Muons in extensive air showers: IV. Search for diffuse -ray emission in the regions 1014-1015 eV and above 1018 eV

Abstract

Using data from the Haverah Park EAS (extensive air showers) detector array (GREX) and the associated muon detector an attempt is made to detect -ray primaries from the plane of the Galaxy. Muon cuts are made which should reduce background but retain the majority of any -ray primaries. Using the GREX array, a 40 m2 muon detector, and a data batch of ~5 × 106 EAS around 1015 eV, no significant -ray signal is seen. Specifically, the /particle ratio is less than 8.7 × 10-4. At energies above 1018 eV and using data from the earlier water Cerenkov arrays at Haverah Park with `muon-poor' cuts, again no signal is recognizable from the 1258 EAS data set. However, there is some evidence for Galactic plane enhancement of magnitude equal to that seen before, and this confirmation has value. In view of the changing nature of high-energy collisions at ultra-high energies it is just conceivable that the enhancement is due to -rays. The results and conclusions are thus consistent with other observations.