The discussion centers on the absence of right-handed neutrinos in the lepton family, contrasting it with the existence of right-handed electrons. This absence is established as an experimental fact, primarily due to the lack of non-null coupling of right-handed neutrinos to known forces. The conversation references the Nobel Prize-winning work of Lee and Yang on parity violation and discusses the implications of CPT symmetry, CP violation, and Lorentz symmetry in the context of neutrino mass and helicity. Theoretical frameworks such as the MSSM and Majorana mass are also mentioned as potential avenues for understanding neutrino behavior.
PREREQUISITESPhysicists, particularly those specializing in particle physics, theoretical physicists exploring neutrino properties, and researchers interested in the implications of symmetry violations in the Standard Model.
ndung200790 said:So,the not existing of righthanded neutrino is based on experiment but not on theoretical theory?
Well that is one way to preserve CPT in the presence of a CP slight violation, another theoretical option instead of a T violation is a Lorentz slight violation.phyzguy said:There are strong theoretical reasons to believe that the product of CPT is a true symmetry of the universe. Once it was discovered that P - symmetry was violated, people started looking at the other discrete symmetries (C and T) to see if they were violated as well. They soon discovered that CP is also slightly violated, which means that T must be violated if CPT is to be preserved.
TrickyDicky said:Well that is one way to preserve CPT in the presence of a CP slight violation, another theoretical option instead of a T violation is a Lorentz slight violation.
phyzguy said:Wouldn't a Lorentz violation imply CPT violation?
TrickyDicky said:Maybe this can be better understood in this way: mathematically you can build a CPT symmetry in various ways, adding the CP asymmetry constraint reduces the possibilities but still we can do it either by having a T asymmetry and Lorentz symmetry or alternatively keeping T symmetry and postulating Lorentz asymmetry, this last way has the advantage of suggesting a mechanism for the CP asymmetry(neutrino left-handedness).
When physical considerations enter, classically Lorentz invariance was assumed since no experiment was able to show violations.
Parlyne said:Independent of Lorentz symmetry, if CP is violated and T is not CPT is violated. Breaking Lorentz symmetry does not allow you to preserve CPT in such a case.
Like I said in post #12, this is stated in CPT theorem which assumes dependency on Lorentz symmetryParlyne said:In fact, the Lorentz violation will follow from the CPT violation
ndung200790 said:I think that because neutrino has nearly zero mass,so that the left and right vertor currents of Dirac field are conserved independently,then this permits the violation of parity happening.But if neutrino were massive,then there must be exist the righthanded neutrinos.Is that correct?
It follows from this argument that if we can't make that kind of boost (no detection of right handed neutrinos) we are always traveling faster than massive neutrinos (thus only left-handed neutrinos are detected), and that could only happen if neutrinos had a preferred rest frame implying a Lorentz violation, as ndung200790 noticed in the previous post.phyzguy said:since if the neutrino has mass I can always boost until I am traveling faster than the neutrino, in which case what was a left-handed particle becomes a right-handed particle. However, we detect only left-handed neutrinos and right-handed anti-neutrinos.