Wednesday, March 19, 2008

HiRes Confirms GZK Cutoff

This could be one of HiRes last triumphs. It has now down a "negative result" experiment and confirms the GZK cutoff (link may be open for a limited time), signifying a threshold of energy for cosmic rays.

This energy ‘cut-off’ was predicted in 1966 by Kenneth Greisen of Cornell University in Ithaca, New York, and in the same year by Soviet physicists Georgiy Zatsepin and Vadim Kuzmin of the Lebedev Institute of Physics in Moscow. They predicted that there would be very few cosmic rays with energies greater than about 6×1019 electronvolts (eV) because of energy losses through interactions with the ubiquitous photons of the cosmic microwave background, the radiation that fills the Universe.


1 comment:

GZK said...

Just read about GZK limit and the source of UHECRs on Wikipedia:
In November 2007, researchers at the Pierre Auger Observatory announced that they had evidence that UHECRs appear to come from the active galactic nuclei (AGNs) of energetic galaxies powered by matter swirling onto a supermassive black hole.
It would be interesting to see how this research develops.