[g13] fitting flux ratio parameter

[Ken Livingston]

Hi Slava,
The shape and position of the coherent peak averaged over all runs for 
any coherent edge / beam energy combination will be different for PARA 
and PERP. That means the distribution of photons and photon 
polarizations as a function of photon energy will, in general, be 
different for PARA and PERP and hence the ratios (flux and polarization) 
will also vary with photon energy.

It would be useful if you could cc such mails to the g13 group, and also 
present your analysis from time to time at the g13 meetings, where many 
such issues get discussed.

( http://clasweb.jlab.org/rungroups/g13/wiki/index.php/Meetings )
( https://mailman.jlab.org/mailman/listinfo/g13 )

Regards,
Ken

On 05/12/2011 06:05 PM, slava at jlab.org wrote:
> Hi Ken,
>
> When I am fitting beam-spin asymmetry for different photon energy bins
> (same beam energy, though) using formula 7 (or right after it) in your
> "Extracting sigma" write-up, the ratio of fluxes (perp to para) parameter
> is different for different photon energy bins.
>
> At first, I was not surprised in the least since this "flux" would be the
> ratio of the numbers of photons with energies falling in this bin.
>
> Now, I am a little worried, because I do not see what would create some
> "shape" to the overall (perp/para) fluxes so that their ratios would
> fluctuate in different energy regions.
>
> Certainly, the fitting is not final, I am still using the old average
> polarizations (they fix one of the parameters) while considering data all
> the way to the coherent edge (not stopping 50 MeV away) since you said
> that polarizations all the way to coherent edges should be available as a
> matter of days. This could affect the flux ratio, but I would expect this
> effect to be on the small-ish side
>
> Could you, please, comment on this.
>
> Best regards,
> Slava
>
>    


-- 
=======================================================
Ken Livingston

Dept. of Physics&  Astronomy,        Tel: +44 141 330 6428
University of Glasgow,               Fax: +44 141 330 5889
Glasgow G12 8QQ.
Scotland. UK.
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