Cosmic ray boosted dark matter with momentum dependent interactions can explain the LZ 248 keV event

The LZ experiment has recently reported an observation of a single event with characteristics of a nuclear recoil at a high recoil energy of 248 keV, where no background events are expected. We show that such nuclear recoil event could be caused by high velocity dark matter particles originating from interactions with energetic cosmic rays. We analyze the expected recoil spectrum due to cosmic ray boosted dark matter within the non-relativistic effective theory formalism, and show that momentum-dependent operators, such as ${\mathcal{O}}_6$ and ${\mathcal{O}}_{10}$, can produce a spectrum that peaks at the observed energy.