<div dir="ltr">Rory,<div><br></div><div>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.</div><div><br></div><div>-Richard J.</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Jul 9, 2021 at 4:33 PM Rory Miskimen <<a href="mailto:miskimen@umass.edu">miskimen@umass.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<div>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
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<div>On Jul 9, 2021, at 3:42 PM, Richard Jones <<a href="mailto:richard.t.jones@uconn.edu" target="_blank">richard.t.jones@uconn.edu</a>> wrote:</div>
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<div dir="ltr">Ilya,
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<div>Sure, that works. I will take whatever you can share with me and parameterize it for use within a Monte Carlo generator.</div>
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<div>-Richard Jones</div>
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<div dir="ltr" class="gmail_attr">On Fri, Jul 9, 2021 at 10:41 AM Ilya Larin <<a href="mailto:ilarin@jlab.org" target="_blank">ilarin@jlab.org</a>> wrote:<br>
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Hello Richard and Elton.</div>
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I do have Fortran code for the lead FF.</div>
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The approach we used takes into account</div>
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internal absorption (reducing FF value accordingly) and thus it gives a complex value</div>
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(like in optics light absorption can be described as an imaginary part of the refraction index).<br>
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I can look it up. It takes about a few seconds for the Fourier Bessel</div>
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nucleus density model to calculate the value. For the low Q^2 values</div>
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it needs more accuracy since the region of integration</div>
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proportional to 1/Q, so it takes even longer.</div>
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Let me know if it is what you are asking.</div>
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Thank you.</div>
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Ilya</div>
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<font style="font-size:11pt" face="Calibri, sans-serif"><b>От:</b> Halld-cpp <<a href="mailto:halld-cpp-bounces@jlab.org" target="_blank">halld-cpp-bounces@jlab.org</a>> от имени Richard Jones <<a href="mailto:rjones30@gmail.com" target="_blank">rjones30@gmail.com</a>><br>
<b>Отправлено:</b> 7 июля 2021 г. 17:12<br>
<b>Кому:</b> Elton Smith <<a href="mailto:elton@jlab.org" target="_blank">elton@jlab.org</a>><br>
<b>Копия:</b> <a href="mailto:halld-cpp@jlab.org" target="_blank">
halld-cpp@jlab.org</a> <<a href="mailto:halld-cpp@jlab.org" target="_blank">halld-cpp@jlab.org</a>><br>
<b>Тема:</b> [Halld-cpp] [EXTERNAL] Re: C++ classes for the 208Pb FFs</font>
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<div dir="ltr">Elton,
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<div>Having them in fortran is just as good, I can do the translation.</div>
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<div>-rtj</div>
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<div dir="ltr">On Wed, Jul 7, 2021 at 4:51 PM Elton Smith <<a href="mailto:elton@jlab.org" target="_blank">elton@jlab.org</a>> wrote:<br>
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Dear colleagues,<br>
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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?<br>
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Thanks, Elton<br>
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------------------------------------<br>
Elton Smith<br>
Jefferson Lab MS 12H3<br>
12000 Jefferson Ave STE 4<br>
Newport News, VA 23606<br>
(757)269-7625<br>
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