Feb 5 – 11, 2017
Hyatt Regency Chicago
America/Chicago timezone

Disentangling flow and signals of Chiral Magnetic Effect in U+U and Au+Au collisions

Feb 7, 2017, 2:40 PM
Regency B

Regency B


Prithwish Tribedy (Brookhaven National Lab)


We present measurements of the charge-dependent, three-particle correlator \gamma=<cos(\phi1+\phi2-2\phi3)> and elliptic flow v2 in central and ultra-central U+U and Au+Au collisions at sqrt{sNN}=200 GeV from STAR. The difference \Delta \gamma = \gamma(like- sign)-\gamma(un-like sign) measures charge separation across the reaction plane, a predicted signal of the Chiral Magnetic Effect (CME) [1]. Although charge separation has been observed, it has been argued that the measured separation can also be explained by elliptic flow related backgrounds [2]. To disentangle the two effects, we use triggered samples of U+U and Au+Au collisions for which predictions from flow related backgrounds and magnetic field dependent effects diverge. Our analysis includes events selected based on asymmetries in spectators observed in the Zero-Degree-Calorimeters which preferentially select body-tip events [3]. We find that for cases where known, flow driven, background expectations differ from CME related predictions driven by the correlation of the magnetic field and the flow; the data are in better accord with the CME related prediction.

[1] S. A. Voloshin, Phys.Rev. C70 (2004) 057901 hep-ph/0406311

[2] S. Schlichting, S. Pratt, Phys.Rev. C83 (2011) 014913

[3] S. Chatterjee, P. Tribedy, Phys.Rev. C92 (2015) 1,011902

Preferred Track Collective Dynamics
Collaboration STAR

Primary author

Prithwish Tribedy (Brookhaven National Lab)

Presentation materials