Hydrogen-Antihydrogen Oscillations and Spontaneously Broken GlobaB−LSymmetry

Within the framework of an $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L\otimes \mathrm{U}\mathrm{}\left(1\right)\mathrm{}\otimes \mathrm{SU}{\mathrm{}\left(3\right)\mathrm{}}_c$ gauge model with suitably extended Higgs sector, the possibility of oscillations between neutral matter and antimatter, such as neutron-antineutron and hydrogen-antihydrogen systems, is discussed. This model incorporates the spontaneous breakdown of global $B-L$ symmetry associated with a Majoron, and as a result, a relation between $n-\overline{n}$ mixing, $\mathrm{H}-\overline{H}$ mixing, and the mass of the electron neutrino is obtained. With present limits on ${\tau }_{n-\overline{n}}$, ${\tau }_{\mathrm{H}-\overline{H}}\gtrsim {10}^{13}$ yr is predicted.