sPHENIX discussion of physics

[Cameron Thomas Dean <cameron.dean AT cern.ch>]

Hi Greg,

Thanks for the nice study, it will be very important for us to know how triggered mode impacts the heavy flavor program and things like this will give us a feel for it. For now, we don’t know exactly where we would lose low momentum kaon or protons and we have people trying to answer that question. We may be lucky and the loss is below where we can track. We should follow up in the tracking meeting, and then rerun these studies when we have the efficiency curves. My guess would be it’s a slow drop in efficiency rather than a hard cut.

Cheers,
Cameron

 

From: sphenix-physics-l-request AT lists.bnl.gov <sphenix-physics-l-request AT lists.bnl.gov> on behalf of Gregory Ottino <gottino AT lbl.gov>
Date: Friday, October 25, 2024 at 12:39 PM
To: sphenix-physics-l AT lists.bnl.gov <sphenix-physics-l AT lists.bnl.gov>
Subject: [[Sphenix-physics-l] ] Fwd: Open Heavy Flavor question and MVTX triggered/streaming mode

 

Hi all,

 

I wanted to reply to Jamie's message with a few slides that I hope are useful. I went ahead and simulated 1M ccbar events to look at the efficiencies of D0 and LambdaC reco taking into account the constraints from MVTX triggered readout presented in Jamie's email from Oct 20th. I simulated 1M pythia pp -> ccbar events and looked at the acceptance effect on the charm hadron reconstruction.

 

Best,

Greg

 

 

---------- Forwarded message ---------
From: Jamie Nagle <jamie.nagle AT colorado.edu>
Date: Sun, Oct 20, 2024 at 12:15 PM
Subject: [[Sphenix-physics-l] ] Open Heavy Flavor question and MVTX triggered/streaming mode
To: <sphenix-physics-l AT lists.bnl.gov>

 

Hello All,

 

When we have been taking AuAu data with the MVTX in triggered mode, the default trigger latency is about 3.7 microseconds.    The auto-recoveries are substantially reduced relative to streaming mode depending on the DAQ rate.   There is a concern that this triggered mode might be clipping the signal from high-charge-deposit signals - which might predominantly be from lower momentum kaons and protons.     There are some initial indicators that in this triggered mode, the MVTX hits are being recorded from most pions (which is a good sign).   See the slides below that were shown at a meeting with C-AD last week.

 

Thus, I have a physics question, if in triggered mode with this latency the hits were lost for the range on the dEdx figure > 150 (arbitrarily chosen), then sPHENIX might have lower efficiency for kaons with p  < 0.4 GeV (total momentum) and protons with p < 0.7 GeV (total momentum).      For the open heavy flavor program (D0, D_s, Lambda_c) what would be the impact on the acceptance as a function of eta and pT for reconstruction of these decays?     A first look might be useful just from PYTHIA (without GEANT) and calculate with nominal sPHENIX acceptance and then with these cuts.

 

As an aside, sPHENIX was running last night with AuAu 111x111 bunches at 1 mrad with a DAQ rate of 1.5 kHz.     The MVTX was in triggered mode with the 3.7 microsecond latency and the number of auto-recoveries was very small -- see below (almost all green, and not red).     This running last night represents the best sPHENIX AuAu sample at higher luminosity for checking the triggered mode -- see the run list below.    This all means we still need significant reduction in backgrounds (factor of 10) from C-AD to run at 10-15 kHz next year, but triggered versus streaming gives us a big part of the step towards running.     That is why the question above is important.    

 

Sincerely,

 

Jamie

Run = 54925 Evts = 0.373 M,  Duration = 5.27 min. Start = Sat Oct 19 18:14:01 2024 EDT
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Run = 54953 Evts = 1.85 M,  Duration = 27.9 min. Start = Sun Oct 20 13:09:12 2024 EDT

||------------------------------------------------------------------------------------------
|| James L. Nagle   
|| Professor of Physics, University of Colorado Boulder

|| EMAIL:   jamie.nagle AT colorado.edu
|| SKYPE:  jamie-nagle        
|| WEB:      http://spot.colorado.edu/~naglej 
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