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Dear all,</div>
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I don't think that anyone interpreted the gas-jet data points as a confirmation (or refutation) of the PRad-I data and I hope that I can explain the situation.</div>
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With only a handful Q2 points and a floating normalization, the gas-jet experiment was not able to differentiate between the MAMI 2010 data set and the PRad-I data points. Figure 8 shows the gas-jet data points fitted with the PRad-I Rationale(1,1) parametrization
in blue and alternatively fitted with the Mainz’s polynomial parametrization in red. Both alternatives are equally possible given the limited statistics. The reduced chi-square value is not a good discriminator for this very small number of degrees of freedom.
It was also not possible to determine a statistically meaningful slope parameter in this Q2 range, and the paper is not reporting its value. </div>
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If you carefully read Section IV. A. of the paper, you will realize that the experiment was mainly focused on commissioning the new gas-jet target and its collimator and veto systems. You can consider this paper as a demonstration that the new system has been
working successfully and that a meaningful form factor extraction can be done if enough statistics were collected and enough kinematic points were covered. This is planned for Summer 2026. </div>
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While statistics is not an issue in typical forward-angle elastic scattering kinematics with a liquid hydrogen target, the gas-jet target provided a limited luminosity and a limited jet over residual gas ratio. There is a new target operation mode that, in
the detector lab, proofed to be very promising. The 2026 beamtime will try to implement this new mode. </div>
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Best, </div>
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Patrick</div>
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<b>From:</b> PRad <prad-bounces@jlab.org> on behalf of Haiyan Gao via PRad <prad@jlab.org><br>
<b>Sent:</b> Friday, November 21, 2025 14:07<br>
<b>To:</b> gasparan <gasparan@jlab.org>; PRad mail group <prad@jlab.org><br>
<b>Subject:</b> [PRad] [EXTERNAL] Re: Fwd: paper on mainz measurements using gas jet target</div>
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Hello Ashot:</div>
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Somehow even Jan Bernauer did not mention much about this work. I just took a quick look, and their results are in better agreement with the PRad fit.</div>
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Best, Haiyan</div>
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<p style="margin: 0in; font-family: Calibri, sans-serif; font-size: 11pt;">Haiyan Gao</p>
<p style="margin: 0in; font-family: Calibri, sans-serif; font-size: 11pt;">Robert C. Richardson Distinguished Professor of Physics</p>
<p style="margin: 0in; font-family: Calibri, sans-serif; font-size: 11pt;">Department of Physics</p>
<p style="margin: 0in; font-family: Calibri, sans-serif; font-size: 11pt;">French Family Science Center 2313</p>
<p style="margin: 0in; font-family: Calibri, sans-serif; font-size: 11pt;">Duke University</p>
<p style="margin: 0in; font-family: Calibri, sans-serif; font-size: 11pt;">Durham, NC 27708</p>
<p style="margin: 0in; font-family: Calibri, sans-serif; font-size: 11pt;">Email:
<span style="color: rgb(5, 99, 193);"><u><a style="color: rgb(5, 99, 193); margin-top: 0px; margin-bottom: 0px;" class="OWAAutoLink" id="OWA42dce169-a7d3-db42-4ce2-a0347a1fdd60" href="mailto:hgao@duke.edu">hgao@duke.edu</a></u></span></p>
<p style="margin: 0in; font-family: Calibri, sans-serif; font-size: 11pt;">Phone: 919-660-2622</p>
<p style="margin: 0in; font-family: Calibri, sans-serif; font-size: 11pt;"><span style="color: rgb(5, 99, 193);"><u><a style="color: rgb(5, 99, 193); margin-top: 0px; margin-bottom: 0px;" data-auth="NotApplicable" class="OWAAutoLink" id="OWA133d3091-acdd-639e-1d8d-01fe312f661d" href="https://urldefense.proofpoint.com/v2/url?u=http-3A__www.tunl.duke.edu_-7Emep&d=DwMGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=V3XNY-MaMKN2LuAaTdObrA&m=oosjxsZaN9Gcq4x9-K3gOa-hx4fhePCHwCzeuoeHV5x4azGRA7fLcgexBIhP2s9d&s=fuOKdNiFdIMdHz3lQ9bJBCTz-h2NPquLrXw0U_A4d4I&e=">www.tunl.duke.edu/~mep</a></u></span></p>
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<b>From: </b>PRad <prad-bounces@jlab.org> on behalf of gasparan via PRad <prad@jlab.org><br>
<b>Date: </b>Friday, November 21, 2025 at 2:01 PM<br>
<b>To: </b>PRad mail group <prad@jlab.org><br>
<b>Subject: </b>[PRad] Fwd: paper on mainz measurements using gas jet target<br>
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Please check this publication pointed out by Adam (a CLAS collaborator)<br>
related the<br>
new form factor date by Minz since 2022.<br>
<br>
Ashot<br>
<br>
<br>
-------- Original Message --------<br>
Subject: paper on mainz measurements using gas jet target<br>
Date: 2025-11-21 12:40<br>
From: ajhobart <ajhobart@jlab.org><br>
To: gasparan@jlab.org<br>
<br>
Dear Ashot,<br>
<br>
The paper I was speaking about is:<br>
<br>
<a data-auth="NotApplicable" class="OWAAutoLink" id="OWAd0d1157c-7d64-df49-5589-1fe26c47446f" href="https://urldefense.proofpoint.com/v2/url?u=https-3A__journals.aps.org_prc_abstract_10.1103_PhysRevC.106.044610&d=DwMGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=V3XNY-MaMKN2LuAaTdObrA&m=oosjxsZaN9Gcq4x9-K3gOa-hx4fhePCHwCzeuoeHV5x4azGRA7fLcgexBIhP2s9d&s=m6XuJw5eedwpHbjZMJ2eC_Pp-TEjgGtbECM-iGcmaeg&e=">https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fjournals.aps.org%2Fprc%2Fabstract%2F10.1103%2FPhysRevC.106.044610&data=05%7C02%7Chaiyan.gao%40duke.edu%7Cc377941c54a8422e9d1f08de29304dbd%7Ccb72c54e4a314d9eb14a1ea36dfac94c%7C0%7C0%7C638993484610776603%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=zk9SYGrYrcxJxwt8%2BFliCt7NS2Pig2SW%2F8pnqWT62aw%3D&reserved=0</a><br>
<br>
if you check figure 8, you can see their claim that their new data is<br>
more compatible with PRad than with previous A1 measurments.<br>
<br>
Best regards<br>
<br>
Adam<br>
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