Antiflow of mesons in the high baryon density region

The E895 and STAR experiments demonstrate that the slopes of directed flow with respect to rapidity ($d{v}_{1}{/dy|}_{y=0}$) of mesons are negative in the low transverse momentum (${p}_{T}$) region, ${p}_{T}<0.8\phantom{\rule{4pt}{0ex}}\mathrm{GeV}/c$, in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=3.0--3.9\phantom{\rule{4pt}{0ex}}\mathrm{GeV}$. Using the transport model JAM, we investigate the directed flow of ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}, {K}^{\ifmmode\pm\else\textpm\fi{}}$, and ${K}^{0}$ as functions of rapidity, ${p}_{T}$, and collision energy in $\mathrm{Au}+\mathrm{Au}$ collisions at the same energies as those in the E895 and STAR experiments. We find that the JAM model can qualitatively reproduce the antiflow of ${K}_{S}^{0}$ observed in the E895 experiment. The ${v}_{1}$ slopes of pions and kaons are analyzed as functions of the ${p}_{T}$ window, revealing a strong ${p}_{T}$ dependence of the ${v}_{1}$ slopes. Negative ${v}_{1}$ slopes are observed in the low ${p}_{T}$ region, ${p}_{T}<0.8\phantom{\rule{4pt}{0ex}}\mathrm{GeV}/c$, while positive slopes are shown in the higher ${p}_{T}$ region. We find that the shadowing effect from spectators is crucial in generating the antiflow of mesons at low ${p}_{T}$ in the high baryon density region.