Background Baseline on CME in Isobar Collisions, Webpage

Title: Estimate of Background Baseline and Upper Limit on the Chiral Magnetic Effect in Isobar Collisions at √sNN=200 GeV at the BNL Relativistic Heavy-Ion Collider

PAs: Yicheng Feng, Fuqiang Wang

Targeted journals:
short paper: Phys. Rev. Lett
long paper: Phys. Rev. C

Abstract: 
We have reported the isobar (9644Ru+9644Ru, 9640Zr+9640Zr) results from a blind analysis on the search for the chiral magnetic effect (CME). The Ru+Ru to Zr+Zr ratio of the CME-sensitive charge-dependent azimuthal correlator (Δγ), normalized by elliptic anisotropy (v2), is observed to be close to but systematically larger than the inverse multiplicity (N) ratio. The background baseline for the isobar ratio Y=(Δγ/v2)Ru/(Δγ/v2)Zr is naively expected to be (1/N)Ru/(1/N)Zr, but genuine two- and three-particle correlations are expected to alter it. We estimate the contributions from those correlations, utilizing the STAR isobar data as well as HIJING simulations. The estimated baseline for Y is found consistent with the isobar data, and an upper limit of ~10% at 95% confidence level is extracted for the CME fraction in the Δγ measurement in isobar collisions at 200 GeV. 

Conclusion: 
In this study we have estimated nonflow contributions in v2 by fitting two-particle (Δη,Δφ) distributions, and the deviations from simple multiplicity scaling of the three-particle correlator using the STAR isobar data. The 3-particle nonflow correlation contributions to C3 are evaluated by HIJING simulations. Using these inputs, we arrive at an improved background estimate of the Ru+Ru to Zr+Zr ratio of the Δγ/v2 variable. The estimated background baselines are consistent with the STAR measurements from both the full-event and subevent methods. We extract an upper limit of the CME fraction in Δγ measurements to be ~10% with 95% confidence level in isobar collisions at 200 GeV.

Status:
2024/07/09: both papers have been published online
                    Short paper on Phys.Rev.Research: journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.6.L032005 
                    Long paper on Phys.Rev.C: journals.aps.org/prc/abstract/10.1103/PhysRevC.110.014905

2024/05/14: short paper transferred to PRResearch

2023/10/24: two papers are submitted jointly: short paper to PRL, long paper to PRC
                    starpapers-l is informed: lists.bnl.gov/mailman/private/starpapers-l/2023-October/008556.html
2023/10/23: long paper on arXiv: arxiv.org/abs/2310.13096
2023/08/31: short paper on arXiv: arxiv.org/abs/2308.16846

Long paper draft, latest version:
drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v44.pdf

Short paper draft, latest version:
drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_S_v28.pdf

Analysis note: 
drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_Note_v16_0.pdf
STAR note: drupal.star.bnl.gov/STAR/starnotes/private/PSN0811

CVS:
www.star.bnl.gov/cgi-bin/protected/viewvc.cgi/cvsroot/offline/paper/psn0811/

Figures.zip:
2023/10/26: long paper figures
→long paper figures: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v28_fig.zip
2023/09/14: short paper figures
→short paper figures: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_S_v22_fig.zip

Journal review: 
2024/07/01: second proof from PRResearch
short paper
    journal pdf: drupal.star.bnl.gov/STAR/system/files/LK18767WR_0.pdf
2024/06/06: first proof from PRResearch
→short paper
    our reply: drupal.star.bnl.gov/STAR/system/files/Reply_IsobarNfBkg_S_20240606.pdf
    journal pdf: drupal.star.bnl.gov/STAR/system/files/LK18767WR.pdf
    journal redlined pdf: drupal.star.bnl.gov/STAR/system/files/LK18767WR_redline.pdf
2024/05/14: transfer short paper to PRResearch
We implemented the comments from referee B for the B-field direction and HIJING charge conservation. 
→short paper
    revised manuscript: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_S_v28.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_S_v26v28.pdf
2024/05/10: long paper proofreading: 
→long paper
    our reply: drupal.star.bnl.gov/STAR/system/files/Reply_IsobarNfBkg_L_20240506.pdf
    journal pdf: drupal.star.bnl.gov/STAR/system/files/CK10905.pdf
    journal redlined pdf: drupal.star.bnl.gov/STAR/system/files/CK10905_redline.pdf
2024/03/25: long paper accepted by PhysRevC with some editorial comments:
→long paper
    reply to comments: drupal.star.bnl.gov/STAR/system/files/Reply_IsobarNfBkg_L_20240402.pdf
    revised manuscript: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v44.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_L_v43v44.pdf
2024/02/20: GPC comments for the replies & manuscripts
→long paper
    reply to comments: drupal.star.bnl.gov/STAR/system/files/Reply_IsobarNfBkg_L_20231209_v13.pdf
    reply to comments with changes suggested by GPC: drupal.star.bnl.gov/STAR/system/files/diff_Reply_IsobarNfBkg_L_20231209_v10v13.pdf
    revised manuscript: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v43.pdf
    latexdiff for total changes: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_L_v28v43.pdf
2024/02/16: GPC comments for the replies & manuscripts
→short paper
    reply to comments: drupal.star.bnl.gov/STAR/system/files/Reply_IsobarNfBkg_S_20231211_v13.pdf
    reply to comments with changes suggested by GPC: drupal.star.bnl.gov/STAR/system/files/diff_Reply_IsobarNfBkg_S_20231211_v11v13.pdf
    revised manuscript: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_S_v26.pdf
    latexdiff for changes from GPC comments: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_S_v25v26.pdf
    latexdiff for total changes: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_S_v23v26.pdf
→long paper
    reply to comments with changes suggested by GPC: drupal.star.bnl.gov/STAR/system/files/diff_Reply_IsobarNfBkg_L_20231209_v10v12.pdf
    revised manuscript: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v42.pdf
    latexdiff for changes from GPC comments: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_L_v40v42.pdf
    latexdiff for total changes: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_L_v28v42.pdf
2024/02/09: referees' reports were received on 2023/12/11
→short paper
    reply to comments: drupal.star.bnl.gov/STAR/system/files/Reply_IsobarNfBkg_S_20231211_v11.pdf
    revised manuscript: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_S_v25.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_S_v23v25.pdf
→long paper
    reply to comments: drupal.star.bnl.gov/STAR/system/files/Reply_IsobarNfBkg_L_20231209_v10.pdf
    revised manuscript: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v40.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_L_v28v40.pdf

Institutional review:
2023/09/20: comments on the long paper from SCSU, ACU, NISER, IMP groups
→reply to comments: drupal.star.bnl.gov/STAR/system/files/Reply_InstRev_IsobarNfBkg_20230821_v7.pdf
→revised long paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v27.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_L_v18v27.pdf
2023/08/19: comments from ACU group
→reply to comments: drupal.star.bnl.gov/STAR/system/files/Reply_InstRev_IsobarNfBkg_20230818.pdf
revised short paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_S_v21.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_S_v18v21.pdf
    latexdiff for latest changes only: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_S_v20v21.pdf
2023/08/18: comments from NISER group
→reply to comments: drupal.star.bnl.gov/STAR/system/files/Reply_InstRev_IsobarNfBkg_20230814_v5.pdf
revised short paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_S_v20.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_S_v18v20.pdf
2023/08/16: comments from Fudan group and SCSU group
→reply to comments: drupal.star.bnl.gov/STAR/system/files/Reply_InstRev_IsobarNfBkg_20230814_v3.pdf
revised short paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_S_v19.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_S_v18v19.pdf

GPC:
2023/07/28: wrapped up with acknowledgments
revised short paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_S_v18.pdf
revised long paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v18.pdf
2023/07/24:
reply to comments: drupal.star.bnl.gov/STAR/system/files/Gpc355_20230724.pdf
→revised long paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v17.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_L_v15v17.pdf
2023/07/21: 
reply to comments: drupal.star.bnl.gov/STAR/system/files/Gpc355_20230719.pdf
revised short paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_S_v16.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_S_v14v16.pdf
revised long paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v15.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_L_v14v15.pdf
revised analysis note: 
2023/07/11: GPC meeting #4
revised long paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v14.pdf
revised short paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_S_v14.pdf
revised analysis note: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_Note_v14.pdf
revised slides: drupal.star.bnl.gov/STAR/system/files/PPRP20230705_v5.pdf
2023/07/07: updates from higher statistics and corrected cuts for HIJING
slides: drupal.star.bnl.gov/STAR/system/files/PPRP20230705_v4.pdf
2023/06/20: GPC meeting #3
→reply to comments: drupal.star.bnl.gov/STAR/system/files/Gpc355_20230626.pdf
→revised long paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v13.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_L_v10v13.pdf
→revised short paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_S_v9.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_S_v8v9.pdf
2023/06/06: GPC meeting #2
→reply to comments: drupal.star.bnl.gov/STAR/system/files/Gpc355_20230606.pdf
→revised long paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v10.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_L_v9v10.pdf
→revised short paper: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_S_v8.pdf
    latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_S_v7v8.pdf
2023/05/23: GPC meeting #1
→Jamie's meeting minutes & Sevil's follow-up email: drupal.star.bnl.gov/STAR/system/files/Gpc355_20230523_v2.pdf

FCV:
2023/04/04:
→long paper draft: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v9.pdf
→latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_L_v8v9.pdf
2023/03/30:
→long paper draft: drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v8.pdf
→latexdiff: drupal.star.bnl.gov/STAR/system/files/diff_IsobarNfBkg_L_v7v8.pdf

Supplementary materials: 
FCV analysis meeting: 2023/06/26, drupal.star.bnl.gov/STAR/blog/fengyich/Analysis-meeting-QM2023-topics-Isobar-CME-backgrounds
PWGC preview, 2023/02/17, drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_PwgcPreview_v5.pdf
                                              drupal.star.bnl.gov/STAR/event/2023/02/17/STAR-PWGC-meeting#comment-2205
FCV meeting, 2023/01/25, paper proposal, drupal.star.bnl.gov/STAR/system/files/PPRP20230125_v2.pdf 
CME focus meeting, 2023/01/20, drupal.star.bnl.gov/STAR/system/files/PPRP20230119_v3.pdf 
CME focus meeting, 2022/12/16, paper proposal,  drupal.star.bnl.gov/STAR/system/files/PPRP20221216pp_v3.pdf 
CME focus meeting, 2022/11/11, drupal.star.bnl.gov/STAR/system/files/PPRP20221111.pdf 
DNP2022, talk, 2022/10/29, meetings.aps.org/Meeting/DNP22/Session/JC.1 
SQM2022, talk, 2022/06/14, indico.cern.ch/event/1037821/contributions/4842110/ 
QM2022, poster, 2022/04/06, indico.cern.ch/event/895086/contributions/4721260/ 

Table (for long paper): 


Figure (for long paper): 



Figure (for short paper): 

Figure 2 in short paper is the same to Fig.12 of long paper.
Figure 3 in short paper is the same to Fig.13 of long paper.
Figure 4 in short paper is the same to Fig.14(a) of long paper.

Cartoons: 

or through links below:
400x400: drupal.star.bnl.gov/STAR/system/files/IsobarDiffText_Pixel400_v1.png
1000x1000: drupal.star.bnl.gov/STAR/system/files/IsobarDiffText_v1.png

The anticipated chiral magnetic effect (CME)-related charge separation was not measured to be larger in ${^{96}_{44}\text{Ru}}+{^{96}_{44}\text{Ru}}$ than in ${^{96}_{40}\text{Zr}}+{^{96}_{40}\text{Zr}}$ collisions because the flow-induced backgrounds do not fully cancel due to nuclear structure differences between the two isobar nuclei. Properly taking this, as well as the next-level non-flow-related backgrounds, into account, the charge separation results are consistent between the isobar systems and an upper limit of 10% CME signal is extracted at 95% confidence level.