Zusammenfassung
The \$\rho\$ meson leptonic decay constant at the physical pion mass is
calculated with chiral fermions. Overlap valence quarks are used on the
\$L^3T=48^396\$ \$N\_f=2+1\$ domain-wall fermion configurations with
light sea quarks at the physical point and the spatial extension of 5.5 fm. The
mass of the vector meson \$\rho\$ is determined to be \$m\_\rho=775.96.0\pm
1.8\$ MeV, and the valence \$\rho\$ sigma term is extracted to be \$\sigma\_\pi
\rho^(val)=9.82(6)\$ MeV from Feynmann-Hellman theorem. By adopting a new
method to reduce the noise of the wall-wall correlation functions of hadrons,
we obtain the \$\rho\$ leptonic decay constant \$f\_\rho=208.55.50.9\$ MeV,
which is in very good agreement with the experimental value \$f\_\rho=209.4\pm
1.5\$ MeV derived from the \$\tau\$ decay \$\tau\nu\_\tau\$.
Nutzer