[Moller_pion_bg] MOLLER Pion Background Phone Meeting Friday 9 am

[Krishna Kumar]

Okay, so the efficiency curve vs Lambda may or may not make sense. If it is the efficiency curve due to photocathode QE, then that curve is unusual. If it is the 1/lambda^2 cherenkov distribution, then there is a cutoff below 250 nm. Perhaps this is the product of the two? That would perhaps make sense, but then it would be good, as a cross-check, to look at both curves (QE curve and raw cherenkov distribution) individually.

My general instinct is that if one doesn’t drill down into Geant and ensure that the physics makes sense, we are liable to get burned….

Cheers, KK

> On Mar 20, 2017, at 4:47 PM, Wouter Deconinck <wdeconinck at wm.edu> wrote:
> 
> Hi KK,
> 
> Sorry, I may not have been very clear about this. This is the PMT efficiency curve that is an INPUT to the simulation. It has nothing to do with the lucite or air emission or absorption spectrum. But, it does mean that any photon energy spectrum at the photocathode will be convoluted with this (can be taken out trivially, of course, for any new simulations).
> 
> The absorption spectrum for lucite is INPUTs as well (although to be fair all previous results were obtained with a fixed absorption length of 1 m to cut down on infinitely bouncing rays). Here's what we'd use for a more realistic lucite simulation.
> 
> <image.png>
> 
> I think technically this data is for quartz, not lucite, but it's qualitatively similar to lucite data I did find but didn't digitize (in particular sharp transmission cut-off below 350 nm).
> 
> As for air, we do not include any optical absorption currently (though we do include Cherenkov radiation, n = 1.000292).
> 
> Cheers,
> Wouter
> 
> On Mon, Mar 20, 2017 at 4:19 PM, Krishna Kumar <krishna.kumar at stonybrook.edu <mailto:krishna.kumar at stonybrook.edu>> wrote:
> Okay, this is pretty conservative. We can do better than this between 200 and 300 if it becomes an issue, but you might decide you don’t need it, which will save us money. I wonder why it cuts off though? If you didn’t explicitly put in a photocathode QE curve, what physics in G4 cuts it off? If it is gas physics, it would start cutting off below 200, not below 250. Is the scintillator material transparent below 250 or not? I don’t recall this from my prior experience. KK
> 
>> On Mar 20, 2017, at 4:08 PM, Wouter Deconinck <wdeconinck at wm.edu <mailto:wdeconinck at wm.edu>> wrote:
>> 
>> Hi all,
>> 
>> Since it came up in MOLLER pion detector simulation discussions last Friday, here is the efficiency curve of the photocathode in the pion simulations. UV photons are definitely not registered below about 230 nm.
>> 
>> <image.png>
>> 
>> Since someone will ask: from the course code I think it uses linear interpolation, constant value extrapolation outside the given range. So it'd make sense to add a zero efficiency point on both sides of the range.
>> 
>> Cheers,
>> Wouter
>> 
>> On Tue, Mar 14, 2017 at 3:20 PM, Kurtis Bartlett <kdbartlett at email.wm.edu <mailto:kdbartlett at email.wm.edu>> wrote:
>> Hello Everyone,
>> 
>> As a reminder to the members of the MOLLER Pion Background/Detector working group, there will be a meeting this week on Friday at 9am.
>> 
>> The agenda for the meeting can be found on the MOLLER wiki:
>> 
>> https://hallaweb.jlab.org/wiki/index.php/MOLLER_Pion_Background_Meeting_Friday%2C_March_17%2C_2017_9:00am_EST <https://hallaweb.jlab.org/wiki/index.php/MOLLER_Pion_Background_Meeting_Friday%2C_March_17%2C_2017_9:00am_EST>
>> 
>> Feel free to add any other points of business to the wiki.
>> 
>> Here is the Bluejeans call information:
>> 
>> URL: https://bluejeans.com/624029893 <https://bluejeans.com/624029893>
>> 
>> Phone Number: 1-888-240-2560 <tel:1-888-240-2560>
>> 
>> Meeting ID: 624029893
>> 
>> Hope to see everyone there.
>> 
>> Cheers,
>> 
>> Kurtis
>> 
>> 
>> 
>> -- 
>> Kurtis D. Bartlett
>> 
>> PhD. Research Candidate 
>> College of William and Mary Physics Department
>> kdbartlett at email.wm.edu <mailto:kdbartlett at email.wm.edu>
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>> 
>> 
>> 
>> 
>> -- 
>> Wouter Deconinck
>> Assistant Professor of Physics
>> College of William & Mary
>> Office: Small Hall 343D
>> Phone: (757) 221-3539 <tel:(757)%20221-3539>
>> 
>> Emails sent to this address are subject to requests for public review under the Virginia Freedom of Information Act.
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> 
> 
> 
> 
> -- 
> Wouter Deconinck
> Assistant Professor of Physics
> College of William & Mary
> Office: Small Hall 343D
> Phone: (757) 221-3539
> 
> Emails sent to this address are subject to requests for public review under the Virginia Freedom of Information Act.

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