At www.insidescience.org/news/what-can-death-neutrons-tell-us-about-dark-ma… … physicists are currently speculating that decaying neutrons may be producing particles unknown to science – that make up the elusive dark matter. Exactly how long a neutron might live is also under debate. If neutrons decay into particles of dark matter it solves a big mystery as some cosmologists actually think dark matter makes up four fifths of all matter in the universe. Added to the protons and electrons the neutrons currently make up the visible universe, it is thought. Without neutrons atomic structures would not be stable. However, once outside an atomic nucleus a neutron may survive around 15 minutes it has been estimated. That is all. They tend to decay into protons and electrons, or even into neutrinos – which is currently recognised as their decay fate. Now it is being proposed they may also decay into other unknown particles – with various scientists hoping to be the progenitors of a new kind of physics. Part of the research has moved on to neutron stars – superdense clusters of neutrons that are regarded as forming when giant stars die (but again, another piece of speculation).
The study is published by Physical Review Letters (May 16th 2018).