Unification of the Standard Model and Dark Matter Sectors in [SU(5)×\timesU(1)]4^4

A simple model of dark matter contains a light Dirac field charged under a hidden U(1) gauge symmetry. When a chiral matter content in a strong dynamics satisfies the t'Hooft anomaly matching condition, a massless baryon is a natural candidate of the light Dirac field. One realization is the same matter content as the standard SU(5)$\times$U(1)$_{(B-L)}$ grand unified theory. We propose a chiral [SU(5)$\times$U(1)]$^4$ gauge theory as a unified model of the SM and DM sectors. The low-energy dynamics, which was recently studied, is governed by the hidden U(1)$_4$ gauge interaction and the third-family U(1)$_{(B-L)_3}$ gauge interaction. This model can realize self-interacting dark matter and alleviate the small-scale crisis of collisionless cold dark matter in the cosmological structure formation. The model can also address the semi-leptonic $B$-decay anomaly reported by the LHCb experiment.Comment: 15 pages, 2 figure

Unification for the Darkly Charged Dark Matter

We provide a simple UV theory for a Dirac dark matter with a massless Abelian gauge boson. We introduce a single fermion transforming as the $\bf{16}$ representation in the SO(10)$'$ gauge group, which is assumed to be spontaneously broken to SU(5)$'\times$U(1)$'$. The SU(5)$'$ gauge interaction becomes strong at an intermediate scale and then we obtain a light composite Dirac fermion with U(1)$'$ gauge interaction at the low-energy scale. Its thermal relic can explain the observed amount of dark matter consistently with other cosmological and astrophysical constraints. We discuss that a nonzero kinetic mixing between the U(1)$'$ gauge boson and the Hypercharge gauge boson is allowed and the temperature of the visible sector and the dark matter sector can be equal to each other.Comment: 6 pages, 2 figure

Self-interacting dark matter with a vector mediator: kinetic mixing with U(1)(B−L)3_{(B-L)_3} gauge boson

A spontaneously broken hidden U(1)$_h$ gauge symmetry can explain both the dark matter stability and the observed relic abundance. In this framework, the light gauge boson can mediate the strong dark matter self-interaction, which addresses astrophysical observations that are hard to explain in collisionless cold dark matter. Motivated by flavoured grand unified theories, we introduce right-handed neutrinos and a flavoured $B - L$ gauge symmetry for the third family U(1)$_{(B-L)_3}$. The unwanted relic of the U(1)$_h$ gauge boson decays into neutrinos via the kinetic mixing with the U(1)$_{(B - L)_3}$ gauge boson. Indirect detection bounds on dark matter are systematically weakened, since dark matter annihilation results in neutrinos. However, the kinetic mixing between U(1)$_{(B - L)_3}$ and U(1)$_Y$ gauge bosons are induced by quantum corrections and leads to an observable signal in direct and indirect detection experiments of dark matter. This model can also explain the baryon asymmetry of the Universe via the thermal leptogenesis. In addition, we discuss the possibility of explaining the lepton flavour universality violation in semi-leptonic $B$ meson decays that is recently found in the LHCb experiment.Comment: 27 pages, 2 figures; v2: minor changes, Appendix A added, published versio

A new constraint on primordial lepton flavour asymmetries

A chiral chemical potential present in the early universe can source helical hypermagnetic fields through the chiral plasma instability. If these hypermagnetic fields survive until the electroweak phase transition, they source a contribution to the baryon asymmetry of the universe. In this letter, we demonstrate that lepton flavour asymmetries above $|\mu|/T \sim 9 \times 10^{-3}$ trigger this mechanism even for vanishing total lepton number. This excludes the possibility of such large lepton flavour asymmetries present at temperatures above $10^6$ GeV, setting a constraint which is about two orders of magnitude stronger than the current CMB and BBN limits.Comment: 4 pages, matches journal versio