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<p style="margin-top:0;margin-bottom:0">Dear All,</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0">There are few differences in selection of gamma_{v} p--> pi^0 p events by Anna and FX:</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
<ol style="margin-bottom: 0px; margin-top: 0px;">
<li>Anna is using
<div>Cook: 5.7.4<br>
Data: skim4_5990.root (12M events)</div>
</li><li>Anna got the photon energy from the sum ECAL+PCAL converted to the photon physical energy, while FX took them directly from EB.</li><li>Anna selected events with a scattered electron, proton, and exactly two neutral which are not necessarily photons. FX selected scattered electron, proton, and > 2 gammas from EB.</li></ol>
<br>
<p style="margin-top:0;margin-bottom:0">I propose after completion of the simulation discussed at the July 5 RG-K Meeting, Anna repeats the selection of
<span>gv p--> pi^0 p events</span> from the same data set and with exactly the same selections as FX successfully accomplished. For me, FX 2gamma inv masses looks great!</p>
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</p>
<p style="margin-top:0;margin-bottom:0"> Best Regards,</p>
<p style="margin-top:0;margin-bottom:0"> Victor<br>
</p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> clas12_rgk <clas12_rgk-bounces@jlab.org> on behalf of L Smith <lcs1956@me.com><br>
<b>Sent:</b> Friday, July 5, 2019 8:57:48 PM<br>
<b>To:</b> Francois-Xavier Girod-Gard<br>
<b>Cc:</b> clas12 rgk<br>
<b>Subject:</b> Re: [clas12_rgk] exclusive neutral pion selection</font>
<div> </div>
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<div class="" style="word-wrap:break-word; line-break:after-white-space">
<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 id="x_8CE8F3CC-0EBE-4763-81C0-D20EA6DF7745" class="" data-outlook-trace="F:1|T:1" src="cid:FBA9B3C0-A552-44FA-903C-BD2905E4A91A@lan"></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 id="x_92349623-FDC8-47B5-ABBF-4A2209DA7A44" class="" data-outlook-trace="F:1|T:1" src="cid:8225E136-610C-4361-B732-6F215687EEB3@lan"><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="x_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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</blockquote>
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