[Halld-cpp] [EXTERNAL] Re: C++ classes for the 208Pb FFs

[Richard Jones]

Rory,

Yes, that's right. The charge form factor should be a real number if the
charge distribution is parity-symmetric, which it should be for a spherical
nucleus like 208Pb. If I recall correctly, this complex form factor
description comes from an optical model that incorporates inelastic
channels as an absorptive component that is embodied in the imaginary part.
I would have to review how this works to use it, but I believe that the
Fourier transform of the charge distribution lives in the real part. As you
say, that is the part I need to complete my generator model for a lead
target.

-Richard J.

On Fri, Jul 9, 2021 at 4:33 PM Rory Miskimen <miskimen at umass.edu> wrote:

> *Message sent from a system outside of UConn.*
>
> Richard, I think for the B.H. calculation you probably just want the
> charge FF, i.e. the Fourier transform of the charge density, and a real
> number, correct? Maybe Ilya and I should converse on this.   I do have a
> Fortran code that calculates the charge FF from a model independent
> parameterization (Fourier Bessel) of the charge density (B. Frois et al.).
> Rory
>
>
> On Jul 9, 2021, at 3:42 PM, Richard Jones <richard.t.jones at uconn.edu>
> wrote:
>
> Ilya,
>
> Sure, that works. I will take whatever you can share with me and
> parameterize it for use within a Monte Carlo generator.
>
> -Richard Jones
>
> On Fri, Jul 9, 2021 at 10:41 AM Ilya Larin <ilarin at jlab.org> wrote:
>>
>>>
>>>  Hello Richard and Elton.
>>>
>>> I do have Fortran code for the lead FF.
>>> The approach we used takes into account
>>> internal absorption (reducing FF value accordingly) and thus it gives a
>>> complex value
>>> (like in optics light absorption can be described as an imaginary part
>>> of the refraction index).
>>> I can look it up. It takes about a few seconds for the Fourier Bessel
>>> nucleus density model to calculate the value. For the low Q^2 values
>>> it needs more accuracy since the region of integration
>>> proportional to 1/Q, so it takes even longer.
>>>
>>> Let me know if it is what you are asking.
>>>
>>>  Thank you.
>>>  Ilya
>>>
>>>
>>> ------------------------------
>>> *От:* Halld-cpp <halld-cpp-bounces at jlab.org> от имени Richard Jones <
>>> rjones30 at gmail.com>
>>> *Отправлено:* 7 июля 2021 г. 17:12
>>> *Кому:* Elton Smith <elton at jlab.org>
>>> *Копия:* halld-cpp at jlab.org <halld-cpp at jlab.org>
>>> *Тема:* [Halld-cpp] [EXTERNAL] Re: C++ classes for the 208Pb FFs
>>>
>>> Elton,
>>>
>>> Having them in fortran is just as good, I can do the translation.
>>>
>>> -rtj
>>>
>>> On Wed, Jul 7, 2021 at 4:51 PM Elton Smith <elton at jlab.org> wrote:
>>>
>>> *Message sent from a system outside of UConn.*
>>>
>>>
>>> Dear colleagues,
>>>
>>> Richard has requested that we provide him with C++ classes for the 208Pb
>>> form factors. I do not think we have them immediately available, but we
>>> should be able to provide them. In fact it might be useful to have them
>>> packaged systematically in that way for our own benefit. We should discuss
>>> how best to get this done at our next meeting. Any volunteers?
>>>
>>> Thanks, Elton
>>>
>>>
>>>
>>> ------------------------------------
>>> Elton Smith
>>> Jefferson Lab MS 12H3
>>> 12000 Jefferson Ave STE 4
>>> Newport News, VA 23606
>>> (757)269-7625
>>>
>>>
>>> _______________________________________________
>>> Halld-cpp mailing list
>>> Halld-cpp at jlab.org
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