[b1_ana] (no subject)

[Dustin Keller]

Truth be told the effects will probably be negligible for all points 
because of the size of our errors, mostly just want us to be aware of the 
issue in case a PAC member brings it up.

dustin

On Thu, 23 May 2013, Elena Long wrote:

> So for our measurement of x<~0.6, we might have to worry about these effects 
> starting to come into play at the highest point but they should have a 
> negligible impact in the three lower points?
>
> Take care,
> Ellie
>
> Elena Long, Ph.D.
> Post Doctoral Research Associate
> University of New Hampshire
> elena.long at unh.edu
> ellie at jlab.org
> http://nuclear.unh.edu/~elong
> (603) 862-1962
>
> On Thu 23 May 2013 09:58:58 AM EDT, Dustin Keller wrote:
>> This is a very good and important question that remains
>> unanswered.  Historically I think we have assumed that
>> Azz~b1/F1 is good for x<1 but we also know the cut off
>> is not sharp.  I think it is not yet understood theoretically
>> how far in x b1 can be associated with Azz.  If b1 were to
>> putter-out it would not be so much an issue.
>> 
>> dustin
>> 
>> On Thu, 23 May 2013, Elena Long wrote:
>> 
>>> Good morning,
>>> 
>>> Just for clarification, what are we considering low x and high x? I'm
>>> assuming 0.5 falls in high x, but I was wondering approximately where
>>> the cut off is for these effects to start becoming important.
>>> 
>>> Thank you,
>>> Ellie
>>> 
>>> Elena Long, Ph.D.
>>> Post Doctoral Research Associate
>>> University of New Hampshire
>>> elena.long at unh.edu
>>> ellie at jlab.org
>>> http://nuclear.unh.edu/~elong
>>> (603) 862-1962
>>> 
>>> On Wed 22 May 2013 07:03:12 PM EDT, Dustin Keller wrote:
>>>> The Hoodbhoy, Jaffe and Manohar paper does express the final
>>>> relationship
>>>> to observables using the beam orientation, and there are several
>>>> proceeding steps that get us to that point that are not covered.
>>>> Its important to be critical of what we are actually measuring in
>>>> terms of
>>>> asymmetry and its definition.
>>>> 
>>>> What we will be measuring is Azz or in Jaffes script ~b1/F1.  As an
>>>> observable Azz seems to have a very generalized definition that does no
>>>> change at various x regions but of course does have orientation
>>>> dependence.  Assuming this is true allows us to bridge to the Arenhovel
>>>> formalism.  Naturally for low x Jaffes relation is valid for a target
>>>> helicity pointing along the electron beam.  In the Arenhovel formalism
>>>> this is only an approximation, but a good one.  This approximation
>>>> likely
>>>> lives in the ratio b1/F1.  Because our last kinematic points may not be
>>>> strictly thought of as low x its probably a little more accurate to use
>>>> the corrections afforded to us by the Arenhovel formalism.  This would
>>>> include a small correction to Azz from the Wigner rotation and
>>>> possible a
>>>> small correction from the vector target-only asymmetry.  By making
>>>> these
>>>> corrections for the higher x points the accuracy to Azz and b1/F1 is
>>>> slightly increased.  This line of thinking would not be valid for the
>>>> sigma_para - sigma_perp case in which you are acquiring b1
>>>> directly.  But
>>>> being we are measuring Azz we are not strictly using Jaffe for
>>>> anything.
>>>> To clarify, I can't think of any reason that for low x that one
>>>> could not
>>>> use the language Jaffe uses to describe the cross section in
>>>> relationship
>>>> to b1 and F1.
>>>> 
>>>> The corrections to Azz come into play for higher x where
>>>> pointing along the q-vector can lead to a measurable difference.  So it
>>>> maybe best to consider a response to any inquires from the PAC about
>>>> this
>>>> with some flexibility around q-vector orientation.  As it is the
>>>> correction
>>>> to Azz is a multiplicative factor of ~0.9 and the target-only vector
>>>> asymmetry is near negligible.
>>>> 
>>>> dustin
>>>> 
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>>> 
>