[Halld-npp] Primakoff cross section

[Elton Smith]

Hi Ilya,

I compared your calculation of the cross section in the LOI. See figs. 
3-5. I get a cross section/nucleus of 345 nb. If you took Jose's cross 
section directly, you need to divide your value 200 nb by 0.8 since it 
is for |costhe|<0.8, which gives 250 nb, or 70% of my value.

You can check my parameterization of sigma(gg->pi0pi0) (Fig. 3) with 
Jose's. I assumed it is essentially flat above the threshold instead of 
having a shape. This may explain most of the remaining discrepancy. We 
may wish to update the document with your value since Jose's 
parameterization is more constrained, but we can discuss this.

Cheers, Elton.

Elton Smith
Jefferson Lab MS 12H3
12000 Jefferson Ave STE 4
Newport News, VA 23606
(757)269-7625
(757)269-6331 fax

On 2/28/20 2:36 PM, Elton Smith wrote:
> Dear collaborators,
>
> I have posted the minutes from the NPP meeting this morning on the 
> wiki at 
> https://halldweb.jlab.org/wiki/index.php/Pi0_Polarizability_Meeting_Feb_28,_2020#Minutes. 
>
>
> Ilya: You can go ahead an link your presentation directly to the 
> meeting page.
>
> Thanks, Elton.
>