Initial orientation effect and selecting desired events in 520AMeV/u U-U collisions

TL;DR

This study uses a relativistic transport model to identify collision orientations in uranium-uranium collisions that produce high-density states, aiding the selection of events for studying nuclear matter under extreme conditions.

Contribution

It introduces a method to select tip-tip like uranium-uranium collision events based on initial orientation and impact parameter, enhancing experimental focus on high baryon density matter.

Findings

Tip-tip collisions with small initial orientations produce extended high density phases.

Forward neutron multiplicity and nuclear stopping power can identify these high-density events.

Events with impact parameter ≤2.6 fm are optimal for studying high baryon density matter.

Abstract

How to select out those collisions with the desired geometry such as tip-tip and/or body-body in experiment is one key point for performing high energy UU collisions. With a relativistic transport model, we performed a simulation for deformed UU collision with vast different orientations at CSR energy area corresponding to the high net-baryon density region in QCD phase diagram. By investigating the centrality and initial collision orientation dependence of the center baryon density, we found that the tip-tip like UU collisions with extended high density phase, which is very important for studying the nuclear EoS of high baryon density matter and the possible end-point of the phase boundary, are those events with small initial orientations ($\leq20^{0}$) for bath projectile and target in reaction plane and small impact parameter ($\leq2.6fm$). We pointed out quantificationally two observations -- multiplicity of forward neutron and nuclear stopping power that both allows us to select out those most interesting events (i.e. tip-tip like), which will be very helpful for the future experiments at performing UU collisions.