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Since we don't want to maintain HPS specific version of G4, we can do as follows. 1) Since we want to separate the target effect very often, we can run EGS5 to simulate the target interactions and save all the particles coming out of the target in stdhep file. Then, run slic to simulate the SVT and Ecal interactions. For this, G4 version does not matter. The multiple scattering problem does not show up. 2) If we want to simulate the target interactions using G4, we can use Wentzel Coulomb scattering model for the target and the standard Urban Model for everything else. As long as we don't use Urban model for the target, G4 version does not matter. Takashi -----Original Message----- From: [log in to unmask] [mailto:[log in to unmask]] On Behalf Of Matt Graham Sent: Wednesday, October 10, 2012 4:47 PM To: McCormick, Jeremy I. Cc: Maurik Holtrop; Graf, Norman A.; hps-software Subject: Re: discussion on HPS G4 version As I understand it (from Norman), multiple scattering will occur in the tracker and other geometry components, rather than single scattering. Though I would assume some single scattering will be invoked by the physics engine, this is not going to influence the primary e+e- events generated from target interactions, which are input externally. So the effect should be small/negligible. (Can we confirm this somehow?) I think it is _probably_ true that the different single scattering treatment has only a small effect for us (outside of the beam/target), we may see an effect in the vertex resolution where we are trying to measure ~10^7 rejection factors. The easiest thing to do is just look at this with both v9.3 and v9.5 and see if there is a difference. I can do this if you can point me to a current slic distribution on the slac machines... ________________________________ Use REPLY-ALL to reply to list To unsubscribe from the HPS-SOFTWARE list, click the following link: https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=HPS-SOFTWARE&A=1 ######################################################################## Use REPLY-ALL to reply to list To unsubscribe from the HPS-SOFTWARE list, click the following link: https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=HPS-SOFTWARE&A=1