<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=Windows-1252">
<style type="text/css" style="display:none;"> P {margin-top:0;margin-bottom:0;} </style>
</head>
<body dir="ltr">
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
My answers are the same.</div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
The eta cross-section and differential cross-sections were measured in Mainz & Bonn with Deuteron, Helium-3, and Helium-4 targets from threshold to ~2.5 GeV in incident photon-beam energies. We found that the Nuclear Incoherent = quasi-free proton + quasi-free
neutron meaning the only obvious nuclear effect is the Fermi motion this was done and I had done it for eta and etaprime by folding the Fermi motion into the eta cross-section and differential cross-sections with a Hydrogen target.</div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
It is fair to assume that it is also the case above 2.5 GeV. Futhermore I can also check it experimentally with the data available.</div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
tks ig.</div>
<div id="appendonsend"></div>
<hr style="display:inline-block;width:98%" tabindex="-1">
<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> gasparan <gasparan@jlab.org><br>
<b>Sent:</b> Friday, November 1, 2024 2:49 PM<br>
<b>To:</b> Igal Jaegle <ijaegle@jlab.org><br>
<b>Cc:</b> primexd@jlab.org <primexd@jlab.org>; Malte Albrecht <malte@jlab.org>; Justin Stevens <jrsteven@jlab.org>; Eugene Chudakov <gen@jlab.org>; Shepherd, Matthew <mashephe@indiana.edu><br>
<b>Subject:</b> Re: [Primexd] Questions on the PrimEx analysis strategy</font>
<div> </div>
</div>
<div class="BodyFragment"><font size="2"><span style="font-size:11pt;">
<div class="PlainText"><br>
Hi Igal,<br>
<br>
I went through the pointed text. Our old question is: what is the <br>
Nuclear Incoherent<br>
amplitude (or the process). We first need to define it clearly then to <br>
see its<br>
properties.<br>
Ashot<br>
<br>
<br>
On 2024-11-01 13:22, Igal Jaegle wrote:<br>
> Please look at this:<br>
> <br>
> <br>
> <a href="https://halldweb.jlab.org/DocDB/0066/006668/001/primexd-igal-jaegle-01112024.pdf">
https://halldweb.jlab.org/DocDB/0066/006668/001/primexd-igal-jaegle-01112024.pdf</a><br>
> <br>
> <br>
> tks ig.<br>
> <br>
> -------------------------<br>
> <br>
> From: gasparan <gasparan@jlab.org><br>
> Sent: Friday, November 1, 2024 12:15 PM<br>
> To: Igal Jaegle <ijaegle@jlab.org><br>
> Cc: primexd@jlab.org <primexd@jlab.org>; Malte Albrecht<br>
> <malte@jlab.org>; Justin Stevens <jrsteven@jlab.org>; Eugene Chudakov<br>
> <gen@jlab.org>; Shepherd, Matthew <mashephe@indiana.edu><br>
> Subject: Re: [Primexd] Questions on the PrimEx analysis strategy<br>
> <br>
> Hi Igal,<br>
> <br>
> I see we have some good agreements on some parts and still have some<br>
> different interpretations, especially on the Nuclear Incoherent<br>
> part.<br>
> Let's discuss this part in our upcoming meeting(s).<br>
> <br>
> Best,<br>
> Ashot<br>
> <br>
> On 2024-10-31 15:13, Igal Jaegle wrote:<br>
>> Thank you, Ashot, for finding the time to give your answers in your<br>
>> busy schedule.<br>
>> <br>
>> Questions #1, I see that we are converging toward the same answer.<br>
>> <br>
>> Questions #2, my understanding is that Ilya used different<br>
> elementary<br>
>> amplitude scenario/model for the Nuclear Coherent but these changes<br>
>> were not applied to the Nuclear Incoherent or what you call<br>
>> background. I do not agree with this approach. If the elementary<br>
>> amplitude used in the Nuclear Coherent is changed then the exact<br>
> same<br>
>> changed must be applied to the Nuclear Incoherent part. This cannot<br>
> be<br>
>> neglected and looking at the variation of the chi^2 will not capture<br>
>> correctly the systematic error linked to the model dependence.<br>
>> <br>
>> Here by different models, I am also referring to the inclusion yes<br>
>> or no of the quasi-free Primakoff/Coulomb and more importantly the<br>
>> corresponding interference between the quasi-free Primakoff/Coulomb<br>
>> and rho+omega terms.<br>
>> <br>
>> Questions #3, we do not agree. Any changes to the elementary<br>
>> amplitudes contributing to the Nuclear Coherent term must also be<br>
>> applied to the Nuclear Incoherent term because any changes to the<br>
>> elementary amplitudes will change automatically the shape of the<br>
>> Nuclear Incoherent particularly at small angle particularly for the<br>
>> eta case.<br>
>> <br>
>> tks ig.<br>
>> <br>
>> -------------------------<br>
>> <br>
>> From: gasparan <gasparan@jlab.org><br>
>> Sent: Thursday, October 31, 2024 2:10 PM<br>
>> To: Igal Jaegle <ijaegle@jlab.org><br>
>> Cc: primexd@jlab.org <primexd@jlab.org>; Malte Albrecht<br>
>> <malte@jlab.org>; Justin Stevens <jrsteven@jlab.org>; Eugene<br>
> Chudakov<br>
>> <gen@jlab.org>; Shepherd, Matthew <mashephe@indiana.edu><br>
>> Subject: Re: [Primexd] Questions on the PrimEx analysis strategy<br>
>> <br>
>> Hi Igal,<br>
>> <br>
>> Here are my initial answers to your three basic questions outlined<br>
> in<br>
>> your recent text. The text is also attached to this email<br>
>> and it is not edited for a wider use.<br>
>> <br>
>> Question #1<br>
>> Which process(es) can we measure?<br>
>> My answer:<br>
>> If one includes the BCAL in coincidence with the eta detected in the<br>
>> FCAL then the list of measurable processes is rather large,<br>
> including<br>
>> some elastic and very many inelastic reactions.<br>
>> However, we cannot measure the gamma + He4 -> eta + He4 elastic<br>
>> process<br>
>> at these small angles since recoil He4 (or alpha) can not reach to<br>
> the<br>
>> <br>
>> BCAL sensitive area due to its small recoil energy. With that in<br>
> mind,<br>
>> <br>
>> all Primakoff type experiments so far are designed to not attempt<br>
>> measuring the recoil nuclei since it is not possible at ~~1-degree<br>
>> angles. In particular, our current eta-proposal is designed/approved<br>
>> without measuring the recoil alpha particles in the elastic<br>
> reaction.<br>
>> Rather we assume that at these angles (0-4 degrees) the events<br>
> without<br>
>> <br>
>> the recoil alpha detection can be: (a) Primakoff coherent; (b)<br>
> nuclear<br>
>> <br>
>> coherent; (c) interference between them; (d) all kind of incoherent<br>
>> and<br>
>> inelastic processes having an eta as a one of final states. We call<br>
>> the<br>
>> (d) as a background in our experiment(s).<br>
>> The remaining question is how to identify them and fit out<br>
> underneath<br>
>> of<br>
>> the Primakoff part but, this is a separate question.<br>
>> <br>
>> Question #2<br>
>> Can we rely on only one model and/or only one scenario for the<br>
>> radiative<br>
>> decay width extraction?<br>
>> My answer:<br>
>> It is always better to have more than one model to use in the<br>
>> extraction<br>
>> process (since any model is not a fundamental theory, also includes<br>
>> some<br>
>> limited information only). If we succeed to have at least two<br>
> models,<br>
>> we<br>
>> need to use them both. If we do not have the second model, then we<br>
>> will<br>
>> rely on it and state it in the publication.<br>
>> About the “…only one scenario…”. Obviously, it is better to<br>
>> have two or<br>
>> more ways to extract the decay width. In pi0 PrimEx in Hall B we had<br>
>> 3.<br>
>> Here we are trying hard to have 2 at least.<br>
>> <br>
>> Question #3<br>
>> Can the built-in model interdependence between the Nuclear<br>
>> Incoherent<br>
>> term and the Primakoff and Nuclear Coherent terms be neglected?<br>
>> My answer:<br>
>> This question needs more clear wording to try answering it. However,<br>
> I<br>
>> <br>
>> will guess the question and try to answer it. Two processes<br>
> (mentioned<br>
>> <br>
>> above) (a) Primakoff (that is electromagnetic coherent exchange<br>
>> reaction) and (b) the “Nuclear coherent” (that is the same only<br>
>> with a<br>
>> hadronic exchange) kinematically (and quantum mechanically) are the<br>
>> same<br>
>> (if you want, similar) elastic and coherent processes. They can be<br>
>> simulated by theory very accurately. Small exception is some<br>
> constants<br>
>> <br>
>> and parameters, mostly for the nuclear coherent part. In addition,<br>
>> since<br>
>> they are quantum mechanically similar, they have an interference<br>
> term<br>
>> as<br>
>> a process, this is also a predictable thing with the phase angle.<br>
>> The so-called “incoherent part” in reality is all processes<br>
> other<br>
>> than<br>
>> first two. We call them as a “background” in the Proposal.<br>
>> The short answer: If we have all these 4 processes simulated<br>
>> (predicted)<br>
>> by model(s) then we should not “… neglect…” or ignore any<br>
>> process, we<br>
>> simply include them in our extracted cross section for all forward<br>
>> angles. This is related to the good case when we are hoping to 1-3%<br>
>> extraction. Since (unfortunately) we are not there yet there are<br>
>> several<br>
>> variations in my previous statement. That is a separate subject, and<br>
>> we<br>
>> had discussed them in our meeting many-many times.<br>
>> <br>
>> Best,<br>
>> Ashot<br>
>> <br>
>> On 2024-10-18 12:08, Igal Jaegle via Primexd wrote:<br>
>>> Hi, Ashot,<br>
>>> <br>
>>> I put into a note my questions,<br>
>>> <a href="https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=6668">
https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=6668</a><br>
> [1]<br>
>>> [1].<br>
>>> <br>
>>> A dedicated PrimEx discussion at the GlueX Physics Working Group<br>
>>> Meeting would be highly beneficial, especially if there are<br>
>> differing<br>
>>> perspectives on how to address these questions. We would greatly<br>
>>> welcome such a discussion.<br>
>>> <br>
>>> tks ig.<br>
>>> <br>
>>> Links:<br>
>>> ------<br>
>>> [1]<br>
>> <a href="https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=6668">
https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=6668</a><br>
>> [1]<br>
>>> _______________________________________________<br>
>>> Primexd mailing list<br>
>>> Primexd@jlab.org<br>
>>> <a href="https://mailman.jlab.org/mailman/listinfo/primexd">https://mailman.jlab.org/mailman/listinfo/primexd</a><br>
>> <br>
>> <br>
>> Links:<br>
>> ------<br>
>> [1]<br>
> <a href="https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=6668">https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=6668</a><br>
> [1]<br>
> <br>
> <br>
> Links:<br>
> ------<br>
> [1] <a href="https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=6668">
https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=6668</a><br>
</div>
</span></font></div>
</body>
</html>