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Contribution à l'étude des Fermions et de leurs angles de mélange en Théorie Quantique des Champs

Abstract : This thesis is divided into two parts. The first one is devoted to the study of the fermion mixing angles in Quantum Field Theory (QFT). We show that, due to the non-orthonormality of its mass eigenstates, the mixing matrix of a nondegenerate system of coupled fermions cannot be considered a priori to be unitary ; then, in the standard model framework, that all mixing angles of quarks and leptons are consistent with a precise structure of neutral currents, in which universality and absence of flavour changing currents are equally violated. This scheme yields the quark-lepton complementarity relation between the Cabibbo angle and the second mixing angle of neutrinos. We also recover perturbatively the nonunitarity of the mixing matrix by cancelling nondiagonal one-loop transitions between mass eigenstates, and show how the gauge symmetry nevertheless guarantees the unitarity of the Cabibbo matrix which occurs in renormalized gauge currents. We finally study the flavour transformations that are relevant in this procedure, and outline a link between the neutral currents and the mass matrix usually considered for coupled systems. The second part presents the first results of a general study of the constraints cast in QFT by the discrete symmetries (parity P, charge conjugation C and time reversal T) on the fermionic Lagrangian and propagator. We show for one generation that the latter, being written in the most general way compatible with Lorentz invariance, are naturally PCT-invariant, and that the eigenstates of a C-invariant propagator are Majorana fermions.
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Contributor : Quentin Duret Connect in order to contact the contributor
Submitted on : Monday, November 24, 2008 - 4:48:06 PM
Last modification on : Wednesday, December 9, 2020 - 3:10:37 PM
Long-term archiving on: : Tuesday, October 9, 2012 - 3:30:29 PM


  • HAL Id : tel-00339236, version 1


Quentin Duret. Contribution à l'étude des Fermions et de leurs angles de mélange en Théorie Quantique des Champs. Physique mathématique [math-ph]. Université Pierre et Marie Curie - Paris VI, 2008. Français. ⟨tel-00339236⟩



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