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Charanjit S. Aulakh

Publications and source records attributed to Charanjit S. Aulakh.

At least 37 records · Page 2Linked to original sources

Msgut Reborn ?

We present examples of fits of fermion mass data using the $\mathbf{10-120-\oot}$ FM Higgs system in Susy SO(10) GUTs that follow the scenario\cite{blmdoom,nmsgutI} in which the $\mathbf{120}$ -plet collaborates with the $ \mathbf{10}$-plet to fit the charged fermion masses while small $\mathbf{\oot} $-plet couplings enhance the Type I seesaw neutrino masses to viable values and make the fit to light fermions accurate. Restricting ourselves to the CP conserving case we use a linear perturbative technique to obtain accurate charged fermion fits ($χ^2_{tot} < .2 $) to all the charged fermion masses and angles. The resulting fits imply Type I neutrino masses that are generically $10^2- 10^3$ times larger than those obtained in the $\mathbf{10-\oot}$ scenario precisely because of the small $\mathbf{\oot} $ coupling. Thus the difficulty of obtaining sufficiently large neutrino masses in the context of these Next to Minimal Susy GUTs is essentially removed. The remaining free parameters allow one to obtain the correct ratio of neutrino mass squared splitting and a large($θ_{23}^{PMNS}$) and small($θ_{13}^{PMNS}$) mixing angle. The $θ_{12}^{PMNS}$ is however small and this indicates that -as in the Type I $\mathbf{10-\oot}$ case - a fully realistic fit to the lepton mixing data also \emph{requires} CP violation.

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Fermion Mass Hierarchy in the Nu MSGUT I : The Real Core

The recent failure of the scenario which uses only $\mathbf{10,\oot}$ Higgs multiplets to yield large enough neutrino masses in the $\mathbf{SO(10) }$ \textbf{MSGUT} motivates an alternative scenario\cite{blmdoom} where the $\mathbf{120}$ -plet collaborates with the $ \mathbf{10}$ -plet to fit the dominant charged fermion masses. The small $\mathbf{\oot} $ -plet couplings give appreciable contributions only to light charged fermion masses {\textit{and}} enhance the Type I seesaw masses to viable values. We analyze the 2-3 generation core of the complete hierarchical fermion mass system in the CP conserving approximation. \emph{Ansatz} consistency \emph{requires} ${\mathbf{m_b-m_s = m_τ-m_μ}} $ at the GUT scale $M_X$ and predicts near maximal (PMNS) mixing in the leptonic sector for central values of charged fermion parameters and for wide ranges of the other relevant parameters : righthanded neutrino masses and relative strength of contributions of the two doublet pairs from the $\mathbf{120}$-plet to the effective MSSM Higgs pair. These features are preserved in the CP preserving 3 generation system whose results are previewed : an additional consistency requirement $\mathbf{θ_{13}^c =θ_{12}^c θ_{23}^c }$ on the CKM angles at $M_X$ arises for 3 generations. Right handed neutrino masses in such scenarios are all less than about $10^{12} GeV$.

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MSGUTs from Germ to Bloom : towards Falsifiability and Beyond

We review the development of minimal renormalizable SO(10) Susy GUTs. Using our $SO(10) \to G_{Pati-Salam} $ label decomposition we calculated the complete GUT scale spectra and couplings and the threshold effects therefrom. The corrections to $α_G, Sin^2θ_W $ and $ M_X $ are sensitive functions of the single parameter $ξ$ that controls symmetry breaking and slow funtions of the others. Scans of the parameter space to identify regions compatible with gauge unification are shown. The tight connection between the phenomenology of neutrino oscillations and exotic ($ΔB\neq 0 $) processes predicted by Susy SO(10) GUTs is discussed in the context of the recent successful fits of all available fermion mass/mixing data using the ${\bf{10 \oplus {\bar {126}}}}$ Higgs representations and Type I/II seesaw mechanisms for neutrino mass. We emphasize that {\it{the true output of these calculations should be regarded as the unitary matrices that specify the orientation of the embedding of the MSSM within the MSGUT}}. Fermion Mass fitting constraints combined with GUT spectra can falsify/constrain the MSGUT and its near relatives. An initial survey indicates that Type I Seesaw neutrino masses dominate Type II and both are too small in the perturbative MSGUT even when the mixing and mass squared splitting ratios are as per data. This motivates a detailed study of the MSGUT constraints using the outputs of the fitting of fermion data, as well as consideration of modifications/extensions of the MSGUT scenario.

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MSGUT a la Pati-Salam : from Futility to Precision

We compute the complete gauge and chiral superheavy mass spectrum and couplings of the Minimal Susy GUT (based on the $ \bf {210- \oot- 126-10}$ irreps as the Higgs system) by decomposing SO(10) labels in terms of Pati Salam subgroup labels. The spectra are sensitive functions of the single complex parameter that controls MSGUT symmetry breaking. We scan for the dependence of the threshold corrections to the Weinberg angle and Unification scale as functions of this parameter. We find that for generic values of the GUT scale parameters the modifications are within 10% of the one loop values and can be much smaller for significant regions of the parameter space. This shows that contrary to longstanding conjectures, high precision calculations are not futile but rather necessary and feasible in the MSGUT. The couplings of the matter supermultiplets are made explicit and used to identify the channels for exotic ($ΔB\neq 0$) processes and to write down the associated bare $d=5$ operators (some of both are novel). The mass formulae for all matter fermions are derived. This sets the stage for a comprehensive RG based phenomenological analysis of the MSGUT.

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On the Consistency of MSGUT Spectra

We show explicitly that, once convention dependent phases are properly accounted for, the mass spectra evaluated by us in hep-ph\0204097 and hep-ph\0405074 satisfy the Trace, SU(5) reassembly and Goldstone counting consistency checks. Furthermore proper phase accounting shows that the transposition symmetry called "Hermiticity" will be manifest only up to signs arising from the product of six phase factors which must be reinserted if the symmetry is to be verified also as regards signs. Thus the claims of hep-ph/0405300 and hep-ph/0412348 concerning the inconsistency of our results are completely mistaken. The Chiral multiplet spectra of the two calculations are equivalent. However our method also gives all gauge and gauge chiral spectra as well as a MSSM decomposition of all SO(10) MSGUT couplings, for both tensors and spinors, which are unavailable, even in principle, using the methods of the above papers.

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MSGUT : from Futility to Precision

We computed the complete gauge and chiral superheavy spectra and couplings in the Minimal Susy GUT and therefrom evaluated the dependence of 1-loop threshold corrections to the Weinberg angle and Unification scale as functions of the single complex parameter $ξ$ that controls MSGUT symmetry breaking. The corrections are generically within 10% showing that contrary to longstanding conjectures,{\it{high precision calculations are not futile but necessary and feasible in the SO(10) MSGUT.}} Effective superpotentials for $B-L$ violation and mass formulae of the MSSM matter supermultiplets including neutrino Type I and II seesaws were derived.

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SO(10) a la Pati-Salam

We present rules for rewriting SO(10) tensor and spinor invariants in terms of invariants of its ``Pati-Salam'' maximal subgroup (SU(4)$\times \rm{SU(2)}_L\times \rm{SU(2)}_R)$ supplemented by the discrete symmetry called D parity. Explicit decompositions of quadratic and cubic invariants relevant to GUT model building are presented and the role of D parity in organizing the terms explained. Our rules provide a complete and explicit method for obtaining the "Clebsch-Gordon" Coefficients for $SO(10)\leftrightarrow G_{PS}$ in a notation appropriate for field theory models. We illustrate the usefulness our methods by calculating previously unavailable mass matrices and couplings of the $SU(2)_L$ doublets and $SU(3)_c $ triplets in the minimal Susy SO(10) GUT which are essential to specify the phenomenology of this model. We also present the bare effective potential for Baryon number violation in this model and show that it recives novel contributions from exchange of triplet Higgsinos contained the in ``neutrino mass'' Higgs submultiplets ${\bf{\barΣ}}_{126}(10,1,3)$. This further tightens the emerging connection between neutrino mass and proton decay.

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The minimal supersymmetric grand unified theory

We show that the minimal renormalizable supersymmetric SO(10) GUT with the usual three generations of spinors has a Higgs sector consisting only of a "light" 10-dimensional and "heavy" 126, 126-bar and 210 supermultiplets. The theory has only two sets of Yukawa couplings with fifteen real parameters and ten real parameters in the Higgs superpotential. It accounts correctly for all the fermion masses and mixings. The theory predicts at low energies the MSSM with exact R-parity. It is arguably the minimal consistent supersymmetric grand unified theory.

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Taming Asymptotic Strength

Using a simple Asymptotically Strong N=1 Susy SU(2) Gauge theory coupled to a {\bf{5}}-plet Chiral superfield we demonstrate the plausibility of the `` truly minimal '' Asymptotically Strong Grand Unification scenario proposed by us recently. Assuming a dynamical superpotential consistent with the symmetries and anomalies is actually induced non-perturbatively we show the gauge symmetry is dynamically and spontaneously broken at a UV scale that is generically {\it{exponentially}} larger than the scales characteristic of the effective low energy theory. The pattern of condensates in a semi-realistic SU(5) ASGUT is analyzed using the Konishi anomaly assuming condensation occurs as shown by our toy model. The necessarily complementary relation of ASGUTs to the Dual Unification program and the novel cosmogony implied by their unusual thermodynamic properties are also discussed.

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Truly Minimal Unification : Asymptotically Strong Panacea ?

We propose Susy GUTs have a UV attractor at E ~ Lambda_{cU} ~ 10^{17} GeV where gauge symmetries ``confine'' forming singlet condensates at scales E ~ Lambda_{cU}. The length l_U ~ Lambda_{cU}^{-1} characterizies the size of gauge non- singlet particles yielding a picture dual to the Dual Standard model of Vachaspati. This Asymptotic Slavery (AS) fixed point is driven by realistic Fermion Mass(FM) Higgs content which implies AS. This defines a dynamical morphogenetic scenario dependent on the dynamics of UV strong N=1 Susy Gauge-Chiral(SGC) theories. Such systems are already understood in the AF case but ignored in the AS case. Analogy to the AFSGC suggests the perturbative SM gauge group of the Grand Desert confines at GUT scales i.e GUT symmetry is ``non-restored''. Restoration before confinement and self-inconsistency are the two other (less likely) logical possibilities. Truly Minimal (TM) SU(5) and SO(10) models with matter and FM Higgs only are defined; AM (adjoint multiplet type) Higgs may be introduced for a Classical Phase Transition (CPT) description. Renormalizability and R-Parity leave only the low energy (SM) data as free parameters in the TM (Quantum PT) case. Besides ab initio resolution of the Heirarchy problem and choice of Susy vacuum, fresh perspectives on particle elementarity and duality, doublet triplet splitting, proton decay suppression, soft Susy masses etc open up. ``Elastic'' (spin 2 and spin 3/2) fluctuations of the AS (or pleromal) condensate coupling universally to SM particles with length scale l_U ~ l_{Pl} imply an effective N=1 (super)gravity in the Grand Desert, in which gaugino condensates yield soft Susy breaking. The AF dogma must be proven or discarded.

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Supersymmetric Unification at the Millenium

We argue that the discovery of neutrino mass effects at Super-Kamiokande implies a clear logical chain leading from the Standard Model, through the MSSM and the recently developed Minimal Left Right Supersymmetric models with a renormalizable see-saw mechanism for neutrino mass, to Left Right symmetric SUSY GUTS : in particular, SO(10) and $SU(2)_L \times SU(2)_R\times SU(4)_c$. The progress in constructing such GUTS explicitly is reviewed and their testability/falsifiability by lepton flavour violation and proton decay measurements emphasized. Susy violations of the survival principle and the interplay between third generation Yukawa coupling unification and the structurally stable IR attractive features of the RG flow in SUSY GUTS are also discussed .

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New Regime for Dense String Networks

We uncover a new transient regime that reconciles the apparent inconsistency of the Martins Shellard one scale damped string evolution model with the initial conditions predicted by the Kibble mechanism for string formation in a second order phase transition. This regime carries (in a short cosmic time $\sim .1 t_c$) the dense string network created by the Kibble {\it{mechanism}} to the (dilute) Kibble {\it{regime}} in which friction dominated strings remain till times $t_* \sim (M_P/T_c)^2 t_c$. This is possible beacause the cosmic time at the phase transition ($t_c$) is much larger than the damping time scale $l_f\sim T_c^2/T^3$. Our result has drastic implications for various non-GUT scale string mediated mechanisms.}

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SO(10) theory of R-parity and neutrino mass

We study the Higgs sector of a SO(10) grand unified theory which predicts exact conservation of R-parity at all scales and incorporates the see-saw mechanism. We find possible intermediate scales and light states compatible with the constraints coming from the running of the gauge couplings. Such a pattern could lower the SO(10) breaking scale, allowing the d=6 proton decay operators to be comparable in magnitude to the d=5 ones.

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A New Regime for Dense String Networks in the One Scale Model with Friction

We examine the compatibility between the one scale model with friction for the evolution of cosmic string networks with the Kibble mechanism for string network formation during a second order phase transition. We find a regime which connects (in a dramatically short time $\sim .1 t_c$) the dense string network (small network scale $L\sim 1/T_c$) created by the Kibble {\it{mechanism}} to the (dilute) Kibble {\it{regime}}(L\sim t^{3/4} in which friction dominated strings remain till times $t_*\sim (M_P/T_c)^2t_c$. The enormous loss of string length implied by this result is due to the continued dissipative motion of the string network which follows from the one scale model's identification of the typical curvature radius with the network scale and the fact that the cosmological phase transition time $t_c\sim M_{Planck}/T_c^2$ is much larger than the damping time scale $l_f\sim T_c^2/T^3$. The significant implications for string mediated Baryogenisis are also discussed briefly.

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Intermediate Scales in Supersymmetric GUTs: the Survival of the Fittest

We show that intermediate scales in supersymmetric grand unified theories may exist naturally. Their origin is traced to the violation of the survival principle: in supersymmetry internal symmetries often forbid cubic couplings in the superpotential. This leads to a plethora of light supermultiplets whose masses are generated only by higher dimensional operators and thus suppressed by the cut-off scale. These new states often carry exotic quantum numbers and may be, in some cases, accessible to experiments in the near future.

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See-saw and Supersymmetry or Exact R-parity

We show how the renormalizable see-saw mechanism in the context of supersymmetry and spontaneously broken B-L symmetry implies exact R-parity at all energies. We argue that supersymmetry plays an important role in providing a "canonical" form for the see-saw, in particular in grand unified theories that solve the doublet-triplet splitting problem via the Dimopoulos-Wilczek mechanism.

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Left-Right SUSY and the Fate of R-Parity

A fresh analysis of Left right symmetric supersymmetric models in the generic case where the scale of right handed symmetry breaking $M_R >> M_{SUSY}\sim M_W$ is presented. We conclude that the low energy effective theory for such models is essentially the MSSM with R parity (and therefore B,L symmetry) but the spectrum includes heavy conjugate neutrino supermultiplets that permit a seesaw mechanism and several characteristic charged supermultiplets over and above those of the MSSM.

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