A Scintillator-Proportional Counter Search For Monopoles
A search for slowly moving superheavy magnetic monopoles has been performed using a combined detector of scintillation counters and proportional chambers. At the first stage, the minimum threshold of the energy loss was set at 1/20 minimum ionization for both detectors. PR gas was used for proportional chambers. An upper flux limit of 1.8 × 10−12 cm−2 sr−1 s−1 for monopoles was obtained over a velocity range from 2.5 × 10−4 c to 1.0 × 10−1 c at 90% confidence level. At the second state, mixed gas of helium + 10% methane was used for proportional chambers, because a methane molecule is ionized through the Penning effect by a helium metastable state excited by the monopole. For this condition, an upper flux limit of 1.6 × 10−12 cm−2 sr−1 s−1 for monopoles was obtained over the velocity range from ~3 × 10−4 c to 1c at 90% confidence level.
KeywordsMetastable State Scintillation Counter Helium Atom Velocity Range Grand Unify Theory
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