Authors

Abstract

We present a calculation of the scalar, vector and tensor form factors for the pion and kaon inlattice QCD. We use an ensemble of two degenerate light, a strange and a charm quark (Nf =2 + 1 + 1) of maximally twisted mass fermions with clover improvement. The corresponding pionand kaon masses are about 265 MeV and 530 MeV, respectively. The calculation is done in bothrest and boosted frames obtaining data for four-vector momentum transfer squared up to q2 = 2.5GeV2 for the pion and 3 GeV2 for the kaon. The excited-states effects are studied by analyzing sixvalues of the source-sink time separation for the rest frame (1.12 2.23 fm) and for four values forthe boosted frame (1.12 1.67 fm). The lattice data are renormalized non-perturbatively and theresults for the scheme- and scale-dependent scalar and tensor form factors are presented in the MSscheme at a scale of 2 GeV. We apply different parametrizations to describe q2-dependence of theform factors to extract the scalar, vector and tensor radii, as well as the tensor anomalous magneticmoment. We compare the pion and kaon form factors to study SU(3) flavor symmetry breakingeffects. By combining the data for the vector and tensor form factors we also obtain the lowestmoment of the densities of transversely polarized quarks in the impact parameter space. Finally,we give an estimate for the average transverse shift in the y direction for polarized quarks in the xdirection.