Journal
PHYSICS LETTERS B
Volume 738, Issue -, Pages 512-518Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.physletb.2014.07.057
Keywords
Dynamical chiral symmetry breaking; Dyson-Schwinger equations; Factorisation in heavy-meson decays; Flavour symmetry breaking; Light pseudoscalar mesons; Parton distribution amplitudes; Strange quarks
Funding
- International Fellow Award from the Helmholtz Association
- National Natural Science Foundation of China [11275097, 11274166]
- National Basic Research Program of China [2012CB921504]
- Research Fund for the Doctoral Program of Higher Education (China) [2012009111002]
- University of Adelaide
- Australian Research Council [FL0992247]
- Department of Energy, Office of Nuclear Physics [DE-AC02-06CH11357]
- Forschungszentrum Julich GmbH
- National Science Foundation [NSF-PHY1206187]
- Direct For Mathematical & Physical Scien
- Division Of Physics [1206187] Funding Source: National Science Foundation
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We compute the kaon's valence-quark (twist-two parton) distribution amplitude (PDA) by projecting its Poincare-covariant Bethe-Salpeter wave-function onto the light-front. At a scale zeta = 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, F-K/F-pi = 1.23 at spacelike-Q(2) = 17 GeV2, which compares satisfactorily with the value of 0.92(5) inferred in e(+)e(-) annihilation at s = 17GeV(2). (C) 2014 Argonne National Laboratory and the authors. Published by Elsevier B. V.
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