Fluctuations of the Initial Conditions and the Continuous Emission in the Hydrodynamical Description of Two-Pion Interferometry

Within the hydrodynamical approach, we study the Bose-Einstein correlation of identical pions by taking into account both event-by-event fluctuating initial conditions and continuous pion emission during the whole development of the hot and dense matter formed in high-energy collisions. Important deviations occur, compared to the usual hydrocalculations with smooth initial conditions and a sudden freeze-out on a well defined hypersurface. Comparison with data at the BNL Relativistic Heavy Ion Collider (RHIC) shows that, despite the rather rough approximation we used here, this description can account for the $m_T$ dependence of $R_L$ and $R_s$, and produces a significant improvement for $R_o$ with respect to the usual version.

Figure 1

Examples of initial conditions for central $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions given by NeXus at midrapidity plane. Energy density is plotted in units of $\mathrm{G}\mathrm{e}\mathrm{V}/{\mathrm{f}\mathrm{m}}^3$. Left: one random event. Right: average over 30 random events.

Figure 2

Correlation functions from fluctuating IC and averaged IC. Sudden FO is used here. The rapidity range is $-0.5\le Y\le 0.5$ and $q_{o,s,l}$, which do not appear in the horizontal axis, are integrated over $0\le q_{o,s,l}\le 35\mathrm{M}\mathrm{e}\mathrm{V}$.

Figure 3

HBT radii and the ratio $R_o/R_s$ for sudden freeze-out (FO) and CE. 1 stands for averaged IC and two fluctuating IC. Data are from 16, 22: $({\pi }^{+}+{\pi }^{-})/2$.

Figure 4

Charged-particle $p_T$ distributions in CEM for the most central $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ at 130 A GeV. The data are from 26.