STAR Flow, Chirality and Vorticity PWG

[Roy Lacey <roy.lacey AT stonybrook.edu>]

Fuqiang,

               This background estimate method is wrong and contrived to obtain any answer you want - I continue to wonder who is minding the store.

The experimental measurements at RHIC and the LHC speak volumes about the magnitude and patterns of the background - use them.

Roy

On Fri, Feb 17, 2023 at 4:16 PM Wang, Fuqiang via Star-fcv-l <star-fcv-l AT lists.bnl.gov> wrote:

Hi Jiangyong,

 

Nonflow is smaller in Ru+Ru because of the larger multiplicity.

If nonflow is significant, then it’s going to have an effect.

For example, if the central collisions have half/half flow/nonflow, then the effect is going to be larger than a factor of 2.

Obviously it depends on nonflow/flow mixture.

Even when the mixture isn’t big, there could be non-negligible effect because the flow ratio and the nonflow ratio are opposite in sign.

 

Best regards,

Fuqiang

 

 

From: Star-fcv-l <star-fcv-l-bounces AT lists.bnl.gov> On Behalf Of Jiangyong Jia via Star-fcv-l
Sent: Friday, February 17, 2023 1:59 PM
To: star-fcv-l AT lists.bnl.gov
Subject: Re: [Star-fcv-l] Request for PWGC preview for our isobar background baseline study

 

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

 

Dear Yicheng,

 

Could I ask what do you mean by true flow In slide 13 of the backup in the following PWGC talk? There are different method of estimate for flow, I do not see one can tell which one is true which one is not.  The fact that standard and two-subevent method give you the same ratio, suggest non-flow only comes in as a small dilution effect and can not change the isobar ratio a lot.

 

My point is that different methods extract different flow signal due to significant flow decorrelation effects in medium size system, so it is not very surprising one get somewhat different answer.  But I caution that you extensive non-flow subtraction method might introduce additional biases, i.e if  the method somehow removes a different amount of non-flow or even removes some flow signal. Also there are decorrelation effects which you might introduce method dependencies.  So I disagree with the conclusion of slide 13. 

 

By the way in a recent AMPT study (2301.01294), we do find flow contains a significant component delta that is uncorrelated with participant eccentricity in both RHIC and LHC, which serves to dilute the response to nuclear deformation effects.  However, we do not interpret this component as non-flow due to its relative mild dependence with Nch, and instead we argue there is a component of flow that is not captured by the PP due to subnucleon fluctuations or final state dynamical effects. 

 

Thanks,

Jiangyong

 

https://drupal.star.bnl.gov/STAR/system/files/IsobarNfBkg_PwgcPreview_v5.pdf

 

On 1/30/23 11:55 AM, Feng, Yicheng via Star-fcv-l wrote:

Hi FCV convenors,

 

We presented a paper proposal in the FCV meeting last week for our isobar background baseline study.

As the next step, I'd like to request a PWGC preview for that.

 

The slides presented last Wednesday can be found through the link below:

https://drupal.star.bnl.gov/STAR/system/files/PPRP20230125_v2.pdf

I wonder what else we need to prepare for this preview request.

 

Please let me know if you have any comments or need any additional information.

 

Thank you,

Yicheng for the PAs

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