Octet meson spectra and chiral phase diagram in the improved soft-wall AdS/QCD model

We give a further study on chiral phase diagram in the improved soft-wall AdS/QCD model with $2+1$ flavors. The equations of motion for the octet pseudoscalar, vector, and axial-vector mesons are derived to compute the octet meson spectra and relevant decay constants, by which the model parameters are determined. The chemical potential effects on thermal transition of chiral condensate are investigated, which enables us to obtain the chiral phase diagram in the $\mu -T$ plane. We find that the critical endpoint linking the crossover transition with the first-order phase transition still exists and locates at $({\mu }_B,T_c)\simeq (390\mathrm{MeV},145\mathrm{MeV})$, which along with the crossover line are consistent with lattice result and experimental analysis from relativistic heavy ion collisions.

Figure 1

The chiral transition behaviors of the condensates ${\sigma }_u$ and ${\sigma }_s$ with the temperature $T$ at ${\mu }_B=0,0.39,0.9,1.5\mathrm{GeV}$.

Figure 2

The chiral phase diagram in the $\mu -T$ plane obtained from the improved soft-wall AdS/QCD model. The colored points with error bars are freeze-out data from experimental analysis. The black-triangle data are taken from Ref. [86, 87], the green-triangle ones are taken from Ref. [88], the purple squares are taken from Ref. [89], and the magenta squares are taken from Ref. [90]. The shaded black region denotes the crossover line obtained from lattice simulation at small ${\mu }_B$, and the light blue band indicates the uncertainty width of lattice simulation [91].