STAR Flow, Chirality and Vorticity PWG

[Takafumi Niida <niida AT bnl.gov>]

Date: 4/2/2021

Participants: Shengli Huang, Maowe Nie, Chunjian Zhang, Jiangyong Jia, Raghav Elayavalli, Daniel Brandenburg, Daniel Cebra, ShinIchi Esumi, Hanna Zbroszczyk, Sooraj Radhakrishnan, Barbara Trzeciak, Qinghua Xu, Maria Zurek, Matt Posik, Md Nasim, Xiaofeng Luo, Prithwish Tribedy, Rongrong Ma, Takafumi Niida

Title: Measurements of v2, v3 in central p+Au, d+Au and 3He+Au collisions at ­200 GeV from STAR collaboration

PWG: FCV

PAs: Shengli Huang, Jiangyong Jia, Roy Lacey, Pengfei Liu, Maowe Nie, Yuri Sato, Chunjian Zhang

Target journal: PRL

Proposal page: https://drupal.star.bnl.gov/STAR/blog/slhuang/measurements-v2-v3-pau-dau-and-3heau-collisions-%C2%AD200-gev-star-collaboration

Presentation: https://drupal.star.bnl.gov/STAR/system/files/smallflowpaperpwgc3_0.pdf

The PWGC panel previewed the paper proposal from FCV PWG. The panel agreed that the paper should move forward. Many conveners think target journal PRL is appropriate but the physics messages need to be clearer for general readers of PRL. The following points were discussed during the preview.

s6: there is a type in the equation for near-side subtraction. c^{pp} should be Y^{pp}

s10: 

Q. PA explained that the near-side subtraction is large contribution in the systematic uncertainty because it oversubtract away-side peak especially in p+Au. Knowing the oversubtraction, why is it still included?

A. Similar question was raised at pwg. Thinking better way. One way is to draw the syst. uncert. from method separately.

C. Since the uncertainty affects constraining power to distinguish theory curves in Fig. 4 and PAs think it’s oversubtracted, it may not be included in final systematic uncertainty. But PAs can/should discuss the effect as additional check.

Fig. 1:

Q. Can I understand that small peak at near side indicates flow, which is not in pp?

A. It supports the picture but keep it mind that CGC also makes such a near side peak.

Fig. 3:

C. The plot looks busy. Please consider to plot v2 and v3 in separate panels, if the length is fine.

C. Cosmetic suggestion for Fig. 3. Better to use the same color for the same system between v2 and v3.

C. pT is shifted for three systems. Please make it clear in the caption.

Q. Why did you choose 0-2% for p+Au and 0-10% for d+Au and He+Au? Same as PHENIX?

A. For p+Au, it was chosen to have similar multiplicity to d+Au. There is ~30% difference in multiplicity between d+Au and He+Au. PHENIX uses a common centrality interval for all systems. Even if we use the same centrality as PHENIX, it’s still not apple-to-apple comparison because of different acceptance. Open to any suggestion since PAs have all data.

C. If the similar multiplicity is better comparison, please consider to do it for all systems.

Fig. 4:

Q. Is it possible to turn off the initial momentum in CGS, ask theorists to calculate?

A. It may be possible but the model was tuned for other observables and the curves here are predictions.

C. It would be useful if PAs can tabulate agreement/disagreement between the data and models and also between STAR and PHENIX, quantitatively. With that, one can reject physics behind the model.

A. The difference from PEHNIX will be clearly mentioned. For model comparison, there is a factor of 2 difference which will be discussed in the paper.

C. Cosmetic suggestion for Fig. 4. Might be better for the curves to have the same color as the data (either v2 or v3) but with different line styles. One could immediately know which lines are for v2 or v3.

s23: 

C. Justification for PRL may not be clear/enough in the current texts. PAs should think about more general way to describe the findings.

A. No system dependence of v3 implies the importance of subnucleon fluctuations or nucleon structure, which is important for broader readers and was not found/discussed by PHENIX paper. PAs will think about the way.

Q. Are you going to discuss about the comparison with PHENIX in the paper?

A. That will be done but it’s also political thing. Will discuss with GPC and task force.

Q. What’s the plan for publication strategy? any plan to write a long paper after this PRL?

A. Currently no plan for another paper but there are some other results such as multiplicity dependence shown in QM. If other physics message can be delivered, PAs will think about a long paper showing more details.