sPHENIX discussion of physics

[Anthony Frawley <afrawley AT fsu.edu>]

Hi Cameron,

The caveat that applies to using tracks from the SvtxTrackMap is that it contains (obviously) only reconstructed​ tracks. That is probably the best we can do right now. Ultimately, we could use reconstructed silicon track stubs for this purpose, which would avoid any inefficiencies in track reconstruction in the TPC, or TPC-silicon matching.

I think there is a good argument to use the vertex objects rather than count all tracks in the track map. That is what we will have to do with real data. The vertex object that we identify as being from the collision of interest contains a list of all track keys associated with that collision only. Practically, I think it will not make much difference for Au+Au. The MDC data set should give us a good feel for that.

Cheers

Tony

 

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From: Dean, Cameron <cdean AT bnl.gov>
Sent: Monday, November 23, 2020 5:40 PM
To: Anthony Frawley <afrawley AT fsu.edu>; sphenix-physics-l AT lists.bnl.gov <sphenix-physics-l AT lists.bnl.gov>
Subject: Re: [Sphenix-physics-l] Centrality selection in MDC analysis

 

Hi Tony,

Your idea here sounds effectively like what we (I) plan to do in the Heavy Flavor TG.

For each event, I use the SvtxTrackMap to iterate over all the tracks in the container, turn them into KFParticle objects and count how many there are. If our selection then wants to save the track, this count is passed to the output class and written to the file (example attached). Currently all the examples I have only contain one collision vertex but the code could be moved into the vertex unpacking rather than track unpacking.

My only hesitation on this was I was unsure if the SvtxTrackMap contained all tracks or whether there was a pre-selection that biased this count.

Cheers,
Cameron

 

From: sPHENIX-physics-l <sphenix-physics-l-bounces AT lists.bnl.gov> on behalf of Anthony Frawley <afrawley AT fsu.edu>
Date: Monday, November 23, 2020 at 3:22 PM
To: "sphenix-physics-l AT lists.bnl.gov" <sphenix-physics-l AT lists.bnl.gov>
Subject: [Sphenix-physics-l] Centrality selection in MDC analysis

 

Hi All,

 

I would like to understand how the topical groups plan to make centrality selections when analyzing the MDC data.

 

What are people planning to do?

 

One could use the vertex object associated with each collision. The existing code (PHVertexFinder) will create a vertex object for each collision vertex and place it on the node tree in SvtxvertexMapActs. Each collision vertex will have a list of track keys associated with that vertex. That list can be used to access the tracks from SvtxTrackMap. The most basic centrality selection could be just the number of tracks associated with the collision vertex. More advanced selections could involve applying cuts on the associated tracks.

 

Cheers

Tony