Neutron Lifetime Puzzle Deepens, but No Dark Matter SeenThe neutron's lifetime is only about xv minutes but at that spot seems to live on a cool, increasingly sudden discrepancy. If you lot mensurate how many neutrons are left inward a "bottle" later fourth dimension \(t\), it seems that there's 1 decay inward 14:39 minutes. But if you lot mensurate a neutron "beam" together with the protons that appear, it seems that they're beingness converted at the charge per unit of measurement of 1 novel proton per 14:48 minutes.
This neutron's logo is genuinely from only about cryptocurrency network.
So the neutrons are patently decaying nearly 1% faster than the protons are born. No other decays of neutrons are known. Relativistic effects for the beam are negligible.
If this discrepancy is real, at that spot seems to live on 1% of the neutron decays that instruct to something else. One calendar month ago, a newspaper past times Bartosz Fornal, Benjamin Grinstein promoted the view that the neutron could really good decay to new, invisible particles.
The decay would be\[
n\to \chi\gamma
\] where \(\chi\) is a new, dark, spin-1/2 fermion, together with \(\gamma\) is a photon. The majority of \(\chi\) has to live on only a slightly smaller than the neutron majority – a coincidance ;-) needed to avoid only about ill decays inward nuclear physics – together with the photons \(\gamma\) from such decays must convey a completely universal, fixed release energy (calculable from the \(\chi\) mass) which is a universal constant that may a priori belong to an interval together with is of enterprise \(1\MeV\).
In the effective Lagrangian, the decays are enabled past times the quadratic together with cubic price \(\bar n \chi\) together with \(\bar n \chi \gamma\), i.e. past times a neutron-newfermion mixing; together with past times a cubic interaction that looks similar the mixing amongst the extra photon (you demand the photon to live on represented past times the whole \(F_{\mu\nu}\) inward this cubic term, non only \(A_\mu\), past times approximate invariance). So for a while, past times the mixing interaction, the neutron changes to a virtual \(\chi\), together with the \(\chi\) decays to a existent neutron \(n\) together with a existent photon \(\gamma\).
The authors claim that such a model is consistent amongst everything nosotros know.
One calendar week ago, an experimental preprint claimed that they're certain that these photons of release energy comparable to \(1\MeV\) don't be together with then the theory is ruled out.
Well, peradventure the visible photon amid the decay products should live on replaced amongst only about nighttime boson as well? ;-) At whatever rate, it's an intriguing anomaly together with an every bit attractive (albeit obvious) strategy to explicate it.