Lattice QCD

In the quark sector, it is a difficult task to extract the fundamental parameters of the SM due to the fact that, at low energies, Quantum Chromodynamics (QCD), the theory that describes the color interaction between quarks and gluons, becomes non-perturbative. Fundamental problems such as if the lightest quark mass is different from zero, related to the problem of the absence of heavy CP violation in the SM, requiere the precise prediction of the lightest hadron masses (pions and kaons) from QCD. The mechanism of chiral symmetry breaking in QCD, which determines the hadronic spectrum at low energy, is a non-perturbative effect that requires a QCD treatment without approximations.

This mechanism could be related to the gauge symmetry breaking in the SM in the context of SM extensions with very strong interactions, such as technicolor theories. The only model-independent method to study QCD non-perturbatively is lattice QCD.

In this area members of our group have studied the QCD chiral regime via its formulation in a space-time grid. There has been great progress in the possibility of regularizing QCD without breaking the chiral symmetry explicitly, with Ginsparg-Wilson fermions. The QCD chiral regime has been studied from first principles and the connection between the fundamental theory with the effective chiral theory that describes the dynamics of pions and kaons at low energy has been established.

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