STAR HardProbes PWG

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

Hi Yuan,

I am very sorry for my delay in getting you comments (see below) on your very interesting study. With these addressed, I’m happy for it to move forward to GPC review. Please let me know if anything I suggest is unclear or misguided. PS for future drafts, line numbers would be very helpful.

Thanks,

Isaac

Paper:

Pg. 1

"QGP...is generated by the hard scattering process"? Please revise.

Should this be x_B rather than chi_B?

Pg. 2

"mid-rapidity (|\eta| < 1)" (also in abstract)

I'm not sure that "and provide relatively accurate measurements in the absence of the Heavy Flavor Tracker (HFT)" is necessary.

Remove "concentric"

Subscript the "r" and "z" for Vr and Vz?

"required in this analysis"

Pg. 3

This was a bit of an abrupt transition from the end of the first column to the beginning of the second. I would recommend starting that first sentence with something like "For particle identification in the TOF, we use nsigma_pi^TOF = ..."

Pg. 4

combination background -> combinatorial background

redundant background -> residual background

Why wouldn't we leave the same marker style/color as subfig. (a) for the zoom-in to make it easier on the reader? I.e. make the upper distribution open blue circles instead of closed black (in that case the residual-subtracted should be some thing else for clarity).

It's not explicitly mentioned in the text or caption what the dashed blue line in Fig. 2(b) is, which would be nice to do.

What exactly do you mean by "It enables us to study the dependence of yield on the...transverse momentum"? You just mentioned making selections on centrality, but with inclusive pT, so it feels out of place. Do you mean that the high significance when selecting on centrality leaves room to make additional selections on pT without losing the signal? If so I would say something like that.

"best significance for semi-central collision..." -> "best significance of the three centrality classes in semi-central collisions."

"single-daughter" -> "single-particle"

Pg. 5

Sorry for my ignorant question, but why do you include the TOF matching efficiency in the definition of eps_PID, since it's already included in the overall efficiency, eps? 

Pg. 6

"Figure 5 shows the total D0 efficiency" should be Figure 4.

"we try changing...and varying..." -> "we change...and vary..."

The sentence "The daughter pT > 0.2 GeV/c cut is used..." is unclear to me.

I would recommend changing "TPC" to something like "efficiency" or "\epsilon" or "TRE" where you would then say "track reconstruction efficiency (TRE)" in the text. It would also be good to introduce them in the same order they appear in the table (e.g. flip efficiency and PID). One last small typographic point -- you write initialisms like PID without any periods, but B.R. is written with them. Either is fine, but they should be consistent.

I don't think it's ever explained what you mean by double counting. I think your Ref. 3 does a good job of it if you want to model what you say on that description.

Pg. 7

I found the sentence "The nuclear modification factor RAA is defined..." distracting. I would recommend moving it after this paragraph, saying "...and the number of binary nucleon-nucleon interactions within isobar collisions (cf. Eq. 12)."

Why is there a different nomenclature for the Nbin scaling of the AuAu and of the pp? I know for pp it's a trivial ratio since it's pp, but would be nice for it to be consistent if possible (e.g. "p+p x N.R.", like you have for the peripheral, above).

I'm not sure the argument at the end of Sec. 4.1 (and in the first paragraph of Sec. 5) can be consistent with later claims and results in the paper. You say that the reason AuAu and isobar spectra are similar is that the hard production is the dominant factor. But then we see e.g. in Fig. 10 that there is a very sizable contribution of energy loss in the high-pT region for more central isobar or AuAu collisions compared to pp. By a similar argument using Fig. 5, we also see that Nbin scaling doesn't render the pp similar to the AA although if it were just about the initial hard scatterings this should be the case. So the fact that AuAu and isobar are similar must also be because for whatever reason(s) that energy loss is similar between the two systems at a given centrality, right? It seems like a more consistent explanation is what you give on pg. 8 when you say "...indicating heavy flavors may have undergone a similar [dynamic] process in the bulk medium with respect to Au + Au collisions." Maybe something more like that can be said here instead. Please let me know if I misunderstood something here.

[By the way, I'm not sure if you mean to include also the effect of energy loss in the "non-thermal and non-equilibrium perturbative QCD processes" in Sec. 4.2.]

Pg. 8

Just to be clear, this must be BW and not TBW in Fig. 7, right? Is the reason you don't use the TBW just for historical reasons (comparing to the older results)? Is it expected that the <beta_T> extracted from TBW is this different? (E.g. ~0.37 in the figure for 10-40% and 0.21 in the table for the same centrality). Could you make a comment about it in the text?

I'm a little confused by the labeling on Fig. 7. There seems to be an extraneous red 0-5% and 70-80%. Am I misunderstanding something? You also say "in central isobar collisions" in the first sentence on this page, and it should be just "for isobar collisions", right?

I'm now remembering having a lot of discussion in the lead-up to Quark Matter about the fact that it's for a fixed centrality that the results in isobar and AuAu are consistent, despite the fact that the same centrality in isobar and AuAu has much different <Npart>. I think it would help the paper for there to be some comment about this around now, given that the reader might be wondering why the initial geometry rather than the energy density would be the major factor. As we know, this is partly related to the fact that the energy loss is somehow not very Npart-dependent, which you show/discuss on pg. 10, but I think as this might already be surprising to some people on this page, it would be good to make a statement even if it's just something like: "see Sec. __ for a discussion of centrality vs. Npart dependence."

Although it is obvious, I don't think you explain anywhere what m0 is, which would be good to be explicit about.

"The fitting result of D0 spectra is slightly shifted for visuality.": It would be good to mention that (it seems) the isobar 0-10% and the AuAu 20-40% are the ones that have both been shifted, if I have my D0 mass correct.

Pg. 9

"Compared with peripheral collision..." -> "Unlike peripheral collisions, ..."

This is a somewhat speculative question, but since we see in Fig. 12 that there is a negligible dependence of the suppression on Npart, but a somewhat strong dependence of the high-pT suppression on centrality, could we make a claim about possible path-length dependence of the charm quark energy loss being a factor here? Or is it complicated by the fact that there is some small dependence of RAA on Npart for the high-pT yields, making it difficult to disentangle? I guess Fig. 11 maybe also shows that the systematic precision isn't there to make the claim since this is a fixed Npart but different centralities, and within uncertainties the suppression is consistent.

Pg. 10

Shouldn't the <Nbin> uncertainty be light green, to be consistent with the previous plots?

You also might want to explain how the 5 bands are related to the 5 <Npart> values for the AuAu RAA (e.g. does the left-most, smallest, one correspond to the left-most Npart bin, or vice versa). 

Pg. 11

"show positive and negative dependence on centrality respectively"... Shouldn't it be flipped? That is, as we get more central, Tkin goes down, and <betaT> goes up. Maybe you meant that as the number in the centrality percentile gets larger rather than increasing how central the collisions are, but I think that's not what most people would find intuitive.

I'm not sure why the sentence "The <betaT> increases with increasing centrality, which has the same trend..." is here. It feels redundant with the first sentence in this paragraph. Maybe you meant T_eff rather than <betaT>?

Analysis Note:

Fig. 23 (b): I don't understand why the K TOF PID eff looks to be exactly 1 across all p, or why the K TPC PID eff is so non-monotonic. Can you explain, and add some text in the analysis note?

On Apr 16, 2024, at 16:51, Yi Yang via Star-hp-l <star-hp-l AT lists.bnl.gov> wrote:

Dear Yuan,

Thanks a lot for the nice results. I read through your analysis and paper draft, and I am happy to let it move forward for GPC formation. 

The analysis note is clear to me, however, I have some comments and suggestions on the paper draft for your consideration. 

 - General: "isobar" is a jargon in STAR, I would suggest avoiding using it too much. 

 - Abstract: 

      - suggestion D0 --> suggestion on D0 

      - Comparisons with the models are also reported --> It would be good  to mention the model(s) here

 -  Introduction 

      - pp --> $pp$

      - m_c,b >> lambda_QCD --> ">>" should be $\gg$

 - Data set and experimental apparatus 

       - in isobar analysis are Time Projection Chamber --> in this analysis are ... 

       - a transverse momentum lower limit of pT > 0.2 GeV/c --> a transverse momentum (pT) lower limit of 0.2 GeV/c

       - (Vr) and (Vz) --> (v_r) and (v_z) 

  - Data analysis

       - The transverse momentum is required to be >= 0.6 GeV/c --> The pT is required to be larger than 0.6 GeV/c

       - (page 3) f_k^min and f_k^max are defined in Eq.5, Eq.6 respectively -->  f_k^min and f_k^max are defined in Eq.5 and Eq.6, respectively

       - kaon and pion --> K and $\pi$   (many places, just need to be consistent with other places) 

       - (page 4) Add reference(s) for cocktail simulation and mixed-event method (or mentioned it has been used in many other papers) 

       - (page 4) The combination of the two functions is used --> Does the "two functions" here mean Gaussian and quadratic polynomial? It is not clear since you mentioned the redundant background is removed in the previous sentence 

       - Figure 3: The legend of $\mu$, $\sigma$, and S should change to "mass", "width", and "Nsig".

       - (page 6): D0 transverse momentum --> D0 pT

       *** I would define RAA, RCP before 3.3 Systematics since you mention RAA and RCP in the beginning of this section and it is a bit strange not defined it before*** 

       -  cross-section --> cross section

       - a pretty weak --> a weak     (pretty is not that scientific...) 

 - Results and discussion 

      - (page 7)  heavy ion collisions --> heavy-ion collisions  (many places) 

      - Figure 6: why don't you put the ratio plot in the bottom like Figure 5? 

      - Figure 7: This plot is very busy, it is a bit hard to catch the relation between data points and centrality. 

      - Figure 8:  why don't you put the ratio plot in the bottom like Figure 5? 

      - Figure 9: It is hard to see your result, probably change it to a different color? 

     

Cheers,

Yi

      

On Thu, Mar 28, 2024 at 10:05 AM <suyuann AT mail.ustc.edu.cn> wrote:

Hi Yi,

  Thanks for your reply and PAs are waiting for your comments.

Cheers,

Yuan

-----原始邮件-----
发件人:"Yi Yang" <yiyang0429 AT gmail.com>
发送时间:2024-03-27 06:08:25 (星期三)
收件人: "STAR HardProbes PWG" <star-hp-l AT lists.bnl.gov>
抄送: suyuann AT mail.ustc.edu.cn
主题: Re: [Star-hp-l] Replies to PWGC preview D0_RAA_isobar

Hi Yuan,

Sorry for the late reply. We will provide our comments on your analysis note and paper draft asap.

Cheers,

Yi 

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