Neutrinos were thought to be massless, but this was not entirely satisfactory in comparison to other particles that feel the short range forces. Then experiments concluded that neutrinos have a tiny mass.
Did Short Range Of Weak Force Guarantee That Neutrinos Must Have Mass?
No-that the W and Z bosons are massive doesn't imply that fermions, carrying weak charge, in particular the neutrinos, are, too. The Yukawa couplings of fermions are independent from the gauge couplings.
Incidentally, there's no such notion as ``time mass''.
And ``unsatisfactory'' is meaningless, since there isn't any theoretical inconsistency in the Standard Model, if the fermions it describes are massless. If they are to have a mass and have electroweak interactions, then this mass can only be described by Yukawa couplings to the Higgs field, that's all.
Dear Jerry,
No, the short range of Weak Force doesn't guarantee that neutrinos must have mass. Actually the neutrinos in the Standard Model need to be massless and this was implemented by a two-component left-handed massless neutrino fields for playin a crucial role in the determination of the charged current structure of short range weak interaction.
Nowadays the (experimental) the three discrete neutrino masses are accepted to be independent of their three flavors: there is a quantum superposition of the three mass states. There is one oscillation between different flavors and in all that I know there is still a clear lack of knowledge of what is the mechanism which allows this physical behaviour which is far beyond the Standard Model.
The neutrinos don't need to be massless in the Standard Model-it's just that since right-handed neutrinos don't interact with any other particles of the Standard Model (that's why they're called ``sterile''), if the neutrinos are Dirac particles like the other fermions, their Yukawa couplings need to be ``very small'', to satisfy experimental bounds. The current bounds on the masses, coming from neutrino oscillations, aren't inconsistent with neutrinos being Dirac particles. The hierarchy of the Yukawa couplings can't be explained, within the Standard Model, anyway-it's part of the inputs--but it doesn't imply any consistency issues.
Dear Stam,
It is well known that in the Standard Model the neutrinos are massless. In fact, in the Standard Model there is a fundamental difference between neutrinos and other fermions: neutrinos electric charges are equal to zero, there is no electromagnetic current of neutrinos. The unification of the weak and electromagnetic interactions does not require right-handed neutrino fields.A minimal possibility is to assume that there are no right-handed neutrino fields in the Standard Model.
In the Standard Model there is a fundamental difference between neutrinos
and other fermions: neutrinos electric charges are equal to zero, there
is no electromagnetic current of neutrinos. The unification of the weak and
electromagnetic interactions does not require right-handed neutrino fields.
A minimal possibility is to assume that there are no right-handed neutrino
fields in the Standard Model.
In such a scenario Majorana mass term is the only possibility for neutrinos to be massive and mixed. Such mass term is generated by the lepton number violating Weinberg effective Lagrangian. In this approach three Majorana neutrino masses are suppressed with respect to the masses of other fundamental fermions by the ratio of the electroweak scale and a scale of a lepton-number violating physics
Dear Stam,
Although Wikipedia is not a sure place, you can see the page devoted to the Standard Model:
https://en.wikipedia.org/wiki/Standard_Model
And look for the sentence which is very clear:
The model does not contain any viable dark matter particle that possesses all of the required properties deduced from observational cosmology. It also does not incorporate neutrino oscillations and their non-zero masses.
Hi
This is a very interesting topic. Neutrino oscillations cannot be described within the standard model (SM). This fact represents a huge challenge in physics. Presently, scientists are looking for a quantum mechanical approach in which neutrino mass states can be studied as eigenstates of a quantum field theory quite similar to the Glashow-Weinberg-Salam (GWS) electroweak theory. Up to now, however, the answer to your question is no.
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