sPHENIX EMCal discussion

["Kistenev, Edouard" <kistenev AT bnl.gov>]

Craig, 

EMCal does not have front face (or it is ugly - saw shape along Z, polygon in phi). If we want something sensible - the best will probably be to know Z at a radius corresponding to location past which the further magnetic field effects on a shower development in calorimeter can be neglected (and track vector in that point). 

Edward

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From: sPHENIX-EMCal-l <sphenix-emcal-l-bounces AT lists.bnl.gov> on behalf of Craig Woody <woody AT bnl.gov>
Sent: Monday, February 22, 2021 2:46 PM
To: sphenix-emcal-l AT lists.bnl.gov <sphenix-emcal-l AT lists.bnl.gov>; sphenix-hcal-l AT lists.bnl.gov <sphenix-hcal-l AT lists.bnl.gov>
Subject: Re: [Sphenix-emcal-l] Track-Calorimeter Projection Radii

 

Hi John, Edward and Joe,
  I agree with John and with Edward that the logical starting point for the shower position would be the front face of the calorimeters, but then we would need to correct that for the average shower depth which depends on the energy. The correction would obviously be less for the EMCAL since it's approximately projective, but I imagine would be a fairly significant effect for both HCALs. However, it also depends on the relative EM to hadronic components of each shower with fluctuates event by event even at a given energy, so there needs to be some iterative procedure to do this and get the optimal shower position (all this with the underlying background to deal with as well). Not a simple procedure for sure. However, we did use a procedure like this when we analyzed the 2016 test beam data, so I imagine that would be a good starting point.

Cheers.
Craig

On 2/22/2021 2:18 PM, Lajoie, John G [PHYSA] wrote:

Hi Joe,

 

As a starting point we would certainly want to have projections to the approximate radii of the entrance face of the EMCal, iHCAL and oHCAL.  I’m not pretending that there is enormous physics value to these particular projections on their own, but they are a logical starting place when trying to develop algorithms and “figure things out”.

 

I like Edward’s suggestion very much; I can certainly see where it would have great value when you have projective geometry, but my feeble mind has a hard time seeing how it works for the tilted tile HCAL.  In any case, I think that is a much deeper layer of discussion.

 

John

John Lajoie

he, him, his

Professor of Physics

Iowa State University

 

(515) 294-6952

lajoie AT iastate.edu

 

From: sPHENIX-HCal-l <sphenix-hcal-l-bounces AT lists.bnl.gov> On Behalf Of Kistenev, Edouard
Sent: Monday, February 22, 2021 12:22 PM
To: Xiaochun He <xhe AT gsu.edu>; Osborn, Joe <osbornjd AT ornl.gov>; sphenix-emcal-l AT lists.bnl.gov; sphenix-hcal-l AT lists.bnl.gov
Subject: Re: [Sphenix-hcal-l] Track-Calorimeter Projection Radii

 

To whom it may concern.

 

Since the day when hadronic calorimeters were first proposed to look like they look today I was trying to make it clear that the only sensible way to assign the energy in particular tower (same in EmCAL - this is the "feature" of nearly projective geometry) is its center of gravity (mass center). This basically means that towers in analysis are 3-vectors pointing to gravity centers with deposited (measured) energies being the vector values. For simplicity (or for the physics analysis) I would suggest to deal with 4-vectors of zero mass. Then the whole analysis can be  based upon vector algebra identical to all (EM and Had) components of calorimeter system from the moment when measured energies are known to your program. 

 

This approach to treating the calorimeter sensitive elements (EM and Had towers) on a common basis allows to collect all information related to calorimeter shower candidates in a very straightforward way. It also has one more beautiful feature which is still ignored by existing analysis chain (at least I am not aware of attempts to use this idea) - it allows (physics dependent) to computationally redefine the shower tracked in the calorimeter  into more then 3-longitudinal sections (remember that in the Outer HCal shower longitudinally always seen by more then two towers (towers overlap). For the shower tracked in EMCal and IHCal the OHCal tracking may result in two correlated crossing points at a different depths in two neighbor towers. It may require a bit of iterating but improved resulting depth dependent energy leakage corrections deserve the effort. 

 

This is my two cents to this discussion.

 

Edward

 

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From: sPHENIX-EMCal-l <sphenix-emcal-l-bounces AT lists.bnl.gov> on behalf of Xiaochun He <xhe AT gsu.edu>
Sent: Monday, February 22, 2021 12:28 PM
To: Osborn, Joe <osbornjd AT ornl.gov>; sphenix-emcal-l AT lists.bnl.gov <sphenix-emcal-l AT lists.bnl.gov>; sphenix-hcal-l AT lists.bnl.gov <sphenix-hcal-l AT lists.bnl.gov>
Subject: Re: [Sphenix-emcal-l] Track-Calorimeter Projection Radii

 

Dear Joe,

 

Having the track projection is indeed very helpful. Thanks for the effort.

 

Given the intrinsic shower fluctuations in each of the calorimeter subsystems, I would think that the only meaningful layer locations are the entry points to each of the calorimeter system. It should be up to the calorimeter person who will take this info for the subsequent analysis needs. This is even more true when there is no PID info for the tracks.

 

With this said, I would think that it may be useful if the tracking package can provide a function call for the calorimeter analyzers for a projection at a given depth.

 

My two cents,

Xiaochun

--

 

From: sPHENIX-HCal-l <sphenix-hcal-l-bounces AT lists.bnl.gov> on behalf of Osborn, Joe <osbornjd AT ornl.gov>
Date: Monday, February 22, 2021 at 8:20 AM
To: sphenix-emcal-l AT lists.bnl.gov <sphenix-emcal-l AT lists.bnl.gov>, sphenix-hcal-l AT lists.bnl.gov <sphenix-hcal-l AT lists.bnl.gov>
Subject: [Sphenix-hcal-l] Track-Calorimeter Projection Radii

Dear EMCal and HCal experts,

 

Following some discussion in the software meeting last week regarding track projection to the calorimeter layers, I am prioritizing getting a new track projection module functional for broader analysis use.

 

One point of discussion was to include the track projection global position with the track, so that analyzers could potentially match this track position to calorimeter clusters or towers in their own specific way depending on what kind of analysis they are performing. The track projection software takes a set of track parameters and projects them to an arbitrary cylindrical surface at a fixed radius from the beam axis.

 

So, my question is, what is the best radius to use for each of the calorimeter layers? I would assume this should correspond to the average maximum shower depth, but perhaps the experts think something else would be best.

 

Thank you,

 

Joe Osborn

 

---------------------------

 

Joe Osborn, Ph.D.

Postdoctoral Research Associate

Oak Ridge National Laboratory

osbornjd AT ornl.gov

(859)-433-8738

 

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