Flavour symmetry breaking in the kaon parton distribution amplitude
Abstract
We 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 = 2 GeV, the PDA is a broad, 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.
- Authors:
- Publication Date:
- Research Org.:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Nuclear Physics (NP)
- OSTI Identifier:
- 1227768
- Alternate Identifier(s):
- OSTI ID: 1212883
- Grant/Contract Number:
- AC02-06CH11357; NSF-PHY1206187; 11275097; 11274166; 2012CB921504; 2012009111002; FL0992247
- Resource Type:
- Published Article
- Journal Name:
- Physics Letters B
- Additional Journal Information:
- Journal Name: Physics Letters B Journal Volume: 738 Journal Issue: C; Journal ID: ISSN 0370-2693
- Publisher:
- Elsevier
- Country of Publication:
- Netherlands
- Language:
- English
- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; dynamical chiral symmetry breaking; Dyson–Schwinger equations; factorisation in heavy-meson decays; flavour symmetry breaking; light pseudoscalar mesons; parton distribution amplitudes; strange quarks
Citation Formats
Shi, Chao, Chang, Lei, Roberts, Craig D., Schmidt, Sebastian M., Tandy, Peter C., and Zong, Hong-shi. Flavour symmetry breaking in the kaon parton distribution amplitude. Netherlands: N. p., 2014.
Web. doi:10.1016/j.physletb.2014.07.057.
Shi, Chao, Chang, Lei, Roberts, Craig D., Schmidt, Sebastian M., Tandy, Peter C., & Zong, Hong-shi. Flavour symmetry breaking in the kaon parton distribution amplitude. Netherlands. https://doi.org/10.1016/j.physletb.2014.07.057
Shi, Chao, Chang, Lei, Roberts, Craig D., Schmidt, Sebastian M., Tandy, Peter C., and Zong, Hong-shi. Sat .
"Flavour symmetry breaking in the kaon parton distribution amplitude". Netherlands. https://doi.org/10.1016/j.physletb.2014.07.057.
@article{osti_1227768,
title = {Flavour symmetry breaking in the kaon parton distribution amplitude},
author = {Shi, Chao and Chang, Lei and Roberts, Craig D. and Schmidt, Sebastian M. and Tandy, Peter C. and Zong, Hong-shi},
abstractNote = {We 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 = 2 GeV, the PDA is a broad, 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.},
doi = {10.1016/j.physletb.2014.07.057},
journal = {Physics Letters B},
number = C,
volume = 738,
place = {Netherlands},
year = {Sat Nov 01 00:00:00 EDT 2014},
month = {Sat Nov 01 00:00:00 EDT 2014}
}
https://doi.org/10.1016/j.physletb.2014.07.057
Web of Science