G4TransportationWithMsc: Always update momentum direction #76
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This fixes a very rare bug when G4Transportation runs without field, G4TransportationWithMsc is allowed to make multiple internal steps, and the last internal step does *not* sample scattering (because the track is either ranging out, or the step is very small). In this case G4Transportation will reset fMomentumChanged = false because linear propagation does not change the momentum direction, when in fact earlier internal steps updated the direction due to scattering. Instead always update the momentum direction because the above is rare. Numerical differences are observed in the simulation histories, but not statistically significant.
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A new Pull Request was created by @hahnjo (Jonas Hahnfeld) for branch cms/v11.1.2. @smuzaffar, @iarspider, @aandvalenzuela, @cmsbuild can you please review it and eventually sign? Thanks. |
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please test |
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-1 Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-bbaa5c/35405/summary.html |
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-1 Failed Tests: UnitTests The following merge commits were also included on top of IB + this PR after doing git cms-merge-topic:
You can see more details here: Unit TestsI found 1 errors in the following unit tests: ---> test testTauEmbeddingProducers had ERRORS Comparison SummarySummary:
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This PR has nothing to do with the failed unit test. Regression for standard tests is seen as expected. Should tests be resubmitted? |
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@civanch , are you happy with this change? |
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+externals lets get this in and update cmsdist/geant4.spec |
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This pull request is fully signed and it will be integrated in one of the next cms/v11.1.2 IBs (but tests are reportedly failing). This pull request will now be reviewed by the release team before it's merged. @antoniovilela, @rappoccio, @sextonkennedy (and backports should be raised in the release meeting by the corresponding L2) |
This fixes a very rare bug when
G4Transportationruns without field,G4TransportationWithMscis allowed to make multiple internal steps, and the last internal step does not sample scattering (because the track is either ranging out, or the step is very small). In this caseG4Transportationwill resetfMomentumChanged = falsebecause linear propagation does not change the momentum direction, when in fact earlier internal steps updated the direction due to scattering.Instead always update the momentum direction because the above is rare. Numerical differences are observed in the simulation histories, but not statistically significant.