A Centrality Detector Concept

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.

19 pages, 11 figures

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• Measuring deformed neutron skin with free spectator nucleons in relativistic heavy-ion collisions
• Free spectator nucleons in ultracentral relativistic heavy-ion collisions as a probe of neutron skin
• Neutron emission in ultraperipheral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV
• Probing configuration of $\alpha$ clusters with spectator particles in relativistic heavy-ion collisions
• Directly probing existence of $\alpha$-cluster structure in ${}^{20}$Ne by relativistic heavy-ion collisions
• Probing Pb+Pb collisions at $\sqrt{S_{NN}}=2760$ GeV with spectators
• Forward proton detectors in heavy ion physics
• Using LHC Forward Proton Detectors to Tag Nuclear Debris
• Probing Geometry of Ion-Ion Collisions with Roman Pot Detectors
• A Method to Constrain Preferential Emission and Spectator Dynamics in Heavy-Ion Collisions