Resonances f0(1370) and f0(1710) as scalar \bar q-q states from an Nf=3 Sigma Model with Vectors and Axial-Vectors

Features of the non-strange \bar n-n and strange \bar s-s scalar mesons are investigated in the Extended Linear Sigma Model (eLSM) with Nf=3 and vector and axial-vector mesons. Our model contains a pure non-strange and a pure strange scalar state; implementing the mixing of the two states originates two new states, a predominantly non-strange and a predominantly strange one. We investigate the possibility to assign the two mixed states to experimentally well-established resonances. To this end, we calculate the masses and the two-pion decay widths of the mixed states and compare them with experimental data. The predominantly non-strange state is found to be consistent with the resonance f0(1370) and the predominantly strange state with the resonance f0(1710).Comment: Prepared for the Proceedings of the Excited QCD 2011 Workshop, Les Houches (France), 20-25 February 2011; 6 pages, 1 figure, 1 Tabl

Quarkonium Phenomenology in Vacuum

Broad meson phenomenology in vacuum is discussed in a single model containing scalar, pseudoscalar, vector and axial-vector states both in the non-strange and strange sectors. Emphasis is given to search for quark-antiquark (quarkonium) states in the scalar and axial-vector channels. In particular, the work examines the question whether the scalar quark-antiquark states are found in the energy region below or above 1 GeV in the physical spectrum. Contrarily to the naive expectation, the mentioned states are found in the region above 1 GeV. Additionally, the axial-vector isotriplet state $a_1(1260)$ is described as a quarkonium. These results have consequences for the building of order parameters for the chiral-symmetry breaking of Quantum Chromodynamics (QCD).Comment: PhD thesis at Frankfurt University, Institute for Theoretical Physics (2012). 269 pages, 55 figure