Particle Physics and Particle Astrophysics Research

Neutrino astrophysics

Detecting neutrinos from astrophysical sources could provide unique insights into the origins of cosmic rays and the inner workings of objects such as quasars and gamma-ray bursts. Neutrino astrophysics may provide an opportunity to study neutrino properties, but is primarily concerned with understanding the highest energy cosmic rays and their astrophysical origins. Any process which accelerates protons to the energies seen in cosmic rays must produce high energy neutrinos, because high-energy protons interacting with matter or radiation produce pions, and the charged pion decay chain involves neutrinos.

If the Galactic dark matter is composed of WIMPs, these offer another potential source of astrophysical neutrinos. The best particle physics candidate for WIMPs is the lightest neutralino (a mixture of the supersymetric partners of the Higgs and gauge bosons), which is likely to have a mass of a few hundred GeV. The neutralino is its own antiparticle, and annihilation of two neutralinos may yield W or Z bosons, tau leptons, or heavy quarks, all of which will produce neutrinos when they decay. Regions where neutralinos are concentrated enough to annihilate at a detectable rate - principally the centres of the Sun and Earth, but possibly also the Galactic centre - should therefore be point sources of neutrinos with typical energies of a few GeV to 100 GeV or so.

Sheffield has been involved with the ANTARES project in the Mediterranean since 1997, and also has involvement in R&D towards larger scale experiments, specifically acoustic detection of neutrinos by underwater hydrophone arrays, and cubic kilometre scale underwater Cherenkov experiments.

Sheffield's projects in this area:

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