Particle theory

Abstract:

As ultra-high energy cosmic ray protons propagate through the universe, they undergo photo-meson interactions with the cosmic microwave background, generating the 'cosmogenic' neutrino flux. If, however, a substantial fraction of the cosmic ray primaries are heavy nuclei rather than protons, they would preferentially lose energy through photo-disintegration so the corresponding neutrino flux may be substantially depleted. We investigate this issue using a Monte Carlo simulation of cosmic ray propagation through intragalactic radiation fields and assess the impact of the altered neutrino fluxes on next-generation neutrino telescopes. © 2004 Elsevier B.V. All rights reserved.

Abstract:

This talk discusses the relative impact of running-coupling and other higher-order corrections on the small-x gluon-gluon splitting function. Comments are made on similarities with some aspects of the Balitsky-Kovchegov equation, which arise because of the presence of an effective infrared cutoff in both cases. It is emphasised that, at least in the splitting-function case, the asymptotic small-x behaviour has little relevance to the phenomenologically interesting preasymptotic region. This is illustrated with the aid of a convolution of the resummed splitting function with a toy gluon distribution.