Selecting specific initial configuration using spectator neutrons in U+U collisions

TL;DR

This paper introduces a method to select specific initial configurations in U+U heavy-ion collisions by analyzing spectator neutron asymmetry, enabling better control over collision geometry in experiments.

Contribution

It proposes a novel approach using spectator neutron asymmetry and a variable S_eta to identify and select body-tip configurations in U+U collisions, enhancing experimental analysis.

Findings

Lower elliptic flow (v2) in selected body-tip events

Effective differentiation between configurations using S_eta

Discussion on the purity of event selection in experiments

Abstract

We present a method to select events with specific initial configuration, namely body-tip, in heavy-ion collisions using deformed Uranium nuclei. We propose to use asymmetry in spectator neutron numbers to filter out these body-tip events from the unbiased configurations in U+U collisions. We have used a variable S_eta to differentiate between the body-tip and unbiased configurations. We have calculated the second order azimuthal anisotropy, namely elliptic flow (v2), for this body-tip configuration in the framework of a transport model and found it to be consistently lower compared to that in unbiased configurations as we expected. The purity of selecting such events in a real experiment is also discussed.