Pseudoscalar decay constants fK= fp, fD and fDs with N f = 2+ 1+ 1 ETMC configurations

We present a lattice QCD calculation of the pseudoscalar decay constants fK, fD and fDs performed by the European Twisted Mass Collaboration with Nf=2+1+1 dynamical fermions. We simulated at three different values of the lattice spacing, the smallest being approximately 0.06fm, and with pion masses as small as 210MeV. Our main results are: fK+/fπ+=1.183(17), fK+=154.4(2.1)MeV, fDs=242.1(8.3)MeV, fD=201.9(8.0)MeV, fDs/fD=1.199(25) and (fDs/fD)/(fK/fπ)=1.005(15).