LETT~RE AL Nuovo ClMENTO VOL. 9, N. 14 6 Aprile 1974 Neutrino Spectrum and the Origin of the Cabibbo Angle (*). S. PAKVASA Department of Physics and Astronomy, University of Hawaii - Honolulu, Hawaii K. TENNAKONE Department o] Physics, Vidyodaya University o] Sri Lanka - Nugegoda (Sri T~anka) (ricevuto il 2 Gennaio 1974) Present experiments do not rule out the possibility that neutrinos emitted in strange- ness-conserving and strangeness-changing processes are different (~). All we know is that the neutrinos coupled to the electron are different from those coupled to the muoa at least in semi-leptonie interactions. In an earlier paper (2) we discussed the possible existence of an infinite series of neutrinos whose properties are completely specified by a universal quantum number n. The masses of the neutrinos are given by (3) m n ~ mo ~n (n: -- 1,--2,--3 .... ), where Q = m~/m~ ~-207. The particles with even values for n are electronlike, those with odd values for n are muonlike. In general, all electronlike neutrinos can couple to the electron and muonlike ones can couple to the muon, with coupling constants dependent only on the universal quantum numbers of the neutrinos (2). In this note we consider the possibility that out of the entire family of neutrinos predicted by us, different subsets are associated with AS = 0 processes and with AS= 1 processes. We show below that in such a scheme, even if the AS = 0 and AS = 1 hadronic currents couple with equal strength, suppression of AS = 1 semi-leptonic decay rates with respect to AS ~ 0 rates is possible. Furhermore, this explanation of Cabibbo angle has observabIe consequences which we discuss later. (*) Work supported in part by the U.S. Atomic Energy Coramission under Contract AT(04-3)-511. (2) This possibility has been discussed briefly in a general way in S. L. GLASgow: Journ. de Phys., 32, C 3 (1971). Specific models which assign different ~strangeness ~) quantum numbers to ~ and vK also exist; see, e.g., V. GLU~rA: Phys. Rev., 135, B 783 (1964); R. ~I. WEIXER: Phys. Rev. Left., 20, 396 (1968). ('~) K. TE~NAKOS~E a n d S. PAI~TASA: Phys. Rev. Lett., 27, 757 (1971); K. TEN-NAKONE and S. PAKVASA" Phys. Rev. D, 6, 2494 (1972). (3) Implications of nonzero masses for neutrinos are discussed in S. PAKVASi and K. TENNAKONE: Phys. Rev. Letf., 28, 1415 (19"72). 565