Ian B. Whittingham

Neutralino dark matter in a class of unified theories

The cosmological significance of the neutralino sector is studied for a class of supersymmetric grand unified theories in which electroweak symmetry breaking is seeded by a gauge singlet. Extensive use is made of the renormalization group equations to significantly reduce the parameter space, by deriving analytic expressions for all the supersymmetry-breaking coupling in terms of the universal gaugino mass m12, the universal scalar mass m0 and the coupling A. The composition of the lightest supersymmetric partner is determined exactly below the W-mass, no approximations are made for sfermion masses, and all particle exchanges are considered in calculating the annihilation cross section; the relic abundance is then obtained by an analytic approximation. We find that in these models, stable neutralinos may make a significant contribution to the dark matter in the universe.

Collisional broadening of alkali doublets by helium perturbers

We report results for the Lorentzian profiles of the Li I, Na I and K I doublets and the Na I subordinate doublet broadened by helium perturbers for temperatures up to 3000 K. They have been obtained from a fully quantum-mechanical close-coupling description of the colliding atoms, the Baranger theory of line shapes and new ab initio potentials for the alkali–helium interaction. For all lines except the 769.9 nm K I line, the temperature dependence of the widths over the range 70 ≤ T ≤ 3000 K is accurately represented by the power law form w = aTbb with 0.38 < b < 0.43. The 769.9 nm K I line has this form for 500 ≤ T ≤ 3000 K with b having the higher value of 0.49. Although the shifts have a more complex temperature dependence, they all have the general feature of increasing with temperature above T ~ 500 K apart from the 769.9 K I line whose shift decreases with temperature.

Ultracold collisions of metastable helium atoms

We report scattering lengths for the (1)Sigma (+)(g), (3)Sigma (+)(u), and (5)Sigma (+)(g) adiabatic molecular potentials relevant to collisions of two metastable 2 S-3 helium atoms as a function of the uncertainty in these potentials. These scattering lengths are used to calculate experimentally observable scattering lengths, elastic cross sections, and inelastic rates for any combination of states of the colliding atoms. at temperatures where the Wigner threshold approximation is valid.

Asymmetric dark matter in braneworld cosmology

We investigate the effect of a braneworld expansion era on the relic density of asymmetric dark matter. We find that the enhanced expansion rate in the early universe predicted by the Randall-Sundrum II (RSII) model leads to earlier particle freeze-out and an enhanced relic density. This effect has been observed previously by Okada and Seto (2004) for symmetric dark matter models and here we extend their results to the case of asymmetric dark matter. We also discuss the enhanced asymmetric annihilation rate in the braneworld scenario and its implications for indirect detection experiments.

Gluon and gluino penguin diagrams and the charmless decays of the b quark

Gluon mediated exclusive hadronic decays of

Close-coupled calculation of self-broadening of helium triplet lines

b

Dark matter relic density in Gauss-Bonnet braneworld cosmology

quarks are studied within the standard model (SM) and the constrained minimally supersymmetric standard model (MSSM). For all allowed regions of the MSSM parameter space

Spontaneous Baryogenesis in Supersymmetric Models

(A,\mathrm{tan}\ensuremath{\beta}{,m}_{0}{,m}_{1/2})

Purely-long-range bound states of He(2s 3S)+he(2p 3P)

the penguin magnetic dipole form factor

Self-broadening of triplet lines of helium

{F}_{2}^{R}