STAR HardProbes PWG

[Tristan Protzman <tlp220 AT lehigh.edu>]

Hello Nihar,

A new draft has been uploaded to Drupal.

Note: it should be written as $p$+$p$ and $p$+Au, etc, which is
different from the guidance. 

Fixed. 

Slide:2
_Second bullet seems out of context here. Coupling is large at low Q^2
then why  is it relevant for the QGP and your jet anisotropy
measurements? This part is not clear here.

It motivates the need for a perturbative object like jets to probe what we actually want to study, the QGP.  Changed text to clarify.

_ Give reference to the running coupling plot. And you could replace
with most updated version where LHC measurements (very highQ2 region)
are included if you want to start with it.

Changed.

_GIve a reference or credit for left cartoon.

Figure removed, I felt it did not add to the message.

Slide:4
_3rd bullet: "Leads to path length…"  this is not the only effect; it
could be various other contributions like color factor, Temp of QGP,
initial gluon density, etc. But you need to mention Your motivation is
to study "path length dependence".

_ same comment for 4th bullet

I have adjusted this section to clarify that the aspect of jet modification I am trying to study is the path length dependent nature of jet energy loss

_ 5th Bullet ("Both collisional and radiative") you need to provide
reference to the theory calculation for this L/L^2 dependence. These are
model calculations.

Removed L/L^2 statements as I am not comparing to any models in this presentation

_ This slide only focus on jet and jet quenching, but it doesn't
motivate your measurement like why jet anisotropy measurement is
required? Need to include some text on it.
I suggest you need to motivate jet anisotropy before you go to any jet
analysis details like in Slide5  underlying event discussion

The way I have structured my talk is to first motivate that we have observed jet quenching.  I am using the dijet analysis to this end.  I then want to contrast that with azimuthal anisotropy, which is not a dissimilar measurement in that it probes jet modification, but it does so in a new way.  Therefore, I think it makes sense to talk about jet measurements and then the dijet measurement before introducing the idea of anisotropy and motivating how that can get us towards the missing path length dependence of a dijet analysis.

SLide:5
_Not clear, what is that right side plot? Is this data or MC simulation.
What is pT, of track or jet? What is Delta phi?

I agree, this plot was not particularly clear.  I have removed it.  
_"Soft processes produce a fluctuating background" what is that
background? Is it track or combinatoric jet background?

I'm not quite sure I understand what you are asking, it is the tracks from soft processes which produce the combinatorial jet background, so I suppose both?
_3rd bulltet (Estimated…) it should be sub-bullet of 2nd bullet (Soft
process…)

Changed.  
_ what is kT?

The k_T jet finding algorithm, clarified.
_ Jet area -> Jet area(A)

Changed.

Slide6:
_Not clear, what is that right side plot? Is this data or MC simulation?
What is pT, eta, and phi?

This is the total track momentum for eta/phi bins for a collision.
_"A jet finder… had scattering and other processes" ->" had scattering
and combinatorial background in heavy-ion collisions"

_2nd bullet is not required if you mention above.

 I have merged this with slide 5 and changed this wording

SLide:7
I would suggest to use jet pT as $p_{\rm T, jet}$ throughout your
presentation.

Changed.
_Used in other STAR analysis -> Proved references
_Provide referecen to ALICE measurement

Done.

Slide:8
_Move this slide or Isobar jet pT distribution after your slide14 where
you discuss about Isobar dataset. It seems the left side plot just
pop-up. This plot should be part of you results discussion even if it is
a STAR performance plot.

Figure removed
_"Statistically unlikely for soft processes…" Please rephrase this… not
clear.

Changed to clarify that it is unlikely for soft processes to produce high pt hadrons which look like jets
_"May bias jet selection towards surface" Not sure the motivation of
this bullet. why it is important? You are not doing jet RAA/RCP study
and you do not study trigger jet v2 then why it is important if this jet
is trigger biased or not. These jets should be treated as inclusive jet.

Is it not important to understand the biases we introduce into our measurements?  By requiring the high pT hadrons the selected jets are biased towards the surface of the QGP.  This is the motivation for one of the items we would like to explore next in this analysis, the variation of the hard core threshold.   

Slide:9
This slide is not relevant. You could put in Backup. (A distraction)

I disagree, the story I am hoping to tell with this talk is that we saw signs of jet quenching with measurements like dijet imbalance, but that it doesn't tell the complete story.  We can continue our understanding of jet quenching from dijet measurements to jet v2 measurements.

Slide:10
_ 1st bullet: Why it is important for Dijet imbalance discussion here?
You are doing inclusive jet v_n measurement. Not clear to me.

See above.

SLide12
_"A jet in plane interacts with less medium than one out of plane" -> "A
jet interacts less with medium in plan than out of plane"

Changed.
_"Since jet production is isotropic, differences in yields are a result
of medium interactions" Not sure, what you want to say here? Please
reprhase.

Changed.
_" like flow" Remove this.

I included this to help give context for the measurement to an audience who may be familiar with flow studies, but not jet anisotropy studies.  If you feel this is misleading I will remove it.
_ you do not discuss what is v_{2}^{jet} is?

Changed equation to remove \Delta\phi -> \Psi_2 - \Phi_jet
_"Not a flow effect though!" Can you elaborate this?

I am stating that although it may be described using the same framework as flow measurements, jet v2 is a different process.  

SLide13
_RHIC produces a different, cooler QGP -> "RHIC produces a cooler QGP
medium than the LHC"

Changed.
_"Down to 10 GeV" -> But you are not going to show down to 10 GeV. So
just remove this extra quantifier subbullet. Main bullet is fine.

I do show down to 10 Gev though, my first point is 10-12.5 GeV/c jets.

Slide15:
- Jet trigger -> You don't use any jet trigger and BEMC info in your
measurement. If yes, just remove.

I do use the barrel high tower trigger in my analysis, as detailed in the preliminary figure request.  I have clarified this as high tower trigger rather than jet trigger.
- Right side STAR detector, please indicate where is TPC, BEMC, EPD

- Mention kinematic acceptance of these detectors

See updated slides, Yi mentioned this as well

Slide16:
_you did not discuss what is Delta_phi?

I did not, but I am not sure I need to on this slide.  I will discuss it on the next slide.
_right side plot, make title/lable of x-, y-axis bigger so that it will
be visible. And also legends in side the plot.

Changed, made entire plot larger as well


Slide18
Move this slide after Slide15

Changed.

Slide19
_INside fig, mention "red line" is fit fun.

Added.
_ inside fig, p_T^reco -> p_{\rm T, jet}^{reco} ; 12.5 -> 12.5 GeV/c

Changed.
_ you did not mention anywhere before what is "R"? And what jet R you
are going to do measurement?

It is labeled on the plot, and I will discuss it further on the following slide.  
_ what is v_{2}^ch? Need to mention it charged jet v2. I would suggest
to use $v_{2}^{\rm ch, jet}$; And the same about v_{2}^ch,abs

Changed.

Slide20:
Before slide20, you need to discuss different jet v2 (all, hard core,
matched jet) and their spectra showing side-by-side

I'm not sure I understand why?  I think that was a good check to make and certainly worth having in the backup, but the measurement being presented is jet v2 using the hard core matching criteria, the need for which is motivated earlier in the talk.  

Slie21:
_  "Jet v2 is a exciting measurement for determining the path-length
dependence of jet quenching" -> This statement is fine to motivate. But
for your conclusion this may not be relevant. Because we don't have jet
v2 measurement for different path length/system size with the same
kinematic coverage. And you did not discuss what is the strategy for
your measurement unless you plan to do the same in AU+AU.

_"Jets which are in plane interact with a different amount of the QGP
than those out of plane" Not sure how do you get this conclusion from
your measurement.

I have updated my conclusions to better reflect the points I wish to make and where I will go next with this analysis.

On Thu, Oct 6, 2022 at 1:34 PM Yi Yang <yiyang0429 AT gmail.com> wrote:

Dear Tristan,

Thanks a lot for the reply and the updated version. 

They look very good to me.

Let's wait for your study and the decision on the preliminary results! 

Cheers,

Yi

On Thu, Oct 6, 2022 at 3:26 AM Tristan Protzman <tlp220 AT lehigh.edu> wrote:

Hi Yi, 

Thank you for the feedback!  I have uploaded an updated version and addressed your comments below.

 - p4: Are the sub-bullet for the 3rd bullet and the 4th bullet the same? 

Yes, I have removed that redundancy.

 - p6: toy mode --> toy model 

Fixed.

 - p9: Just for my own education, could you please tell me why A_j can be less than 0 (I am assuming pT^1 and pT^2 are leading and subleading jet pT, respectively, is it correct)? 

Yes, (pT^1, pT^2) is the (leading, subleading) jet pT.  The red points are the measurement of A_j using only hard cores.  This is where leading and subleading are determined, thus no points below 0.  However, after matching is done, leading and subleading are not recalculate, so it is possible for the subleading hard core to match to a jet with more momentum than the leading hard core does, resulting in negative A_j.  There are a few ways this could happen.  The subleading jet could contain a larger soft component than the leading jet, thus when added to the hard core the magnitudes flip.  Additionally, because of the fluctuating background the leading jet could be over subtracted and the subleading jet under subtracted, again flipping the relative magnitude.  This would not affect the hard core since background subtraction is not done on that collection.

 - p15: It would be good if you can provide more information for the subdetectors, for example eta and phi coverage... 

I added more information about each system and labeled the picture.

 - p18: Jet v2 not feasible --> Jet v2 is not feasible 

Changed to Jet v2 was not feasible

Cheers,

Tristan 

On Wed, Oct 5, 2022 at 1:59 PM Yi Yang <yiyang0429 AT gmail.com> wrote:

Hi Tristan,

Thanks a lot for the nice slide. I have some suggestions/comments for your consideration. 

 - p4: Are the sub-bullet for the 3rd bullet and the 4th bullet the same? 

 - p6: toy mode --> toy model 

 - p8: Title: Hardcore --> Hard core

 - p9: Just for my own education, could you please tell me why A_j can be less than 0 (I am assuming pT^1 and pT^2 are leading and subleading jet pT, respectively, is it correct)? 

 - p15: It would be good if you can provide more information for the subdetectors, for example eta and phi coverage... 

 - p18: Jet v2 not feasible --> Jet v2 is not feasible 

 - Since we are not settled with your preliminary results yet, I will comment on p20 and p21 later. :-) 

Cheers,

Yi 

On Thu, Oct 6, 2022 at 12:36 AM Tristan Protzman via Star-hp-l <star-hp-l AT lists.bnl.gov> wrote:

Hi All,

I submitted this material for review last week, but it seems to have been lost somehow, so I am resending it.

Cheers,

Tristan 

On Wed, Oct 5, 2022 at 12:33 PM 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/61264

Deadline: 2022-10-11
---
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webmaster AT www.star.bnl.gov
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