One-loop flavor changing electromagnetic transitions

Abstract

We discuss the effect of the external fermion masses in the flavor-changing radiative transitions of a heavy fermion (quark or lepton) to a lighter fermion at the one-loop level, and point out an often overlooked crucial difference in the sign of a charge factor between transitions of the down type $s\to d\gamma$ and the up type $c\to u\gamma$. We give formulas for the $F\to f\gamma$ effective vertex in various approximations and the exact formula for $t\to c\gamma$ and $\tau \to \mu \gamma$.

LaTeX 16 pages + 4 postscript figures. Misprints corrected, some Comments added

References in corpus (2)

• Long distance $c\to u\gamma$ effects in weak radiative decays of D-mesons
• Radiative decays of D mesons

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