The 39th International Symposium on Lattice Field Theory (Lattice 2022)

Eta pole contributions to HLbL at the physical point

11 Aug 2022, 11:30

20m

CP1-HSZ/0.001 (CP1-HSZ) - HS3 (CP1-HSZ)

Oral Presentation QCD in searches for physics beyond the Standard Model QCD in searches for physics beyond the Standard Model

Speaker

Sebastian Andreas Burri (University of Bern)

Description

We report on our computation of the eta transition form factor ${\mathcal{F}}_{\eta \to {\gamma }^{\ast }{\gamma }^{\ast }}$ from
twisted mass lattice QCD at physical quark masses and at a single lattice spacing.
On the lattice, we have access to a broad range of (space-like) photon momenta and
can therefore produce data complementary to the experimentally accessible singly
virtual case. We use the form factor to determine the eta pole contribution to the
hadronic light-by-light scattering in the muon $g-2$, leading to a first lattice QCD estimate. Our estimate of $a_{\mu }^{\eta -pole}$ obtained at a single lattice spacing achieves an
accuracy of below 40%. Since so far there are no determinations of this contribution
from first principles, even such a crude determination is interesting from a
phenomenological point of view.

Presentation materials

lattice_2022.pdf