Sliding Dumbbell Method to search for the CME in heavy ion collisions

Abstract

This study explores the Chiral Magnetic Effect (CME) in ultra-relativistic heavy-ion collisions. The CME, observed as back-to-back charge separation along the magnetic field axis, is investigated using the newly developed Sliding Dumbbell Method (SDM) applied to Au+Au events at a center-of-mass energy ${\sqrt{s}}_{\mathrm{NN}}$ = 200 GeV generated by the AMPT model with string melting configuration. The CME-like signal is externally injected in events by flipping charges of pairs of the particles perpendicular to the reaction plane. The study reports a significant enhancement of the CME-sensitive 3-particle $\gamma$ correlator in events with high back-to-back charge separation, in a given collision centrality. Additionally, a linear relationship is observed between the $\sqrt{|\gamma |}$ correlator for same-sign charge pairs and positive charge asymmetry ($⟨A{}^{+}⟩$) across the dumbbell in CME-enriched sub-samples. Furthermore, the fraction of CME in $\Delta \gamma$ (difference between opposite and same sign $\gamma$ correlators) is presented across different collision centralities having different percentages of externally injected CME-like signal. Overall, the research aims to understand and detect the Chiral Magnetic Effect through innovative experimental method and detailed analysis of event structure.

Comments: 12 pages, 7 figures, and 2 Tables