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标题：Pseudo-scalar meson form factors with maximally twisted Wilson fermions at Nf=2
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作者：S. Simula
期刊名称：PoS - Proceedings of Science
印刷版ISSN：1824-8039
出版年度：2007
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.