728 research outputs found
Dynamics of Langevin Simulation
This chapter [of a supplement to Prog. Theo. Phys.] reviews numerical
simulations of quantum field theories based on stochastic quantization and the
Langevin equation. The topics discussed include renormalization of finite
step-size algorithms, Fourier acceleration, and the relation of the Langevin
equation to hybrid stochastic algorithms and hybrid Monte Carlo.Comment: 20 p
Numerical Tests of the Improved Fermilab Action
Recently, the Fermilab heavy-quark action was extended to include
dimension-six and -seven operators in order to reduce the discretization
errors. In this talk, we present results of the first numerical simulations
with this action (the OK action), where we study the masses of the quarkonium
and heavy-light systems. We calculate combinations of masses designed to test
improvement and compare results obtained with the OK action to their
counterparts obtained with the clover action. Our preliminary results show a
clear improvement.Comment: 7 pages, 3 figures, Talk presented at 28th International Symposium On
Lattice Field Theory (Lattice 2010) 13-19 Jun 2010, Villasimius, Sardinia,
Ital
Dual Superconductor Mechanism of Confinement on the Lattice
We investigate the dual superconductor mechanism of confinement for pure
SU(2) lattice gauge theory in the maximally abelian gauge. We focus on the the
dual Meissner effect. We find that the transverse distribution of the
longitudinal chromoelectric field due to a static quark-antiquark pair
satisfies the dual London equation. Moreover we show that the size of the flux
tube scales according to asymptotic freedom.Comment: LaTeX, 9 pages, 6 figures available as a PostScript file from L.
Cosmai, BARI - TH 110/9
Accumulating evidence for nonstandard leptonic decays of D_s mesons
The measured rate for D_s -> l nu decays, where l is a muon or tau, is larger
than the standard model prediction, which relies on lattice QCD, at the 3.8
sigma level. We discuss how robust the theoretical prediction is, and we show
that the discrepancy with experiment may be explained by a charged Higgs boson
or a leptoquark.Comment: 4 pages; v2 conforms with PRL versio
Heavy and Light Quarks with Lattice Chiral Fermions
The feasibility of using lattice chiral fermions which are free of
errors for both the heavy and light quarks is examined. The fact that the
effective quark propagators in these fermions have the same form as that in the
continuum with the quark mass being only an additive parameter to a chirally
symmetric antihermitian Dirac operator is highlighted. This implies that there
is no distinction between the heavy and light quarks and no mass dependent
tuning of the action or operators as long as the discretization error is negligible. Using the overlap fermion, we find that the
(and ) errors in the dispersion relations of the pseudoscalar and
vector mesons and the renormalization of the axial-vector current and scalar
density are small. This suggests that the applicable range of may be
extended to with only 5% error, which is a factor of
larger than that of the improved Wilson action. We show that the generalized
Gell-Mann-Oakes-Renner relation with unequal masses can be utilized to
determine the finite errors in the renormalization of the matrix elements
for the heavy-light decay constants and semileptonic decay constants of the B/D
meson.Comment: final version to appear in Int. Jou. Mod. Phys.
New lattice action for heavy quarks
We extend the Fermilab method for heavy quarks to include interactions of
dimensions 6 and 7 in the action. There are, in general, many new interactions,
but we carry out the calculations needed to match the lattice action to
continuum QCD at the tree level, finding six non-zero couplings. Using the
heavy-quark theory of cutoff effects, we estimate how large the remaining
discretization errors are. We find that our tree-level matching, augmented with
one-loop matching of the dimension-five interactions, can bring these errors
below 1%, at currently available lattice spacings.Comment: 43 pp; v2 conforms with PRD version, improving plots and many minor
thing
- …