Centrality dependence of charged hadron and strange hadron elliptic flow from s(NN)**(1/2) = 200-GeV Au + Au collisions

The collaboration
Phys.Rev.C 77 (2008) 054901, 2008.

Abstract (data abstract)
We present STAR results on the elliptic flow $v_2$ of charged hadrons, strange and multi-strange particles from $\sqrt{s_{NN}} = 200$ GeV $Au+Au$ collisions at RHIC. The detailed study of the centrality dependence of $v_{2}$ over a broad transverse momentum range is presented. Comparison of different analysis methods are made in order to estimate systematic uncertainties. In order to discuss the non-flow effect, we have performed the first analysis of $v_{2}$ with the Lee-Yang Zero method for $K_{S}^{0}$ and $\Lambda$. In the relatively low $p_{T}$ region, $p_{T} \le 2$ GeV/c, a scaling with $m_{T}−m$ is observed for identified hadrons in each centrality bin studied. However, we do not observe $v_{2}(p_{T})$ scaled by the participant eccentricity to be independent of centrality. At higher $p_{T}$ , $2 \le p_{T} \le 6$ GeV/c, $v_{2}$ scales 3 with quark number for all hadrons studied. For the multi-strange hadron $\Omega$, which does not suffer appreciable hadronic interactions, the values of $v_{2}$ are consistent with both $m_{T}−m$ scaling at low $p_{T}$ and number-of-quark scaling at intermediate $p_{T}$. As a function of collision centrality, an increase of $p_{T}$-integrated $v_{2}$ scaled by the participant eccentricity has been observed, indicating a stronger collective flow in more central $Au+Au$ collisions.

• #### Figure 3

Data from Figure 3 for charged hadrons for $0.15 < p_{T} < 2.0$ GeV/c, centrality $10-40\%$ at $\sqrt{s_{NN}} = 200$ GeV.

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$v_{2}(\eta)$ for charged hadrons, $0.15 < p_{T} < 2.0$ GeV/c, centrality $10-40\%$, from $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

• #### Figure 4a (Event Plane)

Data from Figure 4a for Event Plane method (open circles), centrality $10-40\%$ at $\sqrt{s_{NN}} = 200$ GeV.

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• #### Figure 4a (Lee-Yang Zero)

Data from Figure 4a for Lee-Yang Zero method (solid circles), centrality $10-40\%$ at $\sqrt{s_{NN}} = 200$ GeV.

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• #### Figure 5a (Event Plane)

Data from Figure 5a for Event Plane method (open circles), in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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$p_{T}$ integrated charged hadron $v_{2}$ in the TPC as a function of geometrical cross section. Shown are the Event Plane...

• #### Figure 5a (4 Cumulant)

Data from Figure 5a for 4 Cumulant method (solid squares), in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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$p_{T}$ integrated charged hadron $v_{2}$ in the TPC as a function of geometrical cross section. Shown are the 4 Cumulant...

• #### Figure 5a (LYZ_Sum)

Data from Figure 5a for Sum Generating Function (solid circles), in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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$p_{T}$ integrated charged hadron $v_{2}$ in the TPC as a function of geometrical cross section. Shown are the Lee-Yang Zero...

• #### Figure 5a (LYZ_Prod)

Data from Figure 5a for Product Generating Function (open stars), in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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$p_{T}$ integrated charged hadron $v_{2}$ in the TPC as a function of geometrical cross section. Shown are the Lee-Yang Zero...

• #### Figure 6a Lambda($\eta$-sub)

Data from Figure 6a for $\eta$-subevent method (open crosses), in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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$v_{2}$ as a function of $p_{T}$ for $10–40\%$ centrality using $\eta$-subevent method (open crosses), are shown in (a) for $\Lambda$....

• #### Figure 6a Lambda(Event Plane)

Data from Figure 6a for Event Plane method (open circles), in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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$v_{2}$ as a function of $p_{T}$ for $10–40\%$ centrality using Event Plane method (open circles), are shown in (a) for...

• #### Figure 6b $K_{S}^{0}$($\eta$-sub)

Data from Figure 6a for $\eta$-subevent method (open crosses), in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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$v_{2}$ as a function of $p_{T}$ for $10–40\%$ centrality using $\eta$-subevent method (open crosses), are shown in (b) for $K_{S}^{0}$....

• #### Figure 6b $K_{S}^{0}$(Event Plane)

Data from Figure 6a for Event Plane method (open circles), in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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$v_{2}$ as a function of $p_{T}$ for $10–40\%$ centrality using Event Plane method (open circles), are shown in (b) for...

• #### Figure 6a and 6b (LYZ)

Data from Figure 6a and 6b for Lee-Yang Zero method with Sum Generating Function (solid circles), in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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$v_{2}$ as a function of $p_{T}$ for $10–40\%$ centrality using Lee-Yang Zero method with Sum Generating Function (solid circles), are...

• #### Figure 7 ($K_{S}^{0}$)

Data from Figure 7a,b,c,d for $v_{2}$ of $K_{S}^{0}$ (open circles) as a function of $p_{T}$ for (a) $0–80\%$, (b) $40–80\%$, (c) $10–40\%$ and (d) $0–10\%$ centralities in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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$v_{2}$ of $K_{S}^{0}$ (open circles) as a function of $p_{T}$ for (a) $0–80\%$, (b) $40–80\%$, (c) $10–40\%$ and (d) $0–10\%$...

• #### Figure 7 ($\Lambda+\bar{\Lambda}$)

Data from Figure 7a,b,c,d for $v_{2}$ of $\Lambda+\bar{\Lambda}$ (open squares) as a function of $p_{T}$ for (a) $0–80\%$, (b) $40–80\%$, (c) $10–40\%$ and (d) $0–10\%$ centralities in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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$v_{2}$ of $\Lambda+\bar{\Lambda}$ (open squares) as a function of $p_{T}$ for (a) $0–80\%$, (b) $40–80\%$, (c) $10–40\%$ and (d) $0–10\%$...

• #### Figure 7a ($\Xi^{-}+\bar{\Xi}^{+}$)

Data from Figure 7a for $v_{2}$ of $\Xi^{-}+\bar{\Xi}^{+}$ (filled triangles) as a function of $p_{T}$ for (a) $0–80\%$ centrality in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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• #### Figure 7c ($\Xi^{-}+\bar{\Xi}^{+}$)

Data from Figure 7c for $v_{2}$ of $\Xi^{-}+\bar{\Xi}^{+}$ (filled triangles) as a function of $p_{T}$ for (c) $10–40\%$ centrality in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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• #### Figure 7a ($\Omega^{-}+\bar{\Omega}^{+}$)

Data from Figure 7a for $v_{2}$ of $\Omega^{-}+\bar{\Omega}^{+}$ (filled circles) as a function of $p_{T}$ for (a) $0–10\%$ centrality in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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• #### Figure 7a ($p+\bar{p}$ and $\pi^{+}+\pi^{-}$)

Data from Figure 7a for $v_{2}$ of $p+\bar{p}$ (filled squares) and $\pi^{+}+\pi^{-}$ (filled stars) as a function of $p_{T}$ for (a) $0–80\%$ centrality in $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV.

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$v_{2}$ of $p+\bar{p}$ (filled squares) and $\pi^{+}+\pi^{-}$ (filled stars) as a function of $p_{T}$ for (a) $0–80\%$ centrality in $Au+Au$...

• #### Figure 12d inset ($\Lambda$)

Data from Fig12d expansion at low $p_{T}$.

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Fig12d inset $\Lambda$ (open squares) expansion at low $p_{T}$

• #### Figure 12d inset ($K_{S}^{0}$)

Data from Fig12d expansion at low $p_{T}$.

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Fig12d inset for $K_{S}^{0}$ (filled circles) expansion at low $p_{T}$

• #### Figure 13 (charged hadrons)

Fig13 Centrality dependence of $v_{2}$ versus number of participants $N_{part}$ for charged hadrons (crosses)

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