Improving the signal-to-noise ratio in Lattice QCD

Abstract:

Spectra with full towers of levels are expected due to the quantization of the string vibrations, however different theoretical models exist for the excitation spectra. First principle computations are important to test the different models and to search for novel phenomena, but so far only a few excited states of QCD flux tubes have been studied with pure gauge SU(3) lattice QCD in 3+1 dimensions. We thus aim to study a spectrum of flux tubes with static quark and antiquark sources up to a significant number of excitations. In this thesis, we compute the excitation of the flux tube for quantum numbers Λ η =Σ+ g ,Σ− g , Σ+ u , Σ− u , Πg,Πu, ∆g, ∆u, where for some of them just the ground state or up to two levels were calculated and published in the literature. To achieve the highest possible excitation level, we construct a large set of operators with the correct symmetry, solve the generalized eigenvalue problem and compare the results of different lattice QCD gauge actions with different lattice spacings and anisotropies.