sPHENIX bulk physics topical group

["Hodges, Anthony" <ahodges4 AT illinois.edu>]

Hi Vladimir, 

Thanks for the interesting questions:

1. What % of pi0s is created in jets and mini-jets? And how this % of pi0s does depend on the pi0 P_t?

I'm not quite sure about the first part but, I think one can easily assume, and PYTHIA simulations back up, that the higher the p_T of any given particle increases the chance that its production is associated with a jet. Our ability to reconstruct pi0's beyond 4-5GeV/c however is limited due to the position resolution of the EMCal, so I would think the pi0 population in our analysis is dominated by soft processes. 

2. If you did, it would be interesting to see how event plane does depend on the particles P_t? I mean following: you determine the set of event plane angles Psi using only charge particles with P_t > 1., 2., 3.5, 4.5 GeV/C.
   

I'm not sure I understand. This analysis doesn't make explicit use of the event plane, nor would it make sense to use an event plane calculated at mid-rapidity using the TPC or tracking in general (for this analysis) because it would auto-correlate to any jet-like activity in the event. The Scalar Product method we employ uses the PMT's in the MBD arms at forward and backwards pseudorapidity to serve as the reference points to calculate the v_2, so the p_T of the particles is completely uncoupled from anything event-plane like. 

3. How this Psi will depend on P_t cut? Of course MBD will not help in this case. TPC is needed. And it would be interesting to see v2_pi0 for all these event plane angles.
   

Right, I suppose these are interesting questions, but we use the MBD (and, in the future, the sEPD) to avoid exactly the problems you're posing here. Calculating the event plane at mid-rapidity gives you a biased result because multiple physics processes will affect the determination, but using the forward detectors should reduce this bias. We would need to develop another study to look into the behavior of the event plane at mid-rapidity, which I think falls outside the scope of this analysis, unfortunately. 

Best, 

-Anthony

Anthony Hodges, PhD (he/him/his)

High Energy Experimental Nuclear Physics

Postdoctoral Researcher, NSF MPS-Ascend Fellow

University of Illinois Urbana-Champaign

---

From: Sphenix-bulk-l <sphenix-bulk-l-bounces AT lists.bnl.gov> on behalf of Vladimir Bumazhnov <bumaznov AT rcf.rhic.bnl.gov>
Sent: Wednesday, March 13, 2024 8:21 AM
To: sphenix-bulk-l AT lists.bnl.gov <sphenix-bulk-l AT lists.bnl.gov>
Subject: [Sphenix-bulk-l] questions on 03-13-24-pi0-vn-update.pdf

 

                       Dear Apurva, Justin, Grace  and All,
I have some questions on the  03-13-24-pi0-vn-update.pdf
If some questions have already been asked at the presentation, please
skip such my questions.

1) What % of pi0s is created in jets and mini-jets? And how this % of
pi0s does depend on the pi0 P_t?

2) If you did, it would be interesting to see how event plane does
depend on the particles P_t? I mean
    following: you determine the set of event plane angles Psi using
only charge particles with P_t > 1., 2., 3.5, 4.5 GeV/C.
   How this Psi will depend on P_t cut? Of course MBD will not help in
this case. TPC is needed.
   And it would be interesting to see v2_pi0 for all these event plane
angles.

3) Is it necessary to include jet and mini-jet charge particles in
determination of the event plane angle Psi ?
    What does theory talk about it?

With best regards,
                      Vladimir

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