STAR HardProbes PWG

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

Dear Isaac,

Sorry for the late reply. I was traveling from one workshop to another and just got to CERN last night. 

With regards to the discussion on the mu - I think it’s totally fair that we revisit it and discuss what we learn from the observable as we work on the paper draft at this moment. Firstly, I think that the phrasing we discussed for HP should something that we are comfortable to also present now. The reasoning for the faster reduction in virtuality is effectively the argument that if the ‘mu’ is closer to zero, then you effectively lose a lot of virtuality in that split. Meaning that the remaining harder (in mass, not necessarily in pT which is another complication in the interpretation) prong only has a small mass to work with… that will result in smaller particles and a narrower spread etc.. (which we know from previous studies). 

So the ‘rate’ that Monika mentions here is not necessarily a rate per time, but rather a rate per splitting and specifically quantifying how much mass of the mother gets transferred during the hard splitting as defined by softdrop. 

I don’t think we can make any more stronger statement than whats in her slides. I’m personally hoping that conferences like this one where we have theorists and phenomenologists around to discuss the data will help us understand in greater detail the physics of this observable, and all its selection biases etc.... 

Coming to your statement - 

How about just “jets with narrower first hard splits lose more virtuality before this point” or something? This could even be framed as a connection between the hard and soft contributions in the shower similar to e.g. s. 14, which paints a nice consistent picture.

It’s not ‘before this point’ but it’s precisely at this split. So how about "Narrow splits lead to smaller transfer of virtuality or mass”  

Cheers
Raghav 


**************************************
First Name - Raghav 
Last Name - Kunnawalkam Elayavalli
Pronouns - they/them
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
**************************************

On Jun 29, 2023, at 7:27 PM, Mooney, Isaac <isaac.mooney AT yale.edu> wrote:

Thanks for the follow-ups Monika. Please see in-line responses below.

-Isaac

On Jun 29, 2023, at 12:15 PM, Robotkova, Monika via Star-hp-l <star-hp-l AT lists.bnl.gov> wrote:

Hello Nihar and Isaac,

Thank you very much for your useful comments. I've implemented them. Please see my answers below:

For Isaac:

5.
        I think you want the left parenthesis to be to the right of the 2? Or the right one to be to the right of the D.
        "2D unfolding via Iterative Bayesian procedure"

I would like to keep (2+1)D, it should say that both numbers correspond to the dimension. 

Ah! I misunderstood what you meant. Okay, this makes sense to me now.

17.
        I know this statement (2nd bullet) was workshopped before Hard Probes, but in coming back to it now and really thinking about it, I have some questions. The claim is that virtuality is reducing faster in the jet shower. I'm not sure I understand this. First, these are all at the same (first) split. Of course, it's possible for that split to be earlier or later in time (or to be at a different point in the shower depending on how many emissions failed the SD criterion). If we use the rough relation that time is inversely proportional to angle, this would give us a later time on average for smaller Rg splits. Now virtuality would be higher for the mu ~ 1 case than the mu ~ 0 case, so if mu -> 0 for Rg ~ 0, a lower-virtuality state has been arrived at but at a later "time" than the Rg >> 0 case. So it doesn't seem conclusive to me that the actual rate of virtuality shedding is any different in these two populations of jets -- it may just be that these splits occur later.
Am I missing something or having a brain-dead moment? I know Raghav was the one who suggested this in that pre-HP email chain, so maybe they could chime in as well.

I'm not sure if I follow your thoughts, so please let me know, but I would say that mu, since this is a fraction of leading daughter to mother, so it should be a rate of virtuality reduction in the jet, so in this case, if mu goes to smaller values, the reduction is faster and vice versa. This is how I understand the statement.

I agree with your interpretation of more virtuality reduction corresponding to smaller mu, but I don’t understand where you get a rate from that. I.e. what is the time component that you’re using to compare the two populations’ delta(virtuality)/delta(t)? The only time argument I can see is the one I gave above, which would actually show that although mu is lower for smaller Rg, that smaller Rg may correspond to later formation time splittings, meaning that it’s not possible to determine a faster or slower in this case. I’m not sure if I phrased that any better than the first time :). Does it make more sense or am I still confused?

It seems like either you’re assuming that the first split happens at the same time regardless of its kinematics, which I don’t think is true, or you’re referring to a time in “hard splitting space”, in which case I agree with you that they happen at the same 'time' (i.e. the first hard split) but I think the phrase “faster” is not so obvious for people in that context. Also I’m not sure about its broad utility.

How about just “jets with narrower first hard splits lose more virtuality before this point” or something? This could even be framed as a connection between the hard and soft contributions in the shower similar to e.g. s. 14, which paints a nice consistent picture.

Sorry for harping on this point, I just want to make sure I understand what you’re saying. Other than this one point, the updated version looks great to me.

19.     Do you understand what's going on with the bimodal Herwig (and to a lesser extent Pythia6) distribution for high-pT, high-Rg jets? It seems like a significant discrepancy with data, although maybe this is just a statistics issue in the MC which is not apparent because uncertainties aren't shown? I also notice that the Pythia8 cuts off around here, so maybe that's why. Although the data seems not to be stats-limited at all here.

I did not study this region in detail, but MC statistics is really low in this pT and Rg bin, so it should be statistics issue.

Okay, well no problem for this talk but I would be curious to see a follow up on this at some point if possible, when you have a chance.

For Nihar:

Slide19:
_"we move from non-perturbative to perturbative region" -> this is again a vague statement. Not sure how do you claim this. Because look at my comment slide#2.

I think this comes from the statement before the arrow, that we know for log(kT) > 0 the splitting is more perturbative and for log(kT) < 0 the splitting is more non-perturbative, because when kT corresponds to Lambda_QCD, we can separate perturbative and non-perturbative regions.

Best regards,

Monika

---

Od: Star-hp-l <star-hp-l-bounces AT lists.bnl.gov> za uživatele Nihar Sahoo via Star-hp-l <star-hp-l AT lists.bnl.gov>
Odesláno: čtvrtek 29. června 2023 6:31
Komu: Raghav Kunnawalkam Elayavalli <kunnawalkamraghav AT gmail.com>
Kopie: STAR HardProbes PWG <star-hp-l AT lists.bnl.gov>; webmaster <webmaster AT star.bnl.gov>
Předmět: Re: [Star-hp-l] STAR presentation by Monika Robotkova for Physics in and around the Lu... submitted for review

 

Hello Raghav,

I agree with you. And I would like to correct my statement in the line 
you mentioned.

UE and pileup are QCD processes and they contain both p-QCD and np-QCD 
processes.

Thank you
Nihar


On 2023-06-29 17:42, Raghav Kunnawalkam Elayavalli wrote:
> Hi Nihar,
> 
> Pileup are soft collisions in addition to the main hard scattering and
> so they could be in essence  perturbative or non-perturbative by
> themselves, but they don’t belong to the jet in question yes. So
> I’m fine with your sentence below
> 
>> So I would prefer to say "...to mitigate non-perturbative (like
>> hadronization and UE) and pileup effects”
> 
> Cheers
> Raghav
> 
> **************************************
> First Name - Raghav
> Last Name - Kunnawalkam Elayavalli
> Pronouns - they/them
> email - raghav.ke AT vanderbilt.edu
> website - https://www.raghavke.me  [3]
> 
> RHIC/AGS UEC member
> Assistant Professor of Physics
> Stevenson Center 6410
> Physics & Astronomy Department
> Vanderbilt University
> Nashville, TN 37235-1807
> **************************************
> 
>> On Jun 29, 2023, at 11:57 AM, Nihar Sahoo <nihar AT rcf.rhic.bnl.gov>
>> wrote:
>> Hello Raghav,
>> 
>> Yes, non-perturbative effects can be hadronization and UE. But
>> SoftDrop also reduces the pileup effect in jets; and pileup is not a
>> non-perturbative effect and it comes from multiple hadron
>> scatterings.
>> 
>> _ "…SoftDrop used …to mitigate non-perturbative effects " ->
>  So I would prefer to say "...to mitigate non-perturbative (like
> hadronization and UE) and pileup effects"
> 
> Best
> Nihar
> 
> On 2023-06-29 15:08, Raghav Kunnawalkam Elayavalli wrote:
> 
>> Hi Nihar,
>> Just to push back on the point you raise in slide 2 - the abstract
>> of
>> that paper you linked to in the bottom explicitly says -
>> "non-perturbative effects such as hadronization and the underlying
>> even”. Then in section 6 of the paper, they discuss in detail how
>> doing softdrop makes an observable robust to these effects which one
>> cannot calculate w.r.t the jet which would make something
>> perturbative. So it is absolutely true that "SoftDrop is used to
>> mitigate non-perturbative effects”
>> Cheers
>> Raghav
>> **************************************
>> First Name - Raghav
>> Last Name - Kunnawalkam Elayavalli
>> Pronouns - they/them
>> email - raghav.ke AT vanderbilt.edu
>> website - https://www.raghavke.me [1]  [2]
>> RHIC/AGS UEC member
>> Assistant Professor of Physics
>> Stevenson Center 6410
>> Physics & Astronomy Department
>> Vanderbilt University
>> Nashville, TN 37235-1807
>> **************************************
>> On Jun 29, 2023, at 8:16 AM, Nihar Sahoo via Star-hp-l
>> <star-hp-l AT lists.bnl.gov> wrote:
>> Hello Minika,
>> Please find my comments on your nice overview slides.
>> Slide2:
>> _ "…SoftDrop used …to mitigate non-perturbative effects " -> In
>> fact this statement is not correct. SoftDorp is used to mitigate the
>> effect of ISR, UE and pileup. For a reference, have a look at one of
>> original papers  https://arxiv.org/pdf/1402.2657.pdf [2] [1]
>> SLide 6and7:
>> As you discussed in previous slide two corrections methods:
>> RooUnfold and MultiFold
>> I would suggest to put in Title "RooUnfold Method" or similar.
>> Slide10:
>> Title "Motivation" comes abruptly after many slides. Needs to say
>> Motivation for/of what?
>> Slide12:
>> "…and more perturbative" -> a vague statement. Mention why you
>> claim this is "perturbative"? Like 1/z trend of AP, DIGLAP…?
>> SLide18:
>> In the Lund diagram, mention what is "Δ" ? and relate that with R_g
>> Slide19:
>> _"we move from non-perturbative to perturbative region" -> this is
>> again a vague statement. Not sure how do you claim this. Because
>> look at my comment slide#2.
>> Best
>> Nihar
>> On 2023-06-24 06:10, webmaster--- via Star-hp-l wrote:
>> Dear Star-hp-l AT lists.bnl.gov members,
>> Monika Robotkova (robotmon AT fjfi.cvut.cz) has submitted a material
>> for a
>> review, please have a look:
>> https://drupal.star.bnl.gov/STAR/node/64125
>> Deadline: 2023-07-03
>> ---
>> If you have any problems with the review process, please contact
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> [2]
> https://urldefense.com/v3/__https://www.raghavke.me__;!!P4SdNyxKAPE!AXhjVRnfJ_VV4CS3OHZ-j7FEue0LqD-uwhYQga3XapnVP68Ywh4lMcmti2clyHm12pRUc-8Mxh2zCXUQCHQlurUtIC90WCw$
> 
> 
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> ------
> [1] 
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