Seasonal Variations in Soudan 2

Seasonal Variations in an underground detector may be a signature for Dark Matter. 1 The Soudan 2 detector searches for nucleon decay and atmospheric neutrinos. The trigger rate is about 0.5 Hertz. It is dominated by approximately equal numbers of atmospheric muons and low level radioactivity. The muon rate has a seasonal variation of +-2°, which is consistent with a similar e ect at MACRO. The MACRO e ect has been correlated with temperature in the upper atmosphere. Our trigger rate has a seasonal variation of +-15° which we believe is due to radon in the mine, and variations in air ow with outside temperature.