STAR results on strangeness and electric charge-dependent splitting of rapidity-odd directed flow.

Rapidity-odd directed flow ( v 1 ) of multi-strange baryons (Ξ and Ω) at mid-rapidity is reported for Au+Au collisions as recorded by the STAR detector at the Relativistic Heavy Ion Collider (RHIC). We focus on particle species where all constituent quarks are produced, such as K − (ū s) , p ̄ (ū ū d ̄) , Λ ̄ (ū d ̄ s ̄) , ϕ (s s ̄) , Ξ ¯ + (d ̄ s ̄ s ̄) , Ω − (s s s) and Ω ¯ + (s ̄ s ̄ s ̄) , and demonstrate using a novel analysis method that the coalescence sum rule holds in a common kinematic region for hadron combinations with identical quark content. We examine the coalescence sum rule as a function of rapidity for nonidentical quark content having the same quark-level mass but different strangeness (Δ S) and electric charge (Δ q). The difference in the directed flow of different quark and anti-quark combinations, e.g., v 1 (Ω − (s s s)) − v 1 ( Ω ̄ + (s ̄ s ̄ s ̄)) , is a measure of coalescence sum rule violation, and we call it directed flow splitting (Δ v 1 ). We measure Δ S and Δ q dependence of the Δ v 1 slope (d Δ v 1 ∕ d y) between produced quarks and anti-quarks in Au+Au collisions at s N N = 2 7 GeV and 200 GeV. Measurements have been compared with A Multi-Phase Transport (AMPT) and Parton-Hadron String Dynamics (PHSD) models with electromagnetic field calculations. [ABSTRACT FROM AUTHOR]