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Subject: STAR Flow, Chirality and Vorticity PWG

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  • From: "Hu, Yu" <yuhu AT bnl.gov>
  • To: "STAR Flow, Chirality and Vorticity PWG" <star-fcv-l AT lists.bnl.gov>
  • Subject: [Star-fcv-l] Fw: GPC request of the Au+Au 27 GeV CME analysis paper
  • Date: Fri, 18 Dec 2020 18:17:06 +0000


Dear conveners,

Sorry for the delay in the update on this paper. We were busy with some other work (like isobar) and couldn't get back to you for a while.
We include all the comments and suggestions from the PWGC meeting and update our paper draft, analysis note, and webpage.

Here is a link to our webpage:
Link to our paper draft:
Link to our analysis note:
A small note to the PWGC comments and our replies (it's also on page 67-70 in our analysis note):

Please feel free to let us know if you have any questions, suggestions, and comments.

Thank you.
Yu on the behalf of all PAs


From: Star-bulkcorr-l <star-bulkcorr-l-bounces AT lists.bnl.gov> on behalf of star-bulkcorr-l-request AT lists.bnl.gov <star-bulkcorr-l-request AT lists.bnl.gov>
Sent: Friday, July 10, 2020 19:50
To: star-bulkcorr-l AT lists.bnl.gov <star-bulkcorr-l AT lists.bnl.gov>
Subject: Star-bulkcorr-l Digest, Vol 15, Issue 14
 
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Today's Topics:

   1. Notes for PWGC preview: Charge-dependent correlations in
      Au+Au 27 GeV collisions to search for the Chiral Magnetic Effect
      at lower energy (Takafumi Niida)
   2. PWG inputs to BUR: cases for Au+Au 2023 and 2025  running
      (Xiaofeng Luo)


----------------------------------------------------------------------

Message: 1
Date: Sat, 11 Jul 2020 03:25:53 +0900
From: Takafumi Niida <fv0309 AT wayne.edu>
To: Star-bulkcorr-l <star-bulkcorr-l AT lists.bnl.gov>
Subject: [Star-bulkcorr-l] Notes for PWGC preview: Charge-dependent
        correlations in Au+Au 27 GeV collisions to search for the Chiral
        Magnetic Effect at lower energy
Message-ID: <A341A8BD-EEAB-4EE4-B9BF-C1DFF07E1EBF AT wayne.edu>
Content-Type: text/plain; charset="utf-8"

Date: 07/10/2020

Participants: Yu Hu, Prithwish Tribedy, Subikash Choudhury, Daniel Brandenburg, Daniel Cebra, ShinIchi Esumi, Matt Posik  Raghav Elayavalli, Saehanseul Oh, Wangmei Zha, Xiaofeng Luo, Yi Yang, Helen Caines, Rongrong Ma, Takafumi Niida

Title: Charge-dependent correlations in Au+Au 27 GeV collisions to search for the Chiral Magnetic Effect at lower energy
PWG: BulkCorr
PAs: Subikash Choudhury, Yu Hu, Mike Lisa, Prithwish Tribedy
Target journal: PRC Rapid communication
Paper webpage: https://drupal.star.bnl.gov/STAR/blog/ptribedy/charge-dependent-correlations-auau-27-gev-collisions-search-chiral-magnetic-effect-low <https://drupal.star.bnl.gov/STAR/blog/ptribedy/charge-dependent-correlations-auau-27-gev-collisions-search-chiral-magnetic-effect-low>
Presentation: https://drupal.star.bnl.gov/STAR/system/files/PaperProposal_PWG_Meeting_06_10_2020.pdf <https://drupal.star.bnl.gov/STAR/system/files/PaperProposal_PWG_Meeting_06_10_2020.pdf>

The PWGC panel previewed the paper proposal from BulkCorr pwg. The panel found that the analysis is matured and should move forward. There were suggestions and comments on the way of presenting results. The current wording and figure may be misleading and they need clarification. The panel thinks that target journal is appropriate. The following points were discussed.

Q. How can we distinguish spectator protons vs. participant protons in EPD? EPD is dealing with pseudorapidity but not rapidity.
A. EPD measures a mixture of participant and spectator protons. We cannot distinguish them. Based on UrQMD model (slide 15), outer EPD is dominated by produced particles and participant protons while inner EPD is dominated by spectator protons (~30%) and participant protons (and some produced particles).
C. Participant protons v1 would be sensitive to the compressibility of nuclear matter, and therefore the phase transition. Participant protons may have recoil from the interaction but the spectators don?t.
A. Slide 13, because of the sign change in v1, inner EPD is likely to be dominated by spectator protons.
C. The word ?spectator flow" and "participant flow? as well as Fig.1 are misleading. Based on the argument of the compressibility and the picture of UrQMD in slide 13, the sign of v1 in inner EPD region could be driven by participant protons.
A. We don?t need to (cannot) distinguish spectator and participants but need to find large v1 at forward rapidity, where spectators are more included and the event plane using them is more correlated with B-field. PAs will consider more clarification and modification in both texts and Figure 1.

Q. In Fig. 5, why don't you show central value rather than showing only upper limit. Showing central value (and discussing upper limit in the texts) would have more information and better way to present. Also the main conclusion (upper limit) comes from Fig. 5 which is for 10-50% centrality. The centrality should be explicitly mentioned in both abstract and conclusion. The text related to the upper limit in slide 10 may be misleading.
A. PAs will consider the comments and clarify them.

Q. In slide 9 and 10, how is the upper limit calculated? What?s the meaning of that?
A. 4 data points in mid central events in Fig. 4 are fitted by a constant. The ratio>1 indicates CME scenario. We present the upper limit of the excess above unity at 95% CL.

Q. In slide 9, what are the dominant source of systematic uncertainties in central and peripheral events?
A. In central events, the inner EPD has fewer hits because of less spectators, which leads to worse event plane resolution. In peripheral events, the number of particles of interest becomes lower and also EP resolution becomes lower. 

Q. Fig.2: where is a blue data point in most peripheral bin?
A. It is beyond the current range because of large fluctuation.

Q. Other systematic checks are expected by pwg, e.g. measurements with 1st or 2nd event plane using the inner or outer EPD.
A. PAs have studied. They will be presented in future pwg meeting.

Q. Regarding the bottom plot of Fig. 4, it would be beneficial to have any theory/model expectation.
A. In the original proposal, PAs put an counter plot based on B-field calculated from all protons in UrQMD. In the process of pwg review, it was suggested to remove it.
C. Would be nice to have any guide for a comparison. Can be discussed in GPC again.

Q. In the abstract, "directed flow of spectator protons" sounds incorrect. Azimuthal anisotropy or emission might be better?
A. Will consider it.


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Message: 2
Date: Sat, 11 Jul 2020 07:47:55 +0800
From: Xiaofeng Luo <xfluo.star AT hotmail.com>
To: <bulkcorr-hn AT sun.star.bnl.gov>
Subject: [Star-bulkcorr-l] PWG inputs to BUR: cases for Au+Au 2023 and
        2025    running
Message-ID:
        <HKAPR01MB36523E3717721B3AA48102DD9D650 AT HKAPR01MB3652.apcprd01.prod.exchangelabs.com>
       
Content-Type: text/plain; charset=utf-8; format=flowed

Dear ALL,

 ??? During yesterday?s meeting PWGC meeting, STAR management brought
the discussion regarding the physics cases for running STAR in Au+Au
during 2023 and 2025. The BUR is due by end of August so we should point
out what unique measurements that STAR can do using these datasets that
is something that sPHENIX cannot do.
Please find STAR forward upgrade plan with more details:
https://drupal.star.bnl.gov/STAR/starnotes/public/sn0648

Please let us know if you have any ideas on measurements from bulkcorr.

Thank you,
Best Regards,
Xiaofeng


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End of Star-bulkcorr-l Digest, Vol 15, Issue 14
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  • [Star-fcv-l] Fw: GPC request of the Au+Au 27 GeV CME analysis paper, Hu, Yu, 12/18/2020

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