Radiative transitions between $0^{-+}$ and $1^{--}$ heavy quarkonia on the light front

TL;DR

This paper calculates radiative transitions between heavy quarkonia states using light-front Hamiltonian methods, comparing results with experiments, lattice QCD, and quark models, and investigates rotational symmetry effects.

Contribution

The study introduces a light-front Hamiltonian approach with BLFQ for heavy quarkonia, analyzing transition form factors with different currents and magnetic projections, highlighting rotational symmetry features.

Findings

Transition form factors agree with experimental data.

Consistent decay constants from different magnetic projections.

Evidence of rotational symmetry in the light-front model.

Abstract

We present calculations of radiative transitions between vector and pseudoscalar quarkonia in the light-front Hamiltonian approach. The valence sector light-front wavefunctions of heavy quarkonia are obtained from the Basis Light-Front Quantization (BLFQ) approach in a holographic basis. We study the transition form factor with both the traditional "good current" $J^+$ and the transverse current $\vec J_\perp$ (in particular, $J^R=J^x+i J^y$). This allows us to investigate the role of rotational symmetry by considering vector mesons with different magnetic projections ($m_j=0,\pm 1$). We use the $m_j=0$ state of the vector meson to obtain the transition form factor, since this procedure employs the dominant spin components of the light-front wavefunctions and is more robust in practical calculations. While the $m_j=\pm 1$ states are also examined, transition form factors depend on subdominant components of the light-front wavefunctions and are less robust. Transitions between states below the open-flavor thresholds are computed, including those for excited states. Comparisons are made with the experimental measurements as well as with Lattice QCD and quark model results. In addition, we apply the transverse current to calculate the decay constant of vector mesons where we obtain consistent results using either $m_j=0$ or $m_j=1$ light-front wavefunctions. This consistency provides evidence for features of rotational symmetry within the model.