STAR Flow, Chirality and Vorticity PWG

["Tang, Aihong" <aihong AT bnl.gov>]

Hi CW,

Thank you for your response. Upon further consideration, I have additional questions and comments, besides the issue of your results from Full EP and subEP being not consistent.

1) In your procedure, you obtained two samples of kaon pairs, all derived from phi decay. Note that these samples contain pairs where both daughters are from the same real phi, as well as pairs where the K+ and K- are purely combinatorial (i.e., K+ from one phi and K- from another phi). You calculated <cos^2> from the first sample, considering it as the case without detector acceptance. For the second one, you unfolded kaon spectra from data and regarded its <cos^2> as the case with detector acceptance. The difference between these two cases forms your correction. However, in both of your cases, pairs were formed using either rotation or mixed events. These actions destroy the intrinsic correlation between K+ and K- arising from real phi decays. How can you apply the correction obtained from this procedure to realistic cases where the K+ and K- have intrinsic correlation due to some pairs originating from real phi decays ?

2) You demonstrated the ratio obtained with rotation and mixed events, but the input rho_00 was 1/3. Could you repeat this with a larger rho_00, such as rho_00= 0.5 ?

3) Could you repeat your correction procedure with a tighter eta cut of |eta|<0.5 ? If the procedure is self-consistent, the corrected number should remain the same, given that rho_00 is almost flat versus rapidity at 200 GeV.

4) I want to emphasize again the importance of providing derivation supporting whether the correction involves subtraction or multiplication. If one believes the effect is a scaling effect, multiplication is used for the correction. Conversely, if one believes the effect is merely an offset, subtraction is preferred. The choice between these two methods cannot be arbitrary, as these scenarios reflect distinct understandings of the correction procedure. They are _not_ equivalent to each other as Fuqiang claimed during the meeting. 

Thanks,

Aihong

On May 5, 2024, at 12:02 AM, Robertson, Charles William <rober558 AT purdue.edu> wrote:

Hello Aihong, 

Please see my reply below. 

Thank you,

-CW

---

From: Tang, Aihong <aihong AT bnl.gov>
Sent: Friday, May 3, 2024 9:13 AM
To: STAR Flow, Chirality and Vorticity PWG <star-fcv-l AT lists.bnl.gov>
Cc: Robertson, Charles William <rober558 AT purdue.edu>
Subject: Re: [Star-fcv-l] FCV PWG meeting on 01/May/2024 Wed. 9:30 AM EDT

 

---- External Email: Use caution with attachments, links, or sharing data ----

Hi CW, 

I'd like to follow up on your presentation from Wednesday (May 2nd).

In your "true" phi decay combinatorial, you simulated a set of real phi with realistic pt spectra and v2, and then allowed them to decay. Now instead of rotating a daughter in the transverse plane, you used mixed events. However, I'm curious about how you maintain the realistic pt spectra for the "true" phi in this approach. From my perspective, while the rotation distorts rho_00, using mixed events distorts the pt spectra.

Mixed events are just another way to assess the combinatorial decay kaon <cos^2>. There is no mixed event real phi pt. spectra to talk about.

It's worth noting that the small correction you obtained at 200 GeV cannot necessarily be used to justify the correctness of the procedure itself. Corrections tend to be small at 200 GeV anyway, regardless of the method chosen.

Additionally, as I see it, when I commenting on the rotation, you used mixed events, and when I questioning why the correction involved multiplication, you switched to subtraction without providing justification for taking a such change. This raises an important point I wanted to emphasize: this procedure needs a bottom-up derivation to back up its rationale behind each step, as a well-defined procedure should indeed be just that --- well defined. It cannot rely on arbitrary assumptions or guesswork.

Subhash and other convenors suggested we look at mixed events as another way to get the combinatorial <cos^2> vs. mass for decay kaons. Both mixed events and rotated pairs are techniques to look at the combinatorial decay bkg. 

For the correction, as we explained in the meeting, taking the ratio or difference are essentially equivalent for small corrections to finite rho00. So, for now, we show the correction both ways.

Thanks,

Aihong

On May 1, 2024, at 12:13 PM, Robertson, Charles William via Star-fcv-l <star-fcv-l AT lists.bnl.gov> wrote:

Hello,

My slides for today can be found here: https://drupal.star.bnl.gov/STAR/system/files/SpinAlignmentFCV050124_1.pdf

Thank you,

-CW

---

From: Star-fcv-l <star-fcv-l-bounces AT lists.bnl.gov> on behalf of Zhengxi Yan via Star-fcv-l <star-fcv-l AT lists.bnl.gov>
Sent: Wednesday, May 1, 2024 12:06 PM
To: STAR Flow, Chirality and Vorticity PWG <star-fcv-l AT lists.bnl.gov>
Cc: Zhengxi Yan <zhengxi1yan AT gmail.com>
Subject: Re: [Star-fcv-l] FCV PWG meeting on 01/May/2024 Wed. 9:30 AM EDT

 

---- External Email: Use caution with attachments, links, or sharing data ----

Hi All,

Slides for today are in the link below.

https://drupal.star.bnl.gov/STAR/blog/zyan/dAu-two-particle-correlation

Best,

Zhengxi

On Tue, Apr 30, 2024 at 6:11 PM Zhengxi Yan <zhengxi1yan AT gmail.com> wrote:

Dear Subhash and all,

I would like to present "2-Particle Correlation in d+Au at 200 GeV".

If time permits, please add me to the agenda. 

Best,

Zhengxi

On Sun, Apr 28, 2024 at 11:11 PM subhash via Star-fcv-l <star-fcv-l AT lists.bnl.gov> wrote:

Dear All,

We shall have our weekly FCV PWG meeting this Wednesday (01/May/2024) at 
9:30 AM EDT. If you wish to present please let us know. The agenda will 
be collected at: https://drupal.star.bnl.gov/STAR/blog/jjiastar/bulkcorr
Please send us your slides by Tuesday. Zoom details are copied below.


Please take a note of the STAR internal deadlines for CPOD and SQM. 
Presenters are requested to give regular updates in the PWG.
      - CPOD presentations due to PWG by May 6. New preliminary approvals 
should be this week of April 29
      - SQM presentations due to PWG by May 20. New preliminary approvals 
should happen the week of May 13
If you are requesting new STAR preliminary results, you should prepare 
supporting materials following: 
https://drupal.star.bnl.gov/STAR/system/files/Prelim_Request_template.pdf

      - STAR internal deadline for submitting abstracts for HP 2024 to 
the PWGs is May 11

Thanks and regards,
Prithwish, Zhenyu and Subhash


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