sPHENIX bulk physics topical group

["Narde, Apurva" <narde2 AT illinois.edu>]

Dear Vladimir,

Thank you for your feedback and questions regarding our Bulk TG meeting update. After discussing with Anthony, here are our responses to your points:

1) During the meeting, we addressed that we plan to switch the official MBD Q vectors once available and that this is a temporary approach. Yes, the second-order correction does not improve much compared to the first-order, but we are unsure if this increases our statistical uncertainties.

2) If you were referring to the event plane resolutions, no one has tried measuring the psi2 resolution with the TPC.

3) Anthony did an analysis on extracting the background corrected v2 of the pi0s, which can be found here:

This factorizes into two issues: One is the large uncertainty coming from the S/B term, which we're cross-checking. The other is the sensitivity of the background term to the S/B, but that will also be present in the equations you suggested. We can discuss this further during our weekly PPG meeting.

 

Sincerely,

Apurva Narde

---

From: Sphenix-bulk-l <sphenix-bulk-l-bounces AT lists.bnl.gov> on behalf of Vladimir Bumazhnov <bumaznov AT rcf.rhic.bnl.gov>
Sent: Monday, February 12, 2024 8:36 AM
To: sphenix-bulk-l AT lists.bnl.gov <sphenix-bulk-l AT lists.bnl.gov>
Subject: [Sphenix-bulk-l] questions on 'Bulk_TG_2_6 - 02-06-24-pi0-vn-update-v2.pdf'

 

                      Dear Apurva and All,
I have some questions on the 'Bulk_TG_2_6 - 02-06-24-pi0-vn-update-v2.pdf'
If some questions have already been asked at the presentation, please
skip such my questions.

1) page 6    I can see that 2-nd order correction does not give
anything. And probably increases the  stat  error. May be it is not
needed?

2)You measure the azimuthal angles of the particles relative to the
event plane. EMCal overlaps the area (-1.1,1.1) by eta.
You determine the event plane by MBD. MBD overlaps the areas (3.56 ,
4.45 ) and (-4.45,-3.56).
How will the event plane determined by MBD differ from the event plane
determined by the charged particles
in the central region (from TPC) ?

3) page 14   I do not understand the _expression_ for correction of
V2_pi0. It may be better to try this approximation:
    V2_M = V2_pi0/N_pi0 * n_pi0 + V2_bg/N_bg * n_bg     and then
    V2_pi0 = [V2_M - V2_bg *(n_bg/N_bg)] * (N_pi0/n_pi0)
   Here N_pi0 is the number of pi0's in signal region (μ±2σ) , n_pi0 is
the number of pi0's in selected part of signal region
  (μ±x) and |x|<=2σ. At (|x| = 2σ ) n_pi0 = N_pi0. N_bg is the number of
diphoton combinations in background region (μ+3σ, 0.5 GeV) and
  n_bg is the number of background diphoton combinations in the same
signal region  (μ±x) and |x|<=2σ.


With best regards,
                      Vladimir

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