[Halld-physics] [EXTERNAL] polarization orientations

Michael Dugger dugger at jlab.org
Tue Nov 26 12:25:07 EST 2019 

Hi,

Need some corrections to what I wrote :(

PARA: azimuthal angle measured from plane of polarization.

PERP: azimuthal angle measured from plane rotated 90 in azumuth to PARA

Also should have written cos(2phi + 2phi_offset)

Take care,
Michael



On Nov 26, 2019, 9:03 AM, at 9:03 AM, Michael Dugger <dugger at jlab.org> wrote:
>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 I’m not suggesting that all beam asymmetry papers need to
>include
>> this nomenclature, but instead that it’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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>>>>>>>>
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>>>>>>>>
>dOAWQ&m=1l9GEDH1beEMRZ-1rXFyQ03jeS6lDsAbJxIThw6cWz4&s=l5wph5UGumnk
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>>>>>>>
>WQ&m=1l9GEDH1beEMRZ-1rXFyQ03jeS6lDsAbJxIThw6cWz4&s=l5wph5UGumnk_uA_
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>>>>>>
>m=1l9GEDH1beEMRZ-1rXFyQ03jeS6lDsAbJxIThw6cWz4&s=l5wph5UGumnk_uA_cdDM
>>>>>> Mo-UuW3JzpCGXnGLWhMYSsY&e=
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>_mailman_listinfo_halld-2Dphysics&d=DwICAg&c=l45AxH-kUV29SRQusp9vYR0n
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>>>>>
>l9GEDH1beEMRZ-1rXFyQ03jeS6lDsAbJxIThw6cWz4&s=l5wph5UGumnk_uA_cdDMMo-U
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>>>
><https://urldefense.proofpoint.com/v2/url?u=https-3A__mailman.jlab.org_mailman_listinfo_halld-2Dphysics&d=DwICAg&c=l45AxH-kUV29SRQusp9vYR0n1GycN4_2jInuKy6zbqQ&r=zBN4Bgxto13Uvphde6V9iq67cquO40D39On3RCdOAWQ&m=1l9GEDH1beEMRZ-1rXFyQ03jeS6lDsAbJxIThw6cWz4&s=l5wph5UGumnk_uA_cdDMMo-UuW3JzpCGXnGLWhMYSsY&e=>
>>> <Barker-Donnachie-Storrow.pdf>
>>
>>
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