Retrieving "Loop Diagram" from the archives

Cross-reference notes under review

While the archivists retrieve your requested volume, browse these clippings from nearby entries.

1. Weak Decay

   Linked via "loop diagrams"

   Flavor Changing Neutral Currents (FCNC)
   Flavor changing neutral currents (FCNC), processes involving the exchange of a $Z^0$ boson that results in a flavor change (e.g., $s \to d + \gamma$), are strictly forbidden at tree level in the Standard Model due to the required structure of the neutral current. While not strictly a weak decay process in the sense of flavor transformation, observations concerning these currents are highly constrained. The absence of …