Threshold effects in hadron spectrum: a new spectroscopy?

Quenching Effects in the Hadron Spectrum

Lattice QCD has generated a wealth of data in hadronic physics over the last two decades. Until relatively recently, most of this information has been within the “quenched approximation” where virtual quark–anti-quark pairs are neglected. This review presents a descriptive discussion of the effects of removing this approximation in the calculation of hadronic masses. 1 The Quenched Approximatio...

Instanton Effects in Hadron Spectroscopy Revisited

We use an optimised clover action to study spectroscopy on an instanton ensemble reconstructed from smoothed Monte Carlo configurations. Due to the better chirality of the clover action, the artificial configurations show a marked difference from the free field behaviour obtained with the Wilson action. They however still fail to reproduce the physics observed on the smoothed configurations. Th...

Pentaquarks and new hadron spectroscopy at BABAR

Recent results on the search for pentaquarks and on charmonium spectroscopy at BABAR are reviewed. The latter includes the observation of the puzzling new state X(3872) → J/ψ π π− in B decays, and the searches for X(3872) in two-body B decays and initial state radiation events. Contributed to the Proceedings of the XI International Conference on Elastic and Diffractive Scattering, 5/15/2005—20/...

Hadron Spectroscopy

Effects of Nonperturbative Improvement in Quenched Hadron Spectroscopy

with cSW determined nonperturbatively by the Alpha collaboration. (For details see [1,2] and references thereof.) Our runs consist of 104 quenched configurations, at β = 6.2 and volume 24 × 48. We consider 7 values of the hopping parameter κ, and all their nondegenerate flavor combinations. We run at the improved value cSW = 1.61375065 and also, for comparison, at cSW = 0. We have considered po...