An update on the HVP contribution to $g_μ{-}2$ in isoQCD from ETMC

Abstract

We present an update on the determination of the leading-order hadronic vacuum polarisation contribution to the muon anomalous magnetic moment in isospin-symmetric QCD by the Extended Twisted Mass Collaboration. The calculation is based on five $N_f = 2+1+1$ gauge ensembles generated with Wilson-clover twisted-mass quarks at maximal-twist and near-physical pion masses, spanning four lattice spacings and two volumes. For the dominant quark-connected contributions, we employ two distinct valence-quark regularisations and present results for both the isovector and isoscalar components.

Figures (5)

• Figure 1: On the B64 ensemble, comparison between the standard vector--vector correlator computed fully stochastically (green points) and the LMA-improved one (red points).
• Figure 2: Bounding procedure applied to the $I=1$ contribution to $a_\mu^{\mathrm{HVP}}$ on the C80 ensemble for the $\mathsf{tm}$ (left) and $\mathsf{OS}$ (right) regularisations. For each $t_c$, green points correspond to the upper bound and blue points to the lower bound. The red horizontal line and band show the result obtained by averaging the data points between $t_c^{\mathsf{opt}}$ (vertical dashed line) and $t_c^{\mathsf{opt}} + 0.25~\mathrm{fm}$.
• Figure 3: Continuum linear--linear combined extrapolation in $a^2$ of $a_\mu^{\mathrm{HVP}}(I=1)$. Red points correspond to the $\mathsf{tm}$ regularisation, blue points to the $\mathsf{OS}$ one.
• Figure 4: Difference between the B96 and B64 correlators (red points) compared with the GS model: standard (dark blue solid line) and modified (light blue band).
• Figure 5: Left: Bounding procedure for $a_\mu^{\mathrm{HVP}}(I=0)$ on the B64 ensemble. For each $t_c$, green points correspond to the upper bound and blue points to the lower bound. The red horizontal line and band show the result obtained by averaging the data points between $t_c^{\mathsf{opt}}$ (vertical dashed line) and $t_c^{\mathsf{opt}} + 0.25~\mathrm{fm}$. Right: Preliminary continuum extrapolation. Red points correspond to the data obtained on the ensembles of \ref{['tab:iso_EDI_FLAG']}; the green band represents a constant fit to the three finest ensembles, while the blue band shows a linear fit to all ensembles. The black point denotes the result obtained from a Bayesian AIC combination of these fits.