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.
Monte Carlo simulations of the 4d O(4) model in the broken phase are performed to determine the parameters of a resonance. The standard method for extracting them on the lattice is through Luschers formula; recently a new method, based on the probabi
lity distribution concept, has been proposed. We study the application of these methods and compare them with Monte Carlo data.
Automatic Differentiation (AD) allows to determine exactly the Taylor series of any function truncated at any order. Here we propose to use AD techniques for Monte Carlo data analysis. We discuss how to estimate errors of a general function of measur
ed observables in different Monte Carlo simulations. Our proposal combines the $Gamma$-method with Automatic differentiation, allowing exact error propagation in arbitrary observables, even those defined via iterative algorithms. The case of special interest where we estimate the error in fit parameters is discussed in detail. We also present a freely available fortran reference implementation of the ideas discussed in this work.
We show how lattice Quantum Monte Carlo simulations can be used to calculate electronic properties of carbon nanotubes in the presence of strong electron-electron correlations. We employ the path integral formalism and use methods developed within th
e lattice QCD community for our numerical work and compare our results to empirical data of the Anti-Ferromagnetic Mott Insulating gap in large diameter tubes.
A method suitable for extracting resonance parameters of unstable baryons in lattice QCD is examined. The method is applied to the strong decay of the Delta to a pion-nucleon state, extracting the pion-nucleon - Delta coupling constant and Delta decay width.
Using established relations between the scattering matrix in infinite volume and the two-particle spectrum in a periodic box, we compute the mass and width of the rho meson from simulations of N_f=2 flavors of dynamical clover fermions at small pion masses 2 m_pi < m_rho.
Pietro Giudice
,Darran McManus
,Mike Peardon
.
(2012)
.
"A comparison of analysis techniques for extracting resonance parameters from lattice Monte Carlo data"
.
Darran McManus
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