LQCDLIGHTQUARKS · Lattice QCD with light dynamical quarks

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Project objective

Quantum chromodynamics (QCD) has been validated through a large amount of experiments. However, since the theory has not been solved analytically, quantitative predictions of its low-energy phenomenology from first principles (a key element in the understanding of both the strong and the weak interactions) can be achieved only through the use of a lattice regularisation.A recent breakthrough (based on the use of domain decomposition methods) in the field of simulation algorithms has opened the way to simulations with Wilson fermions at quark masses small enough to make contact with chiral perturbation theory, thus allowing controlled extrapolation of lattice results to the physical point.The goal of this project is double.- First the study of processes where small quark masses are crucial such as pion-pion scattering and its resonances. In this case the main difficulty (beyond the small masses and large volumes needed) comes from the fact that lattice field theories are defined in Euclidean space-time. This difficulty can be solved by adopting finite volume techniques, which allow the extraction of the pion-pion scattering phases in infinite volume from the two-pion energy spectrum in finite volume.- Secondly, the study of problems where chiral symmetry (explicitly broken by the Wilson regularisation) is necessary, such as the Delta S=2 transition amplitudes (and the related kaon B-parameter B_K) which require the computation of the matrix elements of four fermion operators.In this case we propose to investigate the use of valence Ginsparg-Wilson quarks (which respect chiral symmetry) on gauge configurations containing light Wilson sea quarks after that appropriate matching of the corresponding quark masses has been performed. One can thus compare simple quantities with those in the pure Wilson approach and finally compute B_K.

Original text from CORDIS.

Participants

• EUROPEAN ORGANISATION FOR NUCLEAR RESEARCH · GENEVA 23CoordinatorCountry levelSwitzerland

Links

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