Dark matter physics in neutrino specific two Higgs doublet model

Abstract

Although the seesaw mechanism is a natural explanation for the small neutrino masses, there are cases when the Majorana mass terms for the right-handed neutrinos are not allowed due to symmetry. In that case, if neutrino-specific Higgs doublet is introduced, neutrinos become Dirac particles and their small masses can be explained by its small VEV. We show that the same symmetry, which we assume a global U(1) X , can also be used to explain the stability of dark matter. In our model, a new singlet scalar breaks the global symmetry spontaneously down to a discrete Z 2 symmetry. The dark matter particle, lightest Z 2 -odd fermion, is stabilized. We discuss the phenomenology of dark matter: relic density, direct detection, and indirect detection. We find that the relic density can be explained by a novel Goldstone boson channel or by resonance channel. In the most region of parameter space considered, the direct detections is suppressed well below the current experimental bound. Our model can be further tested in indirect detection experiments such as FermiLAT gamma ray searches or neutrinoless double beta decay experiments.

Dirac neutrino from the breaking of Peccei-Quinn symmetry

“…Fermions The νTHDM on its own does not provide an axion candidate. We make the Nambu-Goldstone boson coming from the spontaneous breaking of the U (1) X in the model of [3] an axion by introducing either heavy vector-like quarks Ψ L,R (KSVZ-type axion) or additional Higgs doublet (DFSZ-type axion). It turns out that the phenomenology of the axion in the model is very close to that of original KSVZ [5,6] and DFSZ [7,8] axion models, respectively.…”

“…The paper is organized as follows. In Section II, we briefly review the U (1) X model studied in [3] with v S lifted to PQ breaking scale and show that the large hierarchy among the disparate scales is technically natural. In Section III, the model is extended so that the KSVZ-type or the DFSZ-type axion is introduced.…”

“…We briefly recapitulate the model considered in [3] before discussing the VEVs and their naturalness. The scalar fields and a new fermion with their charge assignments under the SM and U (1) X are shown in Table I.…”

Hidden U(1) gauge symmetry realizing a neutrinophilic two-Higgs-doublet model with dark matter

“…The first term of the Yukawa coupling provides the SM charged-lepton masses, while the second term induces the active neutrino masses of Dirac type. The term μ 0 plays a role in forbidding a massless Goldstone boson appearing from Higgs doublets after spontaneous gauge symmetry breaking [3]. Note that we have Z 2 symmetry even after scalar fields developing VEVs where extra fermions fN R i ; N R 3 g are Z 2 odd and the other particles are Z 2 even at renormalizable level.…”

“…Note that v ϕ is expected to be tiny in order to generate active neutrino mass, which can be realized taking a tiny μ 0 value [3,9].…”