STAR HardProbes PWG

[Rosi Reed <rosijreed AT lehigh.edu>]

Hi Peter,

I'm surprised that you're surprised given how long a discussion we had on this result when it was a new preliminary.  I completely agree that the experimentalist should report all of her experimental biases and assumptions, whether this is done properly or not in all papers is a discussion for another time.  In any case, in heavy-ion collisions there is always an additional bias that can be attributed to either the fragmentation and/or the geometry by whatever hard-process selection criteria that we use, whether this is a hard-core jet or a leading constituent requirement.  The nuclear modification factor is a particular observable, that the community largely interprets as a measure of suppression (RAA<1), enhancement (RAA > 1) or a canceling of various effects (RAA = 1).  When you have different kinematic requirements in the numerator and the denominator, you construct a variable that can have RAA < 1, even if we could treat the system as an independent superposition of nucleon-nucleon collisions.  I understand that you indicate this area on the plots with the "biased" vs "unbiased" labels, however, my many discussions with people in other experiments and with theorists has indicated that this isn't appreciated or understood.  As no other experiment is constructing their analysis in this manner, it makes it very difficult to compare the STAR nuclear modification results, which will especially be a shame in the era where we have sPHENIX data.  In addition to this more pragmatic approach, I think it blurs together different physics processes in a way that makes interpretation of the data difficult.  Unfortunately I need to run to another meeting, so I will end this discussion here.

Cheers,

Rosi

On Wed, Aug 24, 2022 at 11:25 AM Peter Jacobs <pmjacobs AT lbl.gov> wrote:

Hi Rosi,

Please see replies below:

On Wed, Aug 24, 2022 at 7:52 AM Rosi Reed <rosijreed AT lehigh.edu> wrote:

Hi Peter,

I agree that this is an important result!  It is somewhat unfortunate that the final result did not have the leading track requirement in the reference, which caused this biased vs unbiased confusion that takes away from the physics message.  I would definitely recommend only including figure 19 which does not show the unbiased points, since it would be somewhat inappropriate to use the plots that are in the AN that did not have this bias.

I am surprised by this comment, which I do not think is correct.

It is the experimentalist's responsibility to measure and report biases. Unfortunately, many heavy ion jet measurements do not do so - this paper is one of the few exceptions.

In this paper we went into detail about the nature of the bias, providing a purely data-driven method to identify where it is negligible. This point is important, because the modeling of bias adds additional uncertainty to theoretical calculations. In JETSCAPE we are comparing to the distributions from this STAR measurement, with the "biased" and "unbiased" regions clearly delineated; see Fig 14 here:

https://inspirehep.net/literature/2062342

This I think is exactly as it should be - this approach to bias brings clarity, not confusion.

The forthcoming RAA analysis being carried out by Robert (who will provide an update at the collab meeting) will improve the first jet RAA measurement in many aspects, but this approach to the bias will be carried out in exactly the same way. There is no reason to change.

There are a number of newer results that should be included too (Raghav's nice jet structure measurements for example), probably what would be good for the conveners to do is to make a list of all papers from the pwg that have been published during this time period to make sure that we don't forget everything.  Once we have that, we can start formulating a succinct and clean message.

Regards,

Peter

 

Cheers,

Rosi

On Wed, Aug 24, 2022 at 10:45 AM Peter Jacobs via Star-hp-l <star-hp-l AT lists.bnl.gov> wrote:

Hi Convenors,

Thanks for the pointer to the slides.

I very well appreciate the need for concision, with only a few key results highlighted. However, I think that the STAR paper on inclusive jet RAA also belongs on slide 3 of STARjetLRP.pdf, as one of the significant STAR jet measurements since the last LRP:

https://inspirehep.net/literature/1798665

Regards,

Peter

On Wed, Aug 24, 2022 at 4:33 AM Nihar Sahoo via Star-hp-l <star-hp-l AT lists.bnl.gov> wrote:

Hello All,

As you all know, we had meeting—LRP planning for STAR/RHIC—to discuss
STAR's achievements/contributions since last Long Range Plan(LRP)-2015
on Monday this week. We also discussed possible STAR experiment
proposals (and their physics) that could be included for upcoming LRP.  

We want to present the same slides at our HP-pwg meeting this week to
get your inputs and to discuss further on this topic.
Those slides can be found here (Highlights for HP both on the jet and HF
discussion slides) along with other presentations:
https://drupal.star.bnl.gov/STAR/event/2022/08/22/LRP-planning-STARRHIC

Please join this week to discuss on this important topic.

Thank you
Barbara, Yi, Sooraj, and Nihar


On 2022-08-22 17:51, Nihar Sahoo via Star-hp-l wrote:
> Hello All,
>
> We will have our regular HP-pwg meeting this Thursday (25th Aug) at 10
> AM BNL time. Let us know if you want to present and update your
> analysis.
>
> If you want to present or update your analysis at collaboration
> meeting, 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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--

Peter Jacobs
pmjacobs AT lbl.gov

Nuclear Science Division,
Lawrence Berkeley National Laboratory,
1 Cyclotron Road,
Berkeley, California,
U.S.A. 94720
Tel. (510)486-5413
Cell: (510) 688-0055

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--

Rosi Reed
RHIC/AGS UEC member
Associate Professor, Physics Department
Lehigh University
(610)758-3907
16 Memorial Drive East Office 406
Bethlehem, PA 18015
she/her/hers

--

Peter Jacobs
pmjacobs AT lbl.gov

Nuclear Science Division,
Lawrence Berkeley National Laboratory,
1 Cyclotron Road,
Berkeley, California,
U.S.A. 94720
Tel. (510)486-5413
Cell: (510) 688-0055

--

Rosi Reed
RHIC/AGS UEC member
Associate Professor, Physics Department
Lehigh University
(610)758-3907
16 Memorial Drive East Office 406
Bethlehem, PA 18015
she/her/hers