The luminosity calibration for the ATLAS detector at the LHC during pp collisions at in 2010 and 2011 is presented. Evaluation of the luminosity scale is performed using several luminosity-sensitive detectors, and comparisons are made of the long-term stability and accuracy of this calibration applied to the pp collisions at . A luminosity uncertainty of is obtained for the 47 pb−1 of data delivered to ATLAS in 2010, and an uncertainty of is obtained for the 5.5 fb−1 delivered in 2011.

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Results of a search for new phenomena in events with at least three photons are reported. Data from proton–proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb, were collected with the ATLAS detector at the LHC. The observed data are well described by the Standard Model. Limits at the 95 % confidence level on new phenomena are presented based on the rate of events in an inclusive signal region and a restricted signal region targeting the rare decay , as well as di-photon and tri-photon resonance searches. For a Standard Model Higgs boson decaying to four photons via a pair of intermediate pseudoscalar particles (a), limits are found to be for 10 GeV 62 GeV. Limits are also presented for Higgs boson-like scalars (H) for 125 GeV, and for a decaying to three photons via . Additionally, the observed limit on the branching ratio of the Z boson decay to three photons is found to be BR, a result five times stronger than the previous result from LEP.

A general formalism is worked out for the description of onedimensional scattering by non-local separable potentials and constraints on transmission and reflection coefficients are derived in the cases of P, T or PT invariance of the Hamiltonian. The case of a solvable Yamaguchi potential is discussed in detail.