0000000000294103
AUTHOR
R. Dahm
showing 2 related works from this author
Linear Wave Equations and Effective Lagrangians for Wigner Supermultiplets
1995
The relevance of the contracted SU(4) group as a symmetry group of the pion nucleon scattering amplitudes in the large $N_c$ limit of QCD raises the problem on the construction of effective Lagrangians for SU(4) supermultiplets. In the present study we suggest effective Lagrangians for selfconjugate representations of SU(4) in exploiting isomorphism between so(6) and ist universal covering su(4). The model can be viewed as an extension of the linear $\sigma$ model with SO(6) symmetry in place of SO(4) and generalizes the concept of the linear wave equations for particles with arbitrary spin. We show that the vector representation of SU(4) reduces on the SO(4) level to a complexified quatern…
Neutral pion production at threshold and low-energy theorems
1990
Abstract Recent experiments of neutral pion photoproduction show a strong discrepancy between experimental data and the predictions of low-energy theorems (LET). The basic ingredients of these theorems are the conservation of the electromagnetic current and the hypothesis of a partially conserved axial current (PCAC). Both, anomalies in the t-channel, and rescattering in a simple R-matrix formalism, lead to small corrections of the order of 10 – 20 %. However, the investigation of the effects of chiral symmetry breaking and isospin symmetry breaking at the quark level in a current algebraic approach leads to substantial contributions of the right order of magnitude.