arXiv subjects
Publications and source records attributed to Ernest Ma.
The notion that dark matter and standard-model matter are connected through flavor implies a generic collider signature of the type 2 jets + $μ^\pm$ + $e^\mp$ + missing energy. We discuss the theoretical basis of this proposal and its verifiability at the Large Hadron Collider.
The standard model of quarks and leptons is extended to connect three outstanding issues in particle physics and astrophysics: (1) the absence of strong CP nonconservation, (2) the existence of dark matter, and (3) the mechanism of nonzero neutrino masses, and that of the first family of quarks and leptons, all in the context of having only one Higgs boson in a renormalizable theory. Some phenomenological implications are discussed.
Models of fermion and scalar dark matter abound. Here we consider instead vector dark matter, from an SU(2)_N extension of the standard model. It has a number of interesting properties, including a possible implementation of the inverse seesaw mechanism for neutrino mass. The annihilation of dark matter for calculating its relic abundance in this model is not dominated by its cross section to standard-model particles, but rather to other new particles which are in thermal equilibrium with those of the standard model.
Many studies have been made on extensions of the standard model with $B-L$ gauge symmetry. The addition of three singlet (right-handed) neutrinos renders it anomaly-free. It has always been assumed that the spontaneous breaking of $B-L$ is accomplished by a singlet scalar field carrying two units of $B-L$ charge. This results in a very natural implementation of the Majorana seesaw mechanism for neutrinos. However, there exists in fact another simple anomaly-free solution which allows Dirac or inverse seesaw neutrino masses. We show for the first time these new possibilities and discuss an application to neutrino mixing with $S_3$ flavour symmetry.
We propose an abelian extension of the Standard Model which can explain the origin of eV scale masses and mixing for active and sterile neutrinos and at the same time providing a natural cold dark matter candidate. One of the three active neutrinos acquires mass at tree level through seesaw mechanism whereas the other two active neutrinos and one sterile neutrino acquire eV scale masses at one-loop level. The model also allows non-trivial mixing between active and sterile neutrinos at one-loop level which could have interesting signatures at neutrino experiments. After the abelian gauge symmetry gets spontaneously broken down to a $Z_2$ symmetry, the lightest $Z_2$ odd particle can naturally give rise to the cold dark matter of the Universe. The phenomenology of both fermionic and scalar dark matter is briefly discussed by incorporating latest experimental constraints.
In the standard model, the Higgs boson $h$ couples to the quarks and charged leptons according to the well-known formula $(m_ψ/v) h \barψψ$, where $ψ$ = quark (q) or lepton (l) and $v$ = 246 GeV is its vacuum expectation value. Suppose $m_ψ$ is of radiative origin instead, then the effective $h \barψψ$ Yukawa coupling will not be exactly $m_ψ/v$. We show for the first time quantitatively how this may shift the observed branching fraction of $h \to \bar{b}b$ and $h \to τ^+ τ^-$ upward or downward. Thus the precision measurements of Higgs decay to fermions at the Large Hadron Collider, due to resume operation in 2015, could be the key to possible new physics.
A variation of the original 2006 radiative seesaw model of neutrino mass through dark matter is shown to realize the notion of inverse seesaw naturally. The dark-matter candidate here is the lightest of three real singlet scalars which may also carry flavor.
Three families of quarks and leptons, one Higgs to rule them all, and in the darkness bind them.
The scotogenic model of radiative neutrino mass with $Z_2$ or $U(1)_D$ dark matter is shown to accommodate $Δ(27)$ symmetry naturally. The resulting neutrino mass matrix is identical to either of two forms, one proposed in 2006, the other in 2008. These two structures are studied in the context of present neutrino data, with predictions of $CP$ violation and neutrinoless double beta decay.
The fundamental issue of the origin of mass for all quarks and leptons (including Majorana neutrinos) is linked to dark matter, odd under an exactly conserved Z(2) symmetry which may or may not be derivable from an U(1) gauge symmetry. The observable sector interacts with a proposed dark sector which consists of heavy neutral singlet Dirac fermions and suitably chosen new scalars. Flavor symmetry is implemented in a renormalizable context with just the one Higgs doublet of the standard model in such a way that all observed fermions obtain their masses radiatively through dark matter.
The U(1)_D gauge sector containing one dark Higgs boson h_D and one dark photon γ_D may be explored through the decays of the 126 GeV particle discovered at the Large Hadron Collider (LHC), assumed here as the heavier mass eigenstate h_1 in the mixing of the standard model h with h_D. The various decays of h_1 to γ_D γ_D, h_2 h_2, h_2 γ_D γ_D and h_2 h_2 h_2 would yield multilepton final states through the mixing of γ_D with the photon and the decay h_2 \to γ_D γ_D, where h_2 is the lighter dark Higgs. Future searches for signals of multilepton jets at the LHC may reveal the existence of this possible dark sector governed simply by the original Abelian Higgs model.
It is shown that the inherent quadratic divergence of the Higgs mass renormalization of the standard model may be avoided in the well-studied scotogenic model of radiative neutrino mass as well as other analogous extensions.
The Peccei-Quinn anomalous global U(1)_{PQ} symmetry is important not only for solving the strong CP problem with a cosmologically relevant axion, but it may also be the origin of a residual Z_2 symmetry. This new symmetry may be responsible for a second component of dark matter composed of an absolutely stable Weakly Interacting Massive Particle, as well as for generating radiative neutrino mass. Two specific realizations of this idea are proposed. In these scenarios, dark matter detection is guaranteed at existing direct detection experiments or axion searches. Observable signals at the Large Hadron Collider are discussed.
The well-studied radiative model of neutrino mass through $Z_2$ dark matter is shown to be naturally realizable in the context of SU(6) grand unification. A recent new proposal based on U(1)_D dark matter is similarly accommodated in SU(7). Just as the proton is unstable at the scale of quark-lepton unification, dark matter is expected to be unstable at a similar scale.
We propose a new realization of the one-loop radiative model of neutrino mass generated by dark matter (scotogenic), where the particles in the loop have an additional $U(1)_D$ gauge symmetry, which may be exact or broken to $Z_2$. This model is relevant to a number of astrophysical observations, including AMS-02 and the dark matter distribution in dwarf galactic halos.
The unifiable supersymmetric left-right model where the neutral fermion $n$ in the $SU(2)_R$ doublet $(n,e)_R$ is a dark-matter candidate, is shown to have the requisite particle content for the neutrino $ν$ in the $SU(2)_L$ doublet $(ν,e)_L$ to acquire a small radiative Majorana mass from dark matter, i.e. scotogenic from the Greek "scotos" meaning darkness. As a result, there are at least three coexisting stable dark-matter particles with different interactions. We study their possible phenomenological impact on present and future experiments.
Predictive spontaneous CP violation is possible if it is obtained geometrically through a non-Abelian discrete symmetry. I propose such a model of neutrino mass and mixing based on Delta(27).
A model proposed in 2004 using the non-Abelian discrete symmetry S3 for understanding the flavor structure of quarks and leptons is updated, with special focus on the quark and scalar sectors. We show how the approximate residual symmetries of this model explain both the pattern of the quark mixing matrix and why the recently observed particle of 126 GeV at the Large Hadron Collider is so much like the one Higgs boson of the Standard Model. We identify the strongest phenomenological bounds on the scalar masses of this model, and predict a possibly observable decay b -> s tau- mu+, but not b -> s tau+ mu-.