The low energy effective theory and nucleon stability

We show that the Standard Model Lagrangian, including small neutrino masses, has an anomaly-free discrete Z_6 symmetry. Anomaly cancellation requires the number of family to be 3 mod 6. This symmetry can ensure the stability of the nucleon even when the threshold of new physics \Lambda is low as 10^2 GeV. All \Delta B=1 and \Delta B=2 (B is the baryon number) effective operators are forbidden by the Z_6 symmetry. \Delta B=3 operators are allowed, but they arise only at dimension 15. We suggest a simple mechanism for realizing reasonable neutrino masses and mixings even with such a low scale for \Lambda.Comment: To appear in the Proceedings of SUSY 2003, held at the University of Arizona, Tucson, AZ, 5-10 June 200

Precision electroweak constraints on Universal Extra Dimensions revisited

We reconsider the constraints on Universal Extra Dimensions (UED) models arising from precision electroweak data. We take into account the subleading contributions from new physics (expressed in terms of the X,Y ... variables), as well as two loop corrections to the Standard Model rho parameter. For the case of one extra dimension, we obtain a lower bound on the inverse compactification scale M = R^{-1} of 600 GeV (at 90% confidence level), with a Higgs mass of 115 GeV. However, in contradiction to recent claims, we find that this constraint is significantly relaxed with increasing Higgs mass, allowing for compactification scales as low as 300 GeV. LEP II data does not significantly affect these results.Comment: 15 pages, 4 eps figures, uses revtex

SU(7) SUSY GUTs with a natural intermediate scale

We investigate the SU(N) supersymmetric Grand Unified Theories with ``custodial symmetry'' mechanism to explane the doublet-triplet hierarchy. We show that in such type of SU(7) SUSY theory intermediate scale appears naturally and the correct value for sin^2(\theta)_W is predicted via vector-like matter superfields splitting. The unification appears to be closed to M_Pl for all the reasonable values of \alpha_s and M_SUSY. Due to the large unification scale the baryon number violating d=5 operator is suppressed in comparison with that in minimal SU(5) theory.Comment: 14 pages, 1 figure (epsfig style

Status Update on Selective SUSY GUT Inspired Models

We perform a status analysis of selective supersymmetric GUT models in light of recent constraints from collider and dark matter detection experiments. We find that a significant region of the parameter space of these models is still accessible to these experiments. Amongst the models we analyze, the split family model provides solutions that can explain the observed deviation in anomalous magnetic moment of the muon. Furthermore, there is a notable region of the parameter space of each model which yields the desired relic abundance for neutralino dark matter. We also present the prediction of spin independent and spin dependent neutralino cross sections in these models and find that there is parameter space which can be probed at future experiments searching for dark matter. Our analysis serves as a motivation to continue the search for supersymmetry at various experimental fronts.Comment: 23 pages, 11 figures; further discussions, figures and references adde

Small Dirac Neutrino Masses and R-parity from Anomalous U(1) Symmetry

We suggest that many of the free parameters in the supersymmetric extensions of the Standard Model can be all linked together to the existence of a non universal U(1) gauge symmetry, which has been spontaneously broken at very high scale. Such a symmetry can easily generate, via non-renormalizable operators, appropriate tree level fermion mass textures as well as the $\mu$-term of the Higgs potential. We give a general parametrization of those terms. As an output, R parity breaking terms only appear at a non-renormalizable level and linked to the Yukawa couplings, giving rise to the possibility of having an effective (exact) R parity conservation. As an interesting application of this idea we explore the case where neutrinos are Dirac particles. The scenario can be embedded in an extended SU(5) unification theory where the extra right handed neutrinos are introduced as singlets. Such theory has an exact R parity conservation and sneutrino as LSP.Comment: 16 pages, no figures. Minor changes, some clarifications and references adde

Inverse Seesaw in NMSSM and 126 GeV Higgs Boson

We consider extensions of the next-to-minimal supersymmetric model (NMSSM) in which the observed neutrino masses are generated through a TeV scale inverse seesaw mechanism. The new particles associated with this mechanism can have sizable couplings to the Higgs field which can yield a large contribution to the mass of the lightest CP-even Higgs boson. With this new contribution, a 126 GeV Higgs is possible along with order of 200 GeV masses for the stop quarks for a broad range of \tan\beta. The Higgs production and decay in the diphoton channel can be enhanced due to this new contribution. It is also possible to solve the little hierarchy problem in this model without invoking a maximal value for the NMSSM trilinear coupling and without severe restrictions on the value of \tan\beta.Comment: 15 pages, 5 figures and 5 table

125 GeV Higgs Boson From Gauge-Higgs Unification: A Snowmass white paper

In certain five dimensional gauge theories compactified on the orbifold $S^1/Z_2$ the Standard Model Higgs doublet is identified with the zero mode of the fifth component of the gauge field. This gauge-Higgs unification scenario is realized at high energies, and the Standard Model as an effective theory below the compactification scale satisfies the boundary condition that the Higgs quartic coupling vanishes at the compactification scale (gauge-Higgs condition). This is because at energies above the compactification scale, the five dimensional gauge invariance is restored and the Higgs potential vanishes as a consequence. We consider scenario where top quark Yukawa and weak gauge coupling unification can be realized and identify the compactification scale as one at which this two coupling couplings have the same value. Taking into account the experimental uncertainties in measurements of the top quark mass and the QCD coupling constant, the Higgs mass prediction of 119-126 GeV from the gauge-Higgs unification scenario is consistent with the experimentally measured value of 125-126 GeV. More precise measurements of the top quark mass and the QCD coupling constant are crucial to reduce the interval of the Higgs mass prediction and thereby test the feasibility of the gauge-Higgs unification scenario.Comment: 6 pages, 2 figures, Snowmass white paper submission, typos correcte

SO(10) as a Framework for Natural Supersymmetry

We consider an SO(10) grand unified theory in which the ratio of the SU(2)_W and SU(3)_c gaugino masses satisfy M_2/M_3 \approx 3, which results in the realization of natural supersymmetry. In the MSSM parameter space this relation looks artificial, but in the SO(10) case it results from a field with a designated vacuum expectation value. We consider two models, namely M_1:M_2:M_3=-1/5:3:1 (Case I), and M_1:M_2:M_3=-5:3:1 (Case II). Focusing on ameliorating the little hierarchy problem, we explore the parameter space of these models which yield small fine-tuning measuring parameters (natural supersymmetry) at the electroweak scale (\Delta_{EW}) as well as at the high scale (\Delta_{HS}). Although both models allow for the solution of the little hierarchy problem, the predicted sparticle spectra can differ markedly in the two cases. Depending on the ratio of the bino mass to the other gaugino masses, Case I leads to stau lepton masses of around a 100 GeV, while in Case II, the stau slepton masses are in the several TeV range. In Case I, the bino-like neutralino can be as light as 90 GeV, while the gluino is heavier than 2 TeV or so. In Case II, due to gluino-bino near degeneracy, the bino cannot be lighter than a TeV or so. Having a light neutralino with sizable bino-higgsino mixture in Case I allows the direct dark matter search experiments to test this class of models.Comment: 22 pages, 9 figures, 2 tables. arXiv admin note: text overlap with arXiv:1212.2593, arXiv:1303.696

Color Triplet Diquarks at the LHC

We consider a class of supersymmetric models containing baryon number violating processes such as observable neutron - antineutron oscillations that are mediated by color triplet diquark fields. For plausible values of the diquark-quark couplings, the scalar diquark with mass between a few hundred GeV and one TeV or so can be produced in the s-channel at the LHC and detected through its decay into a top quark and a hadronic jet.Comment: 14 pages, 2 figure

Reconciling Muon g-2, 125 GeV Higgs and Dark Matter in Gauge Mediation Models

We present a class of models in the framework of gauge mediation supersymmetry breaking where the standard model is supplemented by additional U(1) symmetry which acts only on the third generation fermions. The messenger fields carry non-trivial U(1) charge and are vector-like particles under this symmetry. This leads to additional contribution to the soft supersymmetry breaking mass terms for the third generation squarks and sleptons. In this framework we show that the muon g-2 anomaly, the observed 125 GeV Higgs boson mass and the detected relic dark matter abundance (gravitino in our case) can be simultaneously accommodated. The resolution of the muon g-2 anomaly, in particular, yields the result that the first two generation squark masses, as well the gluino mass, should be <~ 2.5 TeV, which will be tested at LHC14