[Sane-analysis] Updated wiki section on single arm pions

[Oscar Rondon-Aramayo]

Hi Whit,

Comments below.

Cheers,

Oscar

On Fri, 10 Jan 2014 17:59:04 -0500
  Whitney Armstrong <whit at temple.edu> wrote:
> Hi Oscar,
> 
> Thank you for update. I have a few questions.
> 
> Does your version-3 of EPC, which includes OConnell's multi pion
> addition (which we'll call version-2), simply switch between the two cross 
>sections?
> 

Yes, when the pion momentum > 500 MeV/c, it only uses Wiser. But this is 
just the same as O'Connell.


> The thing that keeps confusing me about OConnell's version-2 is that he 
>integrates the bremsstrahlung spectrum
> from Wiser and not the monochromatic photo-production cross section. 

O'Connell uses the Tiator-Wright virtual photon theory, reference [9] is in 
his Computer in Physics paper (please don't post this link, it's copyrighted 
stuff)
https://userweb.jlab.org/~rondon/EPC_Lightbody.pdf

> Since the Wiser Code is a fit to the bremsstrahlung cross section, doesn't 
>the photon cross section have to be unfolded from that data? Skimming over 
>his thesis, there is mention of doing a subtraction, but I am not sure it 
>was ever done with success. 

Appendix B has some explanation of equivalent quanta and other 
bremsstrahlung jargon.

> Here is the thesis 
>http://quarks.temple.edu/~whit/papers/photo-production/Wiser_thesis/
> 
> Also, I was not sure about the "per Equivalent quanta", which after some 
>digging around various papers, I found is just the average photon energy of 
>the bremsstrahlung beam (from the threshold to the beam energy) divided by 
>the the beam energy, Q = <k>/E0
> Is this just a way of normalizing the measured bremsstrahlung photo 
>production cross sections so that they can be compared to each other, 
>independent of the electron beam energy used to produce the photon beam?
> I don't understand how this would do the deconvolution unless it is some 
>approximation...
> 
> Either way, I am not sure that OConnell properly used the Wiser fit, but 
>might be missing something.
> 
> Do you have a copy of the GPC code? 

GPC is included in EPC, just choose the option "Real photons".


> 
> Cheers,
> Whit
> 
> 
> 
> On Fri, Jan 10, 2014 at 04:31:09PM -0500, O. A. Rondon wrote:
>> I've updated my SANE wiki section on inclusive pions
>> https://hallcweb.jlab.org/experiments/sane/wiki/index.php/Inclusive_pion_and_nucleon_electroproduction
>> 
>> I've expanded the discussion of pion production via Deltas, clarifying
>> the epc*.f code cutoff of this contribution above 500 MeV/c pion
>> momentum, and added two plots comparing the cross section with and
>> without the Delta .
>> https://hallcweb.jlab.org/experiments/sane/wiki/index.php/Delta_cutoff/no_cutoff
>> 
>>  For pion momenta above 500 MeV/c, Wiser seems to be the only
>> parameterization that is based on high momentum data, so extrapolating
>> the Delta part of epc can lead to substantial overestimates. A
>> comparison of Wiser to actual pion photoproduction data (Yerevan) is
>> available on the same wiki section.
>> 
>> The assumption that is made when using Wiser to estimate SANE's pion
>> inclusive yields is that pion photoproduction from our electron beam's
>> bremsstrahlung in our 4.6% X0 target (for p.f.=0.6) is the dominant
>> mechanism to produce high momentum pions.
>> 
>> It looks like other processes would be negligible at the values of
>> p_pi > ~ 1000 MeV/c that are required to produce pairs with
>> E_cluster > 700 MeV, but it would be great to have some comparison with
>> actual single arm pion electroproduction. In any case, it doesn't seem
>> like other pion production models would work for the momenta we want.
>> 
>> Cheers,
>> 
>> Oscar
>> 
>> 
>> 
>> 
>> 
>> 
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