21
Mirror Symmetric Weak Force and Neutrino
Mass
The mirror symmetric theory of neutrino mass (or left–right symmetric
theories as they are called in the literature) was proposed in 1974 and 1975
to understand the origin of mirror symmetry breaking by the weak force.
Its connection to neutrino mass came later in 1979. Why was it necessary to
think along these lines when the standard model is so successful? Sometimes,
speculations about the next level of physics are not determined by experimental
facts, but rather by expectations based on aesthetic considerations and conceptual shortcomings. For example, a huge amount of activity right now focuses
on the attempts to understand why the mass of the Higgs boson does not
become arbitrarily large due to quantum corrections, although from a strictly
experimental point of view, there is no need for such thinking.
The discovery of the weak force carriers, the W and Z bosons, at collider
facilities at CERN, as well as other evidence in the domain of low energy weak
force physics has provided spectacular confirmation of the standard model.
The 2012 discovery of the Higgs boson was the crowning success of the model.
There are, however, conceptual problems with it—one is the aforementioned
gauge hierarchy problem or the Higgs mass problem. But more to our concern
is that the weak forces were known since 1956 to break mirror symmetry, and
since 1957, to involve the V − A type of interaction as suggested by Marshak,
Sudarshan, Feynman, and Gell-Mann. How is this fact handled in the standard
model? The answer is that it was put into the theory by hand by simply
choosing the gauge forces that were induced by the charged W bosons. They
were chosen to act on the quarks and leptons having left-handed helicity. As
far as the neutrinos go, only the left-handed helicity neutrino was included in
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer
Nature Switzerland AG 2021
R. N. Mohapatra, The Neutrino Story: One Tiny Particle’s Grand Role in the Cosmos,
https://doi.org/10.1007/978-3-030-51846-2_21
155
Mirror Symmetric Weak Force and Neutrino
Mass
The mirror symmetric theory of neutrino mass (or left–right symmetric
theories as they are called in the literature) was proposed in 1974 and 1975
to understand the origin of mirror symmetry breaking by the weak force.
Its connection to neutrino mass came later in 1979. Why was it necessary to
think along these lines when the standard model is so successful? Sometimes,
speculations about the next level of physics are not determined by experimental
facts, but rather by expectations based on aesthetic considerations and conceptual shortcomings. For example, a huge amount of activity right now focuses
on the attempts to understand why the mass of the Higgs boson does not
become arbitrarily large due to quantum corrections, although from a strictly
experimental point of view, there is no need for such thinking.
The discovery of the weak force carriers, the W and Z bosons, at collider
facilities at CERN, as well as other evidence in the domain of low energy weak
force physics has provided spectacular confirmation of the standard model.
The 2012 discovery of the Higgs boson was the crowning success of the model.
There are, however, conceptual problems with it—one is the aforementioned
gauge hierarchy problem or the Higgs mass problem. But more to our concern
is that the weak forces were known since 1956 to break mirror symmetry, and
since 1957, to involve the V − A type of interaction as suggested by Marshak,
Sudarshan, Feynman, and Gell-Mann. How is this fact handled in the standard
model? The answer is that it was put into the theory by hand by simply
choosing the gauge forces that were induced by the charged W bosons. They
were chosen to act on the quarks and leptons having left-handed helicity. As
far as the neutrinos go, only the left-handed helicity neutrino was included in
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer
Nature Switzerland AG 2021
R. N. Mohapatra, The Neutrino Story: One Tiny Particle’s Grand Role in the Cosmos,
https://doi.org/10.1007/978-3-030-51846-2_21
155