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Generate samples for converted photon studies using Sim10 in Run2

Renato Quagliani requested to merge RD-SplitSim-Sim10 into main

This is a mirror request of !43 (merged) but using Sim10.

According to the Geant4 documentation Sim09 is using a wrong model to describe the angualr spectrum of the di-electron pair from conversion having an impact on the actual estimated background from conversion into very low q2 regions of Phiee, Kstee. An old ANA note was done by @mschune and Fabrice about that. See https://cds.cern.ch/record/2653384/files/LHCb-INT-2019-001.pdf

According to the release notes of Sim09, Geant 4.9 is used , which uses a wrong model. The model has been updated in principle from 4.10.5 onwards according to https://inspirehep.net/files/05affdd84916cfc2e427b82a291ab983 (section 2.1) .

If Sim10 by default is using a more recent Geant4.10 , with this request we could compare the impact of an updated angular model ( G4ModifiedTsai for the use case in question).

FYI: @abiolchi , @rihender , @mschune , @gkhreich

For this study, if the request is not acceptable, we could limit the production to Bs-> Phi gamma only, however i would like all of them being produced since the new stripping lines developed can be better tested and comparison being made on the 2 Sim version in terms of efficeinceis.

About G4 details and versions, i CC also @gcorti and @kreps following up the discussion on the Simulation mattermost channel to eventually correct whether what is said about models used for conversion in material is correct.

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