arXiv subjects

R. N. Mohapatra

Publications and source records attributed to R. N. Mohapatra.

At least 55 records · Page 3Linked to original sources

arXiv2012

B-L Violating Proton Decay Modes and New Baryogenesis Scenario in SO(10)

We show that grand unified theories based on SO(10) generate quite naturally baryon number violating dimension seven operators that violate (B-L), and lead to novel nucleon decay modes such as n \to e^-K^+, e^- π^+ and p \to νπ^+. We find that in two-step breaking schemes of non-supersymmetric SO(10), the partial lifetimes for these modes can be within reach of experiments. The interactions responsible for these decay modes also provide a new way to understand the origin of matter in the universe via the decays of GUT scale scalar bosons of SO(10). Their (B-L)-violating nature guarantees that the GUT scale induced baryon asymmetry is not washed out by the electroweak sphaleron interactions. In minimal SO(10) models this asymmetry is closely tied to the masses of quarks, leptons and the neutrinos.

hep-ph↗

arXiv2012

θ_{13} and Proton Decay in a Minimal SO(10) x S_4 model of Flavor

In a recent paper, a minimal supersymmetric (SUSY) SO(10)xS_4 based unified model of flavor for quarks and leptons was proposed with two 10 and one 126 contributing to fermion masses. An important aspect of this model is that Yukawa couplings emerge dynamically from minimization of the flavon potential, thereby reducing the number of parameters considerably. We make a detailed numerical analysis of this model for fermion mixings including SUSY threshold effects at the TeV scale and type-I corrections to a type-II dominant seesaw for neutrino masses. This is a single-step breaking model with SUSY SO(10) broken at the Grand Unified Theory (GUT)-scale of 2x10^16 GeV to the Minimal Supersymmetric Standard Model (MSSM). The minimal model has only 11 parameters, and therefore, the charged fermion fits predict the masses (up to an overall scale) and mixings in the neutrino sector. We present correlations for the different predictions in the neutrino mixing parameters. The recent experimental "large" θ_{13} value of \sim 9 degrees can be obtained by a simple extension of the minimal model. We also find that proton decay mode p -> K^+\barν_μhas a partial lifetime of \sim10^34 yrs, which is within reach of the next round of planned proton decay searches. The successful fit for fermion masses requires the Higgs mass to be below 129 GeV in this model. If the Higgs mass lies between 120-128 GeV, as suggested by the recent LHC data, we find a lower limit on the light stop mass of 755 (211) GeV for μ>0 (<0).

hep-ph↗

arXiv2012

On trigonometric approximation of functions in the Lp norm

In this paper we obtain degree of approximation of functions in Lp by operators associated with their Fourier series using integral modulus of continuity. These results generalize many know results and are proved under less stringent conditions on the infinite matrix.

math.CA↗

arXiv2012

Degree of Convergence of an Integral Operator

In this paper we define an integral operator on Lp and obtain its degree of convergence in the appropriate norm. By specializing the kernel of the integral operator we obtain many known results as corollaries. We have also applied our results to obtain results on singular integral operators.

math.CA↗

arXiv2012

B-L Violating Nucleon Decay and GUT Scale Baryogenesis in SO(10)

We show that grand unified theories based on SO(10) generate naturally the next-to-leading baryon number violating operators of dimension seven. These operators, which violate B-L, lead to unconventional decays of the nucleon such as n -> e^-K^+, e^- π^+ and p -> νπ^+. In two-step breaking schemes of non-supersymmetric SO(10), nucleon lifetime for decays into these modes is found to be within reach of experiments. We also identify supersymmetric scenarios where these decays may be accessible, consistent with gauge coupling unification. Further, we show that the (B-L)-asymmetry generated in the decays of GUT scale scalar bosons and/or gauge bosons can explain consistently the observed baryon asymmetry of the universe. The induced (B-L)-asymmetry is sphaleron-proof, and survives down to the weak scale without being erased by the electroweak interactions. This mechanism works efficiently in a large class of non-SUSY and SUSY SO(10) models, with either a 126 or a 16 Higgs field employed for rank reduction. In minimal models the induced baryon asymmetry is tightly connected to the masses of quarks, leptons and neutrinos and is found to be compatible with observations.

hep-ph↗

arXiv2012

Sneutrino Dark Matter in Gauged Inverse Seesaw Models for Neutrinos

Extending the Minimal Supersymmetric Standard Model (MSSM) to explain small neutrino masses via the inverse seesaw mechanism can lead to a new light supersymmetric scalar partner which can play the role of inelastic dark matter (iDM). It is a linear combination of the superpartners of the neutral fermions in the theory (the light left-handed neutrino and two heavy Standard Model singlet neutrinos) which can be very light with mass in $\sim 5-20$ GeV range, as suggested by some current direct detection experiments. The iDM in this class of models has keV-scale mass splitting, which is intimately connected to the small Majorana masses of neutrinos. We predict the differential scattering rate and annual modulation of the iDM signal which can be testable at future Germanium- and Xenon-based detectors.

hep-ph↗

arXiv2011

Absence of Spontaneous CP violation in Multi-Higgs Doublet Extension of MSSM

We show that in the multi-Higgs extension of minimal supersymmetric standard model, which has N-pairs of Higgs doublets (called NHMSSM), it is impossible to break CP spontaneously, if we do not allow for fine-tuning relations between parameters. The result holds true even in the presence of spontaneous R-parity breaking.

hep-ph↗

arXiv2011

Type II Seesaw Dominance in Non-supersymmetric and Split Susy SO(10) and Proton Life Time

Recently type II seesaw dominance in a supersymmetric SO(10) framework has been found useful in explaining large solar and atmospheric mixing angles as well as larger values of $theta_{13}$ while unifying quark and lepton masses. An important question in these models is whether there exists consistency between coupling unification and type II seesaw dominance. Scenarios where this consistency can be demonstrated have been given in a SUSY framework. In this paper we give examples where type II dominance occurs in SO(10) models without supersymmetry but with additional TeV scale particles and also in models with split-supersummetry. Grand unification is realized in a two-step process via breaking of SO(10) to SU(5) and then to a TeV scale standard model supplemented by extra fields and an SU(5) Higgs multiplet ${15}_H$ at a scale about $10^{12}$ GeV to give type-II seesaw. The predictions for proton lifetime in these models are in the range $τ_p^0 = 2\times 10^{35}$ yrs. to $τ_p^0 = 6\times 10^{35}$ yrs.. A number of recent numerical fits to GUT-scale fermion masses can be accommodated within this model.

hep-ph↗

arXiv2011

Neutrino Mixings in SO(10) with Type II Seesaw and theta_{13}

We analyze a class of supersymmetric SO(10) grand unified theories with type II seesaw for neutrino masses, where the contribution to PMNS matrix from the neutrino sector has an exact tri-bi-maximal (TBM) form, dictated by a broken S_4 symmetry. The Higgs fields that determine the fermion masses are two 10 fields and one 126 field, with the latter simultaneously contributing to neutrino as well as charged fermion masses. Fitting charged fermion masses and the CKM mixings lead to corrections to the TBM mixing that determine the final PMNS matrix with the predictions theta_{13} ~ 4-6 degrees and the Dirac CP phase to be between -10 and +15 degrees. We also show correlations between various mixing angles which can be used to test the model.

hep-ph↗

arXiv2010

Leptogenesis with TeV Scale Inverse Seesaw in SO(10)

We discuss leptogenesis within a TeV-scale inverse seesaw model for neutrino masses where the seesaw structure is guaranteed by an SO(10) symmetry. Contrary to the TeV-scale type-I gauged seesaw, the constraints imposed by successful leptogenesis in these models are rather weak and allow for the extra gauge bosons W_R and Z' to be in the LHC accessible range. The key differences in the inverse seesaw compared to the type I case are: (i) decay and inverse decay rates larger than the scatterings involving extra gauge bosons due to the large Yukawa couplings and (ii) the suppression of the washout due to very small lepton number breaking.

hep-ph↗

arXiv2010

An SO(10) Grand Unified Theory of Flavor

We present a supersymmetric SO(10) grand unified theory (GUT) of flavor based on an $S_4$ family symmetry. It makes use of our recent proposal to use SO(10) with type II seesaw mechanism for neutrino masses combined with a simple ansatz that the dominant Yukawa matrix (the {\bf 10}-Higgs coupling to matter) has rank one. In this paper, we show how the rank one model can arise within some plausible assumptions as an effective field theory from vectorlike {\bf 16} dimensional matter fields with masses above the GUT scale. In order to obtain the desired fermion flavor texture we use $S_4$ flavon multiplets which acquire vevs in the ground state of the theory. By supplementing the $S_4$ theory with an additional discrete symmetry, we find that the flavon vacuum field alignments take a discrete set of values provided some of the higher dimensional couplings are small. Choosing a particular set of these vacuum alignments appears to lead to an unified understanding of observed quark-lepton flavor: (i) the lepton mixing matrix that is dominantly tri-bi-maximal with small corrections related to quark mixings; (ii) quark lepton mass relations at GUT scale: $m_b\simeq m_τ$ and $m_μ\simeq 3 m_s$ and (iii) the solar to atmospheric neutrino mass ratio $m_\odot/m_{\rm atm}\simeq θ_{\rm Cabibbo}$ in agreement with observations. The model predicts the neutrino mixing parameter, $U_{e3} \simeq θ_{\rm Cabibbo}/(3\sqrt2) \sim 0.05$, which should be observable in planned long baseline experiments.

hep-ph↗

arXiv2010

Electroweak Symmetry Breaking and Proton Decay in SO(10) SUSY-GUT with TeV W_R

In a recent paper, we proposed a new class of supersymmetric SO(10) models for neutrino masses where the TeV scale electroweak symmetry is SU(2)_L\times SU(2)_R\times U(1)_{B-L} making the associated gauge bosons W_R and Z' accessible at the Large Hadron Collider. We showed that there exists a domain of Yukawa coupling parameters and symmetry breaking patterns which give an excellent fit to all fermion masses including neutrinos. In this sequel, we discuss an alternative Yukawa pattern which also gives good fermion mass fit and then study the predictions of both models for proton lifetime. Consistency with current experimental lower limits on proton life time require the squark masses of first two generations to be larger than ~ 1.2 TeV. We also discuss how one can have simultaneous breaking of both SU(2)_R\times U(1)_{B-L} and standard electroweak symmetries via radiative corrections.

hep-ph↗

arXiv2009

TeV Scale Inverse Seesaw in SO(10) and Leptonic Non-Unitarity Effects

We show that a TeV scale inverse seesaw model for neutrino masses can be realized within the framework of a supersymmetric SO(10) model consistent with gauge coupling unification and observed neutrino masses and mixing. We present our expectations for non-unitarity effects in the leptonic mixing matrix some of which are observable at future neutrino factories as well as the next generation searches for lepton flavor violating processes such as μ--> e + γ. The model has TeV scale W_R and Z' bosons which are accessible at the Large Hadron Collider.

hep-ph↗

arXiv2009

Origin of Quark-Lepton Flavor in SO(10) with Type II Seesaw

Diverse mass and mixing patterns between the quarks and leptons makes it challenging to construct a simple grand unified theory of flavor. We show that SO(10) SUSY GUTs with type II seesaw mechanism giving neutrino masses provide a natural framework for addressing this issue. A simple ansatz that the dominant Yukawa matrix (the 10-Higgs coupling to matter) has rank one, appears to simultaneously explain both the large lepton mixings as well as the observed quark flavor hierarchy in these models. A testable prediction of this ansatz is the neutrino mixing, U_{e3}, which should be observable in planned long baseline experiments.

hep-ph↗

arXiv2009

Neutron-Anti-Neutron Oscillation: Theory and Phenomenology

The discovery of neutrino masses has provided strong hints in favor of the possibility that B-L symmetry is an intimate feature of physics beyond the standard model. I discuss how important information about this symmetry as well as other scenarios for TeV scale new physics can be obtained from the baryon number violating process, neutron-anti-neutron oscillation. This article presents an overview of different aspects of neutron-anti-neutron oscillation and is divided into the following parts : (i) the phenomenon; (ii) the physics, (iii) plausible models and (iv) applications to cosmology. In particular, it is argued how the discovery of $n-\bar{n}$ oscillation can significantly affect our thinking about simple grand unified theory paradigms for physics beyond the standard model, elucidate the nature of forces behind neutrino mass and provide a new microphysical view of the origin of matter in the universe.

hep-ph↗

arXiv2008

Seesaw Extended MSSM and Anomaly Mediation without Tachyonic Sleptons

Superconformal anomalies provide an elegant and economical way to understand the soft breaking parameters in SUSY models; however, implementing them leads to the several undesirable features including: tachyonic sleptons and electroweak symmetry breaking problems in both the MSSM and the NMSSM. Since these two theories also have the additonal problem of massless neutrinos, we have reconsidered the AMSB problems in a class of models that extends the NMSSM to explain small neutrino masses via the seesaw mechanism. In a recent paper, we showed that for a class of minimal left-right extensions, a built-in mechanism exists which naturally solves the tachyonic slepton problem and provides new alternatives to the MSSM that also have automatic R-parity conservation. In this paper, we discuss how electroweak symmetry breaking arises in this model through an NMSSM-like low energy theory with a singlet VEV, induced by the structure of the left-right extension and of the right magnitude. We then study the phenomenological issues and find: the LSP is an Higgsino-wino mix, new phenomenology for chargino decays to the LSP, degenerate same generation sleptons and a potential for a mild squark-slepton degeneracy. We also discuss possible collider signatures and the feasibility of dark matter in this model.

hep-ph↗

arXiv2008

Neutrino Mass Hierarchy and neutron-anti-neutron Oscillation from Baryogenesis

It has been recently proposed that the matter-antimatter asymmetry of the universe may have its origin in "post-sphaleron baryogenesis" (PSB). It is a TeV scale mechanism that is testable at the LHC and other low energy experiments. In this paper we present a theory of PSB within a quark-lepton unified scheme based on the gauge group $SU(2)_L\times SU(2)_R\times SU(4)_c$ that allows a direct connection between the baryon asymmetry and neutrino mass matrix. The flavor changing neutral current constraints on the model allow successful baryogenesis only for an inverted mass hierarchy for neutrinos, which can be tested in the proposed long base line neutrino experiments. The model also predicts observable neutron--antineutron oscillation accessible to the next generation of experiments as well as TeV scale colored scalars within reach of LHC.

hep-ph↗

arXiv2008

DUSEL Theory White Paper

The NSF has chosen the site for the Deep Underground Science and Engineering Laboratory (DUSEL) to be in Lead, South Dakota. In fact, the state of South Dakota has already stepped up to the plate and contributed its own funding for the proposed lab, see http://www.sanfordlaboratoryathomestake.org/index.html. The final decision by NSF for funding the Initial Suite of Experiments for DUSEL will be made early in 2009. At that time the NSF Science Board must make a decision. Of order 200 experimentalists have already expressed an interest in performing experiments at DUSEL. In order to assess the interest of the theoretical community, the Center for Cosmology and Astro-Particle Physics (CCAPP) at The Ohio State University (OSU) organized a 3-day DUSEL Theory Workshop in Columbus, Ohio from April 4 - 6, 2008. The workshop focused on the scientific case for six proposed experiments for DUSEL: long baseline neutrino oscillations, proton decay, dark matter, astrophysical neutrinos, neutrinoless double beta decay and N-Nbar oscillations. The outcome of this workshop is the DUSEL Theory White paper addressing the scientific case at a level which may be useful in the decision making process for policy makers at the NSF and in the U.S. Congress. In order to assess the physics interest in the DUSEL project we have posted the DUSEL Theory White paper on the following CCAPP link http://ccapp.osu.edu/whitepaper.html . Please read the white paper and, if you are interested, use the link to show your support by co-signing the white paper.

hep-ph↗