<div dir="ltr">Dear Viktor <div><br></div><div>Here is the complete list of exclusivity cuts I used</div><div><br></div><div>IM( gg ) < 0.8 GeV (two photon invariant mass cut)</div><div>MM( ep -> eggX) < 1.75 GeV (proton missing mass cut)</div><div>Angle( gg , ep->epX ) < 5 degrees (angle between pi0 direction and missing pi0 direction)</div><div>Angle( g* ^ gg , g* ^ p ) < 3 degrees (angle between the g* pi0 scattering plane and g* proton scattering plane, coplanarity of the final state, resolution in phi Trento)</div><div>missing momentum transverse to the beam ep -> epggX pT < 0.25 GeV</div><div>-0.05 < missing mass squared ep -> epggX < 0.05 GeV^2</div><div>missing energy ep -> epggX < 1.5 GeV</div><div><br></div><div>also I imposed a cut on the angle between the scattered electron and the photon direction to be more than 5 degrees</div><div><br></div><div>This set of cuts should produce a clean sample, although the angular cuts might be tight even for the signal and reduce the yield somewhat</div><div><br></div><div>Best regards</div><div>FX</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, Jul 6, 2019 at 9:24 PM Viktor Mokeev <<a href="mailto:mokeev@jlab.org">mokeev@jlab.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<div id="gmail-m_4977217914379598392divtagdefaultwrapper" style="font-size:12pt;color:rgb(0,0,0);font-family:Calibri,Helvetica,sans-serif" dir="ltr">
<p style="margin-top:0px;margin-bottom:0px">Dear All,</p>
<p style="margin-top:0px;margin-bottom:0px"><br>
</p>
<p style="margin-top:0px;margin-bottom:0px">There are few differences in selection of gamma_{v} p--> pi^0 p events by Anna and FX:</p>
<p style="margin-top:0px;margin-bottom:0px"><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:0px;margin-bottom:0px">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>
<p style="margin-top:0px;margin-bottom:0px"><br>
</p>
<p style="margin-top:0px;margin-bottom:0px"> Best Regards,</p>
<p style="margin-top:0px;margin-bottom:0px"> Victor<br>
</p>
</div>
<hr style="display:inline-block;width:98%">
<div id="gmail-m_4977217914379598392divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> clas12_rgk <<a href="mailto:clas12_rgk-bounces@jlab.org" target="_blank">clas12_rgk-bounces@jlab.org</a>> on behalf of L Smith <<a href="mailto:lcs1956@me.com" target="_blank">lcs1956@me.com</a>><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>
</div>
<div style="overflow-wrap: break-word;">
<div>Dear FX,</div>
<div><br>
</div>
<div>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><br>
</div>
<div>Your study of DVCS photons in ECAL in <a href="https://logbooks.jlab.org/entry/3698803" target="_blank">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><br>
</div>
<div>Best regards,</div>
<div>Cole</div>
<div><br>
</div>
<div><br>
</div>
<div>TWO PHOTON INVARIANT MASS ERROR vs OPENING ANGLE </div>
<div><img id="gmail-m_4977217914379598392x_8CE8F3CC-0EBE-4763-81C0-D20EA6DF7745" src="cid:16bc8d50e7d50fcb8231"></div>
<div><br>
</div>
<div>TOP theta_gamma=15.5 BOTTOM theta_gamma=5.5 P_gamma=5 GeV</div>
<div><img id="gmail-m_4977217914379598392x_92349623-FDC8-47B5-ABBF-4A2209DA7A44" src="cid:16bc8d50e7d562b8b292"><br>
<div><br>
<blockquote type="cite">
<div>On Jul 5, 2019, at 7:44 PM, Francois-Xavier Girod <<a href="mailto:fxgirod@jlab.org" target="_blank">fxgirod@jlab.org</a>> wrote:</div>
<br class="gmail-m_4977217914379598392x_Apple-interchange-newline">
<div>
<div dir="ltr">Dear all
<div><br>
</div>
<div>I posted some plots for my selection of exclusive neutral pion events from run 5700 here</div>
<div><br>
</div>
<div><a href="https://logbooks.jlab.org/entry/3698969" target="_blank">https://logbooks.jlab.org/entry/3698969</a><br>
</div>
<div><br>
</div>
<div>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><br>
</div>
<div>Best regards</div>
<div>FX</div>
</div>
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</blockquote>
</div>
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</div>
</div>
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</blockquote></div>