STAR HardProbes PWG

[Barbara Trzeciak <barbara.trzeciak AT gmail.com>]

Date: 06/14/2024

Participants: Isaac Mooney, Joern Putschke, Zaochen Ye, Xiaoxuan Chu, Jae Nam, Nihar Sahoo, Nu Xu, ShinIchi Esumi, Subhash Singha, Ting Lin.

Sooraj Radhakrishnan, Barbara Trzeciak

Title: First measurements of jet substructure in p+Au collisions at sqrt{s_NN} = 200 GeV at STAR

PAs: Isaac Mooney, Joern Putschke

Target journal: PRD

Proposal page: https://drupal.star.bnl.gov/STAR/blog/imooney/Paper-page-jet-substructure-pAu-200-GeV-Run-15

Presentation: https://drupal.star.bnl.gov/STAR/system/files/pAu15_substructure_PWGCpreview.pdf

The PWGC panel previewed a paper proposal from HP PWG. The panel found that the analysis is mature and results are important and interesting, and the paper should move forward. The journal choice was found to be appropriate but a suggestion to consider PRC was also made. 

The following points were discussed.

Q: s9: Is this the detector level quantity ? 

A: Yes

Q: Why do you need to take into account additional activity if you’re using pAu embedding ? 

A:  MC does have activity in mid-rapidity but BBC is not simulated

Q: Adding more statistics would help, but sys. unc are quite large, what is the source?

A:  The biggest unc. come from unfolding. There should be some cancellation in the ratios that will be followed up for the paper. We will look more closely at some other uncertainties as well.

Q: Combine some of the figures e.g. 7-10.

A: We will.

Q: Conclusions, the first bullet seems to be interpretation. Suggest to go first with observation. Do we have evidence that there is hot matter in high activity p+Au.

A:  The point is that jets are not modified due to any effects, we will make it clear in the paper.

Q: Is there any rapidity dependence of the effect?

A:  We didn’t do this for this study. We will have a look.

Q: Motivation, there seems to be some modification in David’s results, how do we understand this?

A:  This is rather a kinematic effect, it is explained in the paper.

Q: Physics seems to be better for PRC than PRD.

A:  That’s a good point. It’s where we published pp, but we can think about PRC.

Q: What is the used simulation?

A: This is pAu Pythia 6 di-jet embedded into pAu MinBias.

Q: How is VPD simulated? Also, HFT is not well simulated.

A: We don’t know about VPD, and the simulation is without HFT for tracking.

We can have a look. But HFT gives background.

Q: Is your VPD Vz cut of 6 cm good for pAu ?

A:  We even cut more, on 3cm in data. We will cross check this.

Q: What is the centrality definition?

A:  It's just an activity in BBC.

Q: But then you quote the percentage, and it’s not corrected. You may just call it high and low activity.

Q: What’s correlation between the BBC activity and mid-rapidity multiplicity, how does it increase for high activity BBC?

A:  We will check this.

Q: Do you have any pileup cuts, or evaluated the effect? 

A:  No, we don’t. The effect is small in this analysis and was just for the earlier pAu analysis, we can check this though in more detail.