STAR Flow, Chirality and Vorticity PWG

["Robertson, Charles William" <rober558 AT purdue.edu>]

Hi Subhash, Convenors,

The new version of the draft has been uploaded to the same place on drupal, and the new file is here https://drupal.star.bnl.gov/STAR/system/files/QM2025AbstractRobertsonWils_Merged_2.pdf

For your comments: 

Title: I would suggest something like: Measurement of Global, Local, and
Helicity Spin Alignment of ϕ-Mesons in High Nuclear Collisions at RHIC
(But in the abstract text you have to clarify what you mean by local)

Done

I would suggest to remove l#2-5: "They are predicted .... physical
mechanisms."
l#5: "However, a significant ...strong force field []" --> We observed
unexpectedly large ρ_00 values for ϕ(1020) mesons in the first phase of the
RHIC Beam Energy Scan (BES-I) in Au+Au collisions. These values exceed
conventional expectations based on global hyperon polarization induced by
orbital angular momentum, suggesting the possible presence of a strong force
field for ϕ mesons [].

We did this with more or less the same wording

l#8-11: "Previous measurements ....decay daughter distributions" --> Previous
ρ00 measurements use a 1D angular distribution in θ* (polar angle of the
daughter kaon in the ϕ meson rest frame relative to the event plane). We
will use both angular dimensions (theta* and \phistar), enabling off-diagonal
element extraction with fewer assumptions about decay daughter distributions.

This is corrected to use beta, which is the correct variable for the 2D extraction, not phi star.

l#11-15: "We wil present .... (BES-II)" --> We will present differential
measurements of ϕ-meson ρ_00 and off-diagonal spin density matrix elements,
using data from the second phase of RHIC BES (BES-II) in Au+Au collisions at
√sNN = 7.7–19.6 GeV collected by STAR. Results will be shown as functions
of rapidity (y), centrality, and transverse momentum (pT).

Done

l#15-17: "Alongside, ... two from" --> Additionally, we will present
differential helicity frame spin alignment results to test their predicted
relation with global spin alignment.

Done
l#18-20: "We will also present ... pair invariant mass" --> We will also
present ρ_00 results using two alternative extraction methods: (i) ⟨cos2
θ*⟩ and (ii) ⟨cos 2ϕ*⟩ (where ϕ* is the projection of θ* onto the
transverse plane) as a function of the kaon pair invariant mass.

Done

l#21-22: I would suggest removing: "We report ... where applicable."

Portion about the revision has been removed
l#23: To me the definition of local is not obvious here, I guess you are
trying to follow the same convention as used in lambda polarization along
beam axis, right?

Clarified the local alignment

Thanks,

-CW, on behalf of the PA's

---

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Sent: Wednesday, November 6, 2024 9:34 PM
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Subject: [[Star-fcv-l] ] STAR presentation by Charles Robertson for Quark Matter 2025 got commented by Subhash Singha

 

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Dear star-fcv-l AT lists.bnl.gov members,

Subhash Singha ( connectsubhash AT gmail.com ) has commented on a material
originally submitted by Charles Robertson ( rober558 AT purdue.edu ) at
https://nam04.safelinks.protection.outlook.com/?url="https%3A%2F%2Fdrupal.star.bnl.gov%2FSTAR%2Fpresentations%2FQuark-Matter-2025%2FPhi-Meson-Local-Global-and-Helicity-Spin-Alignment-STAR&data=05%7C02%7Crober558%40purdue.edu%7Cf9f2189d45d4421826c308dcfed4ca2e%7C4130bd397c53419cb1e58758d6d63f21%7C0%7C0%7C638665437100230692%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=TdiCtdzfOVA%2BesaSp%2FS1TGAJxdn7ZbZ0fUM0nivuW5o%3D&reserved=0

Comment:
Dear PAs,

Nice abstract. I have a few suggestions for your consideration:

Title: I would suggest something like: Measurement of Global, Local, and
Helicity Spin Alignment of ϕ-Mesons in High Nuclear Collisions at RHIC
(But in the abstract text you have to clarify what you mean by local)

I would suggest to remove l#2-5: "They are predicted .... physical
mechanisms."
l#5: "However, a significant ...strong force field []" --> We observed
unexpectedly large ρ_00 values for ϕ(1020) mesons in the first phase of the
RHIC Beam Energy Scan (BES-I) in Au+Au collisions. These values exceed
conventional expectations based on global hyperon polarization induced by
orbital angular momentum, suggesting the possible presence of a strong force
field for ϕ mesons [].

l#8-11: "Previous measurements ....decay daughter distributions" --> Previous
ρ00 measurements use a 1D angular distribution in θ* (polar angle of the
daughter kaon in the ϕ meson rest frame relative to the event plane). We
will use both angular dimensions (theta* and \phistar), enabling off-diagonal
element extraction with fewer assumptions about decay daughter distributions.

l#11-15: "We wil present .... (BES-II)" --> We will present differential
measurements of ϕ-meson ρ_00 and off-diagonal spin density matrix elements,
using data from the second phase of RHIC BES (BES-II) in Au+Au collisions at
√sNN = 7.7–19.6 GeV collected by STAR. Results will be shown as functions
of rapidity (y), centrality, and transverse momentum (pT).

l#15-17: "Alongside, ... two from" --> Additionally, we will present
differential helicity frame spin alignment results to test their predicted
relation with global spin alignment.
l#18-20: "We will also present ... pair invariant mass" --> We will also
present ρ_00 results using two alternative extraction methods: (i) ⟨cos2
θ*⟩ and (ii) ⟨cos 2ϕ*⟩ (where ϕ* is the projection of θ* onto the
transverse plane) as a function of the kaon pair invariant mass.
l#21-22: I would suggest removing: "We report ... where applicable."
l#23: To me the definition of local is not obvious here, I guess you are
trying to follow the same convention as used in lambda polarization along
beam axis, right?

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