Mass Spectra of Heavy-Light Mesons in Heavy Hadron Chiral Perturbation Theory

TL;DR

This paper uses heavy-hadron chiral perturbation theory to accurately predict the masses of charm and bottom mesons, incorporating physical meson masses in loop calculations, and provides predictions for yet-unobserved bottom meson states.

Contribution

It introduces a third-order HHChPT calculation with physical meson masses, improving mass and width predictions and extending results from charm to bottom mesons.

Findings

Predicted bottom meson masses agree with experimental data for odd-parity states.

Confirmed near degeneracy of nonstrange and strange scalar B mesons.

Provided predictions for unobserved bottom meson states to guide experiments.

Abstract

We study the masses of the low-lying charm and bottom mesons within the framework of heavy- hadron chiral perturbation theory (HHChPT). We work to third order in the chiral expansion, where meson loops contribute. In contrast to previous approaches, we use physical meson masses in evaluating these loops. This ensures that their imaginary parts are consistent with the observed widths of the D-mesons. The lowest odd- and even-parity, strange and nonstrange charm mesons provide enough constraints to determine only certain linear combinations of the low-energy constants (LECs) in the effective Lagrangian. We comment on how lattice QCD could provide further information to disentangle these constants. Then we use the results from the charm sector to predict the spectrum of odd- and even-parity of the bottom mesons. The predicted masses from our theory are in good agreement with experimentally measured masses for the case of the odd-parity sector. For the even-parity sector, the B-meson states have not yet been observed; thus, our results provide useful information for experimentalists investigating such states. The near degeneracy of nonstrange and strange scalar B mesons is confirmed in our predictions using HHChPT. We show why previous approaches of using HHChPT in studying the mass degeneracy in the scalar states of charm and bottom meson sectors gave unsatisfactory results.