BEGIN:VCALENDAR VERSION:2.0 PRODID:Data::ICal 0.22 BEGIN:VEVENT DESCRIPTION:Alan Watson\, Leeds University\, England \n\n
This question c an now be asked because of two results obtained using data recorded at the Pierre Auger Observatory. It has been established\, at the 6-sigma level\ , that the flux of the highest energy cosmic rays is suppressed at energie s beyond 5 x 10 19 eV and that above this energy an anisotropy in the arri val directions of the particles is apparent. The arrival directions appear to be associated with sources within the GZK horizon (z ~ 0.018 or 75 Mpc ). From these observations it seems probable that we have observed the lon g-sought Greisen-Zatsepin-Kuzmin effect\, demonstrating that ultra-high en ergy cosmic rays are of extragalactic origin. It is also probable that the se particles are protons\, thus offering the possibility of insights into features of particle physics at centre-of-mass energies 30 times greater t han will be reached at the LHC. Preliminary conclusions from studies of de tailed features of extensive air showers suggest that extrapolations from Tevatron energies may not be what have been anticipated hitherto. Much fur ther work remains to be done.
\n DTSTART:20080418T200000Z LOCATION:Physics Building\, Room 203 SUMMARY:Is the search for the origin of the highest energy cosmic rays over ? END:VEVENT END:VCALENDAR