STAR Flow, Chirality and Vorticity PWG

["Huan Zhong Huang" <huang AT physics.ucla.edu>]

Hi Sooraj,

   Thanks for the suggestion.

  Our study seems to indicate that the CME background does not depend exclusively on hydro v2-h alone. There are also clear correlations between q2 and apparent v2. By using different particles or particle combinations to form q2 and v2, we attempted to reduce the correlations. Perhaps the correction coefficient relating intercept and CME magnitude in the ESS is related to the correlations. Using the apparent v2 as a controlling variable for the background seems to work well within the AVFD and leads to over-subtraction of background within the AMPT model. Maybe the results Zhiwan showed are on the conservative side if we think the background is closer to AMPT than to AVFD. The extent of over-subtraction is hard to quantify reliably. If it is useful to state this, Zhiwan could add one remark in the conclusion.

  Regards,

  Huan

 

 

From: Sooraj Radhakrishnan <skradhakrishnan AT lbl.gov>
Sent: Saturday, August 19, 2023 10:11 PM
To: Huan Zhong Huang <huang AT physics.ucla.edu>
Cc: STAR Flow, Chirality and Vorticity PWG <star-fcv-l AT lists.bnl.gov>; Zhiwan Xu <zhiwanxu AT physics.ucla.edu>
Subject: Re: [Star-fcv-l] [Please Read]: FCV PWG meeting on 16+17/Aug/2023 Wed. 9:30 AM EDT

 

Hi Huan,

   Thanks for the explanation. Yes, the goal is to reduce v2 related background, and we indeed can get to ~zero v2 events with ESS. 

 

My concern was that, given its the true flow in the event that couples to resonance decays and contributes to the background, if we select q2 in the same region as we do analysis, this could bias in the extrapolation or evaluation at zero v2 as the v2 values could be biased. With the evaluation of v2 and delta_gamma in this analysis with the EPD, this may be fine and not be biasing the results. But I think there is still value in checking the extrapolation decoupling the selection and analysis regions. The relevant question would be what is the bias in the v2 values if we do q2 selection in the same region. This may also be checked in some simulation studies, may be HIJING, inputting a given v2 and evaluating the bias.

 

thanks

Sooraj

 

On Sat, Aug 19, 2023 at 2:05 PM Huan Zhong Huang <huang AT physics.ucla.edu> wrote:

Hi Sooraj,

  When we discuss the ESS method, it is often that we got the comment that by selection of particle shape from different eta region or with a large eta gap, one can remove the autocorrelations. Perhaps one should consider the goal of the ESS first. We want to select events with azimuthally spherical shape particle emissions to minimize the v2-related background, we are not interested in a precise measurement of hydro-induced v2 arising from geometrical eccentricity. In fact, we know from comparison of ESS with the other method that the particles from the 20-50 collision centrality we study are mostly spherical, not because the geometrical eccentricity, but largely due to particle emission fluctuations. Basically, for given 20-50% collision centrality, there is a range of geometrical eccentricity fluctuations and it does not fluctuate to azimuthal spherical shape. One can choose more central collisions to force the geometrical eccentricity to close to spherical, then the more central the collisions, the less spectator protons and smaller the B field. That creates other disadvantages for CME search.

  Thanks. Regards,

  Huan

 

From: Star-fcv-l <star-fcv-l-bounces AT lists.bnl.gov> On Behalf Of Sooraj Radhakrishnan via Star-fcv-l
Sent: Saturday, August 19, 2023 11:43 AM
To: Zhiwan Xu <zhiwanxu AT physics.ucla.edu>
Cc: Sooraj Radhakrishnan <skradhakrishnan AT lbl.gov>; STAR Flow, Chirality and Vorticity PWG <star-fcv-l AT lists.bnl.gov>
Subject: Re: [Star-fcv-l] [Please Read]: FCV PWG meeting on 16+17/Aug/2023 Wed. 9:30 AM EDT

 

Hi Zhiwan,

   Thanks for the answers and updates. It certainly helped better understand the measurements 

 

//When we talk about pair q2 (v2), we mean the angle is obtained from adding the momenta of the two POI particles (used in gamma112 correlator).//

--- So you are basically treating all pairs as coming from resonances and calculating v2 of the parent? I wonder how this distribution would look like. Do you have plots of this pair v2 distribution compared to single v2? Also its centrality and pT dependence compared to single v2? For this to give you sensitivity to resonance v2, the number of actual pairs from resonance decays should be significant compared to random pairs, right? I doubt thats the case. And the conclusions you draw from models with this method could depend on what this ratio is in models vs data, the over subtraction or better sensitivity you seen in AFVD could be related to this as well

 

I would suggest you also add a slide similar to S16, with the single v2, q2^2, which would be from the standard ESS technique. Have you done an analysis where you have the q2 selection and v2,gamma analyses done in different eta regions? This should remove autocorrelations in the standard method. 

 

 //The AVFD model confirms that the ESS (c) accurately match the CME signal. AMPT model presented over-subtracts of v2-background. That is why we put a conclusion bullet that states it need further accessmenet.//

--- Could you add the AMPT studies in the backup? How large is the over-subtraction? How do the two models compare for the other choices - a, b d?

 

thanks,

Sooraj

 

On Thu, Aug 17, 2023 at 10:54 PM Zhiwan Xu <zhiwanxu AT physics.ucla.edu> wrote:

Dear Sooraj,

  Thank you for the suggestions. I have updated slide 8 and 9 to add more explanation of pair v2/q2.

  Please check the updated version here:

https://drupal.star.bnl.gov/STAR/blog/zhiwanxu/Preliminary-request-BES-II-CME-ESS

 

 1.) The correction (1- v2)^2 is from the AVFD model study, in the purpose to compare the intercept (at v2 = 0) with the inclusive <dg112> at a finite v2.

 In general, it aims to "restore" the true CME signal from the intercept, which ensures the ratio between numerators and denominator are meaningful. 

 Therefore, the final plot in S16 includes such correction.  

  We first confirmed that this slight correction is needed in Phy.Rev. C 104, 064906 (2021), and later we find it better to use the current form in https://doi.org/10.48550/arXiv.2307.14997.

  

 2.) The term "single" we use here is just to contrast with "pair". The single v2 is ordinary v2 measurement that use POI as \phi.

 When we talk about single q2 (v2), we mean using single particle azimuthal angle of POI.

 When we talk about pair q2 (v2), we mean the angle is obtained from adding the momenta of the two POI particles (used in gamma112 correlator). 

 In math term, the pair angle derives from: tan (\phi_pair) = (pt_1*sin \phi_1 + pt_2*sin \phi_2)/(pt_1*cos\phi_1 + pt_2*cos \phi_2)

 The equations for q2 and v2 are basically the sam except using a different angle, see the updated slide 8 and 9.

 

3.) The systematics source from the data side are listed in slide 7, we check five different event level cuts and track level cuts.

 The systematics from methodology could not be quantified for now. The AVFD model confirms that the ESS (c) accurately match the CME signal. AMPT model presented over-subtracts of v2-background. That is why we put a conclusion bullet that states it need further accessmenet.

 

 

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: "Zhiwan Xu" <zhiwanxu AT physics.ucla.edu>
Sent: Thursday, August 17, 2023 4:44:06 PM
Subject: Re: [Star-fcv-l] [Please Read]: FCV PWG meeting on 16+17/Aug/2023 Wed. 9:30 AM EDT

 

Hi Zhiwan,

   Thanks for this nice study. 

 

On S8, is the correction of (1 - v2)^2 to the intercept based on model closure studies or derived from some assumptions? From S4, we should get the Delta gamma_CME from the intercept directly, isnt so? Are your final results on S.16 including this correction?

For my own understanding, could you add the definitions for single and pair q_2^2 and v_2? Do you use the same particles for v2 calculation and q2^2 binning? 

What are the systematic uncertainty sources you include in the results?

 

thanks,

Sooraj

 

On Mon, Aug 14, 2023 at 4:51 PM Zhiwan Xu via Star-fcv-l <star-fcv-l AT lists.bnl.gov> wrote:

Dear conveners,
 I would like to give an update on the preliminary request for the upcoming QM2023 on this week's PWG meeting.
 Please find my slides in the following link:
 https://drupal.star.bnl.gov/STAR/blog/zhiwanxu/Preliminary-request-BES-II-CME-ESS
 Thank you.

Best,
Zhiwan

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

----- Original Message -----
From: "subhash via Star-fcv-l" <star-fcv-l AT lists.bnl.gov>
To: "STAR Flow, Chirality and Vorticity PWG" <star-fcv-l AT lists.bnl.gov>
Cc: "subhash" <subhash AT rcf.rhic.bnl.gov>
Sent: Monday, August 14, 2023 3:10:35 AM
Subject: [Star-fcv-l] [Please Read]: FCV PWG meeting on 16+17/Aug/2023 Wed. 9:30 AM EDT

Dear All,

We shall have FCV PWG meeting this WEDNESDAY (16/Aug/2023) at 9:30 AM
EDT. As you know the deadline for preliminary approvals is this week and
submission of talk/poster to FCV PWG is August 20. Therefore, we would
like to focus on Quark Matter related analysis updates and preliminary
approvals. Since we will not be able to go through all the remaining
talks and posters related related presentations in one day, we would
like to continue FCV discussions on _THURSDAY_ (17/Aug/2023) at 9:30 AM
EDT. Our tentative plan is following:

1. Wednesday -  QM talks: We would like to request the following
analyzers of QM talks to present: (Baoshan Xi et al, Xiaoyu Liu, Aditya
Prasad Dash, Yicheng Feng and Zhiwan Xu)

2. Thursday - QM posters: We would like to discuss your analysis update
and/or preliminary approvals. The following are the list of poster
presenters that we are aware of, please let us know if we miss any.
(Kosuke Okubo, Guoping Wang, Xing Wu, Junyi Han, Sharang Rav Sharma,
Vipul Bairathi, C.W. Robertson, Zhengxi Yan,  Emmy Duckworth, Chunjian
Zhang and Niseem Magdy)
Note that iff time allows we can take a few of the above poster
preliminary approvals on Wednesday as well.


For preliminary request you can use this template:
https://drupal.star.bnl.gov/STAR/system/files/Prelim_Request_template.pdf
We would also like to discuss the followings in order to assess your
analysis status:
-- list of promised results observables, collision system, beam energies
-- status/readiness of your analysis, new preliminary requests
-- any potential issues, show stoppers, centrality/embedding  etc.


The agenda items will be collected at:
https://drupal.star.bnl.gov/STAR/blog/jjiastar/bulkcorr
Zoom details are copied below.

Thanks and regards,
Prithwish, Zhenyu and Subhash


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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

 

 

--

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

 

--

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