出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We present the results of a lattice QCD calculation of the pseudoscalar meson decay constants
fK, fD and fDs , performed with Nf = 2 dynamical fermions. The simulation is carried out with
the tree-level improved Symanzik gauge action and with the twisted mass fermionic action at
maximal twist. With respect to our previous study [1], here we have analysed data at three values
of the lattice spacing (a ≃ 0.10fm,0.09fm,0.07fm) and performed the continuum limit, and
we have included at a = 0.09fm data with a lighter quark mass (mp ≃ 260MeV) and a larger
volume (L ≃ 2.7fm), thus having at each lattice spacing L ≥ 2.4fm and Mp L ≥ 3.6. Our result
for the kaon decay constant is fK = (157.5±0.8|stat.±3.3|syst.)MeV and for the ratio fK/ fp =
1.205±0.006|stat.±0.025|syst., in good agreement with the other Nf = 2 and Nf = 2+1 lattice
calculations. For the D and Ds meson decay constants we obtain fD =(205±7|stat.±7|syst.)MeV,
in good agreement with the CLEO-c experimentalmeasurement and with other recent Nf = 2 and
Nf = 2+1 lattice calculations, and fDs = (248±3|stat.±8|syst.)MeV that, instead, is 2.3s below
the CLEO-c/BABAR experimental average, confirming the present tension between lattice
calculations and experimental measurements.
