arXiv subjects

Ernest Ma

Publications and source records attributed to Ernest Ma.

At least 253 records · Page 14Linked to original sources

arXiv2002

Gauge Model of Quark-Lepton Nonuniversality

We propose a gauge model where quark-lepton universality is an accidental symmetry which is only approximate, in analogy to the well-accepted notion that strong isospin is accidental and approximate. This is a natural framework for explaining possible small deviations of quark-lepton universality which is applicable to the recently reported apparent nonunitarity of the quark mixing matrix. As a result, small departures from quark-lepton universality are expected in Z decays as well as in the recent neutrino data of the NuTeV collaboration and in future low-energy experiments. New physics is predicted at the TeV scale.

hep-ph↗

arXiv2002

Plato's Fire and the Neutrino Mass Matrix

With the accumulation of many years of solar and atmospheric neutrino oscillation data, the approximate form of the 3 X 3 neutrino mixing matrix is now known. The theoretical challenge is to understand where this mixing matrix comes from. Recently, a remarkable fact was discovered that for a specific pattern of the neutrino mass matrix at a high scale, any flavor-changing radiative correction will automatically lead to the desired mixing matrix. It was also discovered that the required specific pattern at the high scale can be maintained by the non-Abelian discrete symmetry A_4 which is also the symmetry group of the regular tetrahedron, one of five perfect geometric solids known to Plato who associated it with the element ``fire''. I discuss this recent development and add to it a new and very simple mechanism for the implementation of the flavor-changing radiative correction.

hep-ph↗

arXiv2002

New and Useful Gauge Extension of the MSSM

A new nontrivial U(1) gauge extension of the Minimal Supersymmetric Standard Model (MSSM) is proposed which automatically conserves baryon number and lepton number, and solves the mu problem. Naturally small Dirac neutrino masses are also possible in this context.

hep-ph↗

arXiv2002

Supersymmetric Axion-Neutrino Merger

The recently proposed supersymmetric $A_4$ model of the neutrino mass matrix is modified to merge with a previously proposed axionic solution of the strong CP problem. The resulting model has only one input scale, i.e. that of $A_4$ symmetry breaking, which determines both the seesaw neutrino mass scale and the axion decay constant. It also solves the $μ$ problem and conserves R parity automatically.

hep-ph↗

arXiv2002

Theoretical Expectations for Rare and Forbidden Tau Decays

Given the experimental evidence for $ν_μ- ν_τ$ oscillations, the existence of lepton flavor violation in $τ$ decays is a theoretical certainty. In this brief review, I consider the connection between models of neutrino mass and the expected observability of some $τ$ decays.

hep-ph↗

arXiv2002

Neutrino Mass Matrix a la Mode

With the accumulation of many years of solar and atmospheric neutrino oscillation data, the approximate form of the 3 times 3 neutrino mixing matrix is now known. What is not known is the (presumably Majorana) neutrino mass matrix M_{nu} itself. In this chapter, the approximate form of M_{nu} is derived, leading to seven possible neutrino mass patterns: three have the normal hierarchy, two have the inverse hierarchy, and two have three nearly degenerate masses. The generalization of this to allow U_{e3} not equal 0 with maximal CP violation is also discussed. A specific automatic realization of this M_{nu} from radiative corrections of an underlying non-Abelian discrete A_4 symmetry in the context of softly broken supersymmetry is presented.

hep-ph↗

arXiv2002

The All-Purpose Neutrino Mass Matrix

A four-parameter Majorana neutrino mass matrix is proposed, which is exactly diagonalizable with two mixing angles, one of which is pi/4 and the other large but less than pi/4. The form of this mass matrix allows seven realizations of the present data on atmospheric and solar neutrino oscillations: three have the normal hierarchy, two have the inverse hierarchy, and two have three nearly degenerate masses. The possible inclusion of CP violation is also discussed.

hep-ph↗

arXiv2002

Oases in the Desert: Three New Proposals

Two new nontrivial U(1) gauge symmetries are proposed, one based on the particle content of the standard model and the other on that of its supersymmetric generalization. Each is an unexpected first example of its kind. A third new proposal is the successful derivation of a realistic Majorana neutrino mass matrix, based on the underlying symmetry A_4 and its radiative corrections.

hep-ph↗

arXiv2002

New Perspective on Fermion Mass Matrices

It is shown that any $n \times n$ Dirac fermion mass matrix may be written as the sum of $n$ states of equal ``mass''. However, these states are in general not orthogonal. Thus the texture of any such fermion mass matrix may be understood as the nonzero overlap among these states.

hep-ph↗

arXiv2002

Underlying A_4 Symmetry for the Neutrino Mass Matrix and the Quark Mixing Matrix

The discrete non-Abelian symmetry $A_4$, valid at some high-energy scale, naturally leads to degenerate neutrino masses, without spoiling the hierarchy of charged-lepton masses. Realistic neutrino mass splittings and mixing angles (one of which is necessarily maximal and the other large) are then induced radiatively in the context of softly broken supersymmetry. The quark mixing matrix is also calculable in a similar way. The mixing parameter $U_{e3}$ is predicted to be imaginary, leading to maximal CP violation in neutrino oscillations. Neutrinoless double beta decay and $τ\to μγ$ should be in the experimentally accessible range.

hep-ph↗

arXiv2002

Uniqueness of a recently proposed U(1) gauge extension

Consider the addition of a right-handed SU(2) fermion multiplet (with neither color nor hypercharge) to each family of quarks and leptons. The resultant theory admits a new U(1) gauge symmetry only if the additional multiplet is a singlet $N_R$, which corresponds to the well-known case of $U(1)_{B-L}$, or a triplet $(Σ^+, Σ^0, Σ^-)$, which corresponds to the proposal of hep-ph/0112232. This disproves the assertion that the latter is somehow a ``trivial'' or ``expected'' discovery.

hep-ph↗

arXiv2002

Heavy Triplet Leptons and New Gauge Boson

A heavy triplet of leptons $(Σ^+, Σ^0, Σ^-)_R$ per family is proposed as the possible anchor of a small seesaw neutrino mass. A new U(1) gauge symmetry is then also possible, and the associated gauge boson $X$ may be discovered at or below the TeV scale. We discuss the phenomenology of this proposal, with and without possible constraints from the NuTeV and atomic parity violation experiments, which appear to show small discrepancies from the predictions of the standard model.

hep-ph↗

arXiv2002

New U(1) Gauge Extension of the Supersymmetric Standard Model

In extending the minimal standard model of quarks and leptons to include supersymmetry, the conservation of baryon and lepton numbers is no longer automatic. I show how the latter may be achieved with a new U(1) gauge symmetry and new supermultiplets at the TeV scale. Neutrino masses and a solution of the $μ$ problem are essential features of this proposed extension.

hep-ph↗

arXiv2002

Supersymmetric Higgs Triplets and Bilinear R-Parity Nonconservation

The supersymmetric standard model of particle interactions is extended to include two Higgs triplet superfields at the TeV scale, carrying two units of lepton number. Realistic tree-level Majorana neutrino masses are obtained in the presence of soft, i.e. bilinear, R-parity nonconservation.

hep-ph↗

arXiv2002

New U(1) Gauge Symmetry of Quarks and Leptons

Instead of anchoring the seesaw mechanism with the conventional heavy right-handed neutrino singlet, a small Majorana neutrino mass may be obtained just as well with the addition of a heavy triplet of leptons per family to the minimal standard model of particle interactions. The resulting model is shown to have the remarkable property of accommodating a new U(1) symmetry which is anomaly-free and may thus be gauged. There are many possible phenomenological consequences of this proposal which may be already relevant in explaining one or two recent potential experimental discrepancies.

hep-ph↗

arXiv2002

Neutrino Mass from Triplet and Doublet Scalars at the TeV Scale

If the minimal standard model of particle interactions is extended to include a scalar triplet with lepton number $L=-2$ and a scalar doublet with $L=-1$, neutrino masses $m_ν\sim μ_{12}^4 v^2/M^5 \sim 10^{-2}$ eV is possible, where $v \sim 10^2$ GeV is the electroweak symmetry breaking scale, $M \sim 1$ TeV is the typical mass of the new scalars, and $μ_{12} \sim 1$ GeV is a soft lepton-number-violating parameter.

hep-ph↗

arXiv2002

Quark Mass Matrices in the A_4 Model

If the standard model of quark interactions is supplemented by a discrete A_4 symmetry (which may be relevant for the lepton sector), the spontaneous breaking of the electroweak gauge symmetry allows arbitrary quark masses, but all mixing angles are predicted to be zero. A pattern of the explicit breaking of A_4 is proposed, which results in a realistic charged-current mixing matrix.

hep-ph↗

arXiv2002

Neutrinoless Double Beta Decay with Negligible Neutrino Mass

If the electron neutrino has an effective nonzero Majorana mass, then neutrinoless double beta decay will occur. However, the latter is possible also with a negligible neutrino mass. We show how this may happen in a simple model of scalar diquarks and dileptons. This possibility allows neutrino masses to be small and hierarchical, without conflicting with the possible experimental evidence of neutrinoless double beta decay.

hep-ph↗