[b1_ana] (no subject)

[Elena Long]

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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