STAR Flow, Chirality and Vorticity PWG

[Zhiwan Xu <zhiwanxu AT physics.ucla.edu>]

Dear FCV Conveners,

   As promised, we have also finished the accompany long paper draft. Since the short paper draft have been circulated among the CME-group and the FCV for more than one month, we would thereby like to request one GPC formation on the two STAR papers.

The details can be found here:

Title: "Charge seperation measurement in Au+Au collisions at 7.7-200 GeV in search of the CME" 

 PA: Zhiwan Xu, Gang Wang , Huan Huang, Yunshan Cheng, Maria Sergeeva, Jinhui Chen, Diyu Shen

 The webpage: https://drupal.star.bnl.gov/STAR/blog/zhiwanxu/Paper-Proposal-Search-Chiral-Magnetic-Effect-RHIC-Beam-Energy-Scan-II

 The short paper draft (target PRL):

https://drupal.star.bnl.gov/STAR/system/files/STAR_CME_BES_paper_short_v1.pdf

  Accompanying Long paper title: Search for the chiral magnetic effect through beam energy dependence of charge separation using event shape selection

 Draft: https://drupal.star.bnl.gov/STAR/system/files/STAR_CME_BES_paper_long_v1.pdf

The analysis note can be find here:

https://drupal.star.bnl.gov/STAR/system/files/Analysis_Notes_for_ESS_CME_paper_v1.pdf

Thank you!

Best,

Zhiwan

On Mon, Jul 1, 2024 at 2:57 PM Zhiwan Xu <zhiwanxu AT physics.ucla.edu> wrote:

Dear Prithwish and Subhash,

  Since for the past two weeks, we have not received comments from FCV colleagues, we would like to move forward and request the approval from FCV for the GPC on this paper. 

  In the meanwhile, can we suggest Wei Li (Rice U), the same GPC chair for isobar paper blind analysis, to chair the GPC for this new CME paper?

 Since this analysis has been discussed among STAR for a long time, probably many of the important details have been addressed. In addition, as the representative PA, I would be leaving STAR soon after this summer, I would like to sincerely ask if we can move quickly on the procedure. 

 Thank you!

Best,

Zhiwan

On Wed, Jun 19, 2024 at 2:37 AM Zhiwan Xu <zhiwanxu AT physics.ucla.edu> wrote:

Dear FCV conveners,

 

 We have prepared the paper draft and the analysis note for the "Charge seperation measurement in Au+Au collisions at 7.7-200 GeV in search of the CME" that are ready for the GPC. 

 The webpage is here: https://drupal.star.bnl.gov/STAR/blog/zhiwanxu/Paper-Proposal-Search-Chiral-Magnetic-Effect-RHIC-Beam-Energy-Scan-II

 The paper draft can be find here:

https://drupal.star.bnl.gov/STAR/system/files/STAR_CME_BES_paper_short_v1.pdf

The analysis note can be find hete:

https://drupal.star.bnl.gov/STAR/system/files/Analysis_Notes_for_ESS_CME_paper_v1.pdf

We are almost done with the accompanying long paper. 

Below we also include the response for the three checks we promised from the PWGC:

1

Q: Dividing the systematic uncertainties by sqrt(12) is not appropriate for many cases, particularly the Vz range variation. Dividing the data into two Vz ranges will not capture the range of systematic variations from Vz dependence. Several regions should be checked and maximum of the deviation should be divided by sqrt(12). Similar concern for nHitsFit and DCA variations, a single step variation taken to cover the range of systematic variations is not justified.

A: We follow the assessment of systematic uncertainty as Isobar Blind Analysis and the v1 splitting measurement published in PRX, and we stick to the established procedure in evaluating the systematic uncertainty. In general, this measurement is statistically dominated. In practice, at several energies, the systematic uncertainty from Vz often does not pass the Barlow check which aims to remove the statistical contribution. We conducted the check of DCA variation upon several ranges, and presented in the update in March Collaboration meeting (see https://drupal.star.bnl.gov/STAR/system/files/STAR_Collaboration_Meeting_20240320_ZhiwanXu.pdf) which justifies our selection range of sys vs default to be the max-min range. Thus, the sqrt(1/12) is used. The Nhits variation has been checked by other physics working group, which justified the usage of sqrt(1/12). For the additional Track Splitting and nSigma cut, the sys cut covers the only allowed variation or the possibly maximum variation allowed in the physics region. Therefore, we chose to stick to the established assessment procedure with sqrt(1/12).

2 

Q:Are any PID cut efficiencies applied (cut to exclude protons)?

Q: Since you use sigma_p < -2 cut to exclude protons, aren't you rejecting most particles above momentum of ~1.4 GeV/c? Is the 0.2 < p_T < 2 GeV/c range in labels then accurate?

A: The PID cut to exclude protons has been addressed by a modification of the momentum upper limit cut of hadrons to p < 1.4 GeV/c (for >= 9.2 GeV) and p < 1.3 GeV/c (for 7.7 GeV). The results from the new PID cut and corresponding efficiency is applied and presented in March 2024 collaboration meeting, see links here: (https://drupal.star.bnl.gov/STAR/system/files/STAR_Collaboration_Meeting_20240320_ZhiwanXu.pdf). The conclusion is unchanged, and results are consistent with those previously presented.

3

Q: What is the background level at 200 GeV for Au+Au and isobar? Can a comparison to BES-II energies

be shown?

A: The question raised about the background level of 200 GeV in Au+Au has been checked, and can be found from the updated results (https://drupal.star.bnl.gov/STAR/system/files/%7BZDC-SMD%7D%20in%20Au%2BAu%20at%20200%20GeV%20%28run16%29.pdf). After all known background removed with spectator plane (ZDC) and ESS, the delta-gamma 112 CME observable is found to be consistent with zero. And the background indicator delta-gamma 132 is also found to be zero.

Comments are warmly welcomed!

Best,

Zhiwan

From: Sooraj Radhakrishnan via Star-phys-l <star-phys-l AT lists.bnl.gov>
Date: December 22, 2023 at 10:22:13 PM PST
To: STAR experiment physics discussions <star-phys-l AT lists.bnl.gov>
Cc: Sooraj Radhakrishnan <skradhakrishnan AT lbl.gov>
Subject: [Star-phys-l] PWGC meeting discussion on 12/22/2023
Reply-To: STAR experiment physics discussions <star-phys-l AT lists.bnl.gov>



Dear STAR Collaborators,

   Please find below the minutes for the latest PWGC meeting discussion. The meeting recordings can be found here: /star/u/rksooraj/PAC/PWGCmeeting_recording/20231222.mp4

If you have any comments to any of the items, please feel free to bring them up.Thanks!

Best,

Sooraj, Barbara 

=======================================

1) Paper preview: Search for the Chiral Magnetic Effect from the RHIC Beam Energy Scan II

- Brief introduction from the PWG conveners (5’) [Prithwish Tribedy]

- Paper proposal (15')  [Presentation by Zhiwan Xu]

- Open discussions (35')

- Summary from the conveners' panel (5’)

 

Proposal page: https://drupal.star.bnl.gov/STAR/blog/zhiwanxu/Paper-Proposal-Search-Chiral-Magnetic-Effect-RHIC-Beam-Energy-Scan-II

PAs: Zhiwan Xu, Gang Wang, Huan Zhong Huang

Target journal: PRL

NOTES

--

Sooraj Radhakrishnan

Research Scientist,

Department of Physics

Kent State University

Kent, OH 44243

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

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