The new Telescope Array (TA) in Utah will combine fluorescence and scintillation detection methods used in earlier experiments to resolve a discrepancy in the observed rates of ultrahigh-energy cosmic rays. “Looking with both methods simultaneously should settle this,” says the University of Utah’s Pierre Sokolsky, a spokesman for the US–Japan collaboration. “If there’s no cutoff in the energy, there will be quite a lot of excitement. If there is, then we have some understanding. It’s been a burning question in cosmic-ray physics for 30 years.” (See Sokolsky’s article in Physics Today, Physics Today 0031-9228 51 1 1998 31 https://doi.org/10.1063/1.882132 January 1998, page 31 .)
Ground was broken in late August for the first of TA’s three fluorescence detectors. Fluorescence from atmospheric nitrogen relaxing to the ground state is used to reconstruct the energy and directional origin of incident cosmic rays as a function of atmospheric depth.
In addition to...
