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<p class="MsoNormal"><span style="font-size:11.0pt">Hello strangers,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">When we wrote our proposals over a decade ago, we assumed an electron beam energy of 11 GeV.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">We were asked to evaluate the impact on the expected results if we ran at lower energy and the minimum acceptable beam energy. See Latifa’s message below. In the first installation of RGA, we were running
at ~10.6 GeV. Some of RGB was even lower, ~10.4 GeV.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Regarding the strongness program, the higher energy means higher statistics because the incident energy extends farther above thresholds, and we get more virtual photon flux above thresholds, which translates
to higher reaction yield. We should try to quantify the impact, for instance, assuming beam energy 10.4 vs 11 GeV. If this impact is significant, we may request additional beam time to compensate for the losses due to running at lower energy. Any volunteers
to make an estimate? <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Please think about it, send your thoughts and we will discuss this at our meeting next week.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Cheers,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:black">-Eugene</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<b><span style="color:black">From: </span></b><span style="color:black">Latifa Elouadrhiri <latifa@jlab.org><br>
<b>Date: </b>Wednesday, July 31, 2024 at 09:53<br>
<b>To: </b>Rafayel Paremuzyan <rafopar@jlab.org>, Francois-Xavier Girod-Gard <fxgirod@jlab.org>, Harut Avagyan <avakian@jlab.org>, Ralf Gothe <rwgothe@gmail.com>, Derek.Glazier@glasgow.ac.uk <derek.glazier@glasgow.ac.uk>, Eugene Pasyuk <pasyuk@jlab.org><br>
<b>Cc: </b>Stepan Stepanyan <stepanya@jlab.org>, Volker Burkert <burkert@jlab.org>, Latifa Elouadrhiri <latifa@jlab.org><br>
<b>Subject: </b>Fw: Beam Energy Requirements in Hall B<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">Dear all,<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">As we discussed this morning, please see Patrick's email below and provide your answers to the questions regarding your physics experiments and send them to me by Monday, August 12. I
will compile everything for discussion on Wednesday, August 16, in order to finalize the document and send it to Patrick.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">Volker and Stepan, if you could please send me the comments you made this morning to include in the document as a separate note that would be great.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">Let me know if you have any questions.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">Best regards,<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">Latifa<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"> Patrick Achenbach <patricka@jlab.org><br>
<b>Sent:</b> Tuesday, July 23, 2024 5:47 PM<br>
<b>To:</b> Latifa Elouadrhiri <latifa@jlab.org>; Silvia Niccolai <silvia.niccolai@ijclab.in2p3.fr>; Sebastian E. Kuhn <skuhn@odu.edu>; Raphael Dupre <raphael.dupre@ijclab.in2p3.fr>; Hayk Hakobyan <hayk.hakobyan@usm.cl>; Ilya Larin <ilarin@jlab.org>; mcontalb@fe.infn.it
<mcontalb@fe.infn.it>; William Brooks <william.brooks@usm.cl>; Richard G Milner <milner@mit.edu><br>
<b>Cc:</b> Stepan Stepanyan <stepanya@jlab.org><br>
<b>Subject:</b> Beam Energy Requirements in Hall B</span> <o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:36.0pt"> <o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">Dear contact persons of '11-GeV runs' in Hall-B,<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">Earlier this year, DOE has performed an Operations Review which was concluded with a list of comments and recommendations. One particular recommendation is to... "Develop a
<b>beam energy requirement</b> document for the approved experiments in the experimental halls, complete with physics justifications. This document must be distinctly separate from issues pertaining to reliability." <o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">Physics division will compile, for each experiment still to run,
<b>(a) Proposed Energies, (b) Minimum Acceptable Maximum Energy if 12 GeV was proposed, (c) Science Impact of difference from 12 GeV, and (d) any potential mitigation such as run longer.</b><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">The focus of this recommendation is a review/justification for a 12-GeV CEBAF beam (equiv. to 11 GeV delivered to Hall B) as compared to a beam with some 100s MeV less energy. <o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">Can you please give me input to the requested table entries (a) to (d)? Feel free to justify running at 11 GeV for Hall B with some extra narrative if the table is not sufficient. I believe,
we can give common numbers for experiments in run groups for which the science impact and the potential mitigation is similar. However, I don't think that we can combine all experiments from a run group.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">Let me remind you, the scheduled beam energy for the next run is 1060 MeV per linac, equiv. to 10.70 GeV in Hall B. Plans are in place to increase this to 1090 MeV, equiv. to 11 GeV in
Hall B for the FY26, but not at all cost. <o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">Physics division is not moving quickly on this, so a reasonable target to have all information compiled is
<b>August 20, 2024</b>.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">Best regards, <o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="color:black">Patrick<o:p></o:p></span></p>
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