HLbL contribution to the muon g-2 using twisted-mass fermions at the physical point

Abstract

We present updated results for the hadronic light-by-light (HLbL) contribution to the muon anomalous magnetic moment. The calculations are based on ETMC's $N_f=2+1+1$ Wilson-clover twisted-mass ensembles at the physical point. We perform continuum extrapolations for the strange- and charm-quark connected contributions and report on our results for the light-quark connected and light-quark 2+2 disconnected contributions at one lattice spacing.

Figures (3)

• Figure 1: Results for the charm-quark connected contribution evaluated on the ensembles cB64, cC80, cD96 and cE112 for kernel $\overline{\mathcal{L}}^{(\Lambda=0.4)}$ for the 1111 direction (upper two plots) and 0111 direction (lower two plots). The left plots depict the integrand $f(|y|)$ as a function of the distance $|y|$ and the right plots the partially integrated $a_\mu(|y|_\text{max})$ as a function of the cut-off distance $|y|_\text{max}$.
• Figure 3: Results for the strange-quark connected contribution on the ensembles cB64, cC80, cD96 and cE112 for kernel $\overline{\mathcal{L}}^{(\Lambda=0.4)}$ and diagonal direction 1111. The left plot depicts the integrand $f(|y|)$ as a function of the distance $|y|$ and the right plot the partially integrated $a_\mu(|y|_\text{max})$ as a function of the cut-off distance $|y|_\text{max}$.
• Figure 5: Preliminary results for the light-quark connected contribution on the ensemble cB64. The left plot depicts the integrand $f(|y|)$, with a fit of the form $A~|y|^3~e^{-B|y|}$ for $|y| \gtrsim 0.79$ fm shown as a blue band. The right plot displays the partially integrated $a_\mu(|y|_\text{max})$ with the effect of replacing the data by the fit result for $|y| \geq 2.0$ fm shown as a blue band.