Skip to Content.
Sympa Menu

star-fcv-l - Re: [Star-fcv-l] Decompose Purdue Group's Correction-Proceduer for Detector Effect on Global Spin Alignment

star-fcv-l AT lists.bnl.gov

Subject: STAR Flow, Chirality and Vorticity PWG

List archive

Chronological Thread  
  • From: "Robertson, Charles William" <rober558 AT purdue.edu>
  • To: Jinhui Chen <chenjinhui AT fudan.edu.cn>, "STAR Flow, Chirality and Vorticity PWG" <star-fcv-l AT lists.bnl.gov>
  • Cc: "Wang, Fuqiang" <fqwang AT purdue.edu>
  • Subject: Re: [Star-fcv-l] Decompose Purdue Group's Correction-Proceduer for Detector Effect on Global Spin Alignment
  • Date: Sat, 18 May 2024 20:55:21 +0000

Hi Jinhui,

In the Nature paper, the detector effect is modeled by the F parameter:
1 +F*cos^2(\theta*), and it's coupled with the EP resolution to obtain a single correction factor for rho00.

One can also do it in two steps, correcting the data by the F parameter first and then correcting for the EP resolution effect.
These two ways should be equivalent.

My question is not about the correction procedure, but about the correction numbers themselves.
This is the table of correction numbers we deduced from the Nature paper:
Energy 
Our EP Res
Nature raw rho00
Nature rho00
Nature corr.
EP Res Corr'd rho00
Nature detector corr.
11
0.348
0.3503
0.365
0.0147
0.3666
-0.0016
19.6
0.399
0.3453
0.359
0.0137
0.3551
0.0039
27 (Run 18)
0.431
0.3468
0.3608
0.0140
0.3569
0.0039
39
0.459
0.3364
0.3378
0.0014
0.3384
-0.0006
62
0.484
0.3423
0.3488
0.0065
0.3480
0.0008
200 (Run 14)
0.590
0.3341
0.3358
0.0017
0.3344
0.0014

This would mean that your F numbers are irregular and vary over energy by a large amount, positive and negative. Why?
More specifically, the F numbers are negative at 11 and 39 GeV and positive at all other energies by significant amounts.

This is probably the partial reason why the 39 GeV data point is so low.
However, from the AN Fig. 21 on p.24 the F values seem all negative (e.g. the red points at each energy).

Thank you,
-CW


From: Jinhui Chen <chenjinhui AT fudan.edu.cn>
Sent: Tuesday, May 14, 2024 10:09 AM
To: STAR Flow, Chirality and Vorticity PWG <star-fcv-l AT lists.bnl.gov>
Cc: Robertson, Charles William <rober558 AT purdue.edu>; Wang, Fuqiang <fqwang AT purdue.edu>; chenjinhui AT fudan.edu.cn <chenjinhui AT fudan.edu.cn>
Subject: Re: [Star-fcv-l] Decompose Purdue Group's Correction-Proceduer for Detector Effect on Global Spin Alignment
 
---- External Email: Use caution with attachments, links, or sharing data ----

Hi CW,

As Chensheng is not able to answer your question, and Xu is fully occupied, I try to answer your question in the last part of the email,  

A separate but related question: the nature paper has a single correction factor lumping the EP resolution and detector effects together. The corrections are (col. 5).

I guess that you used the same equation as Eqa.(20) of the analysis note to correct for the event plane resolution, right?
https://drupal.star.bnl.gov/STAR/starnotes/private/psn0748

I think that the difference between your iteration and the paper is Chensheng/Xu used the Eqa.(26), for the reasons described in the same page of the analysis note.

Regarding whether one should do the event plane resolution correction and detector acceptance correction separately or combined, they are same for the cos\thetastar^2 term, as written in the Eqa.(75) of the analysis note, where A take care of the event plane resolution, F is for the acceptance.

All the best,
Jinhui

 

On May 12, 2024, at 05:07, Robertson, Charles William via Star-fcv-l <star-fcv-l AT lists.bnl.gov> wrote:

Hello All,

For our correction procedure, the question we ask:
What is the detector effect on pairs of kaons which have (1) identical single-particle level properties as the phi decay kaons but (2) no pair-wise physical correlations?
For (1), we weight the kaons in real data to match the decay kaon kinematics in real data.
For (2), we use mixed-events or rotated pairs.

We will present an update at next week's FCV meeting. 

To your specific comments:
However, while this procedure matched kaon daughter spectra to that from \phi-decayed kaon, it inadvertently distorted the actual \phi spectra. The \phi spectra in group 2 differ from the input in group 1, defeating the purpose of maintaining uniformity across all parameters.

The \phi spectra are not the question here. We are interested in the combinatorial pairs of "decay daughters." 
What we measure in experiment (mixed-event or rotated) are combinatorial pairs of kaons: phi1K-phi2K,phiK-K,K-K. Here phi*K denotes K from a phi decay, K denotes a primordial kaon. Both phi*K and K are after detector effect, and K is scaled to match phi*K by a weight, i.e., phi*K/(phi*K+K).
The detector does not care if a kaon is from a phi decay or not.

So, through this procedure using real data mixed-events or rotated pairs, we have effectively formed <cos^2\theta*> of combinatorial pairs of phi-decay kaons.
Those kaons are impacted by detector effects.

On the other hand, we have the combinatorial <cos^2\theta*> of decay kaons before any detector effect by using the published phi data. 
>From the difference of these two, we get the correction.

A separate but related question: the nature paper has a single correction factor lumping the EP resolution and detector effects together. The corrections are (col. 5).

Energy 
Our EP Res
Nature raw rho00
Nature rho00
Nature corr.
EP Res Corr'd rho00
Nature detector corr.
11
0.348
0.3503
0.365
0.0147
0.3666
-0.0016
19.6
0.399
0.3453
0.359
0.0137
0.3551
0.0039
27 (Run 18)
0.431
0.3468
0.3608
0.0140
0.3569
0.0039
39
0.459
0.3364
0.3378
0.0014
0.3384
-0.0006
62
0.484
0.3423
0.3488
0.0065
0.3480
0.0008
200 (Run 14)
0.590
0.3341
0.3358
0.0017
0.3344
0.0014

We can calculate the EP resolution effect easily (col.6). From that we can get the effective detector correction of the nature paper (last column). Those detector corrections are positive and negative and vary with a rather large range. Why is that? We expect them all to be negative.
Note, we have used our subevent EP resolution, which should be slightly smaller than the nature paper resolution because we exclude all kaons from EP reconstruction. This means that effective detector corrections in the nature paper are event more positive.

Thanks,
-CW



From: Star-fcv-l <star-fcv-l-bounces AT lists.bnl.gov> on behalf of Tang, Aihong via Star-fcv-l <star-fcv-l AT lists.bnl.gov>
Sent: Friday, May 10, 2024 11:09 PM
To: STAR Flow, Chirality and Vorticity PWG <star-fcv-l AT lists.bnl.gov>
Cc: Tang, Aihong <aihong AT bnl.gov>
Subject: [Star-fcv-l] Decompose Purdue Group's Correction-Proceduer for Detector Effect on Global Spin Alignment
 
---- External Email: Use caution with attachments, links, or sharing data ----

Dear all,

I am quite puzzled by the Purdue group's claim made at the FCV meetings. They asserted that a derivation for their correction procedure for detector effects in global spin alignment analysis is unnecessary. I firmly believe that whenever possible a robust correction procedure should be a bottom-up approach, wherein all components are thoroughly understood and their contributions are under control.

Since the Purdue group failed to provide such a derivation despite a number of requests made to them, I took some time to decompose and write down the terms involved in their procedure. Upon careful examination, it was found that the Purdue group's correction procedure does not yield the intended correction.

You can find the link to the document here:

Thanks,

Aihong
_______________________________________________
Star-fcv-l mailing list
Star-fcv-l AT lists.bnl.gov
https://lists.bnl.gov/mailman/listinfo/star-fcv-l




Archive powered by MHonArc 2.6.24.

Top of Page