Abstract
AbstractWe compute the hadronic light-by-light scattering contribution to the muon $$g-2$$
g
-
2
from the charm quark using lattice QCD. The calculation is performed on ensembles generated with dynamical (u, d, s) quarks at the SU(3)$$_\mathrm{f}$$
f
symmetric point with degenerate pion and kaon masses of around 415 MeV. It includes the connected charm contribution, as well as the leading disconnected Wick contraction, involving the correlation between a charm and a light-quark loop. Cutoff effects turn out to be sizeable, which leads us to use lighter-than-physical charm masses, to employ a broad range of lattice spacings reaching down to 0.039 fm and to perform a combined charm-mass and continuum extrapolation. We use the $$\eta _c$$
η
c
meson to define the physical charm-mass point and obtain a final value of $$a_\mu ^\mathrm{HLbL,c}= (2.8\pm 0.5) \times 10^{-11}$$
a
μ
HLbL
,
c
=
(
2.8
±
0.5
)
×
10
-
11
, whose uncertainty is dominated by the systematics of the extrapolation. Our result is consistent with the estimate based on a simple charm-quark loop, whilst being free of any perturbative scheme dependence on the charm mass. The mixed charm–light disconnected contraction contributes a small negative amount to the final value.
Publisher
Springer Science and Business Media LLC
Subject
Physics and Astronomy (miscellaneous),Engineering (miscellaneous)
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