https://doi.org/10.1140/epjc/s10052-020-08578-4
Regular Article - Theoretical Physics
Kaon and pion parton distributions
1
School of Physics, Nanjing University, Nanjing, 210093, Jiangsu, China
2
Institute for Nonperturbative Physics, Nanjing University, Nanjing, 210093, Jiangsu, China
3
European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT*) and Fondazione Bruno Kessler, Villa Tambosi, Strada delle Tabarelle 286, 38123, Villazzano, TN, Italy
4
Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, 69120, Heidelberg, Germany
5
School of Physics, Nankai University, Tianjin, 300071, China
6
Department of Integrated Sciences and Center for Advanced Studies in Physics, Mathematics and Computation, University of Huelva, 21071, Huelva, Spain
7
Helmholtz-Zentrum Dresden-Rossendorf, 01314, Dresden, Germany
8
RWTH Aachen University, III. Physikalisches Institut B, 52074, Aachen, Germany
* e-mail: cdroberts@nju.edu.cn
Received:
1
July
2020
Accepted:
20
October
2020
Published online:
18
November
2020
Beginning with results for the leading-twist two-particle distribution amplitudes of $$\pi $$- and K-mesons, each of which exhibits dilation driven by the mechanism responsible for the emergence of hadronic mass, we develop parameter-free predictions for the pointwise behaviour of all $$\pi $$ and K distribution functions (DFs), including glue and sea. The large-x behaviour of each DF meets expectations based on quantum chromodynamics; the valence-quark distributions match extractions from available data, including the pion case when threshold resummation effects are included; and at $$\zeta _5=5.2\,$$GeV, the scale of existing measurements, the light-front momentum of these hadrons is shared as follows: $$\langle x_{\mathrm{valence}} \rangle ^\pi = 0.41(4)$$, $$\langle x_{\mathrm{glue}} \rangle ^\pi = 0.45(2)$$, $$\langle x_{\mathrm{sea}} \rangle ^\pi = 0.14(2)$$; and $$\langle x_{\mathrm{valence}} \rangle ^K = 0.42(3)$$, $$\langle x_{\mathrm{glue}} \rangle ^K = 0.44(2)$$, $$\langle x_{\mathrm{sea}} \rangle ^K = 0.14(2)$$. The kaon’s glue and sea distributions are similar to those in the pion, although the inclusion of mass-dependent splitting functions introduces some differences on the valence-quark domain. This study should stimulate improved analyses of existing data and motivate new experiments sensitive to all $$\pi $$ and K DFs. With little known empirically about the structure of the Standard Model’s (pseudo-) Nambu-Goldstone modes and analyses of existing, limited data being controversial, it is likely that new generation experiments at upgraded and anticipated facilities will provide the information needed to resolve the puzzles and complete the picture of these complex bound states.
© The Author(s), 2020
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