<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi, MK and Michael,<div class=""><br class=""></div><div class="">In general I agree with Michael what you are showing is reasonable. The 1-photon-only probability plot shows basically the percentage (for Egamma > 3.6GeV) is about 86.6%+-1% (eyeballing). What Will showed from his ppbar channel is about 87%+-1% (also eyeballing, and he starts from 3.9GeV). There is no difference here. The two plots (you and will) looks dramatically different because of the energy range (x-axis), and because of will shows on the Y-axis from 0 to 100%, and you zoomed in from 80% to 90%. It tells exactly the same story.</div><div class=""><br class=""></div><div class="">For the low energy part (Egamma <3.6 GeV), I think Michael’s explanation is probably right — although I won’t call it trigger efficiency or inefficiency. It’s only inefficient when a event that should have triggered and been recorded did not get registered.</div><div class="">But even if you compare these two ranges, it’s really a only 1.5% difference. Do you think our systematic uncertainty on the normalization is less than 1.5%? I think in the big picture, we are fine.</div><div class=""><br class=""></div><div class="">But I do agree with MK that his picture is different from FSU, particularly in the low energy part, since it showed opposite trend. </div><div class=""><br class=""></div><div class="">How does Rafael’s results compare with you, particularly for the low energy part?</div><div class=""><br class=""></div><div class="">Is it possible that again this is due to you and FSU are not showing the data from exactly the same set of runs?</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""><div apple-content-edited="true" class="">
<div class=""><div class=""><div class="">Lei Guo</div><div class="">Assistant Professor</div><div class="">Physics Department</div><div class="">Florida International University</div><div class="">Miami, FL</div></div><div class=""><br class=""></div><div class="">email: <a href="mailto:leguo@fiu.edu" class="">leguo@fiu.edu</a> or <a href="mailto:lguo@jlab.org" class="">lguo@jlab.org</a></div><div class="">Office:305-348-0234</div></div>
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<br class=""><div><blockquote type="cite" class=""><div class="">On Mar 31, 2015, at 2:31 PM, Michael Paolone <<a href="mailto:mpaolone@jlab.org" class="">mpaolone@jlab.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">Hi MK, All,<br class=""><br class="">This looks reasonable, and I think I can explain the energy dependence. <br class="">The key is that all events have to fire a trigger whose efficiency is<br class="">dependent on the momentum and angle of the tracks created from the<br class="">reaction which itself IS photon energy dependent.<br class=""><br class="">Look at the 1 photon probability plot and ask how likely is it that that<br class="">photon is the one that created the trigger. For very low energy photons<br class="">the overall trigger efficiency drops, and since we see an event at all, it<br class="">becomes more likely that another higher energy photon in the same beam<br class="">bucket generated the reaction that triggered the event.<br class=""><br class="">The sharp jump at 3.6 GeV shows that the event is now more likely to<br class="">trigger with just that photon (since that's where the primary trigger<br class="">starts).<br class=""><br class="">The downward slope after 3.6 GeV might again be a trigger efficiency<br class="">effect, where it becomes more likely that we lose small angle tracks down<br class="">the beam hole which could have fired the trigger.<br class=""><br class="">-Michael<br class=""><br class=""><blockquote type="cite" class="">Greetings,<br class=""><br class="">I did not want to show this last night because I thought there was a bug<br class="">in my code. But I do not think I have a bug in my code, so I want to<br class="">show you what I concluded.<br class=""><br class="">First of all, my result does not agree with the values found by FSU or<br class="">FIU. I actually see a strange dependence on energy. What I am depicting<br class="">are plots of the probability of multiple photons within the same bucket<br class="">as clasEvent choose ±1.002 ns, meaning the photon energy on the X-axis<br class="">of the plots are of clasEvent chosen, which was the best timed beam<br class="">photon compared to the average _of_ start times.<br class=""><br class="">The data used for this is only the 566* runs, which is approximately 7%<br class="">of the data.<br class="">Please see:<br class=""><a href="https://clasweb.jlab.org/rungroups/g12/wiki/index.php/TAGR_code#March_31" class="">https://clasweb.jlab.org/rungroups/g12/wiki/index.php/TAGR_code#March_31</a><br class=""><br class="">--<br class="">BR<br class="">MK<br class="">----------------------------------------<br class="">Michael C. Kunkel, PhD<br class="">Forschungszentrum Jülich<br class="">Nuclear Physics Institute and Juelich Center for Hadron Physics<br class="">Experimental Hadron Structure (IKP-1)<br class="">www.fz-juelich.de/ikp<br class=""><br class="">_______________________________________________<br class="">G12 mailing list<br class="">G12@jlab.org<br class="">https://mailman.jlab.org/mailman/listinfo/g12<br class=""><br class=""></blockquote><br class=""><br class="">_______________________________________________<br class="">G12 mailing list<br class=""><a href="mailto:G12@jlab.org" class="">G12@jlab.org</a><br class="">https://mailman.jlab.org/mailman/listinfo/g12<br class=""></div></blockquote></div><br class=""></div></body></html>