DARK MATTER SEARCH AND THE SCALAR QUARK CONTENTS OF THE NUCLEON

We present lattice QCD simulation results from the European Twisted Mass Collaboration (ETMC) for the light, strange and charm quark contents of the nucleon. These quantities are important ingredients to estimate the cross-section for the detection of WIMPs as Dark Matter candidates. By employing a particular lattice QCD formulation, i.e. twisted mass fermions, accurate results of the light and strange scalar contents of the nucleon can be obtained. In addition, we provide a bound for the charm quark content of the nucleon.

PROPERTIES OF SCALAR-QUARK SYSTEMS IN SU(3)c LATTICE QCD

We perform the first study for the bound states of colored scalar particles ϕ (“scalar quarks”) in terms of mass generation with quenched SU (3)c lattice QCD. We investigate the bound states of ϕ, ϕ†ϕ and ϕϕϕ (“scalar-quark hadrons”), as well as the bound states of ϕ and quarks ψ, i.e., ϕ†ψ, ψψϕ and ϕϕψ (“chimera hadrons”). All these new-type hadrons including ϕ have a large mass of several GeV due to large quantum corrections by gluons, even for zero bare scalar-quark mass mϕ = 0 at a−1 ~ 1 GeV . We find a similar mψ-dependence between ϕ†ψ and ϕϕψ, which indicates their similar structure due to the large mass of ϕ. From this study, we conjecture that all colored particles generally acquire a large effective mass due to dressed gluons.

DYNAMICALLY INDUCED SCALAR QUARK CONFINEMENT

We employ a functional approach to investigate the confinement problem in quenched Landau gauge QCD. We demonstrate analytically that a linear rising potential between massive quarks is generated by infrared singularities in the dressed quark–gluon vertex. The self-consistent mechanism that generates these singularities is driven by the scalar Dirac amplitudes of the full vertex and the quark propagator. These can only be present when chiral symmetry is broken. We have thus uncovered a novel mechanism that directly links chiral symmetry breaking with confinement.