Charge separation with fluctuating domains in relativistic heavy-ion collisions

Charge separation induced by the chiral magnetic effect suggested that some ${\cal P}$- or ${\cal CP}$-odd metastable domains could be produced in a QCD vacuum in the early stage of relativistic heavy-ion collisions. Based on a multi-phase transport model, our results suggest that a domain-based scenario with final state interactions can describe the solenoidal tracker at RHIC detector (STAR) measurements of both same- and opposite-charge azimuthal angle correlations, $$, in Au+Au collisions at $\sqrt{s_{_{\rm NN}}}=200$ GeV. The occupancy factor of the total volume of domains over the fireball volume is small, which indicates that the size and number of metastable domains should be relatively small in the early stage of a quark-gluon plasma.Comment: 4 pages, 4 figures, 1 table, final published versio

Effect of Resonant Continuum on Pairing Correlations in the Relativistic Approach

A proper treatment of the resonant continuum is to take account of not only the energy of the resonant state, but also its width. The effect of the resonant states on pairing correlations is presented based on the relativistic mean field theory plus Bardeen-Cooper-Schrieffer(BCS) approximation with a constant pairing strength. The study is performed in an effective Lagrangian with the parameter set NL3 for neutron rich even-even Ni isotopes. The results show that the contribution of the proper treatment of the resonant continuum to pairing correlations for those nuclei close to neutron drip line is important. The pairing gaps, Fermi energies, pairing correlation energies, and binding energies are considerably affected with a proper consideration of the width of resonant states. The problem of an unphysical particle gas, which may appear in the calculation of the traditional mean field plus BCS method for nuclei in the vicinity of drip line could be well overcome when the pairing correlation is performed by using the resonant states instead of the discretized states in the continuum.Comment: 19 pages, 8 Postscript figur

Energy dependence of pion in-medium effects on \pi^-/\pi^+ ratio in heavy-ion collisions

Within the framework of a thermal model with its parameters fitted to the results from an isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, we study the pion in-medium effect on the charged-pion ratio in heavy-ion collisions at various energies. We find that due to the cancellation between the effects from pion-nucleon s-wave and p-wave interactions in nuclear medium, the \pi^-/\pi^+ ratio generally decreases after including the pion in-medium effect. The effect is larger at lower collision energies as a result of narrower pion spectral functions at lower temperatures.Comment: 4 pages, 4 figures, 1 table, minor modifications, version to appear in Physical Review