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sphenix-hcal-l - Re: [Sphenix-hcal-l] Calorimetry papers

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Subject: sPHENIX HCal discussion

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Chronological Thread  
  • From: Edward Kistenev <kistenev AT bnl.gov>
  • To: John Lajoie <lajoie AT iastate.edu>
  • Cc: sphenix-hcal-l AT lists.bnl.gov
  • Subject: Re: [Sphenix-hcal-l] Calorimetry papers
  • Date: Sun, 20 Sep 2015 11:07:19 -0400

I am still thinking of it. 

My smart tiles helped to understand few basics about light propagation (or better about light collection) in tiles with embedded fibers. I believe I have enough data to come with implementation for correctional pattern, and more then enough time to tune it. I am planning for asking my collaborators at Uniplast to keep few of the tiles which would otherwise be “spares” for April run at Uniplast, do the patterning to my design and ship them to us somewhat later for precision scanning (uniformly covered tiles will be available for precision scanning in October).   Most likely one iteration will be sufficient to come with correct solution. At that time - applying this kind of correction to existing simulation data will not be a problem. 

It will take us to early summer 2016 to compare beam data and simulation and into the fall to get a comprehensive picture with nonuniform (without patterning) tiles all rapidities. Testing patterning may at best be done  in spring of 2017 (or rather in the fall, we will have too much data requiring careful analysis from 2016)  sufficiently early to be on track with decision making for ordering mass production in 2018.

Edward

Edward Kistenev, PhD
PHENIX Physicist





On Sep 18, 2015, at 3:33 PM, John Lajoie <lajoie AT iastate.edu> wrote:

Hi Edward, John:

    I really wonder if grading the light response of the scintillator could go in the wrong direction. Wigmans makes the point that "Compensation relies on amplification of the signal from neutrons produced in the shower development, such as to overcome (i.e. compensate for) the effects of nuclear binding energy losses."  By grading the scintillator we are throwing out light in a depth-dependent manner. How this interacts with the distribution of where neutrons interact in the scintillator (the compensation) is something that we really can't rely on simulations to tell us (another point Wigmans continually makes). 

    If we are unlucky then in the real world we might end up making e/h *worse* with the graded tiles,  but as Edward points out this is something we will really only learn from the test beam. We should keep this in mind as we go into the reviews this fall and spring - I think what we are doing with the next prototype is some good old-fashioned calorimetry R&D.

Regards,
John

On 9/18/2015 7:39 AM, Edward Kistenev wrote:
John, once again - the answer for sPHENIX HCal is more complicated then it was in all of the configurations considered by Richard. This worries me - attempts to place this detector into the framework of a published references. On the back of the envelope the physics tells us that there should be few reasons for e/h not being unity: (1) different particle content in showering (no neutrals in em showers); (2) differences in dE/dx (no Dirk law, no columnar effect, no energy transfer to nucleus in em showers); (3) no depth leakage in em showers in hadronic calorimeters - they are always totally absorbed. Maybe more but they all work the same way  - dumping hadronic response (e/h>1). Unless you want to manipulate the absorber your only tool to improve e/h (if needed) is to act on photon component which is dominant in em but to much lesser extent in hadronic showers (and it is by default is different as it comes from large Z absorber into H-dominated scintillator). Here comes critical energy and simulation. 
I am hesitant to suggest but I would think that HCal with variable sampling fraction may have advantage in this aspect - it acts differently on showers in early and late parts, maybe this explains why e/h measured in T1044 is not 1.5 but (need to verify) rather 1.2 or 1.3. Real can of worms - guess how it will be affected by patterning of the coating.
Edward

Edward Kistenev, PhD
PHENIX Physicist




On Sep 18, 2015, at 7:05 AM, Craig Woody <woody AT bnl.gov> wrote:

Hi John,
  The e/h for the whole calorimeter obviously depends on what EMCAL you
put in front of the HCAL, and can often make e/h worse than just the e/h
of the pure HCAL alone if the composition of the two calorimeters are
very different (where might that occur..?). However, I would think
something in the range of about 1.5 would be what you might expect.

Cheers,
Craig

On 9/18/2015 12:06 AM, John Haggerty wrote:
While doing some writing on the pCDR, I was looking up some papers by
Richard Wigmans, a prominent calorimeter expert (who visited with us
early in sPHENIX history), which I put here:

https://www.phenix.bnl.gov/WWW/p/draft/haggerty/sphenix/calorimeter_papers/
If you page through only one, look at

https://www.phenix.bnl.gov/WWW/p/draft/haggerty/sphenix/calorimeter_papers/wigmans_calor11.pdf
which has good advice like

If one wants to make real progress in this field, it is imperative that scientific integrity be the guiding principle.
in addition to a very clear telling of the history of compensation, and
his evidence that you can make e/h = 1 by adjusting the sampling
fraction. I couldn't find the exact reference for Fe/scintillator, but
the plot of e/h here:

https://www.phenix.bnl.gov/WWW/p/draft/haggerty/sphenix/calorimeter_papers/Screen_Shot_2015-09-15_at_12.00.15_AM.png
seems to be consistent with our experience, where the sampling fraction
of the outer HCAL is about 3.5% and the inner is about 7% and we
evidence for e/h in the ballpark of 1.3 to 1.6.


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--

John Lajoie
PHENIX Deputy Spokesperson
Professor of Physics
Iowa State University

 

(515) 294-6952

Contact me: john.lajoie
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