ATLAS has reported anomalous event which has high pT jets not matching any MC truth particle. 2GeV gamma produced 90GeV pi0 and 95GeV lambda !! gamma e=1944.0247 -> Process: PhotonInelastic at Eta=-1.0890 Phi=0.9310 R=1504.9776 Resulting particles: * pi0 e=90219.733 px=-2821.7829, py=-66930.4036, pz=60632.6144 * lambda e=95020.0396 px=5196.8159, py=70747.6641, pz=-64873.6737 * ... This information is extracted from the ATLAS Savannah report (URL above). The material of in the volume of the PhotonInelastic interaction is material: Thinabs mass fraction of elements are Pb 0.7493 Fe 0.1837 C 0.0251 H 0.0034 O 0.0268 Si 0.0117
(From Andrea Dotti's report, 16 June 2010): The problem has been investigated, reproduced in a simple setup. The bug is confirmed to occur in the reaction: Gamma + A -> X (Energy of the gamma of 2 GeV), for which at least one of the secondaries has too much kinetic energy (up to 90 GeV). Typically The bug has been confirmed to affect A=Pb (but other materials may be effected). We have traced down the problem to the relevant parts of the code and we are investigating it. The nature of the bug makes it difficult to measure the frequency of the problematic events, it can be estimated to occur once every 10^6 interactions. A candidate fix has been identified and undergone testing.
Fixed. The fix, which relates only 9.2 series release, has been provided to ATLAS and will be included in release 9.2.p04.
