The $\eta \to {\gamma }^{\ast }{\gamma }^{\ast }$ transition form factor and the hadronic light-by-light $\eta$-pole contribution to the muon $g-2$ from lattice QCD

Constantia Alexandrou, Simone Bacchio, Sebastian Burri +11

We calculate the double-virtual $\eta \to {\gamma }^{\ast }{\gamma }^{\ast }$ transition form factor ${\mathcal{F}}_{\eta \to {\gamma }^{\ast }{\gamma }^{\ast }}(q_1^2,q_2^2)$ from first principles using a lattice QCD simulation with $N…