Hypothesis
A 46 kg liquid-argon time projection chamber with neutron and cosmic-ray vetoes would detect nuclear recoils from weakly interacting massive particles.
What failed
A 1,422 kg·day exposure with atmospheric argon gave a null result, setting a 90% CL upper limit on the WIMP–nucleon spin-independent cross-section of 6.1 × 10⁻⁴⁴ cm² at 100 GeV/c² — the most sensitive argon-target search to that date.
Broken assumption
WIMPs with cross-sections above 6.1 × 10⁻⁴⁴ cm² (at 100 GeV) produce detectable recoils in argon.
Why
No WIMP signal above background was seen at this exposure; the paper reports the limit and makes no claim beyond it.
From the published paper: Agnes et al. Physics Letters B, 2015. ↗CC BY