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K→πlν semileptonic form factors from two-flavor lattice QCD Lubicz, V. Mescia, Federico Simula, S. Tarantino, Carolina ETM Collaboration Física de partícules Experiments Particle physics Experiments We present new lattice results of the K → π ℓ ν semileptonic form factors obtained from simulations with two flavors of dynamical twisted-mass fermions, using pion masses as light as 260 MeV. Our main result is f + ( 0 ) = 0.9560 ( 84 ) , which, combined with the latest experimental data for K ℓ 3 decays, leads to | V u s | = 0.2267 ( 5 ) exp  ( 20 ) f + ( 0 ) . Using the PDG(2008) determinations of | V u d | and | V u b | our result implies for the unitarity relation | V u d | 2 + | V u s | 2 + | V u b | 2 = 1.0004 ( 15 ) . For the O ( p 6 ) term of the chiral expansion of f + ( 0 ) we get Δ f ≡ f + ( 0 ) − 1 − f 2 = − 0.0214 ( 84 ) . 2019-04-08T08:35:41Z 2019-04-08T08:35:41Z 2009-12-30 2019-04-08T08:35:41Z info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Reproducció del document publicat a: https://doi.org/10.1103/PhysRevD.80.111502 Physical Review D, 2009, vol. 80, num. 11, p. 111502(R) https://doi.org/10.1103/PhysRevD.80.111502 (c) American Physical Society, 2009 info:eu-repo/semantics/openAccess American Physical Society Articles publicats en revistes (Física Quàntica i Astrofísica)