Charge separation with fluctuating domains in relativistic heavy-ion collisions

Charge separation induced by the chiral magnetic effect has suggested that some $\mathcal{P}$- or $\mathcal{C}P$-odd metastable domains could be produced in a QCD vacuum in the early stage of relativistic heavy-ion collisions. Based on a multiphase transport model, our results suggest that a domain-based scenario with final state interactions can describe the solenoidal tracker at RHIC (STAR) detector measurements of both same- and opposite-charge azimuthal angle correlations, $\langle cos({\varphi }_{\alpha }+{\varphi }_{\beta })\rangle$, in Au + Au collisions at $\sqrt{s_{\mathit{NN}}}=200$ 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.

Figure 1

A schematic illustration of numerous metastable domain bubbles $(r\sim$ 0.5 fm) in an initial partonic fireball for a typical Au + Au event at $\sqrt{s_{\mathit{NN}}}=200$ GeV $(b=8$ fm), where large dashed circles represent domain bubbles and small solid circles represent partons.

Figure 2

Centrality dependence of $\langle cos({\varphi }_{\alpha }+{\varphi }_{\beta })\rangle$ in Au + Au collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV (with a 10 mb parton interaction cross section). The different symbols represent the results from different settings of AMPT models, and the stars represent experimental data [8, 21]. Some points are slightly shifted for clarity.

Figure 3

Same as Fig. 2, but for $\langle cos({\varphi }_{\alpha }-{\varphi }_{\beta })\rangle$.

Figure 4

Centrality dependences of production rates of different settings of domains in Au + Au collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV.