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:

Neutrino oscillations can be affected by decoherence induced e.g. by Planck scale suppressed interactions with the space-time foam predicted in some approaches to quantum gravity. We study the prospects for observing such effects at IceCube, using the likely flux of TeV antineutrinos from the Cygnus spiral arm. We formulate the statistical analysis for evaluating the sensitivity to quantum decoherence in the presence of the background from atmospheric neutrinos, as well as from plausible cosmic neutrino sources. We demonstrate that IceCube will improve the sensitivity to decoherence effects of O(E2/MPl) by 17 orders of magnitude over present limits and, moreover, that it can probe decoherence effects of O(E3/MPl2) which are well beyond the reach of other experiments. © 2005 The American Physical Society.

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.