Writing Down the HQET Lagrangian

Tabulating a list of effective operators that do not give rise to the same S-matrix elements can be a difficult task. Thankfully, there are some useful group theoretical tools that can make the process easier, and I will discuss how this can be done in heavy particle effective theories. When implemented, an interesting pattern emerges, where the operators in HQET can be organized within representations of the non-relativistic conformal group.