Particle theory

Abstract:

There has recently been renewed interest in massive neutral dark-matter particle candidates with masses greater than ∼ 1 TeV which may be unstable. We re-evaluate the constraints on such particles from the possible effects of their decays on the spectrum of the microwave background-radiation and the primordially synthesised abundances of the light elements, from observations of the diffuse gamma-ray background radiation, and from searches for muons and neutrinos in nucleon-decay and cosmic-ray detectors. We find that such unstable neutral relics may well have the cosmological critical density if their lifetime exceeds ∼ 1016 yr. We illustrate our arguments by applying them to technicolour baryons and to "cryptons" in superstring-inspired models. © 1992.

Abstract:

We use a massively parallel supercomputer to simulate a 483·56 lattice with SU(2) pure gauge theory at β=2.85 which enables us to explore the approach to the continuum limit. The string tension is measured accurately and we find that asymptotic scaling is not restored by this β-value. © 1992.

Abstract:

We present the first physics results for quenched QCD and for pure SU(2) gauge theory from the UKQCD collaboration. We report preliminary results for static quark potentials, the string tension and the quenched hadron spectrum on a 243 × 48 lattice at β = 6.2 using the standard Wilson fermion action and an O(a) improved nearest-neighbour Wilson fermion action. Our codes run at in excess of 1.5 Gflops in the 64-node Meiko i860-based Computing Surface at Edinburgh. We have also simulated pure gauge SU(2) theory on a 483 × 56 lattice at β = 2.85 to explore the approach to the continuum limit. © 1992.