Mixing effects on spectroscopy and partonic observables of mesons with logarithmic confining potential in a light-front quark model

TL;DR

This paper uses a light-front quark model with a logarithmic confining potential to analyze meson spectra, mixing effects, and various observables, achieving good agreement with experimental and lattice data.

Contribution

It introduces a mixing scheme between 1S and 2S states in a light-front quark model with a logarithmic potential, improving spectroscopic predictions.

Findings

Optimal mixing angle found to be 18 degrees.

Predicted mass of B_J(5840) as 2^1S_0 state.

Results consistent with experimental data and lattice simulations.

Abstract

Using the variational principle, we systematically investigate the mass spectra and wave functions of both $1S$ and $2S$ state heavy pseudoscalar $(P)$ and vector $(V)$ mesons within the light-front quark model. This approach incorporates a Coulomb plus logarithmic confinement potential to accurately describe the constituent quark and antiquark dynamics. Additionally, spin hyperfine interactions are introduced perturbatively to compute the masses of pseudoscalar and vector mesons. The present analyses of the $1S$ and $2S$ states require the consideration of mixing between them to account for empirical constraints. These constraints include the mass gap $\Delta M_{P} > \Delta M_{V}$, where $\Delta M_{P(V)} = M^{2S}_{P(V)} - M^{1S}_{P(V)}$ and the hierarchy of the decay constants $f_{1S} > f_{2S}$. We find the optimal value of the mixing angle to be $\theta = 18^{\circ}$, significantly enhancing the consistency between our spectroscopic predictions and the experimental data compiled by the Particle Data Group (PDG). Furthermore, based on the predicted mass, the newly observed resonance $B_J(5840)$ could be assigned as a $2^1S_0$ state in the $B$ meson family. The study also reports various pertinent observables, including twist-2 distribution amplitudes, electromagnetic form factors, charge radii, $\xi$ moments, and transition form factors which are found to be consistent with both available lattice simulations and experimental data. In addition, our predicted branching ratios for the channels of $B^+ \rightarrow \tau^+ \nu_{\tau}$ as well as rare decays of $B^0$ and $B_s^0$ appear in accordance with experimental data.