The leading order strange quark-connected contribution to the muon anomalous magnetic moment from lattice QCD

Abstract

I present a calculation of the leading strange quark-connected contribution to the anomalous magnetic moment of the muon, α_μ^(2)had,s , using lattice QCD. The calculation is performed on two ensembles with lattice extents of 48³ x 96 and 64³ x 128 with associated inverse lattice spacings of 1:730(4)GeV and 2:359(7)GeV. These were generated with the Iwasaki gauge action and 2+1 dynamical quark flavours, which, along with the valence quarks, are represented on the lattice using the Möbius domain wall fermion action. To account for a slight mistuning in the strange quark mass I use both unitary and partially quenched measurements on each ensemble.

I principally use the hybrid method to determine α_μ^(2)had,s , and I implement several variations of the method in order to quantify a systematic error associated with the selection of any particular variation. In addition, I use a Fourier transformation to compute the hadronic vacuum polarisation (HVP) at momenta not accessible on the lattice, a technique called sine cardinal interpolation (SCI). All these techniques produce results that are highly consistent with one another. Finite volume corrections are expected to be negligible, since G-parity prevents the strange vector current from coupling to pions in the isospin limit. My final result is

α_μ^(2)had,s = 53.1(9)(⁺¹_-3) x 10^-10

where the first error is statistical and the second is systematic. The total error on this result (roughly 2%) is dominated by the statistical uncertainty, which suggests that the methods used here to compute α_μ^(2)had,s in the case of the strange HVP are robust.

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ORCID for Andreas Juttner: orcid.org/0000-0002-3978-0927

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