[Halld-physics] [EXTERNAL] polarization orientations

[Michael Dugger]

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://journals.aps.org/prc/pdf/10.1103/PhysRevC.88.065203).  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
>>>>> www.curtismeyer.com
>>>>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.curtismeyer.com&d=DwMFAg&c=CJqEzB1piLOyyvZjb8YUQw&r=p3b5acpwYNkmZ3alLqoe1DpcHi6vq5JvK_7ohJe1WqI&m=uoF2pX6Pqr0jXdX1Yj_zBCYx0Mlfo07-z6Ku8BBVZX8&s=JTIqK28pmrasWN8txNY6iK7aAvgjPibsz134yzdySNY&e=>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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