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existence of these parameters. Hasegawa118 and his collaborators have used neutrons for these tests. Using a neutron interferometer they confirmed the results obtained with photons so demonstrating that the correlations between different degrees of freedom as a result of quantum entanglement were not only a feature of photons but existed also for neutrons.
Physicists have expended enormous effort to develop a theory which accounts for the four types of forces existing in nature: electromagnetic, weak interactions, strong interactions and gravity. The Standard Model has been painstakingly developed. The use of capitals in the name shows the importance given to this theory. The neutron spontaneously dissociates into a proton, an electron, with the emission of a antineutrino. The lifetime
of the neutron is 885.7 seconds119. This process is controlled
by the weak force, and is the simplest known case of β-decay. From the theoretical works of T.-D. Lee and C.-N. Yang, and experimental work of C.S. Wu and co-workers it has been shown that parity is not conserved during this process. That is to say there is a difference between the disintegration of the neutron,
and what one would observe in a mirror image. This results in the electrons being preferentially emitted in a direction opposite to the neutron spin. Measurement of this asymmetry by H. Abele and co-workers, associated with the lifetime of the neutron defines a quantity which should be equal to one, according to the Standard
118 Y. Hasegawa et al., Nature, (2003), 425, p45-48, DOI 10.1038/nature01881. T. Denkmayr et al., Nature Comm. 5, 4492 (2014), DOI 10.1038/ncomm5492.
119 2018 addtion: This was an average over all measurements when B. Jacrot wrote his book (C. Amsler et al., Phys. Lett. B 667, 1-6 (2008), DOI 10.1016/j.physletb.2008.07.018. A discussion on more recent measurements can be found here: Greene G.L. and Geltenbort P., Scientific American 314, 36 - 41 (2016), DOI 10.1038/sci- entificamerican0416-36.
Conclusion - An appraisal
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