpha_{s}v^{2})$ corrections are small for $b\bar{b}$ states but substantial for $c\bar{c}$ states. In particular, the negative contribution of $O(\alpha_{s}v^{2})$ correction to the $h_{c}$ decay can lower the decay width, as compared with previous predictions without the $O(\alpha_{s}v^{2})$ correction, and thus result in a good agreement with the recent BESIII measurement.Comment: version published in PRD, 30 pages, 8 figures, more discussions on LDMEs adde

Formation of superheavy nuclei in cold fusion reactions

Within the concept of the dinuclear system (DNS), a dynamical model is proposed for describing the formation of superheavy nuclei in complete fusion reactions by incorporating the coupling of the relative motion to the nucleon transfer process. The capture of two heavy colliding nuclei, the formation of the compound nucleus and the de-excitation process are calculated by using an empirical coupled channel model, solving a master equation numerically and applying statistical theory, respectively. Evaporation residue excitation functions in cold fusion reactions are investigated systematically and compared with available experimental data. Maximal production cross sections of superheavy nuclei in cold fusion reactions with stable neutron-rich projectiles are obtained. Isotopic trends in the production of the superheavy elements Z=110, 112, 114, 116, 118 and 120 are analyzed systematically. Optimal combinations and the corresponding excitation energies are proposed.Comment: 18 pages, 8 figure

Spin Correlations in top quark pair production near threshold at the e−e+ e^- e^+ Linear Collider

We investigate the spin correlations in top quark pair production near threshold at the $e^- e^+$ linear collider. Comparing with the results above the threshold region, we find that near the threshold region the off-diagonal basis, the optimized decomposition of the top quark spins above the threshold region, does not exist, and the beamline basis is the optimal basis, in which there are the dominant spin components: the up-down (UD) component for $e_L^- e^+$ scattering and the down-up (DU) component for $e_R^- e^+$ scattering can make up more than 50% of the total cross section, respectively.Comment: 12 pages, 3 figures, minor modification