[Halld-physics] [EXTERNAL] polarization orientations

Fri Nov 22 12:16:46 EST 2019

Notice that in this classic paper on the polarization observables, no use of the terms (or symbols) PARA and PERP is present, per se.   ---BGR

Professor Barry G. Ritchie 
Department of Physics 
Arizona State University 
Tempe, AZ 85287-1504

Phone: (480) 965-4707 
Fax: (480) 965-7954

-----Original Message-----
From: Halld-physics <halld-physics-bounces at jlab.org> On Behalf Of Michael Dugger
Sent: Friday, November 22, 2019 9:51 AM
To: Justin Stevens <jrsteven at jlab.org>
Cc: halld-physics at jlab.org
Subject: Re: [Halld-physics] [EXTERNAL] polarization orientations

Justin,

The PARA and PERP are orientations relative to the floor. If we use the PARA and PERP to describe the 0/90 and the 45/-45 we would need to specify that PARA sometime is relative to the floor and sometimes relative to 45 degrees from the floor.

Please note: In my paper that you link to, it is clearly written (page 3, section II, paragraph 3) that PARA and PERP orientations are relative to the floor.

Once we started using 45/-45 orientations, the PARA and PERP designations became confusing when describing those 45/-45 orientations.

It is only in the intermediate results that an orientation is used and those orientations are always experiment specific. There is no need to follow what I (or others) used in past papers for the designation of polarization orientation.

The beam asymmetry has no orientation and that is the physical quantity of interest.

Take care,
Michael

> Hi All,
>
> My 2 cents: PARA and PERP is really only a useful nomenclature for 
> beam asymmetry measurements to define our asymmetry measurement 
> technique and to be consistent with the notation used in previous 
> measurements at other experiments (and included in their papers e.g.
> https://urldefense.proofpoint.com/v2/url?u=https-3A__journals.aps.org_
> prc_pdf_10.1103_PhysRevC.88.065203&d=DwICAg&c=l45AxH-kUV29SRQusp9vYR0n
> 1GycN4_2jInuKy6zbqQ&r=zBN4Bgxto13Uvphde6V9iq67cquO40D39On3RCdOAWQ&m=1l9GEDH1beEMRZ-1rXFyQ03jeS6lDsAbJxIThw6cWz4&s=WOXwz_QeKcg0rwCOG4mObMXNfAyaKmF8KFZbfvAwsoA&e= ).  For most of our ongoing and future analyses of SDMEs, amplitude analyses, etc. the polarization angle is the relevant quantity and PARA/PERP are unnecessary.
>
> So I would suggest we continue using this PARA and PERP nomenclature 
> in our beam asymmetry publications if the paper's authors deem it 
> useful in describing the results.  And it will likely naturally fade 
> away as we move beyond beam asymmetries.
>
> -Justin
>
>> On Nov 22, 2019, at 6:34 AM, Michael Dugger <dugger at jlab.org> wrote:
>>
>> Hi,
>>
>> In my previous email I should have used the new orientations.
>>
>> Where I wrote 135 degree I should have used -45 degree instead.
>>
>> Take care,
>> Michael
>>
>>> Hi,
>>>
>>> I am with Mark. The PARA and PERP orientations are from the past, 
>>> where PARA was parallel to the floor and PERP was perpendicular to the floor.
>>> Internally it hardly matters, but to the outside world the PERP and 
>>> PARA designations used with 45/135 degree orientations will probably 
>>> be confusing. We just need the angles 0, 45, 90, 135.
>>>
>>> Once the orientation is given in degree, the PARA and PERP 
>>> designations are superfluous.
>>>
>>> Take care,
>>> Michael
>>>
>>>> I have never liked the PARA and PERP designations appearing in 
>>>> communications outside the Collaboration. It is jargon IMHO. PARA 
>>>> to what? PERP to what? Why ALL CAPS? Why not PARALLEL and PENDICULAR?
>>>>
>>>> I think 0/90 and -45/45 tell the whole story in a way that is 
>>>> jargon-free or nearly so.
>>>>
>>>> On 11/21/19 8:07 PM, Curtis A Meyer wrote:
>>>>> Hi Everyone -
>>>>>
>>>>>    in regard to the referring to the polarization as -45/+45, Will 
>>>>> has provided the attached plot that may be useful
>>>>>
>>>>> Curtis
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Curtis A. Meyer|MCS Associate Dean for Research The Otto Stern 
>>>>> Professor of Physics cmeyer at cmu.edu
>>>>> <mailto:cmeyer at cmu.edu>|412 268 2745 Carnegie Mellon University 
>>>>> Department of Physics, Wean Hall 8414
>>>>> 5000 Forbes Ave., Pittsburgh PA, 15213 https://urldefense.proofpoint.com/v2/url?u=http-3A__www.curtismeyer.com&d=DwIFAw&c=CJqEzB1piLOyyvZjb8YUQw&r=p3b5acpwYNkmZ3alLqoe1DpcHi6vq5JvK_7ohJe1WqI&m=ZskEP8jwta7XYu_uoqe7CdqAiTq90B1zPY1maLoFqWg&s=_Cn7O4X2MGrtz2hdOwcLVRhTeBQ92nkJFTfTSwlhAB4&e=  
>>>>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.curtismey
>>>>> er.com&d=DwMFAg&c=CJqEzB1piLOyyvZjb8YUQw&r=p3b5acpwYNkmZ3alLqoe1Dp
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>>>>> &s=JTIqK28pmrasWN8txNY6iK7aAvgjPibsz134yzdySNY&e=>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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