Vector form factor inKl3semileptonic decay with two flavors of dynamical domain-wall quarks

Abstract

We calculate the vector form factor in K → πlν semileptonic decays at zero momentum transfer f+(0) from numerical simulations of two-flavor QCD on the lattice. Our simulations are carried out on 163 × 32 at a lattice spacing of a ≃ 0.12 fm using a combination of the DBW2 gauge and the domain-wall quark actions, which possesses excellent chiral symmetry even at finite lattice spacings. The size of fifth dimension is set to Ls = 12, which leads to a residual quark mass of a few MeV. Through a set of double ratios of correlation functions, the form factor calculated on the lattice is accurately interpolated to zero momentum transfer, and then is extrapolated to the physical quark mass. We obtain f+(0) = 0.968(9)(6), where the first error is statistical and the second is the systematic error due to the chiral extrapolation. Previous estimates based on a phenomenological model and chiral perturbation theory are consistent with our result. Combining with an average of the decay rate from recent experiments, our estimate of f+(0) leads to the Cabibbo-KobayashiMaskawa (CKM) matrix element |Vus| = 0.2245(27), which is consistent with CKM unitarity. These estimates of f+(0) and |Vus| are subject to systematic uncertainties due to the finite lattice spacing and quenching of strange quarks, though nice consistency in f+(0) with previous lattice calculations suggests that these errors are not large.

Strange mesons and kaon-to-pion transition form factors from holography

“…3. Of particular interest for comparison to data [39,41] and to chiral perturbation theory [23,24,25,26] or lattice gauge theory [27,28,29,30,31] are the values of f + (0), the slopes of f + and f 0 , and the curvature of f + .…”

Chiral extrapolation of the strangeness changing scalar Kπ form factor

“…[54] different collaborations have extracted the vector form factor at zero momentum transfer either with N f = 2 [55][56][57][58] or N f = 2 + 1 [13] flavours. The idea is to first evaluate the scalar form factor f 0 (t) at the momentum transfer t max = (m K − m π ) 2 .…”

FLAG phase 2: status and prospects

“…The standard procedure underestimates the systematic uncertainties also in this case. Applying the prescription discussed above, we arrive at a somewhat larger error: |V us | = 0.2253 (9). This result is indicated on the left hand side of Fig.…”