More about the Network
Neutrinos are the most abundant particles in the universe, because of their great production during the hot big bang in numbers comparable to the photons of the 2.7K cosmic background radiation. They are also emitted in large numbers by starts, and produced in high-energy processes such as supernovae and, presumably, in the mysterious central engines of gamma-ray bursts.
Yet some of the fundamental properties of neutrinos remain unknown. There is good reason to believe though that key questions will soon be answered, after some recent spectacular discoveries that promise to bring the field to maturity, even if in the immediate term they bring new challenges. Perhaps the most significant development came in 1998 when it was announced that measurements performed by the Super-Kamiokande neutrino observatory left little doubt that different neutrino types do change their identity as they propagate, suggesting that they are not strictly massless as had been assumed. This opened the door to a new era, ensuring that neutrino physics in particular and astrophysics in general would be a prime focus of the scientific community for years to come. There was already considerable commitment within the European Union including underground neutrino observatories and a cubic-kilometre neutrino telescope. There is now a natural eagerness to capitalise on these investments as interest around the world in neutrino physics grows, and this ESF Network is providing a focal point for the research activity.
One of the main tasks of the Network will be to extend particle physics theories to accommodate some recent neutrino observations and experiments that suggest modifications in the model will be needed. It now appears that there may be a fourth non-interacting (i.e. sterile) neutrino state in addition to the three interacting ones already known. The existence of a sterile state has profound implications in turn for astrophysics and cosmology, modifying for example the power spectrum of the temperature fluctuation in the cosmic microwave radiation. This may provide precise evidence for or against the existence of a hot dark matter.
To address these tasks and to articulate the efforts of scientists in the relevant fields, the research objectives of this Network split naturally into five ta
- Reconstructing the Neutrino mass spectrum
The solar and atmospheric neutrino measurements will be analysed, and theoretical explanations for the results sought in the framework of phenomenological models, ranging from the seesaw mechanism to radical alternatives involving extra space-time dimensions. - Cosmological Implications
Ongoing large-scale redshift surveys and CMBR observations are expected to provide data throughout this programme that will provide evidence for or against sterile neutrinos or eV-neutrino masses. This part of the programme will rely utterly on the observational findings. - Supernova Neutrinos
The ongoing Monte-Carlo simulations of neutrino transport on a static supernova background will be concluded within a year. This will lead to an improved model for neutrino transport providing self-consistent dynamical calculations of the initial supernova collapse and subsequent explosion. These calculations will also be helped by improvements in the microscopic input physics to include a more realistic model of the interactions between neutrinos and the nuclear medium. - High-Energy Neutrinos as a Diagnostic for Dark Matter
The aim here is to probe the distribution of dark matter in our galaxy by analysing the signature of neutralino annihilation in the sun, earth and galactic halo. For the first time, neutrino oscillations will be included in such dark-matter studies, and will lead to important modifications of previous results. - Sources for High-Energy Neutrinos and Their Detection
The large neutrino telescopes AMANDA, ANTARES, and the cosmic air-shower array Auger will be able to measure neutrino fluxes from active galactic nuclei, gamma ray bursts, interactions of cosmic rays with the cosmic microwave background, and also more exotic sources such as decaying super-heavy particle relics from the early universe. This will enable previous work on particle acceleration and neutrino production to be continued to improve the predictions for the neutrino fluxes, and to explore their relationship with the measured high-energy cosmic ray and TeV gamma-ray fluxes. The interesting development in the first year of the Network will be the inclusion for the first time of neutrino oscillations into these calculations to take account of the experimentally indicated neutrino masses and mixings.
The Network also envisages efforts towards establishing the discovery potential of the existing neutrino detectors aiming at the possibility of designing future instruments. go to website
