Has LZ seen a WIMP?

One of the candidates for the dark matter that seems to pervade the cosmos is a Weakly Interacting Massive Particle (WIMP, for short). Such particles are hypothetical but, if they exist they could have been produced in large numbers in the early Universe. Among the possible WIMPs are supersymmetric particles, but there are alternative candidates. Whatever their nature it is possible that they could be directed directly in collisions with regular matter but, because they are weakly interacting, the cross-section for such events is low and potentially masked by background events caused by radioactive decays. So far these experiments have drawn a collective blank (and a number of false alarms). One experiment trying to detect dark matter directly is LUX-ZEPLIN (LZ for short) which is based at the Sanford Underground Research Facility in South Dakota in the USA but is a collaboration of 30 institutions worldwide, including the the UK, Portugal and South Korea as well as the USA. This…