Lattice results for D/Ds leptonic and semileptonic decays

This review article summarizes recent lattice QCD results for D and D_s meson leptonic and semileptonic decays. Knowing the meson decay constants and semileptonic form factors from theory, one can extract CKM elements V_cd and V_cs from experimental results. At present, the most accurate results for decay constants are from the Fermilab Lattice and MILC Collaborations: f_D=212.5±0.5_{stat}+0.6−1.5|_{syst} MeV and fDs=248.9±0.2_{stat}+0.5−1.6|_{syst} MeV, giving V_cd=0.2184±0.009_{expt}+0.0008−0.0016|_{lattice} and V_cs=1.017±0.02_{expt}+0.002−0.007|_{lattice}. The shapes of the semileptonic form factors from lattice QCD agree very well with experiment, and the accuracy is currently at the 2-5% level for D→πℓν and 1-2% for D→Kℓν. Extracting the CKM elements from the semileptonic decays yields V_cd=0.225(6)_{expt}(10)_{lattice} (HPQCD Collaboration) and V_cs=0.963(5)_{expt}(14)_{lattice} (HPQCD Collaboration). These lattice calculations also revealed that the semileptonic form factors are insensitive to whether the spectator quark is a light or strange quark

Energies of B_s meson excited states - a lattice study

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 (infinitely heavy) 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 a radial node. A new improvement is the use of hypercubic blocking in the time direction. The calculation is carried out with dynamical fermions on a 16 cubed times 32 lattice with a lattice spacing approximately 0.1 fm generated using a non-perturbatively improved clover action. In nature the closest equivalent of this heavy-light system is the B_s meson, which allows us to compare our lattice calculations to experimental results (where available) or to give a prediction where the excited states, particularly P-wave states, should lie. We pay special attention to the spin-orbit splitting, to see which one of the states (for a given angular momentum L) has the lower energy. An attempt is made to understand these results in terms of the Dirac equation.Comment: 35 pages. v3: Data from two new lattices added. New results in several chapter

Population imbalanced fermions in harmonically trapped optical lattices

The attractive Fermi-Hubbard Hamiltonian is solved via the Bogoliubov-de Gennes formalism to analyze the ground state phases of population imbalanced fermion mixtures in harmonically trapped two-dimensional optical lattices. In the low density limit the superfluid order parameter modulates in the radial direction towards the trap edges to accommodate the unpaired fermions that are pushed away from the trap center with a single peak in their density. However in the high density limit while the order parameter modulates in the radial direction towards the trap center for low imbalance, it also modulates towards the trap edges with increasing imbalance until the superfluid to normal phase transition occurs beyond a critical imbalance. This leads to a single peak in the density of unpaired fermions for low and high imbalance but leads to double peaks for intermediate imbalance.Comment: 4 pages with 4 figures, accepted to appear in PR

P-wave Radial distributions of a Heavy-light meson on a lattice

This is a follow-up to our earlier work for the charge (vector) and matter (scalar) distributions for S-wave states in a heavy-light meson, where the heavy quark is static and the light quark has a mass about that of the strange quark. The calculation is again carried out with dynamical fermions on a 16^3x24 lattice with a lattice spacing of about 0.14 fm. It is shown that several features of the S- and P-wave distributions are in qualitative agreement with what one expects from a simple one-body Dirac equation interpretation.Comment: 5 pages, 2 figures, Quark Confinement and the Hadron Spectrum VI, Sardinia, Italy, September, 200

Instability and wavelength selection during step flow growth of metal surfaces vicinal to fcc(001)

We study the onset and development of ledge instabilities during growth of vicinal metal surfaces using kinetic Monte Carlo simulations. We observe the formation of periodic patterns at [110] close packed step edges on surfaces vicinal to fcc(001) under realistic molecular beam epitaxy conditions. The corresponding wavelength and its temperature dependence are studied by monitoring the autocorrelation function for step edge position. Simulations suggest that the ledge instability on fcc(1,1,m) vicinal surfaces is controlled by the strong kink Ehrlich-Schwoebel barrier, with the wavelength determined by dimer nucleation at the step edge. Our results are in agreement with recent continuum theoretical predictions, and experiments on Cu(1,1,17) vicinal surfaces.Comment: 4 pages, 4 figures, RevTe