We present STAR measurements of the charge-dependent three-particle correlator gamma(a,b) = < cos(phi(a)(1) + phi(b)(2)-2 phi(3))>/v(2){2} and elliptic flow v(2){2} in U+U, Au+Au and p+Au collisions at RHIC. The difference Delta gamma = gamma(opposite sign)-gamma(same sign) measures charge separation across the reaction plane, a predicted signal of the Chiral Magnetic Effect (CME). Although charge separation has been observed, it has been argued that the measured separation can also be explained by elliptic flow related backgrounds. In order to separate the two effects we perform measurements of the gamma-correlator where background expectations differ from magnetic field driven effects. A differential measurement of gamma with the relative pseudorapidity (Delta eta)) between the first and second particles indicate that Delta gamma in peripheral A+A and p+A collisions are dominated by short-range correlations in A. However, a relatively wider component of the correlation in Delta eta tends to vanish the same way as projected magnetic field as predicted by MC-Glauber simulations.

Disentangling flow and signals of Chiral Magnetic Effect in U plus U, Au plus Au and p plus Au collisions

Di Ruzza B;
2017-01-01

Abstract

We present STAR measurements of the charge-dependent three-particle correlator gamma(a,b) = < cos(phi(a)(1) + phi(b)(2)-2 phi(3))>/v(2){2} and elliptic flow v(2){2} in U+U, Au+Au and p+Au collisions at RHIC. The difference Delta gamma = gamma(opposite sign)-gamma(same sign) measures charge separation across the reaction plane, a predicted signal of the Chiral Magnetic Effect (CME). Although charge separation has been observed, it has been argued that the measured separation can also be explained by elliptic flow related backgrounds. In order to separate the two effects we perform measurements of the gamma-correlator where background expectations differ from magnetic field driven effects. A differential measurement of gamma with the relative pseudorapidity (Delta eta)) between the first and second particles indicate that Delta gamma in peripheral A+A and p+A collisions are dominated by short-range correlations in A. However, a relatively wider component of the correlation in Delta eta tends to vanish the same way as projected magnetic field as predicted by MC-Glauber simulations.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11369/426831
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