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Ernest Ma

Publications and source records attributed to Ernest Ma.

At least 37 records · Page 2Linked to original sources

Anomalous Magnetic Moment and Higgs Coupling of the Muon in a Sequential U(1) Gauge Model with Dark Matter

We study an Abelian gauge extension of the standard model with fermion families having non-universal gauge charges. The gauge charges and scalar content are chosen in such an anomaly-free way that only the third generation fermions receive Dirac masses via renormalisable couplings with the Higgs boson. Incorporating additional vector like fermions and scalars with appropriate $U(1)$ charges can lead to radiative Dirac masses of first two generations with neutral fermions going in the loop being dark matter candidates. Focusing on radiative muon mass, we constrain the model from the requirement of satisfying muon mass, recently measured muon anomalous magnetic moment by the E989 experiment at Fermilab along with other experimental bounds including the large hadron collider (LHC) limits. The anomalous Higgs coupling to muon is constrained from the LHC measurements of Higgs to dimuon decay. The singlet fermion dark matter phenomenology is discussed showing the importance of both annihilation and coannihilation effects. Incorporating all bounds lead to a constrained parameter space which can be probed at different experiments.

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Predestined Dark Matter Varieties in the Simplest Left-Right Model

In the simplest left-right extension of the Standard Model of particle interactions with one scalar bidoublet and one $SU(2)_R$ triplet for seesaw Majorana neutrino masses, the addition of a variety of fermion and scalar multiplets automatically makes them stable (predestined) dark matter candidates. We discuss the interplay of this dark ensemble in relic abundance and direct searches.

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New $[SU(3)]^4$ Realization of Lepton/Dark Symmetry

Extending the well-known $SU(3)_C \times SU(3)_L \times SU(3)_R$ model of quarks and leptons to include a fourth $SU(3)_N$ gauge factor, a new realization is obtained, different from leptonic color, which contains a lepton/dark symmetry with the help of an input $Z_4$ symmetry. It is seen to encompass a previous extension of the standard model to $SU(2)_N$ lepton symmetry.

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Non-Abelian Gauge Lepton Symmetry as the Gateway to Dark Matter

Following a previous proposal, lepton number is considered as the result of a spontaneously broken non-Abelian gauge $SU(2)_N$ symmetry. New fermions are added to support this new symmetry, the spontaneous breaking of which allows these new fermions to be part of the dark sector, together with the vector gauge boson which communicates between them and the usual leptons. A byproduct is a potential significant contribution to the muon anomalous magnetic moment.

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Radiative Seesaw Dark Matter

The singlet majoron model of seesaw neutrino mass is appended by one dark Majorana fermion singlet $χ$ with $L=2$ and one dark complex scalar singlet $ζ$ with $L=1$. This simple setup allows $χ$ to obtain a small radiative mass anchored by the same heavy right-handed neutrinos, whereas the one-loop decay of the standard-model Higgs boson to $χχ+ \barχ \barχ$ provides the freeze-in mechanism for $χ$ to be the light dark matter of the Universe.

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Gauged Lepton Number, Dirac Neutrinos, Dark Matter, and Muon $g-2$

Lepton number is promoted to an $U(1)_L$ gauge symmetry in a simple extension of the standard model. The spontaneous breaking of $U(1)_L$ by three units allows a conserved $Z_3^L$ lepton symmetry to remain, guaranteeing that neutrinos are Dirac fermions, which acquire naturally small masses from a previously proposed mechanism. Dark matter appears as a singlet scalar, with dark symmetry $Z_3^D$ derivable from $Z_3^L$. Muon $g-2$ may be explained.

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Naturally Light Dirac Neutrinos from $SO(10) \times U(1)_ψ$

A new solution is presented where the right-handed neutrino $ν_R$ in $SO(10)$ pairs up with $ν_L$ to form a naturally light Dirac neutrino. It is based on the framework of $E_6 \to SO(10) \times U(1)_ψ$, then $SO(10) \to SU(5) \times U(1)_χ$.

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Dark Matter from $SU(6) \to SU(5) \times U(1)_N$

Matter and dark matter are unified under the framework of $SU(6)\to SU(5) \times U(1)_N$. A dark-matter candidate is possible, not because it is stable, but because it has a very long lifetime, in analogy to that of the proton in theories of grand unification. A specific example is presented.

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Cobimaximal Mixing with Dirac Neutrinos

If neutrinos are Dirac, the conditions for cobimaximal mixing, i.e. $θ_{23}=π/4$ and $δ_{CP}=\pm π/2$ in the $3 \times 3$ neutrino mixing matrix, are derived. One example with $A_4$ symmetry and radiative Dirac neutrino masses is presented.

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Dirac Neutrino Mass Matrix and its Link to Freeze-in Dark Matter

Using a mechanism which allows naturally small Dirac neutrino masses and its linkage to a dark gauge $U(1)_D$ symmetry, a realistic Dirac neutrino mass matrix is derived from $S_3$. The dark sector naturally contains a fermion singlet having a small seesaw mass. It is thus a good candidate for freeze-in dark matter from the decay of the $U(1)_D$ Higgs boson.

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Hierarchical Quark and Lepton Masses with Sequential U(1) Gauge Symmetry

Instead of right-handed neutrino singlets, the standard model is extended to include lepton triplets $(Σ^+, Σ^0, Σ^-)$. Each quark and lepton family may now transform under an anomaly-free $U(1)_X$ gauge symmetry, known already for many years. A new sequential application is presented, using just the one Higgs doublet of the standard model, together with two $U(1)_X$ Higgs singlets. The resulting structure has hierarchical quark and lepton masses, as well as a viable seesaw neutrino mass matrix.

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One-Loop Electron Mass and Three-Loop Dirac Neutrino Masses

In the context of a left-right extension of the standard model of quarks and leptons with the addition of a gauged $U(1)_D$ dark symmetry, it is shown how the electron may obtain a radiative mass in one loop and two Dirac neutrinos obtain masses in three loops.

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Universal Scotogenic Fermion Masses in Left-Right Gauge Model

In the conventional left-right gauge model, if the Higgs scalar sector consists only of an $SU(2)_L$ doublet and an $SU(2)_R$ doublet, fermion masses are zero at tree level. There have been many studies on how they would become massive. With the help of a dark sector with $U(1)_D$ gauge symmetry, it is shown how all standard-model fermions may acquire realistic masses radiatively, including that of the top quark. In this context, the particle content of the model also implies the automatic conservation of baryon number $B$ and lepton number $L$ as in the standard model. Observable anomalous Higgs couplings are predicted.

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Gauge Baryon Number and Dibaryonic Dark Matter

The minimal standard model of quarks and leptons is extended with a set of vectorlike fermions to allow baryon number $B$ to become a gauged $U(1)_B$ symmetry. The $B$ assignments of the new particles are determined by renormalizable interactions with the known quarks through a color triplet scalar diquark. The spontaneous breaking of $U(1)_B$ by a scalar with $B=3$ results in a conserved residual global $B$ symmetry. A singlet neutral scalar with $B=2$ is a possible long-lived dark-matter candidate.

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Split Left-Right Symmetry and Scotogenic Quark and Lepton Masses

A model of split left-right symmetry is proposed, where the first family of quarks and leptons transforms under $SU(2)_R$ but the heavier two families do not. The Higgs scalar sector consists only of an $SU(2)_L$ doublet and an $SU(2)_R$ doublet. The $u,d$ quarks and the electron, as well as the neutrinos, are massless at tree level, but become massive radiatively through their interactions with a simple dark sector. Verifiable consequences include $Z'$ and Higgs properties, neutrino mixing and rare decays, etc.

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Dileptonic Scalar Dark Matter and Exotic Leptons

A simple scenario of long-lived dark matter is presented. Assuming lepton number $(L)$ conservation with Dirac neutrinos, the neutral component of an $SU(2)_L$ scalar triplet with $L=2$ is a suitable candidate, which decays to two neutrinos. Exotic leptons with $L=-1$ may also play a role, and act as anchors for small seesaw Dirac neutrino masses.

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