出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We present preliminary results for various electroweak form factors of pseudo-scalar mesons
using the tree-level improved Symanzik gauge action and the maximally twisted mass fermionic
action with Nf =2 dynamical flavors. Our results, obtained for both light and heavy quarkmasses
at a single lattice spacing (a ≃ 0.09 fm) and at a single lattice volume (V ∗ T = 243 ∗ 48), exhibit
a quite remarkable statistical precision thanks to the use of all-to-all quark propagators computed
with a stochastic method. Moreover very low values of the four-momentum transfer are achieved
by making use of twisted boundary conditions on the valence quark fields. The mass dependence
of the pion charge radius is analyzed using Chiral Perturbation Theory, obtaining clear evidence
of relevant two-loop contributions. The universal Isgur-Wise function is computed from heavyto-
heavy electromagnetic transitions and its slope in the case of u(d) spectator quarks is found to
be r 2
IW = 0.77±0.28, where the error is statistical only.
