Abstract
The extension of the Standard model by assuming $U(1)_{\rm B-L}$ gauge symmetry is very well-motivated since it naturally explains the presence of heavy right-handed neutrinos required to account for the small active neutrino masses via the seesaw mechanism and thermal leptogenesis. Traditionally, we introduce three right handed neutrinos to cancel the $[U(1)_{\rm B-L}]^3$ anomaly. However, it suffices to introduce two heavy right-handed neutrinos for these purposes and therefore we can replace one right-handed neutrino by new chiral fermions to cancel the $U(1)_{\rm B-L}$ gauge anomaly. Then, one of the chiral fermions can naturally play a role of a dark matter candidate. In this paper, we demonstrate how this framework produces a dark matter candidate which can address the so-called "core-cusp problem". As one of the small scale problems that $\Lambda$CDM paradigm encounters, it may imply an important clue for a nature of dark matter. One of resolutions among many is hypothesizing that sub-keV fermion dark matter halos in dwarf spheroidal galaxies are in (quasi) degenerate configuration. We show how the degenerate sub-keV fermion dark matter candidate can be non-thermally originated in our model and thus can be consistent with Lyman-$\alpha$ forest observation. Thereby, the small neutrino mass, baryon asymmetry, and the sub-keV dark matter become consequences of the broken B-L gauge symmetry.
Highlights
Despite various evidences for the presence of dark matter (DM), DM’s nature has not been uncovered yet
We show how the degenerate sub-keV fermion dark matter candidate can be nonthermally originated in our model and can be consistent with the Lyman-α forest observation
We present a well-motivated extension of the Standard Model (SM) which can address the core-cusp problem by providing a degenerate sub-keV fermion DM candidate
Summary
Despite various evidences for the presence of dark matter (DM), DM’s nature has not been uncovered yet. Relying on predicted phenomenological consequences arising from a specific mass or nongravitational interaction that DM enjoys, several alternative frameworks to CDM have been suggested so far in an effort to address the core-cusp problem (and other small-scale issues as well) On top of SM particle contents, in its minimal form, the model contains two heavy right-handed neutrinos (Ni1⁄41;2) and a complex scalar (Φ) for breaking Uð1ÞB-L. By means of this basic setting, the model is expected to accomplish the successful explanation for the small neutrino masses via a seesaw mechanism [42,43,44] and the baryon asymmetry via the thermal leptogenesis [45].
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have