STAR HardProbes PWG

["Mooney, Isaac" <isaac.mooney AT yale.edu>]

Hi Nihar,

Sorry for my delay in getting you comments (below) on this nice analysis and manuscript/note. Most comments are relatively minor.

Thanks to you and the other PAs for your consideration,

Isaac

Paper:

31 - Subscript "c".

34 - This sentence seems to suggest that Hard-Probes-like working groups in RHIC and LHC experiments haven't done much. And since this paragraph seems to build to this point (giving some detail about the theoretical expectation for microscopic structure before saying that experimental evidence is lacking), I'm not sure the paragraph is necessary. If the last sentence is only softened (e.g. to "However, there is still much to learn about the microscopic structure of the QGP." or similar) rather than removed, it would still work, but I think if at some point there is a need for trimming, this paragraph would be a good candidate.

42 - "together with the" -> "before the formation of the"

57 - the level of jargon explodes from this sentence on to the end of this section. On line 41 you have just defined a "jet" and suddenly we're talking about direct photon triggers, ET, pT, jet resolution parameter, semi-inclusive, central/peripheral, event mixing, fragmentation, all without definitions. I understand the space constraint, but this is a bit extreme, and I think will turn the general reader off quickly. Since this is aiming for PRL I think that should be avoided if possible.

64 - "is observed"

65 - Missing space. Also l. 126, 

116 - "GeV"

125 - This abbreviation was already defined in line 57.

133 - It might be worth adding a comment here that the resulting jet pT can be negative if the background fluctuates downward under the jet, compared to the event-wide rho, especially if the jet is combinatorial and low-pT. This would be helpful later (l. 177) where you talk about the negative pT region.

170 - "corrected for" or "addressed"

192 - I was initially fine on l. 136 with leaving a description of unfolding for later, but now that you're using the concept of unfolding as if the reader necessarily knows what that is, I think it should be a bit more clear before this (along the lines of my comment on l. 57). It could be as simple a fix on l. 136 as "is refined during a deconvolution of detector effects called "unfolding"" or similar.

230 - Should it be concerning that this off-diagonal weight for 10-15 GeV R = 0.5 jets is so large? This requires a lot of belief in the simulation accuracy, right? Which measured->true mapping is the one that is 44%? [Ah, I see from the analysis note that it's the 2.2-2.5 bin, but why is the 55% not quoted as the maximum then?]

233 - I'll use this as another opportunity to raise a comment that we made during the institutional review of the PRC paper :D. The gamma_dir determination relies on the assumption that the fragmentation photon near-side correlated hadron yields are similar to pi0s. It was stated in response to the request for justification of this assumption that "it is possible that the resulting direct photons have some fraction of fragmentation photons remaining". I think a comment like this should be made in this paper to really bring it to the attention of the reader that there may still be some fragmentation photon contribution, the degree of which is not known.

242 - 

How do I see that the yield is larger in R = 0.5 than in R = 0.2 from Figure 1? The blue distributions are wider for R = 0.5 but also have a lower peak height, so it seems difficult to conclude by eye.

Similarly, I get the "falling \Delta\phi distribution" from comparing across subpanels within a given radius, yes? For R = 0.5 it seems pretty clear by eye, but for R = 0.2 it seems much closer, and qualitatively much different from how precipitously the yield drops between these same two \Delta\phi bins in Figure 2 for this radius. So I don't know if this actually supports the argument that the features in Fig. 2 "are not generated predominantly by corrections."

295 - I'm sorry but I don't understand why the wake would cause a suppression of the R = 0.2 jets w/r/t pp, so I don't see how it does "accommodate all of these observations". I know there may be a contribution from the depletion wake, but not one that I could see producing this behavior for the R = 0.2 jets. But maybe my intuition is incorrect.

328 - Sorry I'm very confused by this statement. How is the suppression "negligible" for the small radius jets? E.g. the bin around 2.6 for the 10 - 15 GeV gamma+jet is at ~0.2 +- 0.1. I'm not sure how many sigma the deviation from 1 is, but it seems sizable to me.

330 - How can we say "All of these measurements can be described consistently by medium-response or wake effects" when in the next sentence we say "theoretical calculations incorporating jet quenching and QGP wake effects fail to describe the data"? I think we need to be more careful not to oversell this conceptual argument as a direct conclusion from the data/theory.

Analysis note:

62 - Is this statement just out of date?

174 - "Figure 9", if I'm not mistaken, but in both Fig. 9 and Fig. 23 I only see one jet pT range, not "three recoil jet pT,jet^ch ranges".

291 - I don't think there's a figure for the distributions of these observables currently.

343 - "Fig 14"?

344 - "< 0", right?

Fig 14 - In the paper it's claimed that the ratio between YSE and YME is "seen to be independent of pT,jet^reco,ch within statistical error over a pT,jet^reco,ch range in which the yield varies by several orders of magnitude", referring to the negative pT region. However, there does seem to be a somewhat significant pT dependence in the left panel of Fig. 14 of the analysis note until the last bin where we run out of statistics. Is this the most extreme pT dependence of all of the triggers, pT ranges, and \Delta\phi ranges? And what is thought to be the cause? I'm also a little confused because that statement in the paper is for both R = 0.2 and 0.5 jets whereas in the analysis note the R = 0.5 jets are explicitly expected to have some pT dependence in the fit. Maybe this is to validate the assumption that there is no pT dependence by obtaining small values (if this is the case, what values were obtained for p1? Could this be added to the analysis note, or did I miss them?), but then I don't understand why it wouldn't also be done for R = 0.2.

401 - "10 < pT,jet^ch < 15"

Fig. 23 - I don't conceptually understand why we would add systematic uncertainties to the closure test. I don't think this is done in other analyses, and to me it isn't what the closure test is supposed to check, which is specifically whether the unfolding method is robust. Why would e.g. the detector-related uncertainty have something to do with that? And without the systematic uncertainty on the plot it seems that there is significant non-closure in 2 of the 5 bins of this example pT range/trigger which I think should be addressed in some way.

Fig. 27 - I remember discussing this at some point in a meeting but can't remember all of the detail. Why would we expect any difference at all between the two analyses, even if the data are consistent (e.g. the pi0+jet for R = 0.2, 15-20 GeV shows a large difference in central value while still being consistent due to the large uncertainty)? Maybe it's because of a smaller range in \Delta\phi used for the previous analysis, but the yields steeply fall at these large deviations from pi anyway, so I wouldn't have expected that to have a large effect on the central value of the bin. So what is the main contribution to the differences? 

On May 6, 2024, at 03:25, Yi Yang via Star-hp-l <star-hp-l AT lists.bnl.gov> wrote:

Hi Nihar,

Thanks a lot for the well-written draft and analysis note. 

I agree with Rongrong's comments, so won't repeat here. I have some minor ones for your consideration. 

Paper draft:

  - L36 - 38: the hyphens look a bit strange to me, it should look like the one in L26.  (similar for L314 and 315)

  - L41: high energy --> high-energy 

  - L58: pT, jet > 30 GeV/c

  - L59: R=0.3 --> R = 0.3

  - L116: Gev --> GeV

  - Eq.(1) and (2): it should be d^2 N_jet and d^2 sigma

  - L156: sqrt(s_NN)=200 GeV --> sqrt(s_NN) = 200 GeV 

  - Figure 1: I would suggest to put the information in the right panel to the left panel as well, just in case someone cut the left panel only and there is no information on that. 

  - L229: What does "TBD" mean here? Will this affect the final physics conclusion? 

  - L245: Fig.2 --> Figure 2

  

Question: (I probably asked it earlier) you show different behavior for R = 0.2 and 0.5, does it make sense to try other R numbers to see the actual R-dependence? 

Analysis note: 

  - L172: Figure 23 --> Figure 9?

  - Question: you are using PYTHIA-8 in the embedding/simulation, but you used PYTHIA-6 for the comparison in the result. Why not use the same version of PYTHIA?

  -  Don't you have the systematics from the unfolding iteration? 

  - Figure 23: It clearly shows the closure is not good between 2.5 and 3, and you are using log in the ratio. Any systematics associated with it? 

  - L403, 404: there are "TBA"s, what does that mean? 

  - L435: The uncertainty on dPhi weights is "TBD"? 

  - Figure 26: do you have a similar plot for R = 0.2? What do the two "light blue" lines mean here? 

Cheers,

Yi

On Mon, Apr 8, 2024 at 10:16 AM Nihar Sahoo via Star-hp-l <star-hp-l AT lists.bnl.gov> wrote:

Hello HP-pwg,

We have finalized STAR gamma+jet and pi0+jet acoplanarity paper draft.
Paper draft, analysis Note, and paper webpage can be found below.
Please send your comment and feedback.
We request to form GPC.

Paper draft:
https://drupal.star.bnl.gov/STAR/system/files/AcoplanarityPaper_v1.pdf

Analysis Note:
https://drupal.star.bnl.gov/STAR/system/files/AcoplanarityAanalysisNote_V0_0.pdf

Paper webpage:
https://drupal.star.bnl.gov/STAR/blog/nihar/Paper-webpage-Measurement-direct-photonjet-and-pi0jet-azimuthal-correlation-AuAu-and-pp-c


Thank you
PAs (Nihar, Derek, Saskia, and Peter)



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