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-------- Original Message --------
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<th valign="BASELINE" align="RIGHT" nowrap="nowrap">Subject: </th>
<td>"Danny Martinez pieschacon" <martdann@isu.edu></martdann@isu.edu></td>
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<th valign="BASELINE" align="RIGHT" nowrap="nowrap">Date: </th>
<td>Tue, 12 Jul 2011 20:01:38 -0400 (EDT)</td>
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<th valign="BASELINE" align="RIGHT" nowrap="nowrap">From: </th>
<td><a class="moz-txt-link-abbreviated" href="mailto:ctaylor@jlab.org">ctaylor@jlab.org</a></td>
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<th valign="BASELINE" align="RIGHT" nowrap="nowrap">To: </th>
<td><a class="moz-txt-link-abbreviated" href="mailto:pcollins@jlab.org">pcollins@jlab.org</a></td>
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<pre>Patrick,
Danny is still having some issues with his Jlab email, and has asked me to
forward this message to you:
******************************************************************************************
Hello Patrick, thanks for your message. I'm sorry we are responding so late
to your email, but you know the issues with Jlab servers for the people
outside the lab.
Below we address your questions and concerns. Please, feel free to
distribute it to the g8b group, since we are still unable to access jlab
email server.
>
> ---------- Forwarded message ----------
> Date: Fri, 01 Jul 2011 20:35:44 -0400
> From: Patrick Collins <a class="moz-txt-link-rfc2396E" href="mailto:pcollins@jlab.org"><pcollins@jlab.org></a>
> To: <a class="moz-txt-link-abbreviated" href="mailto:cole@physics.isu.edu">cole@physics.isu.edu</a>
> Cc: Philip L. Cole <a class="moz-txt-link-rfc2396E" href="mailto:cole@jlab.org"><cole@jlab.org></a>, <a class="moz-txt-link-abbreviated" href="mailto:g8b_run@jlab.org">g8b_run@jlab.org</a>
> Subject: Re: [G8b_run] Fwd: abstract for IX LASNPA
>
> Hello,
>
> Are you actually showing Sigmas for Egamma from 1.1 to 2.1 GeV? The way
> this is worded seems like you will be presenting data from the entire
> range.
>
Only the Sigmas for the Egam for the 1.9 coherent peak will be shown.
> The question of t-channel exchange for the omega isn't a question of
> pseudoscalar vs scalar but of pseudoscalar vs Pomeron, and analysis of
> differential cross-sections says that pion exchange is dominate below 2
> GeV.
>
For natural-parity exchange P = +(-1)*J *and that is for Pomeron and Scalar
Mesons, i.e. J^P = 0^+, 1^-, 2^+,3^-... We can insert the word Pomeron, but
we kept it out because there is always a theorist, who will ask the
question: What is a Pomeron?. If you don't say it, you don't have to answer
that question. For unnatural-parity exchange P = -(-1)*J *and that is for
pseudoscalar mesons, i.e. J^P = 0^-, 1^+, 2^-,3^+... Looking at the
t-channel in the forward direction, coupled with the differential cross
section data, the relative ratio of natural to unnatural-parity exchange
will give further measure of the pion exchange. The SDMEs will also give a
handle on this matter and Sigma, too.
> Being isospin 1/2 makes it useful in understanding the N* spectrum, but
> saying it makes for cleaner data samples doesn't make sense.
>
We have no background arising from Deltas or Delta*s. In that sense, the
data samples must be cleaner. We can add a sentence to that effect.
>
> How are you going to decompose Sigma, which is a measure of the asymmetry
> of the phi distribution of the meson, to get SDMEs, which are a function
> of the decay pions?
>
The Photon Asymmetry Parameter is formed of a combination of the SDMEs. It
gives a nice constraint on this combination of the SDMEs. If one of the
SDMEs is crazy, we will see it in comparing it to Sigma, for example. (See
the proposal for the exact formulation. I cannot access the proposal right
now since the JLab website is down, but I think it is in the early part of
the proposal). And as you say, we will extract the SDMEs from the decay
angular distributions of the pions in both the GJ and Helicity frames.
Cheers,
Danny and Phil
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