sPHENIX HCal discussion

[John Lajoie <lajoie AT iastate.edu>]

Hi Barbara,

    Having dealt with KPP's/UPP's at length for the STAR ITPC upgrade last fall, I completely agree.  For the KPP we are discussing, I think the energy resolution of the HCAL would start to degrade if we failed to meet it. If that happens we wouldn't be working hard just to meet the KPP, but to meet our physics goals. In any case, I'm confident we can meet this KPP based on our test beam experience.

John

On 5/4/2017 2:02 PM, Barbara Jacak wrote:

Dear all,

Having just had some experience with the GRETA project at LBNL, I can report that the KPPs should be a goal that one is **very** confident one will achieve. We tend to think of performance parameters as specifying the technical/scientific performance we are aiming for. But that is not the right interpretation. Starting a project is essentially a contract with congress, and we need to be sure that the KPPs promise things we know we will deliver.

best regards,

Barbara

On Thu, May 4, 2017 at 11:36 AM, John Lajoie <lajoie AT iastate.edu> wrote:

Hi Abhisek,

    Great. So this is what I would propose for a KPP for both the inner an outer HCAL. 

"The standard deviation of the distribution of the Landau width for cosmics in the inner and outer HCAL towers will be <10%."

I don't propose to write a KPP based on the MPV since, as you point out, we will just adjust the voltage to get the gains matched. The Landau width is directly related to the dispersion of the SiPM gains for the scintillators within the tower, and we have demonstrated that with this spec we get adequate energy resolution in the test beam.

If this is OK with everyone I will forward this to Ed.

John

On 5/4/2017 1:11 PM, Abhisek Sen wrote:

Hi John,

    Yes they are also of similar order. (plot attached). I think MPVs are more relevant when we are taking about tower variations because thats what we used for calibration. Anyway I think it is safe to say it will be <10% tower variation in KPP.

Cheers,

Abhisek

On Thu, May 4, 2017 at 1:37 PM John Lajoie <lajoie AT iastate.edu> wrote:

Hi Abhisek,

    Very nice.  So a spec on the sigma of the normalized MPV distribution < 10% should be possible, and as you point out some of this can be removed by adjusting the voltages.

    Did you have a change to look at a measure of the width of the Landau fit to the cosmics?  I think this might be a more relevant spec, as it would tell us something about the variation of the individual SiPM gains within a tower.

John

On 5/4/2017 12:02 PM, Abhisek Sen wrote:

Hi John,

      As we discussed in the yesterday's hcal meeting, I looked into tower variations in the cosmic data from last test beam. It turns out the 12-13% variation that I quoted was without subtracting the geometry variation. Once I normalized the MPVs with respect to the simulation, geometry effect was taken out. Variation is ~6-7% among 16 towers (raw, no fit). I attached the plot below. As I mentioned, it can be further improved by adjusting the bias voltages. 

Cheers,

Abhisek

On Mon, May 1, 2017 at 11:02 AM John Lajoie <lajoie AT iastate.edu> wrote:

Dear HCAL'ers

    I have been charged by PM to come up with 1-2 "Key Performance Parameters" (KPPs) for the HCAL. For those of you not familiar with the DOE-speak on this, KPP's are low-level performance parameters that are necessary for the subsystem to ultimately perform its required role in the physics goals of the experiment. You have to be able to demonstrate that KPP's have been met prior to declaring the project complete, so they can't depend on lots of analysis and calibrations.

    As an example, you couldn't say "measure hadrons with a stochiastic term less than 100%/sqrt(E)".  That will require analysis and calibrations that might take a while after the first data is taken.

    So what should we use as KPP's for the HCAL? I have a few ideas, but I would like to hear what others have to say. For example, we could use something like: 

-> Tower cosmic ray gain calibrations within 10% tower-to-tower variation (Is this good enough? What did we achieve in the test beam?)

Keep in mind we only want 1-2 - NOT a laundry list.  We will be held to every KPP we set down, so they should be few and well thought-out.  Things like the fraction of live channels have already been called out by Ed at a higher level, so I am looking for HCAL-specific KPP's.

Let me know what you think

Regards,
John

--

John Lajoie

Professor of Physics

Iowa State University

 

(515) 294-6952

lajoie AT iastate.edu

Contact me: john.lajoie

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--

John Lajoie

Professor of Physics

Iowa State University

 

(515) 294-6952

lajoie AT iastate.edu

Contact me: john.lajoie

--

John Lajoie

Professor of Physics

Iowa State University

 

(515) 294-6952

lajoie AT iastate.edu

Contact me: john.lajoie

_______________________________________________
sPHENIX-HCal-l mailing list
sPHENIX-HCal-l AT lists.bnl.gov
https://lists.bnl.gov/mailman/listinfo/sphenix-hcal-l

--

John Lajoie

Professor of Physics

Iowa State University

 

(515) 294-6952

lajoie AT iastate.edu

Contact me: john.lajoie