Search

Abstract: The nature and identity of the dark matter of the Universe is one of the most challenging problems facing modern cosmology. Only 5% of the energy density of the Universe can be associated with known forms of matter. Problems for baryonic and neutrino dark matter imply the necessity to search beyond the standard model for dark matter candidates. Emphasis is placed on the prospects for supersymmetric dark matter. [Copyright &y& Elsevier]

Abstract: We discuss the interpretation of present and possible future experimental constraints on decay in the context of the constrained minimal extension of the Standard Model (CMSSM) with universal scalar masses. We emphasize the importance of including theoretical and other experimental uncertainties in calculating the likelihood function, which can affect significantly the inferred 95% confidence-level limit on the CMSSM parameters. The principal uncertainties are the meson decay constant, and . The latter induce uncertainties in the mass of the neutral Higgs boson that dominates the decay amplitude at large , reducing the CMSSM region excluded by present and possible future limits from the Fermilab Tevatron collider and the LHC. [Copyright &y& Elsevier]

Abstract: We reconsider the effects of the radiation from the decays of unstable particles on the production and destruction of the primordial light elements, with a view to reconciling the high primordial 7Li abundance deduced from big bang nucleosynthesis (BBN), as implied by the baryon-to-photon ratio now inferred from the anisotropies of the cosmic microwave background (CMB), with the lower abundance of 7Li observed in halo stars. The potential destruction of 7Li is strongly constrained by observations of deuterium (D), 3He and 6Li. We identify ranges for the unstable particle abundance and lifetime which would deplete 7Li while remaining consistent with the abundance of 6Li. However, in these regions either the D abundance is unacceptably low or the ratio 3He/D is unacceptably large. We conclude that late particle decay is unable to explain both the discrepancy of the calculated 7Li abundance and the observed 7Li plateau. In the context of supersymmetric theories with neutralino or gravitino dark matter, we display the corresponding light-element constraints on the model parameters. [Copyright &y& Elsevier]

Without assuming that Higgs masses have the same values as other scalar masses at the input GUT scale, we combine constraints on the minimal supersymmetric extension of the Standard Model (MSSM) coming from the cold dark matter density with the limits from direct searches at accelerators such as LEP, indirect measurements such as b→sγ decay and the anomalous magnetic moment of the muon. The requirement that Higgs masses-squared be positive at the GUT scale imposes important restrictions on the MSSM parameter space, as does the requirement that the LSP be neutral. We analyze the interplay of these constraints in the (μ,mA), (μ,m1/2), (m1/2,m0) and (mA,tanβ) planes. These exhibit new features not seen in the corresponding planes in the constrained MSSM in which universality is extended to Higgs masses. [Copyright &y& Elsevier]

We derive a general formalism for constructing a four-dimensional effective action for the radion field in 5 dimensions, taking into account the possible dependence of the scale factor on the internal coordinate. First and second variations of the action with respect to the size of the extra dimension reveals two types of algebraic constraints on the combination of brane and bulk Lagrangians that extremize the action, and provide an effective mass for the radion field. We derive a compact formula for the radion mass squared in terms of brane and bulk potentials for the case of a bulk scalar field. We further specialize these constraints for several, five-dimensional realizations of brane world models. [Copyright &y& Elsevier]