Implications of a Purely Right-handed b-decay Coupling

We examine the implications of the hypothesis that the decays of the bottom quark occur via pure right-handed couplings . We show that the existing lower limits on the lifetimes for neutrinoless double beta decay severely restrict the neutrino sector of the model and would be satisfied in a natural manner if there is either an Le −Lμ or an Le −Lτ symmetry in the model. We then show that the cosmological mass density constraints in combination with SN1987A observations imply lower bounds on the masses of the right-handed neutrinos of about 100 MeV ( about 65 MeV if there are Goldstone bosons coupling to νR’s) and also imply that the case of Le−Lμ symmetry is inconsistent with data unless there are flavor-changing neutral currents involving the right-handed neutrinos. Work supported by the National Science Foundation Grant PHY-9119745 Permanent address: Department of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel. It has recently been suggested by Gronau and Wakaizumi[1] that unlike the quarks of the first two generations, the decays of the bottom ( b ) quark occur purely via its right-handed couplings. In such models, the smallness of the b to c coupling is attributed not to a small value of the corresponding entry in the CKM matrix, Vcb but rather to the smaller effective right-handed Fermi coupling constant, G R F compared to the usual left-handed Fermi coupling constant, GF . Implementation of this hypothesis within the framework of the left-right symmetric models of weak interactions [2] requires (i) that the left-handed quark mixing matrix be completely different from the right-handed one; and (ii) that the right-handed W-bosons, WR be rather light such that