Particle theory

Abstract:

We study constraints on models with a flat "Universal'' Extra Dimension in which all Standard Model fields propagate in the bulk. A significantly improved constraint on the compactification scale is obtained from the extended set of electroweak precision observables accurately measured at LEP1 and LEP2. We find a lower bound of M_c = R^{-1} > 700 (800) GeV at the 99% (95%) confidence level. We also discuss the implications of this constraint on the prospects for the direct and indirect detection of Kaluza-Klein dark matter in this model.

Abstract:

States beyond those expected in the simple constituent quark model are now emerging. I focus on the scalar glueball and its mixing with states in the qq nonet, and also on correlations in Strong QCD that may form diquarks and seed qqqq states. Some models of the pentaquark candidate theta(1540) are critically discussed.