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Hi Maurik, For the cosmics I used a plane above the ECal, and for the electrons firing into the ECal, I used a point source located at the origin. This gives good results for tracking (cosmics) but not such good results for rates. I also used a cosine angular distribution for the cosmics. When I look at the actual positions of the MC Particle in the ECal for both of these hits, I observe similar patterns in positions-repeats of using the same numbers (out to several decimal places) which I find unusual. I don't believe there to be a roundoff error, but I certainly won't rule it out. On Sat, May 31, 2014 at 9:59 AM, Maurik Holtrop <[log in to unmask]> wrote: > Hello Holly, > > Perhaps Jeremy can comment on the random engine being used. > > I only know of a flaw in the CLHEP::RanecuEngine, which is used by GEANT4. > The flaw is that for very different seeds the engine will give the exact > same sequence. The periodicity of the engine (i.e. starting with one seed, > how long before the sequence repeats) is huge, as it is for all the CLHEP > random engines. So on a single run, with a single seed, you should NOT see > any repeat or pattern in this engine. I alerted Lynn Garren of this flaw > back in 2010 and they were going to look into it, but never heard anything > since. Best to avoid that particular engine. > > There are many other things that can cause a pattern like the one you are > seeing. One possibility is that there is some subtle effect in roundoff. > Are the cosmics coming from a single point good distance from the ECAL, and > could it thus be numerical limits on the accuracy of the angles? Something > like that? > > Best, > Maurik > > > On May 31, 2014, at 9:45 AM, Holly Vance <[log in to unmask]> wrote: > > Hi, > > When I am running my own events in SLIC from a macro, for small numbers of > events (3k) the distribution looks ok. However, when I run something a bit > larger like 100k events, I keep getting strange checkered patterns. I've > been setting a /random/seed number for different runs, but this seems to > have no effect (using this vs not using this and setting it at different > values). > > I am attaching a photo of what the cosmic run looks like. While the > underlying events look good, there is a very distinct pattern that I need > to get rid of. I also see this same pattern if I shoot electrons at the > ECal. Any suggestions would be very useful. > > I am wondering if GEANT4 is using the TRandom random number generator? I > know there are errors with this. I am not sure what is being used with the > SLIC interface. > > -- > Respectfully, > Holly > > > ------------------------------ > > 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 > <cosmics.png><electrons.png> > > > ------------------------------ > > Spam > <https://www.spamtrap.odu.edu/canit/b.php?i=01M8BXL9f&m=e42a440e8e1d&t=20140531&c=s> > Not spam > <https://www.spamtrap.odu.edu/canit/b.php?i=01M8BXL9f&m=e42a440e8e1d&t=20140531&c=n> > Forget previous vote > <https://www.spamtrap.odu.edu/canit/b.php?i=01M8BXL9f&m=e42a440e8e1d&t=20140531&c=f> > -- Respectfully, Holly ######################################################################## 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