STAR GPC #355

["Feng, Yicheng" <feng216 AT purdue.edu>]

Hi GPC, 

I just got the referees' report from Phys.Rev.Lett for the short paper of the CME isobar baseline study. 

Now I think the short and long papers are reviewed jointly, 

because the referee A for this short paper is also the referee for the long paper. 

We PAs will work on those comments for both papers. 

I plan to also forward this email to starpapers-l later today. 

Sincerely,

Yicheng for PAs

---

From: prl AT aps.org <prl AT aps.org>
Sent: Monday, December 11, 2023 11:19 AM
To: Feng, Yicheng <feng216 AT purdue.edu>
Subject: Your_manuscript LK18767 Collaboration

 

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Re: LK18767
    Upper limit on the chiral magnetic effect in isobar collisions at the
    relativistic heavy-ion collider
    by The STAR Collaboration and Yicheng Feng

Dear Dr. Feng,

The above manuscript has been reviewed by our referees.

On the basis of the resulting reports, it is our judgment that the
paper is unsuitable for publication in Physical Review Letters. We
append comments from the criticism that led to our decision.

Yours sincerely,

Nikhil Karthik
Associate Editor
Physical Review Letters
Email: prl AT aps.org
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----------------------------------------------------------------------
Report of Referee A -- LK18767/Collaboration
----------------------------------------------------------------------

The manuscript concerns the search for the chiral magnetic effect
(CME), an important part of the scientific program of the Relativistic
Heavy Ion Collider. A flagship paper (Ref. [24]) used a blind analysis
technique which did not find evidence for the CME according to the
defined observable. However, post-blinding, it was pointed out that
this measurement did not take into account possible species-dependent
backgrounds. Thus this present study by STAR is a step towards
quantifying these backgrounds and thus potentially re-interpreting the
possible presence of a CME signal, although no longer in a blinded
way. The main conclusion is that, within some model assumptions, after
evaluating several aspects of the backgrounds, the data does not
necessarily exclude the presence of a small signal.

I appreciate the diligent work by the many members of the STAR
Collaboration to treat these issues in a serious and rigorous way.
However, I see the present set of results as being only incremental
and quite specialized. As a referee, I am asked whether the paper fits
the PRL criteria of "validity, impact, innovation, and interest". The
work seems valid, although I will provide some specific feedback for
the accompanying PRC paper. The impact, at this stage, is modest - the
paper is quite technical and itself concludes that it mainly "develops
a workflow to estimate backgrounds". The studies performed for the
background are based on two- and three-particle correlations and are
not so innovative that, by themselves, they demand a high-profile
forum. Finally, I do not think the result at this stage - a
measurement consistent with zero CME signal but with a weak,
model-dependent upper limit - is of unusually broad interest.

Thus, I do not see this manuscript as appropriate for Physics Review
Letters. It may be that when the STAR "final word" on the observation
or best comprehensive limit on the CME is available, this would be of
broader interest to the wider physics community and represent a truly
novel result which is therefore appropriate for PRL. I encourage the
STAR Collaboration to continue working towards this goal.

----------------------------------------------------------------------
Report of Referee B -- LK18767/Collaboration
----------------------------------------------------------------------

Manuscript LK18767 presents an updated version of the analysis
presented in Phys.Rev.C 105 (2022) 1, 014901 by the STAR
collaboration. The manuscript is generally well-written and free of
typographical errors, though the abstract has a few minor grammatical
issues. The motivation, theoretical background, and methodology are
clearly presented and scientifically sound. The manuscript is certainly
of sufficient quality for publication in PRL.

However, whether sufficient impact on the field of heavy on physics
and on physics in general is present is a separate matter, and
difficult to assess. On the one hand, the search for P- and
CP-violation in the strong sector is absolutely a central question in
the physics of our time. For that reason, there is a strong case to be
made for acceptance in PRL. On the other hand, the manuscript
represents a rather modest improvement over the previous PRC
publication, namely the numerical assessment on the upper bound of the
CME fraction present in the correlations. For that reason, sufficient
impact seems not to have been reached to merit publication in PRL.

The final decision rests with the editors. The referee leans towards
acceptance.

General Comments:

The manuscript is rather careless in failing to make the distinction
between the reaction plane, the spectator plane, the magnetic field
plane, and the second harmonic symmetry plane. This is a rather
serious oversight that needs to be addressed prior to acceptance.

A related comment is that would be interesting to see a study of the
correlation between psi_2 and psi_B in both Ru+Ru and Zr+Zr to see if
there are any differences. Considering the small but important
differences in the nuclear geometry between the two nuclei, evinced in
exquisite detail in the aforementioned STAR PRC, the effect will
likely be small but could nonetheless be important. Such a study is
perhaps beyond the scope of the present manuscript, but if nothing
else some amount of informed speculation is warranted.

The case that's made for HIJING giving a reliable estimate of
background correlations is persuasive. However the manuscript needs to
address the absence of charge conservation and whether or how that
could influence the estimates (based on the similarity between HIJING
and data, it seems to be a small effect, but a comment is needed). It
would also be beneficial to include any validation/checks on the
HIJING simulations into some kind of online Supplemental Material for
the manuscript.