STAR HardProbes PWG

[Rosi Reed <rosijreed AT lehigh.edu>]

Hi Rongrong,

I'm a little confused, the greatest contribution to non-flow comes from jets, which is what Tristan is looking at.  So we wouldn't want to subtract non-flow from his results, basically the non-flow is his results.  There is perhaps a question of how much flow is contaminating his results at 5 GeV.  I think writing v_2^obs for the tracks is fine - the main point is that the the track analysis agrees with the jets, so there isn't something in the jet finding that's creating the high v2, and that the tracks agree with Shengli, so that Tristan's methodology is validated (as is Shengli's).  But they're looking at very different physics.

The large value of v2 for flow is also interesting in terms of what all this means.

Cheers,

Rosi

On Tue, Aug 29, 2023 at 8:58 AM Ma, Rongrong via Star-hp-l <star-hp-l AT lists.bnl.gov> wrote:

Hello Tristan

Thanks for looking into this quickly. 

Shengli's study shows that more than 50% of the v2 signal observed at 3-4 GeV/c is due to non-flow effect. After non-flow subtraction, the real v2 signal decreases with pT above 3 GeV/c, while your result shows a clear increasing trend. If I follow the trend of Shengli's result, the real v2 could be very small at high pT. So, I think we probably should at least label your plot as "v_2^obs", and state clearly that the non-flow contribution could be very large and has not been subtracted yet. This also raises the question of how much non-flow contamination is there in your Isobar results. 

Best

Rongrong

On Aug 29, 2023, at 12:03 AM, Tristan Protzman <tlp220 AT lehigh.edu> wrote:

Hi Rongrong,

I have managed to throw together a quick v2 on part of the data down to 0.5 GeV, see slide 16 of https://drupal.star.bnl.gov/STAR/system/files/preliminary_figure_request_OO_v2.pdf.  I believe the open blue squares in Shengli's results are the closest method to what I am using, where we see general agreement interpolating between the 20-40% and 40-60% with the non-subtracted EPD based method.  

Cheers,

Tristan 

On Aug 28, 2023, at 12:10 PM, Ma, Rongrong via Star-hp-l <star-hp-l AT lists.bnl.gov> wrote:

Hello Tristan

I would like to follow up on the comment I brought up during the PWG meeting about the single track v2, which if I remember correctly is about 0.15 at 4 GeV/c. On the other hand, slide 9 of https://drupal.star.bnl.gov/STAR/files/OO-ShengliHuang-QM2023_2.pdf shows that charged hadron v2 is about 0.075 at 2.5 GeV/c in 20-40% centrality. Have you looked at single track v2 down to say 2-3 GeV/c, and check if your results are consistent with Shengli's? Or at least we should put both results together and see if we have a consistent picture. 

Thanks. 

Best

Rongrong

On Aug 25, 2023, at 4:33 AM, webmaster--- via Star-hp-l <Star-hp-l AT lists.bnl.gov> wrote:

Dear Star-hp-l AT lists.bnl.gov members,

Tristan Protzman (tlp220 AT lehigh.edu) has submitted a material for a review,  
please have a look:
https://drupal.star.bnl.gov/STAR/node/64873

Deadline: 2023-09-03
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If you have any problems with the review process, please contact  
webmaster AT www.star.bnl.gov
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Rosi Reed
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Lehigh University
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