The image vector form factor at zero momentum transfer on the lattice Original Research Article

We present a quenched lattice study of the form factors image and image of the matrix elements image. We focus on the second-order SU(3)-breaking quantity image, which is necessary to extract image from image decays. For this quantity we show that it is possible to reach the percent precision which is the required one for a significant determination of image. The leading quenched chiral logarithms are corrected for by using analytic calculations in quenched chiral perturbation theory. Our final result, image, where the systematic error does not include the residual quenched effects, is in good agreement with the estimate made by Leutwyler and Roos. A comparison with other non-lattice computations and the impact of our result on the extraction of image are also presented.