Topological susceptibility and η′ meson mass from Nf=2 lattice QCD at the physical point

P Dimopoulos,L Liu,K Ottnad,C Urbach,B Kostrzewa,Etm Collaboration ,B Knippschild,M Werner,M Petschlies,C Jost,C Helmes,U Wenger

doi:10.1103/physrevd.99.034511

Abstract

In this paper we explore the computation of topological susceptibility and $\eta'$ meson mass in $N_f=2$ flavor QCD using lattice techniques with physical value of the pion mass as well as larger pion mass values. We observe that the physical point can be reached without a significant increase in the statistical noise. The mass of the $\eta'$ meson can be obtained from both fermionic two point functions and topological charge density correlation functions, giving compatible results. With the pion mass dependence of the $\eta'$ mass being flat we arrive at $M_{\eta'}= 772(18)\ \mathrm{MeV}$ without an explicit continuum limit. For the topological susceptibility we observe a linear dependence on $M_\pi^2$, however, with an additional constant stemming from lattice artifacts.

Highlights

Due to the persisting 3– 5σ deviation in the anomalous magnetic moment of the muon aμ between theory and experiment, there is considerable interest in the decays η → γ⋆γ⋆ and η0 → γ⋆γ⋆ because a better knowledge of the corresponding transition form factors could help to reduce the uncertainty in the hadronic light-by-light contribution to aμ; see for instance Ref. [1]
In this paper we explore the computation of topological susceptibility and η0 meson mass in Nf 1⁄4 2 flavor QCD using lattice techniques with a physical value of the pion mass as well as larger pion mass values
We observe that the physical point can be reached without a significant increase in the statistical noise

Summary

Introduction

Due to the persisting 3– 5σ deviation in the anomalous magnetic moment of the muon aμ between theory and experiment, there is considerable interest in the decays η → γ⋆γ⋆ and η0 → γ⋆γ⋆ because a better knowledge of the corresponding transition form factors could help to reduce the uncertainty in the hadronic light-by-light contribution to aμ; see for instance Ref. [1]. Due to the persisting 3– 5σ deviation in the anomalous magnetic moment of the muon aμ between theory and experiment, there is considerable interest in the decays η → γ⋆γ⋆ and η0 → γ⋆γ⋆ because a better knowledge of the corresponding transition form factors could help to reduce the uncertainty in the hadronic light-by-light contribution to aμ; see for instance Ref. Η and η0 mesons are interesting from a theoretical point of view because the large mass of the η0 meson is explained by the anomalously broken UAð1Þ axial symmetry in QCD. The η, η0 mixing pattern and the aforementioned transition form factors can be computed nonperturbatively using lattice techniques. [2,3] the corresponding mixing has been studied for three values of the lattice spacing and a large, but still unphysical, range of pion mass

Methods

Results

Discussion

Conclusion