Lattice calculation of hadronic light-by-light contribution to the muon anomalous magnetic moment

Abstract

The quark-connected part of the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment is computed using lattice QCD with chiral fermions. We report several significant algorithmic improvements and demonstrate their effectiveness through specific calculations which show a reduction in statistical errors by more than an order of magnitude. The most realistic of these calculations is performed with a near-physical, 171 MeV pion mass on a (4.6 fm) 3 spatial volume using the 32 3 × 64 Iwasaki+DSDR gauge ensemble of the RBC/UKQCD Collaboration.

The hadronic vacuum polarization contribution to the muon g − 2 from lattice QCD

“…We have checked explicitly [77] that the violation of the Ward identity has a negligible effect on the determination of Π(Q 2 ). It has been noted in [51,78] (see also [44,79]) that the vacuum polarization tensor does not vanish at Q = 0 in finite volume, Π µν (0) = 0. In order to reduce finite-volume effects it is then advantageous to subtract the contribution Π µν (0), which is easily effected via a simple modification of the phase factor in eq.…”

“…This concerns both a hvp µ , studied in [28][29][30][31][32][33][34][35][36][37][38][39][40], as well as a hlbl µ [41][42][43][44][45][46][47][48][49]. Lattice calculations of a hvp µ proceed by evaluating a convolution integral over Euclidean momenta Q 2 [28,50].…”

Baryons as relativistic three-quark bound states

“…[702] for an overview. There are ongoing efforts in lattice QCD [703] and dispersive approaches [704,705] to provide model-independent information on the magnitude of the HLbL contribution. , τ , η−, or t, σ, ω.…”

A precise determination of the HVP contribution to the muon anomalous magnetic moment from lattice QCD

“…For the QED contributions we used a stochastic position-space sampling technique similar to the one used in our hadronic light-by-light calculation of Ref. [15]. We have re-tuned the quark masses and checked the prediction of the pion mass splitting against the experimental result.…”

“…We utilize an importance sampling technique in position space similar to Ref. [15] and an appropriately normalized local vector current coupling to the photon fields. The photons are regulated with the QED L prescription in this work and the universal 1/L and 1/L 2 corrections are taken into account for the mass spectrum [16].…”