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P- and D-wave spin-orbit splittings in heavy-light measons

Presenter: Jonna Koponen — University of Helsinki

UKQCD Collaboration, J. Koponen

This is a follow-up to our earlier work on the energies and radial distributions of heavy-light mesons. The heavy quark is taken to be static and the light quark has a mass about that of the strange quark. We now concentrate on the energies of the excited states with higher angular momentum (and with radial nodes), using a “fuzzy” static quark. A new improvement is the use of hypercubic blocking in the time direction, which effectively constrains the heavy quark to move within a 2a hypercube (a is the lattice spacing).

The calculation is carried out with dynamical fermions on a 163 × 32 lattice with a lattice spacing a≈ 0.11 fm generated using the non-perturbatively improved clover action.

In nature the closest equivalent of this heavy-light system is the Bs meson, which allows us to compare our lattice calculations to experimental results (where available) or give a prediction where the P-wave states should lie. We pay particular attention to the spin-orbit splitting, to see which one of the states (for a given orbital angular momentum L) has the lower energy. Attempts are now being made to understand these results in terms of the Dirac equation.