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<p>Theres two thing sthat come to my mind: <br>
</p>
<p><br>
</p>
<p>The TAPS forward wall was not in the trigger, so they probably
used only the central detector for photon detection. <br>
</p>
<p><br>
</p>
<p>And, even at MAMI-C most etas are produced at threshold, so most
events are below the omega threshold and omegas would have more fw
boost.<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 26.08.21 16:22, Igal Jaegle wrote:<br>
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Thank you, Susan, that is really helpful. They do not mention
and observe any omega background!<br>
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<br>
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tks ig.<br>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt"
face="Calibri, sans-serif" color="#000000"><b>From:</b> Jef
<a class="moz-txt-link-rfc2396E" href="mailto:jef-bounces@jlab.org"><jef-bounces@jlab.org></a> on behalf of Susan Schadmand
<a class="moz-txt-link-rfc2396E" href="mailto:s.schadmand@gmail.com"><s.schadmand@gmail.com></a><br>
<b>Sent:</b> Thursday, August 26, 2021 10:01 AM<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:jef@jlab.org">jef@jlab.org</a> <a class="moz-txt-link-rfc2396E" href="mailto:jef@jlab.org"><jef@jlab.org></a><br>
<b>Subject:</b> [Jef] [EXTERNAL] eta->pi0gg background from
eta->gg, eta->3pi0</font>
<div> </div>
</div>
<div>There might be something useful in the A2 paper, see <a
class="x_moz-txt-link-freetext"
href="https://urldefense.proofpoint.com/v2/url?u=https-3A__arxiv.org_pdf_1405.4904.pdf&d=DwMCaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=JOJ62NEwwkI7R0M2R59fbQ&m=5Y7472olvxXv6Sd2q8sF8W26idKXgIvLAMwmtRvD4Go&s=KfiAGstPDb0aCDfflS4VlAXi4oKW2L-lrTxXtRyBPDk&e="
moz-do-not-send="true">
https://arxiv.org/pdf/1405.4904.pdf</a>:<br>
<br>
contribution to eta->pi0gg from eta->gg decay:<br>
<ul>
<li>due to split offs from both outgoing photons</li>
<li>they cut on the smaller values of the two possible
invariant masses m(pi0gg)</li>
<li>(this is a way of cutting on gg opening angles)<br>
</li>
</ul>
<p>contribution to eta->pi0gg from eta->3pi0 decay:</p>
<ul>
<li>showers of some outgoing photons overlap (or are not
detected)</li>
<li>they cut on an "effective radius" of the clusters to
suppress the case of overlapping<br>
</li>
<li>(this is a simple cut on cluster shape)</li>
</ul>
<p><br>
</p>
<br>
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