Abstract

A decisive experimental test of the Chiral Magnetic Effect (CME) is considered one of the major scientific goals at the Relativistic Heavy-Ion Collider (RHIC) towards understanding the nontrivial topological fluctuations of the Quantum Chromodynamics vacuum. In heavy-ion collisions, the CME is expected to result in a charge separation phenomenon across the reaction plane, whose strength could be strongly energy dependent. The previous CME searches have been focused on top RHIC energy collisions. In this Letter, we present a low energy search for the CME in Au+Au collisions at $\sqrt{s_{_{\rm{NN}}}}=27$ GeV. We measure elliptic flow scaled charge-dependent correlators relative to the event planes that are defined at both mid-rapidity $|\eta|<1.0$ and at forward rapidity $2.1 < |\eta|<5.1$. We compare the results based on the directed flow plane ($\Psi_1$) at forward rapidity and the elliptic flow plane ($\Psi_2$) at both central and forward rapidity. The CME scenario is expected to result in a larger correlation relative to $\Psi_1$ than to $\Psi_2$, while a flow driven background scenario would lead to a consistent result for both event planes. In 10-50% centrality, results using three different event planes are found to be consistent within experimental uncertainties, suggesting a flow driven background scenario dominating the measurement. We obtain an upper limit on the deviation from a flow driven background scenario at the 95% confidence level. This work opens up a possible road map towards future CME search with the high statistics data from the RHIC Beam Energy Scan Phase-II.

Figure-2-Tabel-1

Subset of Data from figure 2

10.17182/hepdata.133216.v1/t1

This dataset corresponds to Figure 2, the v2 value estimated by tpc (\Psi_2) in the paper
Figure-2-Tabel-2

Subset of Data from figure 2

10.17182/hepdata.133216.v1/t2

This dataset corresponds to Figure 2, the v2 value estimated by epd (\Psi_2) in the paper
Figure-2-Tabel-3

Subset of Data from figure 2

10.17182/hepdata.133216.v1/t3

This dataset corresponds to Figure 2, the v2 value estimated by epd (\Psi_1) in the paper
Figure-2-Tabel-4

Subset of Data from figure 2

10.17182/hepdata.133216.v1/t4

This dataset corresponds to Figure 2, the v2 ratio value estimated between epd (\Psi_1) and tpc (\Psi_2) in the paper
Figure-2-Tabel-5

Subset of Data from figure 2

10.17182/hepdata.133216.v1/t5

This dataset corresponds to Figure 2, the v2 ratio value estimated between epd (\Psi_1) and epd (\Psi_2) in the paper
Figure-3-Tabel-1

Subset of Data from figure 3

10.17182/hepdata.133216.v1/t6

This dataset corresponds to Figure 3, the \Delta\gamma_{112}multiply N_{part} value estimated by tpc (\Psi_2) in the paper
Figure-3-Tabel-2

Subset of Data from figure 3

10.17182/hepdata.133216.v1/t7

This dataset corresponds to Figure 3, the \Delta\gamma_{112}multiply N_{part} value estimated by epd (\Psi_2) in the paper
Figure-3-Tabel-3

Subset of Data from figure 3

10.17182/hepdata.133216.v1/t8

This dataset corresponds to Figure 3, the \Delta\gamma_{1111}multiply N_{part} value estimated by epd (\Psi_1) in the paper
Figure-3-Tabel-4

Subset of Data from figure 3

10.17182/hepdata.133216.v1/t9

This dataset corresponds to Figure 3, the ratio between \Delta\gamma_{1111} (by epd \Psi_1) and \Delta\gamma(112) (by tpc \Psi_2) in the...
Figure-3-Tabel-5

Subset of Data from figure 3

10.17182/hepdata.133216.v1/t10

This dataset corresponds to Figure 3, the ratio between \Delta\gamma_{1111} (by epd \Psi_1) and \Delta\gamma(112) (by epd \Psi_2) in the...
Figure-4-Tabel-1

Subset of Data from figure 4

10.17182/hepdata.133216.v1/t11

This dataset corresponds to Figure 4, the \Delta\gamma_{112}multiply N_{part} and scaled by v_2 estimated by tpc (\Psi_2) in the paper
Figure-4-Tabel-2

Subset of Data from figure 4

10.17182/hepdata.133216.v1/t12

This dataset corresponds to Figure 4, the \Delta\gamma_{112}multiply N_{part} and scaled by v_2 estimated by epd (\Psi_2) in the paper
Figure-4-Tabel-3

Subset of Data from figure 4

10.17182/hepdata.133216.v1/t13

This dataset corresponds to Figure 4, the \Delta\gamma_{1111}multiply N_{part} and scaled by v_2 estimated by epd (\Psi_1) in the paper
Figure-4-Tabel-4

Subset of Data from figure 4

10.17182/hepdata.133216.v1/t14

This dataset corresponds to Figure 4, the ratio between \Delta\gamma_{1111} scaled by v_{211} (by epd \Psi_1) and \Delta\gamma(112) scaled by...
Figure-4-Tabel-5

Subset of Data from figure 4

10.17182/hepdata.133216.v1/t15

This dataset corresponds to Figure 4, the ratio between \Delta\gamma_{1111} scaled by v_{211} (by epd \Psi_1) and \Delta\gamma(112) scaled by...

Figure-2-Tabel-1

Figure-2-Tabel-2

Figure-2-Tabel-3

Figure-2-Tabel-4

Figure-2-Tabel-5

Figure-3-Tabel-1

Figure-3-Tabel-2

Figure-3-Tabel-3

Figure-3-Tabel-4

Figure-3-Tabel-5

Figure-4-Tabel-1

Figure-4-Tabel-2

Figure-4-Tabel-3

Figure-4-Tabel-4

Figure-4-Tabel-5

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