New method for measuring longitudinal fuctuations and directed flow in ultrarelativistic heavy ion reactions

TL;DR

This paper introduces a new method to measure longitudinal fluctuations and directed flow in ultrarelativistic heavy ion collisions, enhancing sensitivity to global collective flow patterns over random fluctuations.

Contribution

It proposes a novel approach to identify longitudinal rapidity fluctuations and analyze flow in the event-by-event center of mass frame, improving flow pattern discrimination.

Findings

Effective separation of fluctuation-induced flow from global symmetry flow.

Enhanced sensitivity to collective flow patterns.

Method applicable to ultrarelativistic heavy ion collision data.

Abstract

It has been shown in recent ALICE@LHC measurements that the odd flow harmonics, in particular a directed flow, v1, occurred to be weak and dominated by random fluctuations. In this work we propose a new method, which makes the measurements more sensitive to the flow patterns showing global collective symmetries. We demonstrate how the longitudinal center of mass rapidity fluctuations can be identified, and then the collective flow analysis can be performed in the event-by-event center of mass frame. Such a method can be very effective in separating the flow patterns originating from random fluctuations, and the flow patterns originating from the global symmetry of the initial state.