arXiv subjects
Publications and source records attributed to Nils A. Tornqvist.
The mechanism where flavor symmetry is broken spontaneously is discussed within a scalar QCD model with effective three-meson couplings. For sufficiently large coupling the model is unstable with respect to quantum loops from mesonic vacuum polarization. It is argued that color and gluons naturally can account for the Goldstone degrees of freedom expected when flavor symmetry is spontaneously broken.
A new mechanism for spontaneous breaking of flavour symmetry is demonstrated. An exactly flavour symmetric model with degenerate bare nonets and with sufficiently strong tri-linear meson couplings is shown to lead to self-consistency equations which are unstable. Instead there exists a stable solution, which break flavour symmetry spontaneously in the mass spectrum. For a C-degenerate meson spectrum the stable mass spectrum obeys the Okubo-Zweig-Iizuka (OZI) rule and the approximate equal spacing rule.
We reply to the comment of Harada, Sannino and Schechter (hep-ph/9609428) on our recent paper in the Phys. Rev. Letters on the sigma meson. This concerns the question, raised by Isgur and Speth in another comment, of whether a detailed crossing symmetric form is necessary to understand the data. The discussion gives further support on the existence of the broad sigma near 500 MeV.
It is shown from a very general model and an analysis of data on the lightest 0++ meson nonet that the f0(980) and f0(1200) resonance poles are two manifestations of the same ss state. Similarily the a0(980) and the a0(1450) are likely to be two manifestations of the same qq state. On the other hand, the uu+dd state, when unitarized and strongly distorted by hadronic mass shifts, becomes an extremely broad Breit-Wigner-like background, m=860 MeV, Gamma=880 MeV, with its pole at s=(0.158-i0.235) GeV^2. This we identify with the sigma meson required by models for spontaneous breaking of chiral symmetry.
A summary of two conferences on the hadron and gluonium spectrum is given, with personal comments on the status of the best candidates for gluonium or non-qq states, such as f0(1370), f0(1500), fJ(1720), fJ(2230), eta(1410), eta(1460), and f1(1420).