[Halld-cal] Rework Plan for Glued Light Guides

Fri May 10 17:21:55 EDT 2013

Dear collaborators,

At the last Cal Working group meeting we discussed ideas for deciding 
which light guides with partial detachment should be reglued. We also 
discussed the effort required to complete simulations, which could 
provide some guidance about how to make this decision. This question was 
further discussed at the Bcal reconstruction meeting (see 
https://halldweb1.jlab.org/wiki/index.php/BCAL_Reconstruction_Meeting_2013-05-23). 
It seems the simulations are not easily adapted to the question before 
us and the long term stability of partially detached light guides 
stability is uncertain in any case. Therefore, we have decided to simply 
replace all light guides with detached surfaces. This may be slightly 
more work, but clearly this is the time to do any repairs.

We have put together a draft plan for the rework on the wiki at 
https://halldweb1.jlab.org/wiki/index.php/Light_Guide_Rework_Plan, which 
we will refine and follow in the coming weeks. Feedback and comments are 
welcome.

Cheers, Elton.

-------- Original Message --------
Subject: 	Re: [Halld-offline] BCAL software update
Date: 	Tue, 7 May 2013 10:47:36 -0600
From: 	Zisis Papandreou <Zisis at uregina.ca>
To: 	Will Levine <wlevine at gmail.com>
CC: 	Elton Smith <elton at jlab.org>, David Lawrence <davidl at jlab.org>, 
Andrei Semenov JLab <semenov at jlab.org>, Beni Zihlmann <zihlmann at jlab.org>

Hi Will:

I will pout this item on the top of our agenda this Thursday so we can 
discuss whether going with the full code is a good way or maybe using a 
toy Monte Carlo.  We have a few of those kicking around in Regina.

Cheers, Zisis...

On 2013-05-07, at 10:02 AM, Will Levine <wlevine at gmail.com 
<mailto:wlevine at gmail.com>> wrote:

> I think what you are asking is that we simulate a light loss in a
> specific area within a specific waveguide (rather than a smaller light
> loss over the whole area of the waveguide). Is this correct? This
> sounds non-trivial, but I'm not sure exactly how hard this would be to
> implement in hdgeant, hopefully David can comment on this.
>
> As far as observing the effects on energy and position resolution: the
> shower reconstruction code is not yet extensively tested or
> bulletproofed, but the total energy and the transverse position are
> the easy quantities to calculate, so I think this will be fine.
> Anything involving the timing or z-position is more iffy, but it
> doesn't sound like you are worried about that.
>
> Will
>
> On Tue, May 7, 2013 at 8:28 AM, Elton Smith <elton at jlab.org 
> <mailto:elton at jlab.org>> wrote:
>> Hi Will,
>>
>> Glad to hear that the software environment is getting settled. I have a
>> practical question that I hope you or someone can help out with. We 
>> have run
>> into problems with light guides detaching after gluing and need to 
>> develop a
>> plan for fixes. In particular we need to establish clear guidelines 
>> for the
>> technical staff about which light guides to reglue. Some situations are
>> clear such as complete or major detachments. In addition, guides on the
>> periphery of the array will be replaced since there is clear access. A
>> single light guide with partial detachment (say 10-20%) in the middle 
>> of the
>> array creates a conundrum. This situation will lead to a light 
>> decrease in
>> the affected area of about 10%. The guides are difficult to pull off to
>> begin with and cleaning the area before regluing is not easy.
>>
>> We need to develop criteria over the next couple of weeks for deciding on
>> precisely which guides to replace. The small detachments can affect both
>> energy and position resolution. I assume the effect on energy resolution
>> will be small (10% loss of 20% area is a 2% effect), but should be
>> confirmed. The effect on transverse position resolution might be more
>> dramatic, since it will create asymmetries in the energy profile
>> distribution.
>>
>> My question is: can our present simulation study the effects of partial
>> light loss from areas on the light guide on energy and position 
>> resolution?
>> I assume this would be done with single photons and not be complicated
>> initially by multiple showers. I assume one would have to modify 
>> hdgeant to
>> implement the light loss because the information is lost when the 
>> energy is
>> collected into output channels.
>>
>> Thanks, Elton.
>>
>> Elton Smith
>> Jefferson Lab MS 12H5
>> 12000 Jefferson Ave STE 16
>> Newport News, VA 23606
>> (757) 269-7625
>> (757) 269-6331 fax
>>
>>
>> On 5/6/13 8:16 PM, Will Levine wrote:
>>>
>>> I recently checked in some changes that enable the new BCAL simulation
>>> and reconstruction code by default. This new code treats ADC and TDC
>>> hits separately and does timewalk corrections, among other things. In
>>> addition, the default BCAL clustering algorithm has been switched from
>>> the KLOE algorithm to the IU algorithm.
>>>
>>> A few notes:
>>>
>>> When updating to the latest code, you must rerun the simulation
>>> (mcsmear in particular) before running the reconstruction. Old hddm
>>> files will not work properly with the new code.
>>>
>>> Analyzing REST files from the data challenge is still possible, but
>>> you must use the -PDEFTAG:DBCALShower=KLOE option.
>>>
>>> Will
>>> _______________________________________________
>>> Halld-offline mailing list
>>> Halld-offline at jlab.org <mailto:Halld-offline at jlab.org>
>>> https://mailman.jlab.org/mailman/listinfo/halld-offline
>>
>>

Dr. Zisis Papandreou
Professor of Physics, Ph.D, P.Phys.
---------------------------------------------------------
Department of Physics
University of Regina
3737 Wascana Parkway
Regina, SK  S4S 0A2  CANADA

*Phone: (306) 585-5379*
Fax: (306) 585-5659
Email: zisis at uregina.ca <mailto:zisis at uregina.ca>
Website: http://kronos.phys.uregina.ca/~zisis/professional/ 
<http://kronos.phys.uregina.ca/%7Ezisis/professional/>

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