<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Dear Sung,<div><br></div><div>it is very good you looked into this. </div><div><br></div><div>It is interesting that the effect is rather independent of the particle type (with the proton results offset by 0.5 units in momentum pull compared to the pions). The phi dependence of the pull within each sector is almost everywhere quite similar, monotone, and decreasing. It seems that the holding field is not responsible for the effect as the results are independent of the particle charge.</div><div><br></div><div>Earlier, Michael Dugger pointed out to me Mike Williams' CLAS note (CLAS-NOTE 04-017, </div><a href="http://www1.jlab.org/ul/Physics/Hall-B/clas/public/2004-017.pdf">http://www1.jlab.org/ul/Physics/Hall-B/clas/public/2004-017.pdf</a> <div>In this report momentum corrections are discussed and drift chamber misalignments are said to be responsible for the effect.</div><div><div><div><br></div><div>All the best,</div><div>Steffen</div><div><br></div><div><br><div><div>On Jun 22, 2010, at 3:56 PM, Sungkyun Park wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>Hi Steffen,<br><br>To check the phi-dependence in our double-pion data, I make some histograms in the following web:<br><br> <a href="http://hadron.physics.fsu.edu/~skpark/research/research_jun2110.html">http://hadron.physics.fsu.edu/~skpark/research/research_jun2110.html</a><br><br>I make 2D-histogram whose x-axis is the phi angle (LAB) of each particle and y-axis is the momentum pull of each particle and project it to 36 plots. I make the histogram using the mean of the Gaussian fitting. <br>I think momentum pulls of each particle have some phi-dependence like your result. <br><br>Sung<br>Florida State University<br><br><blockquote type="cite">Dear Sung et al.,<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">we may or may not have a tagger-sag problem in g9a. I agree with <br></blockquote><blockquote type="cite">Michael that it is important to have all 'known' corrections <br></blockquote><blockquote type="cite">implemented before the kinematic fitter is applied. The fitter is <br></blockquote><blockquote type="cite">probably not a good tool to correct for 'systematic' errors. In <br></blockquote><blockquote type="cite">terms <br></blockquote><blockquote type="cite">of these systematic effects I am still very concerned about the <br></blockquote><blockquote type="cite">azimuthal dependence of the g9a single-pion data. The variation of <br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">the measured pi+ momentum from the expected momentum (assuming <br></blockquote><blockquote type="cite">correctly measured pion angles and photon energy) is very large; up <br></blockquote><blockquote type="cite">to <br></blockquote><blockquote type="cite">10-15 MeV/c within one sector's coverage.<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">See: <a href="http://www.jlab.org/Hall-B/secure/g9/g9_strauch/mtg/20100414.pdf">http://www.jlab.org/Hall-B/secure/g9/g9_strauch/mtg/20100414.pdf</a><br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">I wonder if you see such a phi-dependence also in your double-pion <br></blockquote><blockquote type="cite">data or if the many particles in the final state wash out any such <br></blockquote><blockquote type="cite">effect. We need to address this phi dependence.<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">All the best,<br></blockquote><blockquote type="cite">Steffen<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite"><br></blockquote></div></blockquote></div><br></div></div></div></body></html>