# Inferring nuclear structure from heavy isobar collisions using Trajectum

### Submission summary

 Authors (as Contributors): Wilke van der Schee
Submission information
Date submitted: 2022-09-25 21:35
Submitted by: van der Schee, Wilke
Submitted to: SciPost Physics
Ontological classification
Specialties:
• Nuclear Physics - Theory
Approach: Theoretical

### Abstract

Nuclei with equal number of baryons but varying proton number (isobars) have many commonalities, but differ in both electric charge and nuclear structure. Relativistic collisions of such isobars provide unique opportunities to study the variation of the magnetic field, provided the nuclear structure is well understood. In this Letter we simulate collisions using several state-of-the-art parametrizations of the $^{96}_{40}$Zr and $^{96}_{44}$Ru isobars and show that a comparison with the exciting STAR measurement arXiv:2109.00131 of ultrarelativistic collisions can uniquely identify the structure of both isobars. This not only provides an urgently needed understanding of the structure of the Zirconium and Ruthenium isobars, but also paves the way for more detailed studies of nuclear structure using relativistic heavy ion collisions.

###### Current status:
Awaiting resubmission

### Submission & Refereeing History

Submission 2112.13771v1 on 25 September 2022

## Reports on this Submission

### Strengths

This paper explored the new connections between nuclear structure and high-energy relativistic heavy-ion collisions.

### Report

This manuscript studied how to use measurements in ultra-relativistic heavy-ion collisions to probe the nuclear structure of the colliding nuclei. The authors performed high statistics numerical simulations for Ru+Ru and Zr+Zr collisions at the top RHIC energy with the Trajectum framework. They studied how particle yield, mean transverse momentum, and anisotropic flow coefficients depend on different nuclear structure configurations parameterized by five sets of Woods-Saxon parameters. The paper was written clearly and contained important physics insights for the RHIC isobar program. This study also builds connections between low-energy nuclear structures and high-energy relativistic heavy-ion collisions. I would recommend it for publication once the authors clarify the following questions.

To build a connection between the structure of nuclei and high-energy heavy-ion collisions, the authors should explain the underlying assumptions for how the produced initial-state energy density profile in the heavy-ion collision is related to the nucleus' structure. For example, will different energy deposition models weaken the sensitivity of the Woods Saxon deformation parameters on heavy-ion observables?

The Woods-Saxon parameters listed in Table 1 assumed the nucleon were point-like objects. However, in the Trento initial condition model, the nucleons are assumed to have finite sizes. Did the authors correct the Woods-Saxon parameters for finite nucleon sizes, as discussed in Phys. Rev. C 79, 064904 (2009)?

Did the authors consider the short-range hard-core repulsion between nucleons in their nuclear configurations? Would these short-range correlations affect the observable ratios between the two isobar collisions?

• validity: high
• significance: high
• originality: high
• clarity: high
• formatting: excellent
• grammar: excellent