Mitchell Golden

Department of Physics
Harvard University
Cambridge, MA 02138
golden@physics.harvard.edu

Recently read papers

Recently I have perused the following papers:

Two Heavy Quark Effective Theories, by S.Balk, A.Ilakovac, J.G.Korner and D.Pirjol and Heavy Quark Effective Theory at Large Orders in 1/m, by S.Balk, J.G.Korner and D.Pirjol.

These two papers outline a new way to construct the Heavy Quark Effective Theory. They - annoyingly - refer to the old way as the "Harvard HQET" even though it was developed by people around the world. It seems to me that the authors vastly overstate the difference between their way of doing things and everyone else's. They want to do the order $\alpha^0$ matching by doing a set of manipulations to separate the large and small components of the field. These differ from the ordinary ones starting at order $1/m^2$. The field they arrive at is normalized differently than the ordinary one. Their manipulations are probably simpler at high orders in $1/m$, but, despite what the papers appear to imply, it is entirely possible to do everything the old way. It is unclear to me that the matching is going to be easier this new way at order $\alpha^1$ or higher, which is of course the important issue in any realistic problem.