STAR Flow, Chirality and Vorticity PWG

["Wang, Fuqiang" <fqwang AT purdue.edu>]



Hi Shengli,

My last email was addressing your second last message. I just noticed this last message of yours. Please see my reply below. 

Best regards,

Fuqiang

On Jan 24, 2024, at 10:43 PM, Wang, Fuqiang <fqwang AT purdue.edu> wrote:



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Well, taking face value, the nonflow would 0.75+/-0.25 (with 1 unit standing for the total nonflow in full-event) as done in the U paper. The nonflow one would want to achieve in the corrected data would be (0 +/- some syst. uncertainty).

With that said, |Deta|>0.7 and subevent 0.1<|eta|<1 aren't the same.

Best regards,

Fuqiang

---

From: Shengli Huang <shengli.huang AT stonybrook.edu>
Sent: Wednesday, January 24, 2024 10:34 PM
To: 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] Nonflow paper in today PWG discussion

 

You don't often get email from shengli.huang AT stonybrook.edu. Learn why this is important

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I apologize for the name typo, Fuqiang.

Additionally, I have compared v22(Full Event)=10e-4 from your newly submitted paper [https://drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_L_v27.pdf] with STAR published v22(deta>1.0)=8.5e-4 in [https://arxiv.org/pdf/2109.00131.pdf] for 0-5% RuRu collisions. There is only a 15% difference between them, and we believe this difference arises mainly from nonflow.

These full event and subevent V22 numbers are essentially from the isobar blind analysis paper. Yicheng reanalyzed data as well and what he got were consistent with the published data.

Indeed there’s only 15% reduction from full event to subevent. Part of the reason is that there’s a significant track merging effect in full event causing an “anti-nonflow” sort to speak, which is more severe in recent data than old data (tracking algorithm has evolved). Nevertheless in the 2015 nonflow publication we’ve excluded the small Deta from analysis. 

Referring to Fig4 in [https://arxiv.org/pdf/1409.2043.pdf], we can estimate the ratio of nonflow between deta>1.0 and deta>0, which is approximately 1/3. Based on these figures, the nonflow contribution would be only 22% in 0-5% RuRu collisions. However, in your newly submitted paper, the nonflow estimation is reported as 60%.

It would be dangerous to take the AuAu nonflow ratio estimate and directly apply to isobar. Also I don’t think the subevent in the isobar data is Deta>1.

Regarding the 60%, this is epsilon_nf which is defined as nonflow/(v2^2-nonflow). So 60% means 60%/(1+60%)=40% nonflow. This is consistent with central AuAu nonflow of 20% (multiplicity dilution).

Please let me know if any of this is unclear.  

Best regards,

Fuqiang

I am having difficulty understanding this inconsistency. Could you provide further clarification or insights into this matter?

Shengli

On Wed, Jan 24, 2024 at 9:37 PM Shengli Huang <shengli.huang AT stonybrook.edu> wrote:

Dear Fuqing,

    If full event nonflow is a factor two of subevent with deta>0.7 as paper state, then the difference between full event and subevent will cover the nonflow of subevent, right? 

Thanks!

Shengli

On Wed, Jan 24, 2024 at 9:10 PM Wang, Fuqiang via Star-fcv-l <star-fcv-l AT lists.bnl.gov> wrote:

Hi Shengli,

Yes, this is the right paper. Fig.5 left most central point (black/open circle)^2~10% (note the open is scaled down by x2). This is for Deta>0.7. From Fig.4 left full event is about x2 of that at Deta>0.7. So that’s the 20% I was saying. The uncertainties are relatively large. 

Best regards,

Fuqiang

On Jan 24, 2024, at 1:49 PM, Shengli Huang via Star-fcv-l <star-fcv-l AT lists.bnl.gov> wrote:



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Dear Fuqiang,

     I just read the paper about nonflow in PWG discussion today:

https://arxiv.org/pdf/1409.2043.pdf. 

First I hope I find the correct one and understand it accurately. 

According to this paper, it is stated that the nonflow is only 5% in 20-30% AuAu with deta>0.7, which differs significantly to 20% in central AuAu as you said. Can you tell us more details to understand it?

Thanks!

Shengli

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