A Centrality Detector Concept

TL;DR

This paper proposes a novel centrality detector for heavy ion collisions that directly measures spectator fragments' deflection, reducing systematic uncertainties inherent in traditional indirect methods based on particle detection and the Glauber model.

Contribution

It introduces a new concept for a centrality detector that measures total mass number of fragments via magnetic deflection, bypassing model-dependent assumptions.

Findings

Conceptual design of the centrality detector

Potential reduction in systematic uncertainties

Direct measurement of spectator fragments

Abstract

The nucleus-nucleus impact parameter and collision geometry of a heavy ion collision are typically characterized by assigning a collision "centrality". In all present heavy ion experiments centrality is measured indirectly, by detecting the number of particles or the energy of the particles produced in the interactions, typically at high rapidity. Centrality parameters are associated to the measured detector response using the Glauber model. This approach suffers from systematic uncertainties related to the assumptions about the particle production mechanism and limitations of the Glauber model. In the collider based experiments there is a unique possibility to measure centrality parameters by registering spectator fragments remaining from the collision. This approach does not require model assumptions and relies on the fact that spectators and participants are related via the total number of nucleons in the colliding species. This article describes the concept of the centrality detector for heavy ion experiment, which measures the total mass number of all fragments by measuring their deflection in the magnetic field of the collider elements.