STAR Flow, Chirality and Vorticity PWG

[Sooraj Radhakrishnan <skradhakrishnan AT lbl.gov>]

Date: 09/06/2024

Participants: Gaoguo Yan, Maowu Nie, Zhenyu Chen, Hanna Zbroszczyk, Nu Xu, Subhash Singha, Prithwish Tribedy, Isaac Mooney, Nihar Sahoo, Qian Yang, Guannan Xie, Tommy Tsang, Yue Hang Leung, Barbara Trzeciak, Sooraj Radhakrishnan

Title: Collision energy and system size dependence of longitudinal flow  de-correlation at RHIC

PAs: Gaoguo Yan, Zhenyu Chen, Shengli Huang, Jiangyong Jia, Michael  Lisa, Xiaoyu Liu, Maowu Nie, Li Yi

Target journal: PRL

Proposal page: https://drupal.star.bnl.gov/STAR/blog/gyan/Paper_proposal_LDeCorr_energy_system

Presentation:https://drupal.star.bnl.gov/STAR/system/files/20240906_PWGC_preview.pdf

The PWGC panel previewed a paper proposal from FCV PWG. The panel found that the analysis is mature and results are important and interesting, and the paper should move forward. The journal choice was also found to be appropriate. It was suggested to sharpen the physics message and add model comparisons to strengthen the case for PRL. The following points were discussed.

Q: What models do you plan to compare to data?

A: We will add calculations from 3D Glauber model 

Q: Are there other models you plan to compare to with different underlying physics?

A: We could also get hydro and AMPT model calculations. 

Q: You say there is energy dependence at LHC, but for r2, the energy dependence is very weak

A: Yes, r2 does not show much energy dependence from LHC measurements. r3 shows significant energy dependence. r3 gets contribution from fluctuations , r2 has intrinsic geometry. This results in weak energy dependence for r2 and stronger dependence for r3

Q: S9, why difference eta_ref for r2 and r3?

A: There is eta_ref dependence for r2 for eta_ref < 3.1, but not for r3. So eta_ref for r2 is taken to be the region where it is stable

Q: Shouldn't the eta_ref dependence be shown in the paper?

A: We will include in the supplementary materials 

Q: Does UrQMD also show this de-correlation?

A: We can add comparisons. UrQMD comparisons were shown in previous QM presentation

Q: What is physics we learn from the measurements? Should add model comparisons 

A: Measurements give constraints to the 3D initial state. We will try to get more model calculations. But it may not be practical to wait to get the calculations 

Q: Fig.1, please change markers for different energies 

A: Yes, will do

Q: Can you add comparisons to LHC results on Gig.2 

A:  Yes, we will add the comparisons 

Q: On S.8, is there an upper cut on nMIP in the analysis? Is it different from different energies?

A: Yes, use a cut of nMPI < 4 at 200 GeV. This is lower at lower energies

Q: FMS and EPD have different eta ranges and FMS is one sided? Does this cause any systematics? Were the EPD results checked with same range and one sided acceptance as FMS?

A: Yes, this was checked. The results are consistent for these cross-checks  

Q: Why do you need mixed-events in the analysis? 

A: This is to correct for detector effects for EP par correlations 

Q: How do we understand the observed energy dependence of the decorrelation?

A: We see the energy dependence is not linear, with stronger dependence at lower energies. This could be due to change in stopping. 

C: It would be good to have model calculations to better the understanding 

Q: Would you see decorrelation in p+p? 

A: Yes, we see decorrelation in small collision systems 

Q: Is it smaller or larger than in Au+Au

A: In small systems the decorrelation is larger. This is because in Au+Au there is average geometry, while small systems don't have 

--

Sooraj Radhakrishnan

Research Scientist,

Department of Physics

Kent State University

Kent, OH 44242

Physicist Postdoctoral Affiliate

Nuclear Science Division
Lawrence Berkeley National Lab
MS70R0319, One Cyclotron Road

Berkeley, CA 94720

Ph: 510-495-2473

Email: skradhakrishnan AT lbl.gov