[Jef] [EXTERNAL] eta->pi0gg background from eta->gg, eta->3pi0

[Susan Schadmand]

Theres two thing sthat come to my mind:


The TAPS forward wall was not in the trigger, so they probably used only 
the central detector for photon detection.


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.


On 26.08.21 16:22, Igal Jaegle wrote:
> Thank you, Susan, that is really helpful. They do not mention and 
> observe any omega background!
>
> tks ig.
> ------------------------------------------------------------------------
> *From:* Jef <jef-bounces at jlab.org> on behalf of Susan Schadmand 
> <s.schadmand at gmail.com>
> *Sent:* Thursday, August 26, 2021 10:01 AM
> *To:* jef at jlab.org <jef at jlab.org>
> *Subject:* [Jef] [EXTERNAL] eta->pi0gg background from eta->gg, eta->3pi0
> There might be something useful in the A2 paper, see 
> https://urldefense.proofpoint.com/v2/url?u=https-3A__arxiv.org_pdf_1405.4904.pdf&d=DwICaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=JOJ62NEwwkI7R0M2R59fbQ&m=2_h8BdJDO9vKCZ8KeQImdymMqzITiKR0IfYUKK2AtVw&s=0QiWsYEB4UwFaur7nGuj_QPyLyS_hCbHd5rRD5kQzvY&e=  
> <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=>:
>
> contribution to eta->pi0gg from eta->gg decay:
>
>   * due to split offs from both outgoing photons
>   * they cut on the smaller values of the two possible invariant
>     masses m(pi0gg)
>   * (this is a way of cutting on gg opening angles)
>
> contribution to eta->pi0gg from eta->3pi0 decay:
>
>   * showers of some outgoing photons overlap (or are not detected)
>   * they cut on an "effective radius" of the clusters to suppress the
>     case of overlapping
>   * (this is a simple cut on cluster shape)
>
>
>
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