Transverse momentum distributions of valence quark in light and heavy vector mesons

Abstract

We study the leading-twist time-reversal even transverse momentum dependent parton distribution functions (TMDs) of light and heavy vector mesons, i.e., the $\rho$, $J/\psi$ and $\Upsilon$. We employ the leading Fock-state light front wave functions (LF-LFWFs) of $\rho$ and $J/\psi$ from our recent study, and supplement with $\Upsilon$'s LF-LFWFs. These LF-LFWFs are extracted from dynamically solved Bethe-Salpeter wave functions. The vector meson TMDs are then studied with the light front overlap representation at leading Fock-state. All the obtained TMDs are non-vanishing and evolve with current quark mass, in particular the tensor polarized TMDs $f_{1LT}$ and $f_{1TT}$ which undergo a sign flip. The $\rho$ TMDs are compared with other model studies and agreement is found, aside from $f_{1LT}$ and $f_{1TT}$. Finally, the collinear PDFs of vector mesons are studied. The $\rho$'s valence PDFs $f_{1,v}(x)$ and $g_{1L,v}(x)$ are evolved to the scale of 2.4 GeV, with their first three moments compared to lattice QCD prediction. The qualitative behavior of tensor polarized PDF $f_{1LL}(x)$ in $\rho$ at large $x$ is also discussed.