[Halld-physics] [EXTERNAL] polarization orientations

Tue Nov 26 11:03:18 EST 2019

Hi,

Perhaps we can state that PARA means the azimuthal angle is measured
in-plane (parallel) with the polarization and PERP means that the
azimuthal angle is measured normal (perpindicular) to the polarization.
That way we recover the meaning of PARA and PERP without having to
reference the floor and we get the desired use of the PARA and PERP terms.
We would just have to add that the 0 degree and -45 degree polarization
directions are chosen as PARA directions.

Another way is to use the offset angle in cos(2*phi + phi_offset) and be
careful to state what phi_offsets correspond to PARA and PERP.

I am fine with whatever causes the least amount of confusion.

Take care,
Michael

> Hi Mike and Barry,
>
> Thanks for your comments.  I recognize that the PARA/PERP (or in LaTeX
> $\perp/\parallel$) nomenclature is not required to describe the beam
> asymmetry observable, but it can be handy in describing the yield
> asymmetry (or moment) measurement technique, such as
>
> \frac{Y_\perp - Y_\parallel}{Y_\perp + Y_\parallel}
>
> So Iâ€™m not suggesting that all beam asymmetry papers need to include
> this nomenclature, but instead that itâ€™s up to the discretion of the
> paper's authors if this notation is useful to describe our measurement
> technique.
>
> As I mentioned before, I think this nomenclature will naturally disappear
> as we move toward more complex observables.  So I hope we can be flexible
> with this to allow authors to draft text as they see fit and we can
> evaluate in the Review Committee and Collaboration Review if changes
> should be made.
>
> -Justin
>
>> On Nov 22, 2019, at 12:16 PM, Barry Ritchie <Barry.Ritchie at asu.edu>
>> wrote:
>>
>> 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
>> <mailto: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 <mailto:jrsteven at jlab.org>>
>> Cc: halld-physics at jlab.org <mailto: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_
>>> <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
>>>> <mailto: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>
>>>>>>> <mailto: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=nTWoLox3qePKkU3jkN4zKWpZiD5wwsYi6X23ArE2v3s&m=tKsT0r0GoTCIvY-VCDLwLAfEK8xewTz3KgRpaRNDtP8&s=qFYlKWGSijOvWXdeGtb400qROp-lPRQlaYUcrC8bO2k&e=
>>>>>>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.curtismeyer.com&d=DwIFAw&c=CJqEzB1piLOyyvZjb8YUQw&r=nTWoLox3qePKkU3jkN4zKWpZiD5wwsYi6X23ArE2v3s&m=tKsT0r0GoTCIvY-VCDLwLAfEK8xewTz3KgRpaRNDtP8&s=qFYlKWGSijOvWXdeGtb400qROp-lPRQlaYUcrC8bO2k&e=>
>>>>>>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.curtismey
>>>>>>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.curtismey>
>>>>>>> er.com
>>>>>>> <http://er.com/>&d=DwMFAg&c=CJqEzB1piLOyyvZjb8YUQw&r=p3b5acpwYNkmZ3alLqoe1Dp
>>>>>>> cHi6vq5JvK_7ohJe1WqI&m=uoF2pX6Pqr0jXdX1Yj_zBCYx0Mlfo07-z6Ku8BBVZX8
>>>>>>> &s=JTIqK28pmrasWN8txNY6iK7aAvgjPibsz134yzdySNY&e=>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
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>>>>>>> dOAWQ&m=1l9GEDH1beEMRZ-1rXFyQ03jeS6lDsAbJxIThw6cWz4&s=l5wph5UGumnk
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>>>> l9GEDH1beEMRZ-1rXFyQ03jeS6lDsAbJxIThw6cWz4&s=l5wph5UGumnk_uA_cdDMMo-U
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>>
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>> <Barker-Donnachie-Storrow.pdf>
>
>