STAR HardProbes PWG

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

Hi Monika,

This is a great overview of much of STAR’s substructure program. I have some 
comments below.

Thanks,
Isaac

2.
        "angular tree" -> "angular-ordered tree via C/A reclustering"
        Recommend stylizing SoftDrop and CollinearDrop the same way 
throughout (i.e. without the space for the latter).

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"

12.
        I'm getting a little confused by the cartoon. It makes it seem like 
the zg and the Rg are measured at different splits, which is not the case, 
right?
        You say in the first bullet that we're moving to softer splittings 
(by increasing the Rg), which then affects the zg distribution. But this 
logic seems a bit circular, since the way we know if it is soft or hard is by 
looking at the z. So maybe it would be better to remove "hard" and "soft" 
here.

13.
        Here I was trying to figure out for a while how the colored boxes on 
the left corresponded to your cartoon on the right. So I suggest removing 
them until s. 14.
        Speaking of the cartoon, you have some gluon lines, which makes me 
think that the straight lines are meant to be quarks (rather then everything 
being generic subjet prongs), so the emission you X out to demonstrate SD 
should probably be a gluon, no? And because of the jet cone you draw for the 
groomed jet on this slide, the SD'd emission is a little harder to 
distinguish than it was on the previous slide. So it would be good to make 
the angle wider, or maybe it will be more visible as a gluon.
        One last thing about the cartoon: since you're now talking about CD, 
maybe instead of a red X, you could do a green check mark (and optionally 
additionally increase the transparency of everything in the groomed cone to 
demonstrate DeltaM.

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.

18.     Would it be possible to find a sharper image for the Lund plane?

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.

22.     I think I would flip the third bullet the other way around: selecting 
on jet substructure observables and correlations between them allows us to 
access different regions of the Lund Plane. Let me know what you think.

> On Jun 23, 2023, at 8:40 PM, webmaster--- via Star-hp-l 
> <star-hp-l AT lists.bnl.gov> wrote:
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> 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
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