Flavour symmetry breaking in the kaon parton distribution amplitude

Shi, Chao; Chang, Lei; Roberts, Craig D.; Schmidt, Sebastian M.; Tandy, Peter C.; Zong, Hong-shi

doi:10.1016/j.physletb.2014.07.057

Title: Flavour symmetry breaking in the kaon parton distribution amplitude

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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, F_K/F_π=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:

Shi, Chao; Chang, Lei;

; Schmidt, Sebastian M.; Tandy, Peter C.; Zong, Hong-shi

Publication Date:: Sat Nov 01 00:00:00 EDT 2014

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.

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                    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

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                    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.

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@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}

}

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