STAR Flow, Chirality and Vorticity PWG

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

Dear All,

 I have incorporated the comments from yesterday's pre-QM rehearsal, please find my updated talk slides:

https://drupal.star.bnl.gov/STAR/presentations/Quark-Matter-2023/Search-Chiral-Magnetic-and-Vortical-Effects-Using-Event-Shape-Vari-0

Main points:

> s14, the money plot. I added a panel of Psi_2 results from Han-Sheng, including the two data points of without and with low mass cut, as suggested by Fuqiang.

> s11-13, BES-II results. following the good suggestion by Rongrong, I removed other information of ESS and focus on presenting ESS(c).  Those are put into back-up slides.

> s15, for CVE measurement, a summary plot is added. 

Also, "non-flow" is changed to "residual non-flow" effects, following the advice by the conveners. "signal" change to "larger charge separations"

Let me know if you have any more comments! Thank you.

Best,

Zhiwan

------------------------------------
Zhiwan Xu,
Department of Physics and Astronomy, UCLA
zhiwanxu AT physics.ucla.edu

---

From: "Zhiwan Xu via Star-fcv-l" <star-fcv-l AT lists.bnl.gov>
To: "Sooraj Radhakrishnan" <skradhakrishnan AT lbl.gov>
Cc: "Zhiwan Xu" <zhiwanxu AT physics.ucla.edu>, "STAR Flow, Chirality and Vorticity PWG" <star-fcv-l AT lists.bnl.gov>
Sent: Wednesday, August 30, 2023 11:01:28 AM
Subject: Re: [Star-fcv-l] STAR presentation by Zhiwan Xu for Quark Matter 2023

Dear Sooraj,
Thank you for the comments. I have incorporated your suggestions on several bullets for my slides:

https://drupal.star.bnl.gov/STAR/presentations/Quark-Matter-2023/Search-Chiral-Magnetic-and-Vortical-Effects-Using-Event-Shape-Vari-0

More points regarding the method: 

-S3: Intuitively CVE is to replace the magnetic field "B" in the CME with "μ_Β*ω".

When we measure lambda-proton separation, the a_1 corresponds to the CVE.

I have corrected the Eqts that you pointed out. Please kindly let me know if you have further comments.

-S4: cartoon. Ideally, we can control eccentricity for BKG subtraction, because zero eccentricity means zero flow bkg.

However, this is technically very difficult, because even with the same eccentricity, the large fluctuation in the emission pattern could dominate the BKG.

The theorist pointed it out years ago, but we just learned it the hard way.

That's why we resort to a more direct handle on event shape, the 2nd-order flow vector based on emission pattern.

This approach is technically robust, and the only concern is how well it represents the BKG.

Through extensive model studies, we finally found the optimal approach of ESS (c).

-S5 + S6: pair v2. We agree that the pair quantities are new, and require more technique details.

I added them in backup slides due to limited time. Also, I added on that slide a detailed explanation of intercept ordering, which relies on the same maths. 

-S7: BES- data. I will confirm with other collaborators working on BES-II to make sure that the event numbers are consistent. I did not utilize iTPC in this analysis so I removed that mention.

-S12: 7.7 GeV. I am using preliminary centrality definition & bad runs, pile-up cuts, from the QA group and centrality group.

-S15: non-flow. Some of Han-Sheng's ESE measurements use the 2nd-order participant plane from TPC, which entails non-flow bkg that was not subtracted.
The ESS measurements use the spectator 1st-order plane on purpose, to avoid the non-flow contribution. Han-Sheng also tried ZDC to avoid non-flow contributions for the same purpose.

Again, thank you for helping me with my talk!

Best,

Zhiwan

------------------------------------
Zhiwan Xu,
Department of Physics and Astronomy, UCLA
zhiwanxu AT physics.ucla.edu

---

From: "Sooraj Radhakrishnan" <skradhakrishnan AT lbl.gov>
To: "STAR Flow, Chirality and Vorticity PWG" <star-fcv-l AT lists.bnl.gov>
Cc: "subhash" <subhash AT rcf.rhic.bnl.gov>, "Zhiwan Xu" <zhiwanxu AT physics.ucla.edu>
Sent: Wednesday, August 30, 2023 12:03:36 AM
Subject: Re: [Star-fcv-l] STAR presentation by Zhiwan Xu for Quark Matter 2023

Hi Zhiwan,

   Nice results and very well prepared slides. I have a few comments, please find below

S2: 3rd bullet -  baryon imbalance --> net baryon density?

S3: In the red box, why CME/CVE? Arent the a1 CME signal?

S4: Your cartoons seem to imply that emission fluctuations are driving the elliptic event shape. There are event by event fluctuations in the participating nucleon distribution which leads to shape fluctuations. The emission fluctuations are localized (in azimuth also) which will contribute to your q2, but would also have other order anisotropies. 

S5: Since the pair quantities are new, you may want to split this slide and also show some distributions of pair v2, so that people get an idea of the quantity

S6: first bullet - true SME signal for AFVD simulations. You could add a bullet on why the mixed selection is conceptually better

S7: Please use consistent number of events as in other presentations. The numbers we quote for BES-II are total HLTGood events collected. For Au+Au Run 14+16 had 2.1 B MB events, Run 11 should also have close to 1 B? Why is your number smaller?

S7: Why not also mention iTPC in the detector upgrade?

S7: 20 times - not a fixed number for all energies

S8: last bullet - is less than one sigma significance

S8: residual non-flow effects need to be assessed?

S9: residual non-flow

S9: May be question to Han-sheng, can you point me to the extrapolations for the K0s mass window range? I remember one of the mass windows in a more fine binned case with non-zero intercept was having negative slope, contrary to what the assumption is. How is the slope when you merge the bins as in this case?

S10: You could add reference for the correction

S12: Are the 7.7 GeV results using the official centrality definition?

S13: Why do you want the last bullet? With better precision we get more information than in BES-I, doesnt?

S14: Results lack significance

S14: You might want to briefly explain the quantity and measurement here

S15: Why say the non-flow effects need to be assessed for the invariant mass ESE results alone? The extrapolation is intended to evaluate the signal ar zero v2, isnt? In general, the ESS and ESE results need better understanding of non-flow. You dont have to highlight that in the summary here

Best,

Sooraj

  

On Tue, Aug 29, 2023 at 10:25 AM Zhiwan Xu via Star-fcv-l <star-fcv-l AT lists.bnl.gov> wrote:

Hi Subhash,
 Thank you for the comments. I have updated a STAR logo on each slides.
 Please find the new version: https://drupal.star.bnl.gov/STAR/presentations/Quark-Matter-2023/Search-Chiral-Magnetic-and-Vortical-Effects-Using-Event-Shape-Vari-0

 AVFD and AMPT: The AMPT does not handle the coupling between v2 and momentum conservation and/or local charge conservation as well as AVFD. The ensembled average of dg112 measured with AMPT is much smaller than data or AVFD. AVFD has tuned the LCC to the experimental values, and as a hydro model it resonably well deals the momentum conservation. Therefore, to our understanding so far, AMPT can not fully represents the background in CME measurement. It still requires some further accessmenet.

 s#7 the number of events in BES-II is from my own cuts. Thank you for point that out, I will confirm with other BES-II measurements.

 s#8 the large statistic error mainly derives from a long-linear extrapoation, which is referring to the large gap between first data point and v2=0. I added an arrow pointing to the region on plot. Thank you for catching that.


Best,
Zhiwan
------------------------------------
Zhiwan Xu,
Department of Physics and Astronomy, UCLA
zhiwanxu AT physics.ucla.edu

----- Original Message -----
From: "subhash" <subhash AT rcf.rhic.bnl.gov>
To: "STAR Flow, Chirality and Vorticity PWG" <star-fcv-l AT lists.bnl.gov>
Cc: "Zhiwan Xu" <zhiwanxu AT physics.ucla.edu>
Sent: Monday, August 28, 2023 7:28:29 PM
Subject: Re: [Star-fcv-l] STAR presentation by Zhiwan Xu for Quark Matter 2023 got commented by Zhenyu Chen

Dear Zhiwan,

Very well polished slides. I have only a few comments/suggestions for
your consideration:

General: we usually keep a star logo in the corner of each slide or
mention STAR in each slides. But it's up to you.

s#3: 1st bullet v_2 and in other slides # 11

s#6: Could you help me understand why the ESS method works for AVFD, but
not for AMPT?

s#7: Please make sure number of events are consistent with other QM
talks or mention analyzed events or accepted good events.

s#8: I don't understand the first bullet. What drives large statistic
error?

Thanks and regards,
Subhash


On 2023-08-22 03:16 AM, Zhiwan Xu via Star-fcv-l wrote:
> Dear Zhenyu,
>  Thank you for the comments. In Slide 8, the right plot of measurement
> at 200 GeV is using ZDC.
>  I have implemented the other suggestions. Please take a look at the
> link:
>
> https://drupal.star.bnl.gov/STAR/presentations/Quark-Matter-2023/Search-Chiral-Magnetic-and-Vortical-Effects-Using-Event-Shape-Vari-0
>
> Best,
> Zhiwan
>
> ------------------------------------
> Zhiwan Xu,
> Department of Physics and Astronomy, UCLA
> zhiwanxu AT physics.ucla.edu
>
>
> ----- Original Message -----
> From: "webmaster--- via Star-fcv-l" <star-fcv-l AT lists.bnl.gov>
> To: star-fcv-l AT lists.bnl.gov
> Cc: webmaster AT star.bnl.gov
> Sent: Sunday, August 20, 2023 11:39:29 PM
> Subject: [Star-fcv-l] STAR presentation by Zhiwan Xu for Quark Matter
> 2023 got commented by Zhenyu Chen
>
> Dear star-fcv-l AT lists.bnl.gov members,
>
> Zhenyu Chen ( zhenyuchen AT sdu.edu.cn ) has commented on a material
> originally
> submitted by Zhiwan Xu ( zhiwanxu AT physics.ucla.edu ) at
> https://drupal.star.bnl.gov/STAR/presentations/Quark-Matter-2023/Search-Chiral-Magnetic-and-Vortical-Effects-Using-Event-Shape-Vari-0
>
> Comment:
> Dear Zhiwan,
>
> Nice slides. Please find few suggestions below:
> - Slide8: is the Psi1 results wrt to EPD or ZDC?
> - Slide10: y-int -> y-intercept
> - Slide12&13&15: errors -> uncertainties
>
> Cheers,
> Zhenyu
>
> ---
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--

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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