EPJ Web of Conferences 316, 06007 (2025)
https://doi.org/10.1051/epjconf/202531606007

Extracting the dependence of directed flow differences on conserved charges

¹ Department of Physics, East Carolina University, Greenville, NC, 27858, USA
² Department of Physics, Panchayat College, Sambalpur University, Bargarh 768028, Odisha, India
³ Key Laboratory of Quark & Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University, Wuhan, 430079, China

^* e-mail: linz@ecu.edu

Published online: 27 January 2025

Abstract

Recently, seven produced hadron species have been used to construct multiple hadron sets with given differences in the net electric charge (∆q) and strangeness (∆S) between the two sides. A nonzero directed flow difference △v₁ has been proposed as a consequence of the electromagnetic field produced in relativistic heavy ion collisions. Previously, we have shown with quark coalescence that Av1 and the slope difference △v′₁ depend linearly on both △q and ∆S with zero intercept. Here we emphasize that a two-dimensional function or fit is necessary for extracting the △q- and △S-dependences of △v₁. On the other hand, a one-dimensional fit gives a different value for the slope parameter of the ∆q- or ∆S-dependence. Furthermore, a one-dimensional fit is incorrect because its slope parameter depends on the arbitrary scaling factor of a hadron set and is thus ill-defined. We use test data of △v₁ to explicitly demonstrate these points.