# Flow decorrelation in heavy-ion collisions at $\sqrt{s_{_{\rm NN}}}$=27 and 200 GeV with 3D event-by-event viscous hydrodynamics

### Submission summary

 As Contributors: Jakub Cimerman Arxiv Link: https://arxiv.org/abs/2110.14783v2 (pdf) Date submitted: 2021-11-15 06:57 Submitted by: Cimerman, Jakub Submitted to: SciPost Physics Proceedings Proceedings issue: 50th International Symposium on Multiparticle Dynamics (ISMD2021) Academic field: Physics Specialties: Nuclear Physics - Theory Approaches: Theoretical, Phenomenological

### Abstract

We present the first calculation of longitudinal decorrelation of anisotropic flow at RHIC Beam Energy Scan (BES) energies using event-by-event viscous hydrodynamic model (vHLLE), with two different initial states (GLISSANDO2 and UrQMD) and hadronic cascade. We investigate the origin of the observed decorrelation by checking separately flow angle and flow magnitude decorrelation and by calculating decorrelation in the initial state eccentricity.

###### Current status:
Has been resubmitted

### Submission & Refereeing History

Resubmission 2110.14783v3 on 8 February 2022

Submission 2110.14783v2 on 15 November 2021

## Reports on this Submission

### Strengths

1. The paper is clearly written
2. The paper attempts a clear explanation of a hot-topic issue
3. The calculation is novel, to my knowledge it has not been performed before

### Weaknesses

1. It is unclear what the physics origin of the difference between the two employed initial state models is

### Report

These proceedings presents a calculation of flow decorrelation in pseudo-rapidity, using state-of-the-art viscous hydro with two different initial state models. By repeating the same calculation with two different initial state model, the authors point out the importance of the initial state model in explaining elaborate flow-related quantities.

While the authors present (in fig. 3) a clear demonstration of the difference in initial state eccentricity decorrelation between the two initial state models (UrQMD and GLISSANDO), the initial state models are not explained to a degree that the readers understand why this difference comes about (are they not both Glauber models?) My only requested change relates to that.

### Requested changes

1. I would like the authors to spend a couple of lines explaining why the initial state eccentricity decorrelation is so drastically different between the two models. I would naively have expected them to be almost identical, since I thought the two were both based on simple Glauber.

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

### Author:  Jakub Cimerman  on 2022-02-07  [id 2163]

(in reply to Report 1 on 2022-01-03)
Category:
correction

We thank the referee for the report. Due to page limitations, we did not go into details describing the difference between models. However, to respond to the referee's request, we added a line to the UrQMD model description to emphasize the difference between the models. We also added a sentence to the interpretation of Fig. 3 describing the other effect causing the difference between the models - switching from hadron cascade to fluid.