STAR Flow, Chirality and Vorticity PWG

[Takafumi Niida <niida AT bnl.gov>]

Date: 11/12/2021

Participants: Shengli Huang, Roy Lacey, Chunjian Zhang, Maowu Nie, Zhenyu Chen, Takahito Todoroki,

Barbara Trzeciak, Daniel Brandenburg, Daniel Cebra, Hanna Zbroszczyk, Jiangyong Jia, Qinghua Xu, Raghav Elayavalli, Hanseul Oh, ShinIchi Esumi, Sooraj Radhakrishnan, Xiaofeng Luo, Xin Dong, Yi Yang, Rongrong Ma, Takafumi Niida

Title: Systematically studying of vn(n=2,3) via di-hadron correlations at middle rapidity in p/d/He+Au collisions at 200 GeV

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

Target journal: PRC

Proposal page: https://drupal.star.bnl.gov/STAR/blog/slhuang/long-prc-paper-small-system-flow

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

The PWGC panel previewed a paper from FCV PWG. The paper contains a lot of materials which would be useful in the community. The panel found that the results are mature and the paper should move forward. The target journal is appropriate. The following points were discussed during the preview.

Q. What is the status of short paper and plan? 

A. PAs are planning to submit both papers together. 

Q. We had d+Au run last year which can allow us to do more direct comparison with PHENIX data. Do we have any (internal)preliminary result with express production?

A. PAs did check the express production (~10% of all the data) with EPD, but because of limited statistics no conclusion can be obtained.

Q. In slide 23, near-side peak looks very similar among He+Au, d+Au, p+Au, but not for p+p. This is a bit surprising. Any simple explanation?

A. PAs are also surprised for this but no clear answer.

Q. In slide 24, why do you use c0 as a reference when making the ratio?

A. c0 is based on naive assumption that the other systems are superposition of p+p and no jet modification. If no jet modification, c1-method should be close to c0-method.

Q. In slide 26, are these models all hydro? What do you say from this comparison?

A. “Sonic” is purely hydro with standard Glauber initial condition, underestimating v3. “Supersonic” has pre-flow in addition which may be fancy assumption but close to the data. Then the last one is IP-Glasma+hydro which is also used for HI data but overestimate v2. These will be mentioned. Glauber vs subnucleon Glauber will be discussed with Fig. 20.

C. Related to slide 31, please put 2D plots of BBC vs. TPC multiplicity for the three systems in analysis note.

Q. In slides 34-35, “ultra central dAu” is compared to 0-10% He+Au. What’s the fraction? Top 1%? 2%?

A. Need to check, but the events were selected to have similar multiplicity to He+Au.

C. Please mention what the percentile (and also <Nch>) is.

Q. Independent check was done by Takahito, which shows good agreement, but concern about centrality determination (luminosity and vz dependence of multiplicity) was brought up. Any comment?

A. PAs are considering those points and will give an update at PWG soon.

Other discussion:

- Same GPC as the short paper will be asked for this long paper if they agree. 

- For short paper, it was sent out to PWG around Aug. 2021 (some comments from pwg, seems the discussion is ongoing and in PA side). Once conveners approve the paper draft and analysis note, it should move to GPC.

Best regards,

Takafumi