153 research outputs found
Excited-state contribution to the axial-vector and pseudo-scalar correlators with two extra pions
We study multi-particle state contributions to the QCD two-point functions of
the axial-vector and pseudo-scalar quark bilinears in a finite spatial volume.
For sufficiently small quark masses one expects three-meson states with two
additional pions at rest to have the lowest total energy after the ground
state. We calculate this three-meson state contribution using chiral
perturbation theory. We find it to be strongly suppressed and too small to be
seen in present-day lattice simulations.Comment: 17 pages, 5 figure
Multi-hadron states in Lattice QCD spectroscopy
The ability to reliably measure the energy of an excited hadron in Lattice
QCD simulations hinges on the accurate determination of all lower-lying
energies in the same symmetry channel. These include not only single-particle
energies, but also the energies of multi-hadron states. This talk deals with
the determination of multi-hadron energies in Lattice QCD. The
group-theoretical derivation of lattice interpolating operators that couple
optimally to multi-hadron states is described. We briefly discuss recent
algorithmic developments which allow for the efficient implementation of these
operators in software, and present numerical results from the Hadron Spectrum
Collaboration.Comment: 5 pages, 3 figures, talk given at Hadron 2009, Tallahassee, Florida,
December 1, 200
A comparison of analysis techniques for extracting resonance parameters from lattice Monte Carlo data
Different methods for extracting resonance parameters from Euclidean lattice
field theory are tested. Monte Carlo simulations of the O(4) non-linear sigma
model are used to generate energy spectra in a range of different volumes both
below and above the inelastic threshold. The applicability of the analysis
methods in the elastic region is compared. Problems which arise in the
inelastic region are also emphasised.Comment: 17 pages, 20 figures; clarification and minor corrections added, to
appear in PR
Calculation of the heavy-hadron axial couplings g_1, g_2, and g_3 using lattice QCD
In a recent letter [Phys. Rev. Lett. 108, 172003 (2012), arXiv:1109.2480] we
have reported on a lattice QCD calculation of the heavy-hadron axial couplings
, , and . These quantities are low-energy constants of
heavy-hadron chiral perturbation theory (HHPT) and are related to the
, , and couplings.
In the following, we discuss important details of the calculation and give
further results. To determine the axial couplings, we explicitly match the
matrix elements of the axial current in QCD with the corresponding matrix
elements in HHPT. We construct the ratios of correlation functions used
to calculate the matrix elements in lattice QCD, and study the contributions
from excited states. We present the complete numerical results and discuss the
data analysis in depth. In particular, we demonstrate the convergence of
HHPT for the axial-current matrix elements at pion masses up to
about 400 MeV and show the impact of the nonanalytic loop contributions.
Finally, we present additional predictions for strong and radiative decay
widths of charm and bottom baryons.Comment: 42 pages, 20 figures, updated calculation of Xi_b^{*0} width using
mass measurement from CMS, published versio
The excited hadron spectrum in lattice QCD using a new method of estimating quark propagation
Progress in determining the spectrum of excited baryons and mesons in lattice
QCD is described. Large sets of carefully-designed hadron operators have been
studied and their effectiveness in facilitating the extraction of excited-state
energies is demonstrated. A new method of stochastically estimating the
low-lying effects of quark propagation is proposed which will allow reliable
determinations of temporal correlations of single-hadron and multi-hadron
operators.Comment: 5 pages, 4 figures, talk given at Hadron 2009, Tallahassee, Florida,
December 1, 200
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