sPHENIX discussion of software

[John Lajoie <lajoie AT iastate.edu>]

Dear sPHENIX Simulators,

    As many of you are aware, there has been a lot of discussion lately about ways to reduce the overall cost of sPHENIX, and making modifications to the inner HCAL design is a part of that discussion.  One of the things that we have been looking at is the possibility of making the inner HCAL from a cheaper non-magnetic material, like Al, as opposed to SS310 stainless steel.  Another option is replacing the inner HCAL with a frame to hold up the EMCal.

    Sasha Lebedev and Abhisek have been looking at simulations of single-particle energy resolution and hadron rejection in embedded HIJING events for a Al inner HCAL, and they will present their results at next week's HCAL meeting.  At the risk of starting a discussion without most people having seen their results, I will say that the results are promising enough that I would like the simulations group and Jet ToG to start an effort to look at the jet energy resolution. As the timescale for some of these decisions is shortening, it would be helpful if there could be a discussion at this week's simulation meeting, and a start of the necessary production soon.

    As a staring point for discussion, what I suggest is the following - repeat the pythia jets production that was used in the existing jets note with the standard configuration (inner HCAL made from SS310) and a modified inner HCAL with the material made from G4_Al.  I believe that both are necessary as there have been changes to the simulation code since the previous results, most notably the HCAL digitization has now been included in the standard macros. These simulations will be able to serve two purposes:

-> Examine the effect of changing this inner HCAL material change on the jet energy resolution, and compare to the single-particle results from Abhisek.

-> Examine the effect of no inner HCAL - just an Al frame.

I believe that the latter can be done by just ignoring the inner HCAL in calculating the jet energy in the Al inner HCAL simulations, but this takes some explanation.

Let's assume that we want to replace the inner HCAL with just an Al frame. It will still need to support the weight of the EMCal. In talking with the engineers, it will still most likely be some sort of a box-beam structure (as it is now) as that is mechanically very strong.  In addition, we won't design the frame with large gaps as that would create non-uniformities and open areas that would allow the soft part of a jet to spread out in the magnetic field.  The combination of these two dictates that an Al frame would look very much like the existing inner HCAL mechanical structure, so, in the absence of a detailed frame design we can simulate the effect by just including and inner HCAL made from Al and ignoring the energy collected in the scintillator.

Including a frame of dead material will have two effects - it will degrade the energy resolution, and it could spread out the shower.  What I'm suggesting is we take the approach that we won't design a frame that makes the latter any worse, and look at the effect on the former.  This has the advantage of being something we can do right now.

Rather than doing the full pythia embedded in HIJING first, I would suggest that the jets ToG look at the energy for pythia jets first. Based on those results we could decide if a full embedded study is warranted.

Regards,
John Lajoie

On 8/28/2017 6:53 AM, Huang, Jin wrote:

Hello everyone,

 

We will have a regular sPHENIX simulation and software meeting, Tue Aug 29nd, 1PM EST @ 2-219

 

Following last week’s discussion, Tony will introduce new tunes for tracking simulation to reflect updated understanding of the TPC occupancy. Further contributions will be welcomed too.

 

The agenda page is at https://indico.bnl.gov/conferenceDisplay.py?confId=2708  , for which the common modification password is "1008"

•         For residents at BNL, we will meet at the 2-219 conference room if not closed for snow •         To join the Meeting via phone bridge:  https://bluejeans.com/619960505  •         To join via Phone:

1) Dial:

        +1.408.740.7256

        +1.888.240.2560(US Toll Free)

        +1.408.317.9253(Alternate number)

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2) Enter Conference ID: 619960505

 

Looking forward to talking to you,

 

Cheers,

 

Jin

 

 

______________________________

 

Jin HUANG

 

Associate Physicist

Brookhaven National Laboratory

Physics Department, Bldg 510 C

Upton, NY 11973-5000

 

Office: 631-344-5898

Cell:   757-604-9946

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John Lajoie

Professor of Physics

Iowa State University

 

(515) 294-6952

lajoie AT iastate.edu

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