Abstract
The neutrino remains as exotic and challenging today as it was seventy years ago when first proposed by Pauli. What is known for certain about neutrinos is minimal indeed. They have spin 12, charge 0, negative helicity, and exist in 3 flavors, electron, mu, and tau. Strictly speaking, only 2 flavors are certain: direct observation of the tau neutrino has not yet been achieved, but an experiment, DONUT, at Fermilab is in progress with this objective [1]. Limits on the masses from direct, kinematic experiments (ones that do not require assumptions about the non-conservation of lepton family numbers) have been steadily lowered by experiments of ever-increasing sophistication over the years, with the results given in Table 1. As will be discussed below, there are stronger limits on the mass of νe from tritium beta decay [2, 3], but the data show curious distortions near the endpoint that are not at present understood.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
