Abstract
A physical model is presented for the nonperturbative parton distributions in the nucleon. This is based on quantum fluctuations of the nucleon into baryon-meson pairs convoluted with Gaussian momentum distributions of partons in hadrons. The hadronic fluctuations, here developed in terms of hadronic chiral perturbation theory, occur with high probability and generate sea quarks as well as dynamical effects also for valence quarks and gluons. The resulting parton momentum distributions $f(x,{Q}_{0}^{2})$ at low momentum transfers are evolved with conventional Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equations from perturbative QCD to larger scales. This provides parton density functions $f(x,{Q}^{2})$ for the gluon and all quark flavors with only five physics-motivated parameters. By tuning these parameters, experimental data on deep-inelastic structure functions can be reproduced and interpreted. The contribution to sea quarks from hadronic fluctuations explains the observed asymmetry between $\overline{u}$ and $\overline{d}$ in the proton. The strange-quark sea is strongly suppressed at low ${Q}^{2}$, as observed.
Highlights
The parton distribution functions (PDFs) of the nucleon are of great importance
Of particular importance here is that the PDFs fðx; Q2Þ have the property that for Q2 > Q20 ∼ 1 GeV2 the dependence on Q2 can be calculated by the DokshitzerGribov-Lipatov-Altarelli-Parisi (DGLAP) equations [1,2,3] derived from perturbative QCD, which is well established theoretically and experimentally confirmed
This study has demonstrated that the momentum distribution of partons in the proton, and thereby the observed proton structure functions, can be understood in terms of basic physical processes
Summary
One reason is that they provide insights into the structure of the proton and neutron as bound states of quarks and gluons, which is still a largely unsolved problem due to our limited understanding of strongly coupled QCD. Another reason is their use for calculations of cross sections for high-energy collision processes. Of particular importance here is that the PDFs fðx; Q2Þ have the property that for Q2 > Q20 ∼ 1 GeV2 the dependence on Q2 can be calculated by the DokshitzerGribov-Lipatov-Altarelli-Parisi (DGLAP) equations [1,2,3] derived from perturbative QCD (pQCD), which is well established theoretically and experimentally confirmed.
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