Multiphase transport model predictions of isobaric collisions with nuclear structure from density functional theory

Isobaric ${}_{44}{}^{96}\mathrm{Ru}+{}_{44}{}^{96}\mathrm{Ru}$ and ${}_{40}{}^{96}\mathrm{Zr}+{}_{40}{}^{96}\mathrm{Zr}$ collisions were performed at the Relativistic Heavy Ion Collider in 2018. Using the “a multiphase transport” model with nuclear structures calculated by the density functional theory (DFT), we make predictions for the charged hadron multiplicity distributions and elliptic azimuthal anisotropies in these collisions. Emphases are put on the relative differences between the two collision systems that can decisively discriminate DFT nuclear distributions from the commonly used Woods-Saxon densities.

Figure 1

The nucleon densities of ${}_{44}{}^{96}\mathrm{Ru}$ and ${}_{40}{}^{96}\mathrm{Zr}$ calculated by DFT [8] (solid curves). The $\mathrm{WS}-{\mathrm{R}}_Q$ densities [5] (dashed curves) are shown for comparison.

Figure 2

Impact parameter ($b$) probability distributions in Ru+Ru and Zr+Zr collisions simulated by AMPT-SM(DFT). Proton and neutron density distributions of the ${}_{44}{}^{96}\mathrm{Ru}$ and ${}_{40}{}^{96}\mathrm{Zr}$ nuclei are assumed spherical and calculated by DFT.

Figure 3

Midrapidity charged hadron multiplicity ($N_{\mathrm{ch}}$) distributions in Ru+Ru and Zr+Zr collisions simulated by AMPT-SM(DFT). $N_{\mathrm{ch}}$ is the sum of charged pion, charged kaon, proton, and antiproton multiplicities within $\left|\eta \right|<0.5$ and $p_T>0.2 \mathrm{GeV}/c$.

Figure 4

Ratio of the $N_{\mathrm{ch}}$ distributions in Ru+Ru and Zr+Zr collisions simulated by AMPT-SM. Three types of nuclear density distributions are shown: DFT [8], $\mathrm{WS}-{\mathrm{R}}_Q$, and $\mathrm{WS}-{\mathrm{R}}_{\mathrm{DFT}}$.

Figure 5

Eccentricity ratios in Ru+Ru to Zr+Zr collisions calculated by MC-Glb. Three types of nuclear density distributions are shown: DFT [8], $\mathrm{WS}-{\mathrm{R}}_Q$ (Table 1), and $\mathrm{WS}-{\mathrm{R}}_{\mathrm{DFT}}$ (Table 1).

Figure 6

Charged particle multiplicity per participant pair as a function of $\frac{N_{\mathrm{bin}}}{N_{\mathrm{part}}/2}-1$ in Ru+Ru and Zr+Zr collisions simulated by AMPT-SM(DFT). The star and open square represent AMPT results. The line are two-component model fits to the 5–50% centrality range.

Figure 7

Difference of the invariant mass ($m_{\mathrm{inv}}$) distributions of opposite-sign (OS) pion pairs and same-sign (SS) pion pairs in MB Ru+Ru and Zr+Zr collisions simulated by AMPT-SM(DFT). Pions within $\left|\eta \right|<1$ are used.

Figure 8

Azimuthal anisotropies $v_2$ of charged hadrons (within $\left|\eta \right|<1$) with respect to the EP in Ru+Ru and Zr+Zr collisions as a function of centrality, simulated by AMPT-SM(DFT).

Figure 9

Ratios of charged hadron $v_2$ in Ru+Ru to Zr+Zr collisions as a function of $b$. Three nuclear density distributions are simulated: DFT, $\mathrm{WS}-{\mathrm{R}}_Q$, and $\mathrm{WS}-{\mathrm{R}}_{\mathrm{DFT}}$.

Figure 10

Ratios of charged hadron $v_2$ in Ru+Ru to Zr+Zr collisions as a function of centrality. Three nuclear density distributions are simulated: DFT, $\mathrm{WS}-{\mathrm{R}}_Q$, and $\mathrm{WS}-{\mathrm{R}}_{\mathrm{DFT}}$.