Shi, C.Chang, L.Roberts, C.Schmidt, S.Tandy, P.Zong, H.2016-08-112016-08-112014Physics Letters B: Nuclear Physics and Particle Physics, 2014; 738:512-5180370-26930370-2693http://hdl.handle.net/2440/100416We compute the kaon’s valence-quark (twist-two parton) distribution amplitude (PDA) by projecting its Poincaré-covariant Bethe–Salpeter wave-function onto the light-front. At a scale ζ = 2GeV, the PDA is abroad, concave and asymmetric function, whose peak is shifted 12–16% away from its position in QCD’s conformal limit. These features are a clear expression of SU(3)-flavour-symmetry breaking. They show that the heavier quark in the kaon carries more of the bound-state’s momentum than the lighter quark and also that emergent phenomena in QCD modulate the magnitude of flavour-symmetry breaking: it is markedly smaller than one might expect based on the difference between light-quark current masses. Our results add to a body of evidence which indicates that at any energy scale accessible with existing or foreseeable facilities, a reliable guide to the interpretation of experiment requires the use of such nonperturbatively broadened PDAs in leading-order, leading-twist formulae for hard exclusive processes instead of the asymptotic PDA associated with QCD’s conformal limit. We illustrate this via the ratio of kaon and pion electromagnetic form factors: using our nonperturbative PDAs in the appropriate formulae, Fk/Fπ=1.23 at spacelike-Q2=17 GeV2, which compares satisfactorily with the value of 0.92(5) inferred in e+e− annihilation at s=17 GeV2.en© 2014 Argonne National Laboratory and the authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/ . Funded by SCOAP3.dynamical chiral symmetry breaking; Dyson–Schwinger equations; factorisation in heavy-meson decays; flavour symmetry breaking; light pseudoscalar mesons; parton distribution amplitudes; strange quarksJournal article003001309910.1016/j.physletb.2014.07.0570003446249000772-s2.0-849086158292-s2.0-8490602473596300