sPHENIX discussion of physics

["Dean, Cameron" <cdean AT bnl.gov>]

Hi all,

Please find the minutes for todays meeting below.

Cheers,
Cameron, Tony and Marzia

 

Primary particle - Jakub

 

• Cameron and Jin noted that the 1nm requirement on primary particles was only present in pythia8 and was used to ensure particles were sent to Geant for a correct material description and magnetic field effect.

 

• It was also decided to preliminarily adopt a definition of primary particles having a ctau > 1 cm which is in line with LHC experiments. This will be brought up for discussion at the next PCM, and the Jet TG have been informed of these plans for discussion before the PCM.

 

• Xuan noted that the requirement of a ctau > 1 cm is specific to the LHC and we may need to use a different value to account for the different beam energy at RHIC. It was felt that because the requirement is based on the proper time then the different energies and momenta spectrum wont impact the decay time cut

 

• Marzia noted that changing the definition before QM would require a redo on all the simulations and recalculate all the observables in the jet TG which we wouldn't have time for. As an example, Derek Anderson noted that Lambdas are not decayed by pythia and have been included in the truth definition

 

K short reco - Xudong

 

• Tony recommended to set the number of INTT hits > 1

 

• On simulations, Shane Horner is running min bias simulations to estimate the upper limit on the number of K-shorts we expect to see. Preliminary is 2500 K shorts in 100000 events

 

• Joe asked about QM plans for the invariant mass plot on D0 and Lambda_c. When will we be confident enough in the alignment and K-short reconstruction to start looking for a D0 peak? Alignment vertex resolution is down to 100 microns in field-off data so we may be able to find something. Greg Ottino is looking at the vertex resolution in field-on data where we have pT information to check the resolution as a function of pT. Cameron stated that the D0 yield is about 1 in a million collisions. Say we want 1000 D0s then we want 2.5M trigger frames processed as each frame is about 400 collisions. 2.5M trigger frames corresponds to about 4 minutes of data with a 10 kHz trigger.

 

• Xin also raised the point that reconstructed signals is one thing but the background is also important which requires kinematic cuts to reduce. Cameron noted that his 1 in a million production of D0 is before selections to reduce the background.

 

• Xin also noted that the expected mass resolution is about 4 or 5 MeV for the K short. Tony then noted that the issue with the resolution currently being 15 MeV for the K short is with the space charge distortions which are not well understood at this moment

 

From: sphenix-hf-jets-l-request AT lists.bnl.gov <sphenix-hf-jets-l-request AT lists.bnl.gov> on behalf of Cameron Thomas Dean <sphenix-hf-jets-l AT lists.bnl.gov>
Date: Tuesday, February 4, 2025 at 7:28 PM
To: Osborn, Joseph via sPHENIX-physics-l <sphenix-physics-l AT lists.bnl.gov>, Huang, Jin via sPHENIX-HF-jets-l <sphenix-hf-jets-l AT lists.bnl.gov>, Anthony Frawley via sPHENIX-upsilons-l <sphenix-upsilons-l AT lists.bnl.gov>
Subject: [[Sphenix-hf-jets-l] ] Next Joint Heavy Flavor/Quarkonium Topical Group Meeting

Dear friends,

We will have our next joint open heavy flavor and quarkonia meeting tomorrow, Wednesday February 5^th at 1:30 pm ET.

The current agenda is:

 

1. Introduction - Conveners
2. Primary particle definition – Jakub Kvapil, LANL
3. K short update – Xudong Yu, Peking University

 

The agenda can be found at https://indico.bnl.gov/event/26523/ and the zoom link is https://bnl.zoomgov.com/j/1613938007?pwd=QjYzUnpYQ2xNZWZLSy9qd3Z4dFpzZz09

We look forward to talking to you tomorrow,

Cameron, Tony and Marzia