On the chromomagnetic expectation value μ_G^2 and higher power corrections in heavy flavor mesons

Abstract

The important parameter μ_G^2 of the heavy quark expansion is analyzed including perturbative and power corrections. It is found that μ_G^2(2GeV) is known with a few percent accuracy. The perturbative corrections are computed and found small. A nonperturbative relation is suggested which allows to control the power corrections. We conclude that μ_G^2(1GeV)=(0.35+0.03- 0.02)GeV^2. The two-loop expression for the effective `ME' radiation coupling alpha_s^(me)(ω) is given which improves reliability of the perturbative evolution of μ_G^2 towards the low momentum scale. On the nonperturbative side, we advocate the utility of combining the heavy quark expansion with expanding around the `BPS'-type approximation for the meson wavefunction, which implies relations μ_π^2 \approx μ_G^2 and -ρ_{LS}^3 \approx ρ_D^3 as well as similar ones for the nonlocal correlators.

13 pages, 3 figures, LaTeX. Enhanced version incorporates two-loop calculation by Czarnecki and Grozin allowing to find the two-loop evolution of μ_G^2. Error bar decreased, the effective coupling is dicussed in more detail including the nonperturbative component. Two references added

References in corpus (2)

• A Vademecum on Quark-Hadron Duality
• A Few Aspects of Heavy Quark Expansion

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