A Realistic Radiative Fermion Mass Hierarchy in Non-supersymmetric SO(10) (2008)
A non-supersymmetric grand unified theory can exhibit a "radiative fermion mass hierarchy", in which the heavier quarks and leptons get mass at tree level and the lighter ones get mass from loop...
Doubly Lopsided Mass Matrices from Supersymmetric SU(N) Unification (2008)
It is shown that in supersymmetric SU(N) models with N>5 the so-called doubly lopsided mass matrix structure can emerge in a natural way. The non-trivial flavor structure is entirely accounted for by...
Doubly Lopsided Mass Matrices from Unitary Unification (2008)
It is shown that the stratified or "doubly lopsided" mass matrix structure that is known to reproduce well the qualitative features of the quark and lepton masses and mixings can arise quite...
Family Unification with SO(10) (2007)
Babu, K. S., Barr, S. M., Gogoladze, Ilia
Unification based on the group SO(10)^3 \times S_3 is studied. Each family has its own SO(10) group, and the S_3 permutes the three families and SO(10) factors. This is the maximal local symmetry for...
Radiative Fermion Mass Hierarchy in a Non-supersymmetric Unified Theory (2007)
In non-supersymmetric grand unified models a ``radiative fermion mass hierarchy" can be achieved in which the spectrum of quark and lepton masses is determined entirely by physics at the unification...
Anthropic tuning of the weak scale and of m_u/m_d in two-Higgs-doublet models (2007)
It is shown that in a model in which up-type and down-type fermions acquire mass from different Higgs doublets, the anthropic tuning of the Higgs mass parameters can explain the fact that the...
Extra $Z$ bosons and low-energy tests of unification (2006)
If there is an extra U(1) gauge symmetry broken at low energies, then it may be possible from the charges of the known quarks and leptons under this U(1) to make inferences about how much gauge...
Flat-Directions in Grand Unification With $U(1)_R$ Symmetry (2005)
Barr, S. M., Kyae, Bumseok, Shafi, Qaisar
It is shown that in SO(10) and SU(5) models having a $U(1)_R$ symmetry, the requirement of breaking the unified group to the Standard Model leads to flat directions in the scalar potential. These can...
A Prediction from the Type III See-saw Mechanism (2005)
A simple ansatz that is well-motivated by group-theoretical considerations is proposed in the context of the type III neutrino see-saw mechanism. It results in predictions for m_s/m_b and m_b/m_tau...
The Origin of a Peculiar Extra U(1) (2005)
The origin of a family-independent "extra U(1)", discovered by Barr, Bednarz, and Benesh and independently by Ma, and whose phenomenology has recently been studied by Ma and Roy, is discussed. Even...
How a Non-hierarchical Neutrino Mass Matrix Can Arise (2005)
One puzzle of neutrino masses and mixings is that they do not exhibit the kind of strong "hierarchy" that is found for the quarks and charged leptons. Neutrino mass ratios and mixing angles are not...
Time-varying Quark Masses and Cosmological Axion Energy (2004)
The possibility is examined that the masses of the light quarks $u$ and $d$ have varied over the course of the universe's evolution. Such a variation would have an effect on axion cosmology, and can...
A General Analysis of Corrections to the Standard See-saw Formula in Grand Unified Models (2004)
In realistic grand unified models there are typically extra vectorlike matter multiplets at the GUT scale that are needed to explain the family hierarchy. These contain neutrinos that, when...
Resonant leptogenesis in a predictive SO(10) grand unified model (2004)
Albright, Carl H., Barr, S. M.
An SO(10) grand unified model considered previously by the authors featuring lopsided down quark and charged lepton mass matrices is successfully predictive and requires that the lightest two...
Leptogenesis in the type III seesaw mechanism (2003)
Albright, Carl H., Barr, S. M.
It is shown that the type III seesaw mechanism proposed recently can have certain advantages over the conventional (or type I) seesaw mechanism for leptogenesis. In particular a resonant enhancement...
A different see-saw formula for neutrino masses (2003)
In a wide class of unified models there is an additional (and possibly dominant) term in the neutrino mass formula that under the simplest assumption takes the form M_{\nu} = (M_N + M_N^T)u/M_G,...
SUSY GUT Models of Neutrino Mass and mu to e gamma (2003)
It is explained why excessive mu to e gamma can be a problem in SUSY GUT see-saw models of neutrino mass, and ways that this problem might be avoided are discussed.
Explaining Why the u and d Quark Masses are Similar (2003)
An approach is suggested for modeling quark and lepton masses and mixing in the context of grand unified theories that explains the curious fact that m_u ~ m_d even though m_t >> m_b. The structure...
Atmospheric neutrino mixing and b-tau Unification (2002)
Extrapolating the tau and b masses in the MSSM tends to give for their ratio at the GUT scale a number around 1.2, for most viable values \tan \beta, rather than the minimal SU(5) prediction of 1. We...
Lifting a Realistic SO(10) Grand Unified Model to Five Dimensions (2002)
Albright, Carl H., Barr, S. M.
It has been shown recently that the problem of rapid proton decay induced by dimension five operators arising from the exchange of colored Higgsinos can be simply avoided in grand unified models...
Four Puzzles of Neutrino Mixing (2002)
There are four puzzling questions about by the magnitudes of neutrino mixings and mass splittings. A brief sketch is given of the various kinds of models of neutrino masses and how they answer these...
Unifying flipped SU(5) in five dimensions (2002)
It is shown that embedding a four-dimensional flipped SU(5) model in a five-dimensional SO(10) model, preserves the best features of both flipped SU(5) and SO(10). The missing partner mechanism,...
Family Unification in Five and Six Dimensions (2002)
Babu, K. S., Barr, S. M., Kyae, Bumseok
In family unification models, all three families of quarks and leptons are grouped together into an irreducible representation of a simple gauge group, thus unifying the Standard Model gauge...
Flavon exchange effects in models with abelian flavor symmetry (2002)
In models with abelian flavor symmetry the small mixing angles and mass ratios of quarks and leptons are typically given by powers of small parameters characterizing the spontaneous breaking of...
Eliminating the d=5 proton decay operators from SUSY GUTs (2002)
A general analysis is made of the question whether the d=5 proton decay operators coming from exchange of colored Higgsinos can be completely eliminated in a natural way in supersymmetric grand...
Bimaximal Neutrino Mixings from Lopsided Mass Matrices (2001)
Current solar and atmospheric neutrino oscillation data seem to favor a bimaximal pattern for neutrino mixings where the matrix elements U_{e2} and U_{\mu 3} are of order one, while U_{e3} is much...
Obtaining the large angle MSW solution to the solar neutrino problem in models (2001)
The large mixing angle (LMA) MSW solution to the solar neutrino problem seems favored by the data at the moment over the small mixing angle (SMA) MSW solution and the vacuum (VAC) solution. In this...
The Cosmological Constant, False Vacua, and Axions (2001)
It is suggested that the true ground state of the world has exactly vanishing vacuum energy and that the cosmological constant that seems to have been observed is due to our region of the universe...
Flavor without Flavor Symmetry (2001)
Non-trivial patterns of quark and lepton masses and mixings can arise without there being any underlying flavor symmetry that distinguishes among the three families. Two realistic examples are given.
An SO(10) supersymmetric grand unified model proposed earlier leading to the solar solution involving ``just-so'' vacuum oscillations is reexamined to study its ability to obtain the other possible...
The scaling of lepton dipole moments with lepton mass (2000)
Babu, K. S., Barr, S. M., Dorsner, Ilja
The dipole moments of the leptons and quarks are matrices in flavor space, which can potentially reveal as much about the flavor structure of the theory as do the mass matrices. The off-diagonal...
Explicit SO(10) Supersymmetric Grand Unified Model (2000)
Albright, Carl H., Barr, S. M.
A complete set of Higgs and matter superfields is introduced with well-defined SO(10) properties and U(1) \times Z_2 \times Z_2 family charges from which the Higgs and Yukawa superpotentials are...
A mass relation for neutrinos (2000)
A generalization of the well-known Georgi-Jarlskog relation m_{\mu}/m_{\tau} = 3 (m_s/m_b) to neutrinos is found in the context of SO(10). This new relation is m_{\nu_\mu}/m_{\nu_\tau} = 16...
Construction of a Minimal Higgs SO(10) SUSY GUT Model (2000)
Albright, Carl H., Barr, S. M.
A full account is given of the procedure used by the authors to construct an SO(10) supersymmetric grand unified model of the fermion mass matrices. Various features of the model which gives...
Neutrino Oscillations: Some theoretical ideas (2000)
Talk given at Orbis Scientiae Conference, Coral Gables, FLA, Dec. 16-19, 1999. Talk surveys some recent three-neutrino models of neutrino masses and mixings.
A General Classification of Three-Neutrino Models and U_e3 (2000)
A classification of models with three light neutrinos is given. This classification includes virtually all of the three-neutrino models proposed in the last few years, of which there are...
Explicit SO(10) Supersymmetric Grand Unified Model for the Higgs and Yukawa Sectors (2000)
Albright, Carl H., Barr, S. M.
A complete set of fermion and Higgs superfields is introduced with well-defined SO(10) properties and U(1) x Z_2 x Z_2 family charges from which the Higgs and Yukawa superpotentials are constructed....
SO(10) and Large nu_mu - nu_tau Mixing (2000)
A general approach to understanding the large mixing seen in atmospheric neutrinos is explained, as well as a highly predictive SO(10) model which implements this approach. It is also seen how...
Bimaximal Mixing in an SO(10) Minimal Higgs Model (1999)
Albright, Carl H., Barr, S. M.
An SO(10) SUSY GUT model was previously presented based on a minimal set of Higgs fields. The quark and lepton mass matrices derived fitted the data extremely well and led to large mixing of muon-...
We examine the cancellation mechanism between the different contributions to the electric dipole moment of the neutron in a model with dilaton-dominated SUSY breaking. We find these accidental...
A mechanism for lifting the cosmological upper bound on the axion decay constant, $f_a$, is proposed. It entails the near masslessness of the radial mode whose vacuum expectation value is $f_a$....
Predicting quark and lepton masses and mixings (1999)
Albright, Carl H., Barr, S. M.
A model is presented that fits the quark and lepton masses and mixings wherein five dimensionless parameters and a phase account for fifteen dimensionless observables. Among these are the Wolfenstein...
The Problem of \alpha_s in Supersymmetric Unified Theories (1998)
It is shown that in SO(10) there is a general connection between the suppression of higgsino mediated proton decay and the value of $\alpha_s$. However, agreement with the experimental value of...
Implications of a Minimal SO(10) Higgs Structure (1998)
Albright, Carl H., Babu, K. S., Barr, S. M.
A minimal SO(10) Higgs structure involving a single adjoint field along with spinors, vectors and singlets has been shown to break the SO(10) gauge symmetry to the standard model while stabilizing...
A Minimality Condition and Atmospheric Neutrino Oscillations (1998)
Albright, Carl H., Babu, K. S., Barr, S. M.
A structure is proposed for the mass matrices of the quarks and leptons that arises in a natural way from the assumption that the breaking of SO(10) gauge symmetry is achieved by the smallest...
Agrawal, V., Barr, S. M., Donoghue, John F., Seckel, D.
One of the puzzles of the Standard Model is why the mass parameter which determines the scale of the Weak interactions is closer to the scale of QCD than to the Grand Unification or Planck scales. We...
Fermion masses in SO(10) with a single adjoint Higgs field (1997)
Albright, Carl H., Barr, S. M.
It has recently been shown how to break SO(10) down to the Standard Model in a realistic way with only one adjoint Higgs. The expectation value of this adjoint must point in the B-L direction. This...
The anthropic principle and the mass scale of the Standard Model (1997)
Agrawal, V., Barr, S. M., Donoghue, J. F., Seckel, D.
In theories in which different regions of the universe can have different values of the the physical parameters, we would naturally find ourselves in a region which has parameters favorable for life....
Minimal SO(10) Unification (1997)
It is shown that the doublet-triplet splitting problem can be solved in SO(10) using the Dimopoulos-Wilczek mechanism with a very economical Higgs content and simple structure. Only one adjoint Higgs...
Flavor Alignment Solutions to the Strong CP Problem in Supersymmetry (1997)
An approach to solving the Strong CP Problem in supersymmetric theories is discussed which uses abelian family symmetries to align the mass matrices of the quarks and squarks. In this way both the...
The Sliding-singlet Mechanism Revived (1997)
It is shown, using a modification of an idea of Sen, that completely realistic supersymmetric grand-unified theories based on SU(6) or larger unitary groups can be constructed using the...
Supersymmetric Solutions to the Strong CP Problem (1996)
It is argued that in the context of supersymmetry, the Strong CP Problem is most naturally seen as an aspect (particularly severe) of the whole complex of flavor-violating and CP-violating problems...
Predictive Models of Large Neutrino Mixing Angles (1996)
Several experimental results could be interpreted as evidence that certain neutrino mixing angles are large, of order unity. However, in the context of grand unified models the neutrino angles come...
The Stability of the Gauge Hierarchy in $SU(5) \times SU(5)$ (1996)
It has been shown that the Dimopoulos-Wilczek (or missing-VEV) mechanism for doublet-triplet splitting can be implemented in $SU(5) \times SU(5)$ models, which requires no adjoint Higgs fields. This...
Gauged SO(3) family symmetry and squark mass degeneracy (1996)
It is shown that a gauged SO(3) family symmetry can suppress flavor-changing processes from squark-mass non-degeneracy to an acceptable level. The potentially dangerous SO(3) D-terms can be rendered...
Realistic Quark and Lepton Masses through SO(10) Symmetry (1995)
In a recent paper a model of quark and lepton masses was proposed. Without any family symmetries almost all the qualitative and quantitative features of the quark and lepton masses and...
Large neutrino mixing angles in unified theories (1995)
Typically in unified theories the neutrino mixing angles, like the Cabibbo-Kobayashi-Maskawa (CKM) angles of the quarks, are related to the small mass ratios between fermions of different generations...
Proton decay and realistic models of quark and lepton masses (1995)
It is shown that in realistic SUSY GUT models of quark and lepton masses both the proton decay rate and branching ratios differ in general from those predicted in the minimal $SU(5)$ supersymmetric...
"An SO(10) Solution to the Puzzle of Quark and Lepton Masses" (1995)
It is shown that almost all features of the quark and lepton masses can be satisfactorily and simply explained without family symmetry, including the threefold mass hierarchy among the generations,...
Supersymmetric SO(10) Simplified (1994)
In the context of supersymmetric $SO(10)$ grand unified models, it is shown that the gauge symmetry breaking as well as a natural doublet--triplet splitting can be achieved with a minimal Higgs...
Axion Dissipation Through the Mixing of Goldstone Bosons (1994)
Babu, K. S., Barr, S. M., Seckel, D.
By coupling axions strongly to a hidden sector, the energy density in coherent axions may be converted to radiative degrees of freedom, alleviating the ``axion energy crisis''. The strong coupling is...
Natural Gauge Hierarchy in SO(10) (1994)
It is shown that a natural gauge hierarchy and doublet-triplet splitting can be achieved in SO(10) using the Dimopoulos-Wilczek mechanism. Artificial cancellations (fine-tuning) and arbitrary forms...
A Solution to the Small Phase Problem of Supersymmetry (1993)
It is a well--known problem that in supersymmetric models there are new CP--violating phases which, if unsuppressed, would give a neutron electric dipole moment $10^2$ to $10^3$ times the present...
Spontaneous CP violation in the Supersymmetric Higgs Sector (1993)
Spontaneous CP--violation in the minimal supersymmetric standard model with a gauge singlet and a cubic superpotential is examined. Although the tree--level Higgs potential conserves CP, it is shown...
Natural Suppression of Higgsino-Mediated Proton Decay in Supersymmetric SO(10) (1993)
In supersymmetric Grand Unified Theories, proton decay mediated by the color--triplet higgsino is generally problematic and requires some fine--tuning of parameters. We present a mechanism which...
Family Symmetry, Gravity, and the Strong CP Problem (1992)
We show how in a class of models Peccei--Quinn symmetry can be realized as an automatic consequence of a gauged $U(1)$ family symmetry. These models provide a solution to the strong CP problem either...
Vita.
Chen, N N, Chang, C F, Gallia, G L, Kerr, D A, Johnson, E M, Krachmarov, C P, ...
Human JC polyomavirus (JCV) is the etiologic agent of the neurodegenerative disease progressive mulifocal leukoencephalopathy. By using JCV as a model, we investigated the role of the viral early...
Chen, N N, Chang, C F, Gallia, G L, Kerr, D A, Johnson, E M, Krachmarov, C P, ...
Human JC polyomavirus (JCV) is the etiologic agent of the neurodegenerative disease progressive mulifocal leukoencephalopathy. By using JCV as a model, we investigated the role of the viral early...
Ethanol and platelet intracellular free calcium concentrations.
Lees, K R, Barr, S M, Butters, L, Rubin, P C
The effect of 0.8 g kg-1 absolute ethanol orally on platelet intracellular free calcium was assessed in a random order study in 24 normotensive subjects with an isocaloric control. Platelet calcium...