<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">The minimum Eg is 25% of the endpoint energy, which is fixed by the tagger field and TAGH counter geometry. So the minimum Eg for these runs would be ~2.9 GeV.<div class="">-Justin<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Oct 23, 2018, at 9:22 AM, Igor Strakovsky <<a href="mailto:igor@gwu.edu" class="">igor@gwu.edu</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div class="">Hi Justin,</div><div class=""><br class=""></div><div class="">Plan looks great. I have two small comments</div><div class=""><br class=""></div><div class="">- The min Eg is still unclear. So, if one can possible to go a little bit below 3 GeV then CLAS</div><div class="">g1c data for pi0 is reachable [DUGGER, PRC76, 025211(2007)]: Eg = 2875, 2825, 2775 and so on</div><div class=""><br class=""></div><div class="">- I would not use <span style="color:rgb(37,37,37);font-family:sans-serif;font-size:14px" class=""> </span><a rel="nofollow" class="external gmail-text" href="https://halldweb.jlab.org/DocDB/0008/000809/002/GlueX_doc_809.pdf" style="color:rgb(102,51,102);padding-right:13px;font-family:sans-serif;font-size:14px">previous measuremen</a>as the source to compare with because most of data</div><div class="">came from brem Bonn measurements which systematics is out the control.</div><div class=""><br class=""></div><div class="">Cheers, igor</div><br clear="all" class=""><div class=""><div dir="ltr" class="gmail_signature"><div dir="ltr" class=""><div class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div class="">-----</div><div class="">Igor Strakovsky, SAID INS The George Washington University</div><div class="">Tel: 571-553-8344(VC),202-994-4742(FB),Skype: igors1945_2, </div><div class=""><span style="font-size:12.8px" class="">Cell: 703-728-5627,</span><span style="font-size:12.8px" class="">Emails: </span><a href="mailto:igor@gwu.edu" style="font-size:12.8px" target="_blank" class="">igor@gwu.edu</a><span style="font-size:12.8px" class="">, </span><a href="mailto:igor@jlab.org" style="font-size:12.8px" target="_blank" class="">igor@jlab.org</a></div></div></div></div></div></div></div></div></div></div><br class=""></div></div></div></div></div><br class=""><div class="gmail_quote"><div dir="ltr" class="">On Tue, Oct 23, 2018 at 7:54 AM Justin Stevens <<a href="mailto:jrsteven@jlab.org" class="">jrsteven@jlab.org</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space" class="">Hi Igor, All,<div class=""><br class=""></div><div class="">Yes, as we discussed at the Physics WG meeting last week, there are 2 possibilities for low energy measurements which correspond to your bullets below. The priority was given to proposing a run plan for this Fall, since time is limited. Thanks to Sean for collecting the relevant data and rate estimates for this Fall’s proposal at <a href="https://halldweb.jlab.org/wiki-private/index.php/2018_Low_energy_measurements" target="_blank" class="">https://halldweb.jlab.org/wiki-private/index.php/2018_Low_energy_measurements</a>. The short summary is that we would like to propose a ~5 day run with a lower PS field setting to give statistical errors <10% on cross sections for comparison to previous measurements, and this is on the agenda for today’s bi-weekly meeting.</div><div class=""><br class=""></div><div class="">This Fall’s proposal of course does not preclude running in Summer 2019, but would give us some data in the short term to compare with previously measured cross sections. To make a decision on Summer 2019 running, we would need a similar proposal with the stated goals, rate estimates, and required running time.</div><div class=""><br class=""></div><div class="">-Justin<br class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">On Oct 17, 2018, at 4:34 PM, Igor Strakovsky <<a href="mailto:igor@gwu.edu" target="_blank" class="">igor@gwu.edu</a>> wrote:</div><br class="m_4800783550453654789Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class=""><div dir="ltr" class="m_4800783550453654789gmail_signature" data-smartmail="gmail_signature"><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div class="">Hi Justin,</div><div class=""><br class=""></div><div class="">According to my understanding there are two different run periods</div><div class=""><br class=""></div><div class="">- this fall which will allow to cover 4-9 GeV or so. CLAS6 does not have pol measurements</div><div class=""><br class=""></div><div class="">- next summer which is a low energy run which you spelled out. that is different story</div><div class=""><br class=""></div><div class="">Cheers, igor</div></div></div></div></div></div></div></div><br class=""></div><br class=""><div class="gmail_quote"><div dir="ltr" class="">On Wed, Oct 17, 2018 at 1:15 PM Justin Stevens <<a href="mailto:jrsteven@jlab.org" target="_blank" class="">jrsteven@jlab.org</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space" class="">Hi Igor,<div class=""><br class=""></div><div class="">Thanks for your feedback. My understanding is the accelerator would run at half energy (Ee ~ 5.5 GeV), and as usual we could choose to set the coherent peak as we prefer. The hodoscope in this case would cover Eg ~ 1.5 GeV to the endpoint, although it will still be only half instrumented (sampling) between 1.5 and 3.5 GeV. So data below Eg = 4 GeV could be possible in this scenario, but at a lower efficiency.</div><div class=""><br class=""></div><div class="">-Justin<br class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">On Oct 15, 2018, at 3:11 PM, Igor Strakovsky <<a href="mailto:igor@gwu.edu" target="_blank" class="">igor@gwu.edu</a>> wrote:</div><br class="m_4800783550453654789m_-965336248231162288Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="">Hi Justin,</div><div class=""><br class=""></div><div class="">It would be good to spell out a possible Eg range and our goals for summer of 2019. Then all depends. </div><div class=""><br class=""></div><div class="">I reported twice that if our range is limited by 4 - 6 GeV and our main goal is diff cross sections then </div><div class="">g12 from CLAS6 will work for us. There are no CLAS pol measurements in this case. So, we have </div><div class="">gp-->pi0p cross sections published several month ago and Volker's analyses for gp-->etap and </div><div class="">gp-->omegap are under the HW group review now.</div><div class=""><br class=""></div><div class="">If one can possible to go below 3 GeV then we will have more options including polarized <br class="">measurements. Additional benefit will come from the ability to use the PWA technology to evaluate</div><div class="">new data and possibility to provide "good" event generators for MC. See my slides at DB</div><div class=""><br class=""></div><div class="">Cheers, igor</div><div class=""><br class=""></div><div class=""><br class=""></div><br clear="all" class=""><div class=""><div dir="ltr" class="m_4800783550453654789m_-965336248231162288gmail_signature" data-smartmail="gmail_signature"><div dir="ltr" class=""><div class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div class="">-----</div><div class="">Igor Strakovsky, SAID INS The George Washington University</div><div class="">Tel: 571-553-8344(VC),202-994-4742(FB),Skype: igors1945_2, </div><div class=""><span style="font-size:12.8px" class="">Cell: 703-728-5627,</span><span style="font-size:12.8px" class="">Emails: </span><a href="mailto:igor@gwu.edu" style="font-size:12.8px" target="_blank" class="">igor@gwu.edu</a><span style="font-size:12.8px" class="">, </span><a href="mailto:igor@jlab.org" style="font-size:12.8px" target="_blank" class="">igor@jlab.org</a></div></div></div></div></div></div></div></div></div></div><br class=""></div><br class=""><div class="gmail_quote"><div dir="ltr" class="">On Mon, Oct 15, 2018 at 12:50 PM Justin Stevens <<a href="mailto:jrsteven@jlab.org" target="_blank" class="">jrsteven@jlab.org</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space" class="">Hi All,<div class=""><br class=""></div><div class="">There’s been a proposal to have a short discussion about a potential low-energy run in Summer 2019 during tomorrow’s physics meeting. To frame the discussion: the accelerator plans to run at ~half energy during June/July 2018 and GlueX could potentially run parasitically during this period. </div><div class=""><br class=""></div><div class="">We had some discussion about the potential usefulness of low-energy running earlier this year (comparison to cross section measurements from CLAS, energy-dependence of polarization observables, etc.), but that was in a different context of using the full energy electron beam with lower coherent peak settings (see <a href="https://halldweb.jlab.org/wiki-private/index.php/Aug_7,_2018,_Physics_Working_Group" target="_blank" class="">https://halldweb.jlab.org/wiki-private/index.php/Aug_7,_2018,_Physics_Working_Group</a>).</div><div class=""><br class=""></div><div class="">If you have something you would like to contribute to the discussion, please let me know.</div><div class=""><br class=""></div><div class="">-Justin<br class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">On Oct 14, 2018, at 1:46 PM, Justin Stevens <<a href="mailto:jrsteven@jlab.org" target="_blank" class="">jrsteven@jlab.org</a>> wrote:</div><br class="m_4800783550453654789m_-965336248231162288m_-160429451515303739Apple-interchange-newline"><div class=""><div class="">Hi All,<br class=""><br class="">Our next Physics WG meeting we be Tuesday, October 16 at 11:15 am, <a href="https://halldweb.jlab.org/wiki-private/index.php/Oct_16,_2018,_Physics_Working_Group" target="_blank" class="">https://halldweb.jlab.org/wiki-private/index.php/Oct_16,_2018,_Physics_Working_Group</a>. Please let me know if you have something you would like to present.<br class=""><br class="">-Justin<br class="">_______________________________________________<br class="">Halld-physics mailing list<br class=""><a href="mailto:Halld-physics@jlab.org" target="_blank" class="">Halld-physics@jlab.org</a><br class=""><a href="https://mailman.jlab.org/mailman/listinfo/halld-physics" target="_blank" class="">https://mailman.jlab.org/mailman/listinfo/halld-physics</a><br class=""></div></div></blockquote></div><br class=""></div></div>_______________________________________________<br class="">
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