The langleSPPrangle Green function and SU(3) breaking inK_ell3decays

Abstract

Using the 1/N C expansion scheme and truncating the hadronic spectrum to the lowestlying resonances, we match a meromorphic approximation to the SP P Green function onto QCD by imposing the correct large-momentum falloff, both off-shell and on the relevant hadron mass shells. In this way we determine a number of chiral low-energy constants of O(p 6 ), in particular the ones governing SU (3) breaking in the K ℓ3 vector form factor at zero momentum transfer. The main result of our matching procedure is that the known loop contributions largely dominate the corrections of O(p 6 ) to f + (0). We discuss the implications of our final value f K 0 π − + (0) = 0.984 ± 0.012 for the extraction of V us from K ℓ3 decays.

Improved estimates of rareKdecay matrix elements fromKℓ3decays

“…where C 12 ∼ a few 10 −6 [26]. This indicates that indeed, there are strong cancellations at play in the ratio r between isospin-breaking corrections induced by the spectator quark.…”

Fingerprints of heavy scales in electroweak effective Lagrangians

“…The other quark and lepton doublets are organized similarly. The fermions transform under G like 18) with g X ∈ U(1) X . The corresponding covariant derivatives of these fermion doublets are given by…”

Status of Kaon physics on the lattice

“…Relevant for lattice computations are also the more recent evaluations of f 2 in partially quenched chiral perturbation theory and the evaluation of finite volume corrections [36,37]. A first estimate of the higher order corrections was given in [33] and more recently estimates for f 4 were given in [38,39,40]. Thus, relying on our knowledge of f 2 in chiral perturbation theory, on the lattice one computes only the corrections,…”