Eur. Phys. J. A 24, s1.69-s1.73 (2005)
DOI: 10.1140/epjad/s2005-05-012-0

SU(3)-breaking effects in kaon and hyperon semileptonic decays from lattice QCD

D. Becirevic¹, D. Guadagnoli², G. Isidori³, V. Lubicz^{4, 5}, G. Martinelli², F. Mescia^{3, 4}, M. Papinutto⁶, S. Simula⁵, C. Tarantino^{4, 5} and G. Villadoro<sup>2

1</sup>  Laboratoire de Physique Théorique, Université Paris Sud, Centre d'Orsay, F-91405 Orsay-Cedex, France
²  Dipartimento di Fisica, Università di Roma "La Sapienza", and INFN, Sezione di Roma, P. le A. Moro 2, I-00185 Rome, Italy
³  Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, Via E. Fermi 40, I-00044 Frascati, Italy
⁴  Dipartimento di Fisica, Università di Roma Tre, Via della Vasca Navale 84, I-00146 Rome, Italy
⁵  Istituto Nazionale di Fisica Nucleare, Sezione di Roma III, Via della Vasca Navale 84, I-00146, Rome, Italy
⁶  NIC/DESY Zeuthen, Platanenallee 6, D-15738 Zeuthen, Germany

(Received 20 September 2004 / Published online 08 February 2005)

Abstract

We present a quenched lattice study of the vector form factors at zero-momentum transfer, f_V(0), relevant for the determination of |V_us| from semileptonic K -> π l ν (K_l3) and Σ^- -> n l ν decays. Using suitable double ratios of three-point correlation functions we show that in case of both kaon and hyperon decays it is possible to calculate the form factor f_V(0) at the percent precision, which is the one required for a significant determination of |V_us|. In case of K_l3 decay the leading quenched chiral logarithms are corrected for by using analytic calculations in quenched chiral perturbation theory. Our final result, f_V(K⁰π^-) = 0.960 ± 0.005_stat ± 0.007_syst, where the systematic error does not include the residual quenched effects, is in good agreement with the estimate made by Leutwyler and Roos. The impact of our result on the extraction of |V_us| is briefly illustrated.

PACS: 12.15.Hh Determination of CKM matrix elements - 13.20.Eb Semileptonic decays of K mesons - 13.30.Ce Semileptonic decays of baryons - 12.38.Gc Lattice QCD calculations

© Società Italiana di Fisica, Springer-Verlag 2005