STAR Flow, Chirality and Vorticity PWG

[申迪宇 <dshen AT rcf.rhic.bnl.gov>]

Hi ShinIchi,

Thanks for your attention, please find my answers below:

1. Could you please tell me the importance on the azimuthal acceptance correction for the PIDed particle for this measurement?

 A: The azimuthal acceptance correction I assume you are referring to the phi-weight. It was introduced to minimize the non-zero a1=<sin(\phi-\Psi), because a1 should be zero from the physics. The comparison of \Delta v1-slope before and after phi-weighting can be found in plots of Fig13, Fig 23, Fig 33, Fig 45, Fig 54, and Fig 63 in my analysis note. By looking at those plots, we didn’t find obvious difference. 

2.Do you see any difference between X and Y contributions of the event plane resolution from ZDC? 

 A: The X and Y contributions do you mean the X and Y component of Q vector? I don’t have that plot now. The event plane resolution is determined by east-west ZDC-SMD. For AuAu 200 GeV, I have checked the resolution obtained in this analysis with the publication of "PHYSICAL REVIEW C 98, 014910 (2018)”, it looks good for me. I have also compared the final v1 in this analysis with the BEI publication as illustrated in plots Fig.14, Fig. 24 and Fig. 34 in my analysis note. Those plots give us confidence of the event plane reconstruction. 

3. For your a1 parameter (sin term in stead of cos), they are mostly zero, but some of the delta_a1 parameters are comparable to delta_v1, which might be needed to be studied and discussed more in the PWG, which could be important and interesting, is it somewhat significant only for pi+/pi-?

A: The \Delta a1 measurement serve as the base line as there should be no splitting in a1. In principal the a1(and \Delta a1) should be zero within uncertainty, and it is at least for kaons and protons. For pion, there is residual deviations which is more obvious in central collisions. We have tried many ways to minimize it , like \eta asymmetry cut and phi-weighting, but this is what we have. As the \Delta v1 splitting for pion is not significant, and introducing \Delta a1 is for the safety of drawing conclusion. For that purpose, we are safe to say we didn’t observe v1 splitting of pion. 

For the question of why it is significant only for pion, I thinks this deviation may comes from the systematic uncertainty which is small and the statistical uncertainty for pion is small so it makes the deviation looks 'significant’. 

4. Do you understand why the signal seems to be stronger including phi-weighting correction (default) than without the weighting correction? 

 A: Actually the \Delta v1-splitting looks better before phi-weighting, for example Fig.23 shows more obvious decreasing trend in right panel(without phi-weighting). What driven us to use the phi-weighting correction is we found the a1(instead of \Delta a1) is more consistent with zero after weighting. 

5. Do you use other event plane information from TPC or BBC or EPD to determine the resolution of ZDC?

A: I didn’t. As the resolution looks good by using east-west ZDC-SMD in 200 GeV, I don’t think we will have large improvement on the resolutions by using other detectors. For current analysis, we have enough significance(larger than 5\sigma), but in the future we do have plan to use EPD in isobar.

    

6.Could you describe a little more about how you determine (and calibrate) the event plane to get the event plane and resolution? 

(1) gain correction on each strip in ZDC/SMD

 There are 8 horizontal and 7 vertical strips on east and west side. For each strip I have a histogram to fill the corresponding ADC signal, there are (7+8)*2 histograms. I looped all good events, then I fit the curve with a exponential function, A*exp(-B*x), the fitted parameter B is used as gain factor.   

This has been done for run14 Au+Au 200 GeV, run16 Au+Au 200 GeV, Zr+Zr, Ru+Ru separately.

(2) re-centering of Qx and Qy.

The good events have been grouped according to the run number and centrality. For example, events with centrality 0-5% and run number start from 15098100 to 15098110 will be grouped together. The mean value of Qx and Qy is calculated in each groups. Qx of an event is calculated by \sum(xi*wi)/\sum(xi), where xi is the position of a strip, wi is the corresponding ADC-signal. 

In the analysis, I subtract the <Qx> from the raw Qx of an event, then use the new Qx, Qy fill the shifting parameter. This is done for east and west separately.

 

(3) Fourier flattening of Psi.

The equation is illustrated in my analysis note, I use it up to n=20. The events are grouped as what I did in recentering. For this step, I first shift the \Psi_east and \Psi_west, then combine them to get the full event plane. 

The full event plane has also been shifted to make it more smooth.

Best,

Diyu

 

On Mar 15, 2022, at 11:40 PM, ShinIchi Esumi via Star-fcv-l <star-fcv-l AT lists.bnl.gov> wrote:

Dear Diyu
Could you please tell me the importance on the azimuthal acceptance correction 
for the PIDed particle for this measurement? Do you see any difference between 
X and Y contributions of the event plane resolution from ZDC? For your a1 
parameter (sin term in stead of cos), they are mostly zero, but some of the 
delta_a1 parameters are comparable to delta_v1, which might be needed to 
be studied and discussed more in the PWG, which could be important and 
interesting, is it somewhat significant only for pi+/pi-?  Do you understand why 
the signal seems to be stronger including phi-weighting correction (default) than 
without the weighting correction? Do you use other event plane information from 
TPC or BBC or EPD to determine the resolution of ZDC? Could you describe a 
little more about how you determine (and calibrate) the event plane to get the 
event plane and resolution? (1) gain correction on each strip in ZDC/SMD, 
(2) re-centering of Qx and Qy, (3) Fourier flattening of Psi. Everything is done 
as a function of centrality and z-vertex? Then get the resolution by two-sub 
method with chi extraction etc...
Best regards, ShinIchi

On Mar 1, 2022, at 18:38, dshen via Star-fcv-l <star-fcv-l AT lists.bnl.gov> wrote:

Dear Conveners and all,

Please find the slides for our updates via link below:
https://drupal.star.bnl.gov/STAR/system/files/Updates%20on%20paper%20proposal%20II.pdf

We also prepared a draft of analysis note for your reference:
https://drupal.star.bnl.gov/STAR/system/files/main_11.pdf

This update mainly focus on addressing the comments collected in my last presentation.
Just a quick reminder, those comments are:

General recommendation:
Combine relevant items from various presentation materials and prepare
a document with analysis details in one place and share with FCV. This
will help focus our discussion, help experts to pinpoint their
comments and save time for PAs and everyone. Also, this document can
eventually metamorphose into the analysis note. While making further
materials please consider addressing the following points, maybe make
small notes on the points.

i) Estimate Delta_v1 expected from coulomb interaction in peripheral collisions

ii) Address how to understand large Delta_v1 is seen for protons and
not for kaons and pions.

iii) It seems we see a difference in "Delta_v1" vs "y" between Au,
Zr+Ru species. How do we understand this system size dependence?

v) Consider adding differential v1 measurements, pt differential v1,
v1 separately for Zr+Zr and Ru+Ru species (if statistics is not enough
can consider two pt bins for example). If <pT> values are different
between different species it will be good to show the pT dependence
for each species even with two pt bins.

vi) Is it possible to estimate the relative contribution of
transported quark in Delta_v1?

vii) Consider a model calculation w/o EM field (e.g. UrQMD, AMPT) to
strengthen the point that the centrality dependent sign change cannot
be reproduced by non EM-field effects.

viii) Short summary for why PRX (250 words) will be useful. Usually
published along with paper. For now even a short para will be helpful
to move forward (e.g. during PWGC proposal).

Thanks,
Diyu


On 2022-03-01 15:08, dshen via Star-fcv-l wrote:

Dear Conveners,
I would like to give an update on the research of change splitting of
v1 in Au+Au and isobar collisions at 200 GeV.
The slides will be send later.
Best,
Diyu
On 2022-02-28 14:34, subhash via Star-fcv-l wrote:

Dear All,
We shall have our FCV PWG meeting this Wednesday (02/Mar/2022) at 9:30
AM in BNL (NY time zone). If you would like to present, please let us
know. Please try posting your slides by Tuesday. The agenda items will
be collected at:
https://drupal.star.bnl.gov/STAR/blog/jjiastar/bulkcorr
Thanks and regards,
Jiangyong, Prithwish and Subhash
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