Abstract
We determine the leading Fock-state light front wave functions (LF-LFWFs) of the $\rho$ and J/$\psi$ mesons, for the first time from the Dyson-Schwinger and Bethe-Salpeter equations (DS-BSEs) approach. A unique advantage of this method is that it renders a direct extraction of LF-LFWFs in presence of a number of higher Fock-states. Modulated by the current quark mass and driven by the dynamical chiral symmetry breaking (DCSB), we find the $\rho$ and $J/\psi$ LF-LFWFs different in profile, i.e., the former are broadly distributed in $x$ (the longitudinal light-cone momentum fraction of meson carried by quark) while the latter are narrow. Moreover, the $\rho$ LF-LFWFs contribute less than 50% to the total Fock-state normalization, suggesting considerable higher Fock-states in $\rho$. We then use these LF-LFWFs to study the diffractive $\rho$ and $J/\psi$ electroproduction within the dipole picture. The calculated cross section shows general agreement with HEAR data, except for growing discrepancy in $\rho$ production at low photon virtuality. Our work provides a first dipole picture analysis on diffractive $\rho$ electroproduction that confronts the parton nature of the light (anti)quarks.
Highlights
Diffractive vector meson production provides an important probe to the gluon saturation [1]
A unique advantage of this method is that it renders a direct extraction of LF-LFWFs in presence of a number of higher Fockstates
Modulated by the current quark mass and driven by the dynamical chiral symmetry breaking, we find the ρ and J=ψ LF-LFWFs different in profile, i.e., the former are broadly distributed in x while the latter are narrow
Summary
Diffractive vector meson production provides an important probe to the gluon saturation [1]. The LF-LFWFs of vector mesons and photon are important nonperturbative element of the dipole picture. Their determination in connection with QCD greatly helps reduce the theoretical uncertainties, and substantially deepens our understanding of the hard diffractions. We project the ρ and J=ψ covariant BS wave functions onto the light front and extract the LF-LFWFs from the many Fock-states embedded [16,17,18]. We confront these LF-LFWFs with diffractive ρ and J=ψ electroproduction at hadron-electron ring accelerator (HERA) within the color dipole approach. The leading Fock-state configuration of a vector meson state is expressed with the nonperturbative LFWFs ΦΛλ;λ0
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