[Primexd] About eta decays in MC

[Igal Jaegle]

Thank you, Eugene, for the explanation. For the post-decay, I used evtgen and the Belle II decay configuration file which includes all PDG particles and their recorded decay mechanisms. I will check if Jon's eta decay file is different from the Belle II one.

tks ig
________________________________
From: Primexd <primexd-bounces at jlab.org> on behalf of Eugene Chudakov via Primexd <primexd at jlab.org>
Sent: Friday, August 9, 2024 7:31 PM
To: primexd at jlab.org <primexd at jlab.org>
Subject: [Primexd] About eta decays in MC

The eta->gamma+gamma decay is simple - isotropic in the eta CM frame. The 3-body decays are isotropic, but different from the phase space. One may look into the analysis note by Jon Zarling on the eta cross section. There is a package decay_evtgen which does these decays. It reads in a hddm file and writes out a hddm file.
eta decays are turned off in bggen_upd. It sends etas to the output. The decays are left to GEANT(4). I am sure GEANT4 uses the right BRs, but not sure it does the 3-body decays right. GEANT3 did not. One may find it out, or may try to do the decays using decay_evtgen.

PS. PYTHIA uses a model for 3-body pseudoscalar decays.

Eugene

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/primexd/attachments/20240810/e6eb0eaf/attachment-0001.html>