Canonical seesaw implication for two-component dark matter

Abstract

We show that the canonical seesaw mechanism implemented by the $U(1{)}_{B-L}$ gauge symmetry provides two-component dark matter naturally. The seesaw scale that breaks $B-L$ defines a residual gauge symmetry to be $Z_6=Z_2\otimes Z_3$, where $Z_2$ leads to the usual matter parity, while $Z_3$ is newly recognized, transforming quark fields nontrivially. The dark matter components -- that transform nontrivially under the matter parity and $Z_3$, respectively -- can gain arbitrary masses, despite the fact that the $Z_3$ dark matter may be heavier than the light quarks $u,d$. This dark matter setup can address the XENON1T anomaly recently observed and other observables, given that the dark matter masses are nearly degenerate, heavier than the electron and the $B-L$ gauge boson $Z^{\prime }$, as well as the fast-moving $Z_3$ dark matter has a large $B-L$ charge, while the $Z^{\prime }$ is viably below the beam dump experiment sensitive regime.

Comments: 11 pages, 5 tables, 4 figures; substantially improved with references added