STAR HardProbes PWG

[Tong Liu <tong.liu AT yale.edu>]

Hi Nihar,

Thanks for your comments. Please find my responses below-- those not mentioned are applied to my slides already. However I'd like to take until Sunday night and hopefully make some more changes to them before uploading again, since we already have a lot to discuss here.

Title: good catch; I meant “high-pt”. One of the worst places to have a typo :p

Slide#3:

_Do you want to say something about right side plots? Any link to your

analysis…please point out that.

Here it’s just an introduction to high pt hadron as a proxy to jet quenching effect. The plot I used is the Au+Au high-pt hadron Raa, which is going to be used later as well; in the text I was really trying to be general and not talk about any specific measurement, but I might talk about it orally. If you think it’s too much though I can take it off; but I’d say let’s wait till a first rehearsal. Also it might be a good idea to put this slide right after the title slide?

Slide#4:

STAR TPC eta acceptance is |eta| < 1.4 (without iTPC)

What acceptance you are quoting here?

I'm pretty sure it's |eta|<1… Please see slide 4 in https://indico.cern.ch/event/689846/contributions/2947105/attachments/1635225/2608617/Yichang-ChiYang.pdf

Slide#6

_Can you please remind me where do you get this "p+p uncertainty"?

That comes from this paper:STAR Phys. Rev. Lett. 91, 172302 (2003)

Slide#10:

It is important to mention for Au+Au, d+Au, and Cu+Cu, what pT ranges

were used?

It’s also using 5.1-10 GeV, same as isobar. The statement at the bottom of the graph was meant for all measurements, but apparently it was not clear enough. Any suggestions?

Slide#12:

_ you have now two models: I) HG-PYTHIA QM2022 preliminary and II) new

results that you labeled as "X+X N_hard"

AFAIK, the difference between I) and II) is due to choice of N_hard and

N_part . Is not that?

But from your labels it seems for I) you used pT>5 GeV, and for II)

N_hard is used but all pT range.

Is that true?

_ Why your uncertainty band for I) QM2022 preliminary results has been

changed? It looks wider band in your preliminary results.

OK let me explain further here… what the HG-PYTHIA model does is, it generates a Glauber-level collision, throw a Poisson dice and determine how many hard collisions each NN collision has (Nhard). Then it goes to PYTHIA and ask for a p+p collision with nMPI=Nhard (yeah that part I don’t understand yet either); then all the tracks from all the PYTHIA collisions are stacked together to be the synthetic event. Here in the plot, both options categorized events into centralities with the “refmult” of this synthetic event, but the “benchmark values” are calculated in different ways: in the “Nhard” option, the average Nhard in each centrality class is compared to <Nhard> of pp collisions, while in the “Y_ch” option, the invariant yield of 5 GeV+ tracks is used (<Ncoll> scaling is applied in both cases, of course). I didn’t use any <N_part> in this baseline beyond the x axis.

As for the change to QM prelim, that one  was easy: I squeezed much larger statistics out of the simulation. In fact this one is still statistical error only, and I’ll try to get a crude systematics in the next week. 

Slide#14:

Do you have associated systematic uncertainty for <Ncoll> and <Npart>

scaled?

The systematic uncertainty assigned to <Ncoll> and <Npart> by the centrality group is VERY small, and I suspect they are correlated between species, so they also largely cancel out.

Tong Liu

Ph.D. Student '2023 

Physics Dept., Yale University

Tel: 203-435-2130

On Sat, Oct 1, 2022 at 3:03 AM Nihar Sahoo via Star-hp-l <star-hp-l AT lists.bnl.gov> wrote:

Hello Tong,

Please find my comments below  on your nice presentation slides.

Slide#1:
Title: System size dependence of pT hadron yield modification…"  ->
"System size dependence of hadron yield suppression…" or something like
that
Here, "pT hadron yield modification" sounds awkward.

Slide#3:
_Title: "…QGP probe" -> "…QGP Probe"
_"..lose energy to QGP" -> "… lose energy in QGP"
_"…RAA: comparison to p+p collisions" -> not quite right? Define RAA
using Au+Au and nuclear thickness function..
    It is important for your previous bullet for Npart and Ncoll
_Do you want to say something about right side plots? Any link to your
analysis…please point out that.

Slide#4:
STAR TPC eta acceptance is |eta| < 1.4 (without iTPC)
What acceptance you are quoting here?

Slide#6
_Can you please remind me where do you get this "p+p uncertainty"?

Slide#8-9
I would make that blue box transparent such that the data points can be
visible behind.

Slide#10:
It is important to mention for Au+Au, d+Au, and Cu+Cu, what pT ranges
were used?

Slide#12:

_ you have now two models: I) HG-PYTHIA QM2022 preliminary and II) new
results that you labeled as "X+X N_hard"
AFAIK, the difference between I) and II) is due to choice of N_hard and
N_part . Is not that?
But from your labels it seems for I) you used pT>5 GeV, and for II)
N_hard is used but all pT range.
Is that true?

_ Why your uncertainty band for I) QM2022 preliminary results has been
changed? It looks wider band in your preliminary results.

Slide#14:
Do you have associated systematic uncertainty for <Ncoll> and <Npart>
scaled?


Cheers
Nihar



On 2022-09-29 09:54, webmaster--- via Star-hp-l wrote:
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