<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="">Dear FX,</div><div class=""><br class=""></div><div class="">It may be the invariant mass dependence on pi0 energy is more related to opening angle. For symmetric decays the two are directly related. There is persistent evidence of a theta,phi error in cluster angle reconstruction for PCAL which you originally noticed (it goes through zero at the mid-plane and theta=25) which would cause an accumulative error as opening angle increased.</div><div class=""><br class=""></div><div class="">Your study of DVCS photons in ECAL in <a href="https://logbooks.jlab.org/entry/3698803" class="">https://logbooks.jlab.org/entry/3698803</a> shows tails and shoulders in the missing energy/mass distributions. Of course there is considerable energy loss from both transverse and longitudinal leakage at small angles (bottom two plots) so a comparison with GEMC would be instructive. </div><div class=""><br class=""></div><div class="">Best regards,</div><div class="">Cole</div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">TWO PHOTON INVARIANT MASS ERROR vs OPENING ANGLE </div><div class=""><img apple-inline="yes" id="8CE8F3CC-0EBE-4763-81C0-D20EA6DF7745" src="cid:FBA9B3C0-A552-44FA-903C-BD2905E4A91A@lan" class=""></div><div class=""><br class=""></div><div class="">TOP theta_gamma=15.5 BOTTOM theta_gamma=5.5 P_gamma=5 GeV</div><div class=""><img apple-inline="yes" id="92349623-FDC8-47B5-ABBF-4A2209DA7A44" src="cid:8225E136-610C-4361-B732-6F215687EEB3@lan" class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Jul 5, 2019, at 7:44 PM, Francois-Xavier Girod <<a href="mailto:fxgirod@jlab.org" class="">fxgirod@jlab.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Dear all<div class=""><br class=""></div><div class="">I posted some plots for my selection of exclusive neutral pion events from run 5700 here</div><div class=""><br class=""></div><div class=""><a href="https://logbooks.jlab.org/entry/3698969" class="">https://logbooks.jlab.org/entry/3698969</a><br class=""></div><div class=""><br class=""></div><div class="">I get only few statistics with two photons in the FTCal but I get a decent sample (10k events) with the two photons in the ECal. Checking the pi0 mass dependence I did not find a polar angle or much azimuthal angle dependence, but I do see a bit of dependence on the pi0 energy</div><div class=""><br class=""></div><div class="">Best regards</div><div class="">FX</div></div>
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