STAR Flow, Chirality and Vorticity PWG

[Takafumi Niida <niida AT bnl.gov>]

Date: 1/13/2023

Participants: Niseem Magdy, Chunjian Zhang, Roy Lacey, Barbara Trzeciak, 
Daniel Brandenburg, Maria Zurek, Hanna Zbroszczyk, Shuai Yang, Subhash 
Singha, Toshihiro Nonaka, Xiaoxuan Chu, Yi Yang, Yue-Hang Leung, Rongrong Ma, 
Takafumi Niida

Title: Beam-energy dependence of transverse momentum-flow correlations in 
RHIC collisions
PAs: Niseem Magdy, Olga Evdokimov, Chunjian Zhang, Shengli Huang, Jiangyong 
Jia, Roy Lacey
Target journal: PLB
Proposal page: 
https://drupal.star.bnl.gov/STAR/Beam-energy-dependence-transverse-momentum-flow-correlations-RHIC-collisions-0
Presentation: https://drupal.star.bnl.gov/STAR/system/files/Flow_PT_PWGC.pdf

The PWGC panel previewed a paper proposal from FCV PWG. The panel found that 
the analysis is mature and interesting and the paper should move forward. The 
target journal is appropriate. The following points were discussed.

Q. What are systematic sources?
A. Variation of eta-gap for non-flow study, nHits cut, DCA cut etc. Main 
contribution is rapidity gap. subevents “a” and “b” are changed to eta<-0.4 
and eta>0.4, corresponding to eta-gap=0.8 instead of 0.7 for 2PC. eta-gap=0.9 
was also tried but the uncertainty was large and it was not included.

Q. How about 3 sub case regarding non-flow?
A. The effect is small as it’s designed to suppress it. It was studies with 
Hijing by J. Jia et al.

Comment (after the meeting): It would be good if you can add one or two 
slides on systematic sources/study in the slides and update the file in your 
paper proposal page.

Q. Did you correct for tracking efficiency?
A. No, but it was studied and found to be small.
C. Even though the effect is small, it would be better to correct it.

Slide 2
Q. What do you mean by eta/s=0.1 for AMPT SM-OFF since there is no 
parton-parton scattering?
A. It was meant that parameters were not changed between SM-ON and SM-OFF.

Slide 7
Q. why is the systematic uncertainty asymmetric?
A. This is due to non-flow.

Q. Hydro-A and B use different eta/s. How can we constrain the model or 
initial condition?
A. Model study shows rho correlator depends very weakly on eta/s. No non-flow 
in the models. So the main difference comes from the initial condition.

Q. TRENTO has a parameter which can make the initial condition more 
Glauber-like or CGC-like one. What parameter was used here?
A. Parameter for Glauber type was used.
C. It would be better to explicitly mention in the paper. Also, it would be 
very useful if we have curve with CGC-like IC, so that one can fairly compare 
two calculations with data.
A. Will ask theorists about this.

Q. Any specific reason to chose eta/s=0.12 for Hydro-A and 0.05 for Hydro-B?
A. These are taken from the papers listed in the slide. In Hydro-A, another 
calculation was T-dependent eta/s with bulk viscosity. In Hydro-B, there is 
no bulk viscosity.

Q. Why do you stop at 60% centrality?
A. For lower energies, uncertainties become large but it’s possible to extend 
to 80% for 200 GeV. It’s also related to other paper.
C. It would be great if you can add it. At least show them in the analysis 
note.

Slide 9
Q. 19.6 GeV is from BES2? Have you considered to include BES2 14.6 and 7.7 
GeV?
A. Yes, 19.6 is from BES2. PAs are also looking at 14.6 and 7.7 GeV data. 7.7 
GeV seems to have large statistical uncertainty, but hopefully we could add 
14.6 GeV.

Other comment (after the meeting):
Paper proposal page doesn’t include necessary information. Please see the 
following page and update your proposal page.
https://drupal.star.bnl.gov/STAR/pwg/common/policies/pwgc-preview-requirements