Excited B mesons from the lattice

TL;DR

This paper calculates the energies of excited $b ar{s}$ mesons using lattice QCD, predicting narrow states near the $BK$ threshold, which are relevant for experimental searches.

Contribution

It provides the first detailed lattice QCD study of excited $b ar{s}$ mesons including orbital, spin-orbit, and radial excitations with both quenched and dynamical fermions.

Findings

Orbital excitations up to L=3 are explored.

The scalar (L=1) meson is predicted to be very narrow.

Up to six excited states are near the $BK$ threshold and likely narrow.

Abstract

We determine the energies of the excited states of a heavy-light meson $Q\bar{q}$, with a static heavy quark and light quark with mass approximately that of the strange quark from both quenched lattices and with dynamical fermions. We are able to explore the energies of orbital excitations up to L=3, the spin-orbit splitting up to L=2 and the first radial excitation. These $b \bar{s}$ mesons will be very narrow if their mass is less than 5775 MeV -- the $BK$ threshold. We investigate this in detail and present evidence that the scalar meson (L=1) will be very narrow and that as many as 6 $b \bar{s}$ excited states will have energies close to the $BK$ threshold and should also be relatively narrow.