STAR HardProbes PWG

[Raghav Kunnawalkam Elayavalli <kunnawalkamraghav AT gmail.com>]

Dear Nihar, Barbara, Yi, Sooraj, all

Apologies for the delay from my side. I have a few comments on the current writeup of our hot qcd white paper on the jet section and the few sentences in promised related to the time/temperature dependence. Based on the discussion during last week’s meeting, I also discuss a few words on a general paragraph related to jets that we can present as a bigger picture. Your thoughts and comments are most welcome. 

Line numbers are based on the pdf attached below. 

L 62 - instead of ’shorter and shorter length scales’ -> ‘varying scales, from the macroscopic to microscopic lengths’ 

L 63 - the QGP’s transport properties 

L 63-66- you mention the usefulness of jets and then in the next sentence describe what they are… so maybe reverse this order? 

L 66 - loses a fraction of its energy 

L 69-71- this sentence seems a bit redundant here, especially when considering the next sentence. 

L 75 - jet quenching -> jet-medium interactions (of which quenching is a part)

L 76 and later on - I think we should fold in our studies on pp substructure as a necessary prerequisite towards quantitative studies of the QGP evolution in both its perturbative description and hadronization (which is still unknown). The way its currently written seems a bit like its something else that we do on the side with the connection unclear. 

It would be good to emphasize here that one of the next steps in studying the QGP is to quantify its properties during its evolution. And one way in which we can do that is to use jets via their multi-scale evolution from pQCD to npQCD and hadronization. This provides a natural timescale that one can exploit in heavy ion collisions to then extract a temperature dependence of the transport parameters such as \hat{q}. This is the reason why we want to quantify jet topologies and that requires us to understand the substructure and clustering tree in pp collisions. So I would rephrase the sentence in L 76 with something along the lines of what i mentioned above and head into the next paragraphs. 

L 99 - I understand the point here but i would probably rephrase this as a feature than a bug (which is how its written with the emphasis on a measurement ‘bias’). Different jets lose energy differently and potentially same jets lose energy differently (depending on the strength of fluctuations vs path length for example). Such a system essentially forces us to make all possible types of measurements at varying kinematics and selections so that one can put the pieces of the puzzle together. 

L 101 - this paragraph seems overly technical, especially with the comparison of pp data to pythia which doesnt really add much to the discussion here.

L 113 - This can just be on jet substructure or something like jet-qgp space-time evolution where the pp is not only a reference, but a necessary step to comprehend before we move to heavy ions. We have measured the evolution of jet substructure along its shower and found deviations from perturbative description of the splitting kinematics for later emissions/splits. This points to significant non-perturbative contribution to the description of jet substructure along the jet where at a particular formation time which can be experimentally measured.   

So this is where we can bring back a bigger picture to summarize - From our measurements, we have two sets of studies which are complementary to each other with the scattering tomography and the space-time evolution picture. Both of which are necessary and have extensions to heavy flavor, such as heavy flavor jets and resonances, and other aspects we are yet to study about the medium such as hadron production affected by jet quenching etc. 

 

Cheers
Raghav 


**************************************
First Name - Raghav 
Last Name - Kunnawalkam Elayavalli
email - raghav.ke AT vanderbilt.edu 
website - https://www.raghavke.me 

RHIC/AGS UEC member
Assistant Professor of Physics
Stevenson Center 6410
Physics & Astronomy Department
Vanderbilt University 
Nashville, TN 37235-1807
<he/them>
**************************************

On Sep 5, 2022, at 6:43 AM, Nihar Sahoo via Star-hp-l <star-hp-l AT lists.bnl.gov> wrote:

Hello All,

We will have our regular HP-pwg meeting this Thursday (Sep 8th) at 10 AM BNL time. Let us know if you want to present and update your analysis.

As you may know from the minutes of last week pwgc meeting (Rongrong's email), currently conveners from all pwg are preparing a first draft of STAR Hot QCD white paper which should be ready by Sep 7-9; then that will be sent to the collaboration for comments during the weekend before the collaboration meeting. And the final white papers is aimed to be ready by Sep. 21st. It is very tight schedule.

Hence, this week we will discuss on the STAR Hot QCD white paper and also STAR contribution for next LRP. So please try to join this week to discuss more on this topic and it would be helpful for us to get your inputs. If you are interested in to contribute, please let us know.


HP working group weekly meeting info:
https://drupal.star.bnl.gov/STAR/pwg/Hard-Probes/Weekly-HP-PWG-meeting

Join ZoomGov Meeting
https://bnl.zoomgov.com/j/1611419615?pwd=VW1hNm43ZDd5d2EvK2R4aEJsQ2ZNZz09

Meeting ID: 161 141 9615
Passcode: 744968


Regards,
Barbara, Yi, Sooraj, and Nihar
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