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Homework:

1) 

  

EFT Concepts:

1) Power counting not in the rest frame

What happens to this discussion and to the power counting rule  when we are doing HQET in a frame other than the rest frame, where the leading kinetic energy term is a single gradient term with no m suppression? It sounds like the problem you point out, that    is the first term inducing not trivial dynamics, would go away!


Yes, in HQET you do not count   . That counting only arises because    for a Non-Relativistic EFTs of two or more heavy particles. HQET, with a single heavy particle, has a homogeneous scaling for    in frames that are close to the rest frame. You can also look at the power counting of derivatives for HQET in a boosted frame (which is called bHQET). This gives you exactly what you'd expect by applying the boost. See this paper for a description and application of bHQET.

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