Cosmogenic production of $^{37}$Ar in the context of the LUX-ZEPLIN
  experiment
  We estimate the amount of $^{37}$Ar produced in natural xenon via cosmic
ray-induced spallation, an inevitable consequence of the transportation and
storage of xenon on the Earth's surface. We then calculate the resulting
$^{37}$Ar concentration in a 10-tonne payload~(similar to that of the
LUX-ZEPLIN experiment) assuming a representative schedule of xenon
purification, storage and delivery to the underground facility. Using the
spallation model by Silberberg and Tsao, the sea level production rate of
$^{37}$Ar in natural xenon is estimated to be 0.024~atoms/kg/day. Assuming the
xenon is successively purified to remove radioactive contaminants in 1-tonne
batches at a rate of 1~tonne/month, the average $^{37}$Ar activity after
10~tonnes are purified and transported underground is 0.058--0.090~$\mu$Bq/kg,
depending on the degree of argon removal during above-ground purification. Such
cosmogenic $^{37}$Ar will appear as a noticeable background in the early
science data, while decaying with a 35~day half-life. This newly-noticed
production mechanism of $^{37}$Ar should be considered when planning for future
liquid xenon-based experiments.
