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Register a new userComparisons of electric charge and axial charge meson cloud distributions in the PCQM
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The meson cloud distributions in $r$-space are extracted from the nucleon electromagnetic and axial form factors which are derived in the perturbative chiral quark model. The theoretical results indicate that the electric charge and axial charge distributions of the three-quark core are the same, the magnetic charge distributions of the meson cloud and three-quark core are more or less in the same region and peak at distances of around 2 $rm GeV^{-1}$, but the axial charge meson cloud distributes mainly inside the three-quark core.
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We reconsider the question of electric charge quantization, which leads to the existence of a dark charge nontrivially unified with weak isospin in a novel gauge symmetry, $SU(3)_Cotimes SU(2)_Lotimes U(1)_Yotimes U(1)_N$, where $Y$ and $N$ determine the electric and dark charges, respectively. The new model provides neutrino masses and dark matter appropriately, a direct consequence of the dark dynamics. We diagonalize the fermion, scalar, and gauge sectors as well as obtain relevant interactions, taking into account the kinetic mixing of $U(1)_{Y,N}$ gauge bosons. The new physics signals at colliders are examined. The dark matter observables are discussed.
The unpolarized, helicity and transversity parton distribution functions of the nucleon are studied within a convolution model where the bare nucleon is dressed by its virtual meson cloud. Using light-front time-ordered perturbation theory, the Fock states of the physical nucleon are expanded in a series involving a bare nucleon and two-particle, meson-baryon, states. The bare baryons and mesons are described with light-front wave functions (LFWFs) for the corresponding valence-parton components. Using a representation in terms of overlap of LFWFs, the role of the non-perturbative antiquark degrees of freedom and the valence quark contribution at the input scale of the model is discussed for the leading-twist collinear parton distributions. After introducing perturbative QCD effects through evolution to experimental scales, the results are compared with available data and phenomenological extractions. Predictions for the nucleon tensor charge are also presented, finding a very good agreement with recent phenomenological extractions.
We use the meson cloud model of the nucleon to calculate distribution functions for $(bar {d} - bar{u})$ and $ bar{d}/bar{u}$ in the proton. Including the effect of the omega meson cloud, with a coupling constant $g_omega^2/4piapprox 8$, allows a reasonably good description of the data.
The axial form factor as well as the axial charge of octet baryons are studied in the perturbative chiral quark model (PCQM) with the quark wave functions predetermined by fitting the theoretical results of the proton charge form factor to experimental data. The theoretical results are found, based on the predetermined quark wave functions, in good agreement with experimental data and lattice values. This may indicate that the electric charge and axial charge distributions of the constituent quarks are the same. The study reveals that the meson cloud plays an important role in the axial charge of octet baryons, contributing 30%-40% to the total values, and strange sea quarks have a considerable contribution to the axial charge of the $Sigma$ and $Xi$.
Exact expression is obtained for the differential cross section of elastic electroweak scattering of longitudinal polarized massive Dirac neutrinos with the electric charge and anomalous magnetic moment on a spinless nucleus. This formula contains all necessary information about the nature of the neutrino mass, charge and magnetic moment. Some of them state that between the mass of the neutrino its electric charge there exists an interconnection.
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