From Chris Heron
Maxim Pospelov of the Perimeter Institute in Waterloo, Ontario, invokes negatively charged supersymmetric particles – “staus” – to explain anomalies in the abundances of primordial lithium isotopes (5 July, p 28).
You also say that staus had their main effects 3 hours after the big bang, so the half-life of the stau must be of the order of hours, or at least minutes.
If such a relatively long-lived and heavy particle existed, surely we would have found one produced in our atmosphere by the reactions of very energetic cosmic rays.
Cambridge, UK
