E. de Rafael — Page 2

arXiv1995

Weak $K$--Amplitudes in the Chiral and $1/N_c$--Expansions

It is shown that there exist symmetry constraints for non--leptonic weak amplitudes which emerge when the $1/N_c$--expansion restricted to the leading and next--to--leading approximations only is systematically combined with $χ$PT limited to the lowest non--trivial order. We discuss these constraints for the couplings $\mbox{\bf g}_8$ and $\mbox{\bf g}_{27}$ of $ΔS=1$ transitions and the $\mbox{\bf B}_{K}$--parameter of $K^0-{\bar K}^0$ mixing.

hep-ph↗

arXiv1995

Two--Loop Electroweak Corrections to the Muon g-2: a new class of Hadronic Contributions

We discuss, within the framework of the Standard Model, the calculation of the two-loop electroweak contributions to the anomalous magnetic moment of the muon involving triangle fermionic loops of leptons and quarks. Because of the large ratios of masses involved, these contributions are rather large. The result we obtain differs from a previous estimate reported in the literature. The discrepancy originates in the cancellation of anomalies in $SU(3)_c\times SU(2)_L\times U(1)_Y$, a cancellation that requires the consideration of both leptons {\it and} quarks within each generation and that had been previously overlooked.

hep-ph↗