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标题：SU(2) ChPT analysis of the scalar and vector form factors of the kaon semileptonic decay obtained from twisted-mass fermions with Nf = 2
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作者：L. Orifici ; V. Lubicz ; F. Mescia 等
期刊名称：PoS - Proceedings of Science
印刷版ISSN：1824-8039
出版年度：2010
卷号：2010
出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We investigate the vector and scalar form factors relevant for K`3 semileptonic decays using maximally twisted-mass fermions with two flavors of dynamical quarks (Nf = 2). The simulations cover pion masses as light as 260 MeV and four values of the lattice spacing, ranging from 0.05 up to 0.1 fm, which allow to compute directly, for the first time, the continuum limit for the vector form factor at zero-momentum transfer, f+(0). The preliminary result is f+(0) = 0.9544 (68stat), where the error is statistical only. We also extrapolate both form factors to the physical point and study their momentum dependence. Our results are in good agreement with those obtained from a dispersion analyses of the experimental data. Together with the form factors, we analyze the ratio of the leptonic decay constants fK/ fp , by imposing the constraint coming from the Callan-Treiman theorem, obtaining at the physical point fK/ fp = 1.190 (8stat ). Combining our results for f+(0) and fK/ fp with the experimental measurements of the leptonic and semilpetonic decay rates, and using the determination of |Vud| from nuclear beta decays, we determine the values of the Cabibbo angle |Vus| from both K`3 and K`2 decays, obtaining |Vus|K`3 = 0.2266 (17) and |Vus|K`2 = 0.2258 (16).