arXiv subjects

Finn M. Stokes

Publications and source records attributed to Finn M. Stokes.

22 records · Page 2Linked to original sources

arXiv2017

Parity-expanded variational analysis for non-zero momentum

In recent years, the use of variational analysis techniques in lattice QCD has been demonstrated to be successful in the investigation of the rest-mass spectrum of many hadrons. However, due to parity-mixing, more care must be taken for investigations of boosted states to ensure that the projected correlation functions provided by the variational analysis correspond to the same states at zero momentum. In this paper we present the Parity-Expanded Variational Analysis (PEVA) technique, a novel method for ensuring the successful and consistent isolation of boosted baryons through a parity expansion of the operator basis used to construct the correlation matrix.

hep-lat↗

arXiv2016

Search for low-lying lattice QCD eigenstates in the Roper regime

The positive-parity nucleon spectrum is explored in $2 + 1$-flavour lattice QCD in a search for new low-lying energy eigenstates near the energy regime of the Roper resonance. In addition to conventional three-quark operators, we consider novel, local five-quark meson-baryon type interpolating fields that hold the promise to reveal new eigenstates that may have been missed in previous analyses. Drawing on phenomenological insight, five-quark operators based on $σ{N}$, $π{N}$ and $a_0{N}$ channels are constructed. Spectra are produced in a high-statistics analysis on the PACS-CS dynamical gauge-field configurations with $m_π = 411\textrm{ MeV}$ via variational analyses of several operator combinations. Despite the introduction of qualitatively different interpolating fields, no new states are observed in the energy regime of the Roper resonance. This result provides further evidence that the low-lying finite-volume scattering states are not localised, and strengthens the interpretation of the Roper as a coupled-channel, dynamically-generated meson-baryon resonance.

hep-lat↗

arXiv2016

Hamiltonian effective field theory study of the $\mathbf{N^*(1535)}$ resonance in lattice QCD

Drawing on experimental data for baryon resonances, Hamiltonian effective field theory (HEFT) is used to predict the positions of the finite-volume energy levels to be observed in lattice QCD simulations of the lowest-lying $J^P=1/2^-$ nucleon excitation. In the initial analysis, the phenomenological parameters of the Hamiltonian model are constrained by experiment and the finite-volume eigenstate energies are a prediction of the model. The agreement between HEFT predictions and lattice QCD results obtained on volumes with spatial lengths of 2 and 3 fm is excellent. These lattice results also admit a more conventional analysis where the low-energy coefficients are constrained by lattice QCD results, enabling a determination of resonance properties from lattice QCD itself. Finally, the role and importance of various components of the Hamiltonian model are examined.

hep-lat↗

arXiv2014

Visualisations of coherent centre domains in local Polyakov loops

Quantum Chromodynamics exhibits a hadronic confined phase at low to moderate temperatures and, at a critical temperature $T_C$, undergoes a transition to a deconfined phase known as the quark-gluon plasma. The nature of this deconfinement phase transition is probed through visualizations of the Polyakov loop, a gauge independent order parameter. We produce visualizations that provide novel insights into the structure and evolution of center clusters. Using the HMC algorithm the percolation during the deconfinement transition is observed. Using 3D rendering of the phase and magnitude of the Polyakov loop, the fractal structure and correlations are examined. The evolution of the center clusters as the gauge fields thermalize from below the critical temperature to above it are also exposed. We observe deconfinement proceeding through a competition for the dominance of a particular center phase. We use stout-link smearing to remove small-scale noise in order to observe the large-scale evolution of the center clusters. A correlation between the magnitude of the Polyakov loop and the proximity of its phase to one of the center phases of SU(3) is evident in the visualizations.

hep-lat↗