STAR HardProbes PWG

[Youqi Song <youqi.song AT yale.edu>]

Hi Rongrong,

Yes, I agree that the discrepancy between data and MC could be due to different decay contributions.

I do have a similar plot for HERWIG, see attached. However, there's a caveat to these plots - for sign preserving decays, I have only included rho+->pi+pi0, K*+->K+pi0 and Delta+->p+pi0 (and the same for their antiparticles), since these are the dominant contributions for pi, K and p. Perhaps these three channels cover most of the sign-preserving decay contributions in PYTHIA, but since there seems to be more resonance decays in HERWIG, there is probably "contamination" in the orange and green curves.

For the top table on slide 21, here are other contributions that are >1% in HERWIG:

a0^+ 1.6% (0% in PYTHIA)

b1^+ 1.9% (PYTHIA doesn't produce this by default)

K*^+ 2.6% (2.7% in PYTHIA)

f2 2.9% (0% in PYTHIA)

a2^+ 1.5% (0% in PYTHIA)

Note that "0% in PYTHIA" means that PYTHIA can still produce these particles, and it's just they never happen to be a direct parent of a leading pi+ in jets.

Best,

Youqi

On Sat, Sep 21, 2024 at 3:17 AM Ma, Rongrong <marr AT bnl.gov> wrote:

Hello Youqi

Thanks for pointing me this very nice study. 

So the difference between data and MC could be due to that the resonance decay contributions are different, right? I feel this is an important aspect that should be stated.

Do you have a similar plot for HERWIG as what's shown on your slide 22 for PYTHIA? This could help us understand better the difference between the two. 

On your slide 23, top table, the percentages for those resonances in HERWIG add up to 43%. What other resonances do these leading pi+ originate from in HERWIG?

Best

Rongrong

On Sep 20, 2024, at 12:40 PM, Youqi Song <youqi.song AT yale.edu> wrote:

Hi Rongrong,

I would like to clarify this point you raised:

Here HERWIG7 and PTYHIA8 predict basically same r_c values. Given that HERWIG uses clusters while PYTHIA uses strings, does this mean there are something else that dictate r_c values rather than the fragmentation scheme? 

In addition to string or cluster hadronization, we now believe that resonance decays could also play a role. I have details of this study in my slide 9 and backup slides 22 and 23. But to summarize, I found that if I look at the parent of the leading track in jet, then: 

In PYTHIA, 50% of the time it’s from a quark or diquark, and 50% of the time it’s from resonance decay.

In HEREIG, 30% of the time it’s from a cluster, and 70% of the time it’s from resonance decay.

So one takeaway is that although PYTHIA and HEREIG predict the same r_c, there is actually a huge difference in how they arrive at it.

On the other hand, a lot of these resonance decays are what we call “sign preserving”, eg, rho+ goes to pi+ pi0, so when we measure a leading pi+, we still have the charge information from its rho+ parent.

Best,

Youqi

On Fri, Sep 20, 2024 at 11:14 AM Ma, Rongrong <marr AT bnl.gov> wrote:

Hello Isaac

Very nice set of slides to showcase STAR results. 

I have some comments for your consideration. 

- While it is already challenging to highlight 10 talks, still I think it will be good to include at least new preliminary results from posters since yours is the only STAR highlight talk. If we do not highlight them, others won't either. 

slide 2

- not sure if "Zr+Zr, Ru+Ru" in gray is easy to see on a projector

- remove "provides"

slide 5

- text beneath is a bit too small

- "perfectly correlated" points to empty space?

- "Pythia predicts more string-like fragmentation": I thought there is only string-like fragmentation in Pythia, but this statement seems to imply that there are other fragmentation mechanisms. What are they?

- Here HERWIG7 and PTYHIA8 predict basically same r_c values. Given that HERWIG uses clusters while PYTHIA uses strings, does this mean there are something else that dictate r_c values rather than the fragmentation scheme?  

slide 8

- It might be better to show jet dv1/dy vs. pt plot. 

- I do not think our data can rule out possible pT dependence. The statement of "independent of jet p_T" is a bit too strong, especially given that we do not correct for jet p_T. 

slide 9

- I suggest to show the R = 0.4 plot since the effect is supposed to be stronger for larger jets.

- It is important to highlight in the figure and emphasize in the text that this measurement is for jets with pT_raw > 9 GeV/c and pT_cons > 2 GeV/c. The effect could be there if we go to lower jet or consistent pT. 

 

slide 10

- since you focus on radius dependence, maybe remove the left figure to save you some time

- "predict minimal suppression": I think you want to say minimal radius dependence of the suppression

slide 12

- The text size is significantly larger than other slides. Maybe make them consistent

- Consistent with SPS at 17.3 GeV

slide 14

- For the LHC results, are they measured using mid-rapidity J/psi and mid-rapidity multiplicity as we do? If not, it won't be a fair comparison. 

slide 16

- Your conclusions are based on the extracted temperatures. I suggest to make them significantly bigger. 

slide 19

- It might be useful to make it clear that this measurement is w.r.t. the event plane

slide 20

- "First measurements": many other results are also first measurements, or you mean something else?

- How does r_c cleanly separate perturbative and non-perturbative physics?

- Add some qualification to the third bullet

slide 21

- "minimal impact of regeneration at RHIC energies": on slide 12, model calculation shows that about half of the J/psi come from regeneration at 200 GeV. Probably add "below 62.4 GeV"?

- Third bullet does not read like a physics message

Best

Rongrong

On Sep 19, 2024, at 4:01 PM, Mooney, Isaac <isaac.mooney AT yale.edu> wrote:

Hi all,

v2 uploaded now with comments from the STAR practice talk addressed. Will be uploading a v3 with comments from the Yale group implemented as well. Not sure yet of the timescale for that version as I need to prepare for the trip tonight.

Thanks,

Isaac

On Sep 18, 2024, at 22:27, Mooney, Isaac <isaac.mooney AT yale.edu> wrote:

Hi all,

Trimmed version (v1) uploaded now (aesthetics still to be improved).

Thanks,
Isaac

On Sep 18, 2024, at 20:01, Mooney, Isaac <isaac.mooney AT yale.edu> wrote:

Hi all,

This is a rough draft of the talk. The organizers today let us know that the talks in this session are 15’+5’. So I am in the process of significantly trimming down. I’ll upload a new draft when that is done, but wanted to let you see the talk as soon as possible. PS I am aware that the aesthetics are not good right now — I will improve them in a future version.

Thanks,
Isaac

On Sep 18, 2024, at 19:55, webmaster AT star.bnl.gov wrote:

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