Can Gravity Distinguish between Dirac and Majorana Neutrinos?

We show that spin-gravity interaction can distinguish between Dirac and Majorana neutrino wave packets propagating in a Lense-Thirring background. Using time-independent perturbation theory and the gravitational phase to generate a perturbation Hamiltonian with spin-gravity coupling, we show that the associated matrix element for the Majorana neutrino differs significantly from its Dirac counterpart. This difference can be demonstrated through significant gravitational corrections to the neutrino oscillation length for a two-flavor system, as shown explicitly for SN 1987A.

Figure 1

$F_1$ as a function of $q$ due to the SN 1987A gravitational source, for varying neutrino beam angle $\theta$. Besides having opposite sign, $F_1^{\mathrm{Dirac}}$ is 2 orders of magnitude larger than $F_1^{\mathrm{Maj}.}$.

Figure 2

$F_2$ as a function of $q$ applied to SN 1987A for varying $\theta$. The gravitational correction for $F_2^{\mathrm{Dirac}}$ is larger than $F_2^{\mathrm{Maj}.}$ by 3 orders of magnitude.