<html><head></head><body><div dir="auto">Hi,<br><br></div>
<div dir="auto">Need some corrections to what I wrote :(<br><br></div>
<div dir="auto">PARA: azimuthal angle measured from plane of polarization.<br><br></div>
<div dir="auto">PERP: azimuthal angle measured from plane rotated 90 in azumuth to PARA<br><br></div>
<div dir="auto">Also should have written cos(2phi + 2phi_offset)<br><br></div>
<div dir="auto">Take care,<br></div>
<div dir="auto">Michael<br><br></div>
<div class="gmail_quote" >On Nov 26, 2019, at 9:03 AM, Michael Dugger <<a href="mailto:dugger@jlab.org" target="_blank">dugger@jlab.org</a>> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<pre class="blue">Hi,<br><br>Perhaps we can state that PARA means the azimuthal angle is measured<br>in-plane (parallel) with the polarization and PERP means that the<br>azimuthal angle is measured normal (perpindicular) to the polarization.<br>That way we recover the meaning of PARA and PERP without having to<br>reference the floor and we get the desired use of the PARA and PERP terms.<br>We would just have to add that the 0 degree and -45 degree polarization<br>directions are chosen as PARA directions.<br><br>Another way is to use the offset angle in cos(2*phi + phi_offset) and be<br>careful to state what phi_offsets correspond to PARA and PERP.<br><br>I am fine with whatever causes the least amount of confusion.<br><br>Take care,<br>Michael<br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;"> Hi Mike and Barry,<br><br> Thanks for your comments. I recognize that the PARA/PERP (or in LaTeX<br> $\perp/\parallel$) nomenclature is not required to describe the beam<br> asymmetry observable, but it can be handy in describing the yield<br> asymmetry (or moment) measurement technique, such as<br><br> \frac{Y_\perp - Y_\parallel}{Y_\perp + Y_\parallel}<br><br> So Iâm not suggesting that all beam asymmetry papers need to include<br> this nomenclature, but instead that itâs up to the discretion of the<br> paper's authors if this notation is useful to describe our measurement<br> technique.<br><br> As I mentioned before, I think this nomenclature will naturally disappear<br> as we move toward more complex observables. So I hope we can be flexible<br> with this to allow authors to draft text as they see fit and we can<br> evaluate in the Review Committee and Collaboration Review if changes<br> should be made.<br><br> -Justin<br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #ad7fa8; padding-left: 1ex;"> On Nov 22, 2019, at 12:16 PM, Barry Ritchie <Barry.Ritchie@asu.edu><br> wrote:<br><br> Notice that in this classic paper on the polarization observables, no<br> use of the terms (or symbols) PARA and PERP is present, per se. ---BGR<br><br> Professor Barry G. Ritchie<br> Department of Physics<br> Arizona State University<br> Tempe, AZ 85287-1504<br><br> Phone: (480) 965-4707<br> Fax: (480) 965-7954<br><br><br> -----Original Message-----<br> From: Halld-physics <halld-physics-bounces@jlab.org<br> <mailto:halld-physics-bounces@jlab.org>> On Behalf Of Michael Dugger<br> Sent: Friday, November 22, 2019 9:51 AM<br> To: Justin Stevens <jrsteven@jlab.org <mailto:jrsteven@jlab.org>><br> Cc: halld-physics@jlab.org <mailto:halld-physics@jlab.org><br> Subject: Re: [Halld-physics] [EXTERNAL] polarization orientations<br><br> Justin,<br><br> The PARA and PERP are orientations relative to the floor. If we use the<br> PARA and PERP to describe the 0/90 and the 45/-45 we would need to<br> specify that PARA sometime is relative to the floor and sometimes<br> relative to 45 degrees from the floor.<br><br> Please note: In my paper that you link to, it is clearly written (page<br> 3, section II, paragraph 3) that PARA and PERP orientations are relative<br> to the floor.<br><br> Once we started using 45/-45 orientations, the PARA and PERP<br> designations became confusing when describing those 45/-45 orientations.<br><br> It is only in the intermediate results that an orientation is used and<br> those orientations are always experiment specific. There is no need to<br> follow what I (or others) used in past papers for the designation of<br> polarization orientation.<br><br> The beam asymmetry has no orientation and that is the physical quantity<br> of interest.<br><br> Take care,<br> Michael<br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #8ae234; padding-left: 1ex;"> Hi All,<br><br> My 2 cents: PARA and PERP is really only a useful nomenclature for<br> beam asymmetry measurements to define our asymmetry measurement<br> technique and to be consistent with the notation used in previous<br> measurements at other experiments (and included in their papers e.g.<br> <a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__journals.aps.org_">https://urldefense.proofpoint.com/v2/url?u=https-3A__journals.aps.org_</a><br> <<a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__journals.aps.org_">https://urldefense.proofpoint.com/v2/url?u=https-3A__journals.aps.org_</a>><br> prc_pdf_10.1103_PhysRevC.88.065203&d=DwICAg&c=l45AxH-kUV29SRQusp9vYR0n<br> 1GycN4_2jInuKy6zbqQ&r=zBN4Bgxto13Uvphde6V9iq67cquO40D39On3RCdOAWQ&m=1l9GEDH1beEMRZ-1rXFyQ03jeS6lDsAbJxIThw6cWz4&s=WOXwz_QeKcg0rwCOG4mObMXNfAyaKmF8KFZbfvAwsoA&e=<br> ). For most of our ongoing and future analyses of SDMEs, amplitude<br> analyses, etc. the polarization angle is the relevant quantity and<br> PARA/PERP are unnecessary.<br><br> So I would suggest we continue using this PARA and PERP nomenclature<br> in our beam asymmetry publications if the paper's authors deem it<br> useful in describing the results. And it will likely naturally fade<br> away as we move beyond beam asymmetries.<br><br> -Justin<br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #fcaf3e; padding-left: 1ex;"> On Nov 22, 2019, at 6:34 AM, Michael Dugger <dugger@jlab.org<br> <mailto:dugger@jlab.org>> wrote:<br><br> Hi,<br><br> In my previous email I should have used the new orientations.<br><br> Where I wrote 135 degree I should have used -45 degree instead.<br><br> Take care,<br> Michael<br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #e9b96e; padding-left: 1ex;"> Hi,<br><br> I am with Mark. The PARA and PERP orientations are from the past,<br> where PARA was parallel to the floor and PERP was perpendicular to<br> the floor.<br> Internally it hardly matters, but to the outside world the PERP and<br> PARA designations used with 45/135 degree orientations will probably<br> be confusing. We just need the angles 0, 45, 90, 135.<br><br> Once the orientation is given in degree, the PARA and PERP<br> designations are superfluous.<br><br> Take care,<br> Michael<br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #ccc; padding-left: 1ex;"> I have never liked the PARA and PERP designations appearing in<br> communications outside the Collaboration. It is jargon IMHO. PARA<br> to what? PERP to what? Why ALL CAPS? Why not PARALLEL and<br> PENDICULAR?<br><br> I think 0/90 and -45/45 tell the whole story in a way that is<br> jargon-free or nearly so.<br><br> On 11/21/19 8:07 PM, Curtis A Meyer wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #ccc; padding-left: 1ex;"> Hi Everyone -<br><br> in regard to the referring to the polarization as -45/+45, Will<br> has provided the attached plot that may be useful<br><br> Curtis<br><br><br><br><br> Curtis A. 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