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On light-by-light interactions in QED

Thiescheffer, J (2017) On light-by-light interactions in QED. Bachelor's Thesis, Physics.

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In classical electrodynamics photons do not interact. However, in QED this becomes possible. The low energy effective field theory of Euler and Heisenberg is used to describe these interactions, which lead to non-linear corrections to the classical Maxwell equations in vacuum. The influence of effective QED light-by-light scattering on the polarization angle of light is discussed. Axions inducing a birefringence of the vacuum is mentioned. Recent experimental observations of the Very Large Telescope on the polarization angle and polarization degree of optical light from isolated neutron star RX J1856.5-3754 are compared to predictions of the Euler-Heisenberg Lagrangian in the weak field limit. A non-perturbative calculation could potentially yield better predictions. The measured values are too low to provide evidence for QED vacuum birefringence. Reduction of the experimental error in the future could lead to strong evidence for QED vacuum birefringence. In addition, possible observations on light-by-light scattering of the ATLAS collaboration at CERN are discussed. A non-zero virtuality and a diphoton invariant mass greater than 6 GeV exclude detection of real QED light-by-light scattering. ATLAS detects quasi-real QCD LbyL scattering. Better statistical information concerning the diphoton invariant mass spectrum around 10 GeV is necessary to conclude whether quasi-real QCD light-by-light scattering is detected at this point. At the moment, a diphoton detection from χb,0 and χb,2 diphoton decays cannot be excluded.

Item Type: Thesis (Bachelor's Thesis)
Degree programme: Physics
Thesis type: Bachelor's Thesis
Language: English
Date Deposited: 15 Feb 2018 08:31
Last Modified: 15 Feb 2018 08:31

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