5,430 research outputs found

    Lepton-number violation and right-handed neutrinos in Higgs-less effective theories

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    Following previous work, we identify a symmetry S_nat that generalizes the concept of custodial symmetry, keeping under control deviations from the Standard Model (SM). To realize S_nat linearly, the space of gauge fields has to be extended. Covariant constraints formulated in terms of spurions reduce S_nat back to SU(2)_L x U(1)_Y. This allows for a covariant introduction of explicit S_nat-breaking parameters. We assume that S_nat is at play in a theory of electroweak symmetry-breaking without a light Higgs particle. We describe some consequences of this assumption, using a non-decoupling effective theory in which the loop expansion procedure is based on both momentum and spurion power counting, as in Chiral Perturbation Theory. A hierarchy of lepton-number violating effects follows. Leading corrections to the SM are non-oblique. The effective theory includes stable light right-handed neutrinos, with an unbroken Z_2 symmetry forbidding neutrino Dirac masses. nu_R contribution to dark matter places bounds on their masses.Comment: Corresponds to published version: added subsection VI-D about order-of-magnitude estimate

    Classical trajectories and quantum supersymmetry

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    We analyze a supersymmetric system with four flat directions. We observe several interesting properties, such as the coexistence of the discrete and continuous spectrum in the same range of energies. We also solve numerically the classical counterpart of this system. A similar analysis is then done for an alike, but non-supersymmetric system. The comparison of theses classical and quantum results may serve as a suggestion about classical manifestations of supersymmetry.Comment: 16 pages, 12 figures, 5 tables, some misspellings correcte

    The flavor physics in unified gauge theory from an S_3*P discrete symmetry

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    We investigate the phenomenological implication of the discrete symmetry S_3*P on flavor physics in SO(10) unified theory. We construct a minimal renormalizable model which reproduces all the masses and mixing angle of both quarks and leptons. As usually the SO(10) symmetry gives up to relations between the down sector and the charged lepton masses. The underlining discrete symmetry gives a contribution (from the charged lepton sector) to the PMNS mixing matrix which is bimaximal. This gives a strong correlation between the down quark and charged lepton masses, and the lepton mixing angles. We obtain that the small entries V_{ub}, V_{cb}, V_{td}, and V_{ts} in the CKM matrix are related to the small value of the ratio "dm^2_{sol}/dm^2_{atm}": they come from both the S_2*P structure of our model and the small ratio of the other quark masses with respect to m_t.Comment: 5 pages, revtex4. v2: published versio

    (De)Constructing Dimensions

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    We construct renormalizable, asymptotically free, four dimensional gauge theories that dynamically generate a fifth dimension.Comment: 10 pages, late

    Evolution of Structure Functions And Their Moments In Chiral Field Theory

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    Evolution of structure functions and their moments at low and moderate Q2Q^2 is studied in the chiral field theory. Evolution equations based on perturbation expansion in the coupling constant of the effective theory are derived and solved for the moments. The kernels of evolution arising from different processes have been calculated with contributions from direct and cross channels, the interference terms being non-negligible in the kinematic regions under consideration. This is shown to lead to flavor-dependence of the kernels which manifests in observable effects. The invalidity of the probabilistic approach to the evolution process is also pointed out.Comment: 18 pages, LaTex, 5 figure

    Proton Decay and Fermion Masses in Supersymmetric SO(10) Model with Unified Higgs Sector

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    We make a detailed analysis on the proton decay in a supersymmetric SO(10) model proposed by K.Babu, I.Gogoladze, P.Nath, and R. Syed. We introduce quark mixing, and find that this model can generate fermion mass without breaking the experimental bound on proton decay. We also predict large CKM unitarity violations.Comment: 7 page

    Tri-N-ification

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    We consider a natural generalization of trinification to theories with 3N SU(3) gauge groups. These theories have a simple moose representation and a gauge boson spectrum that can be interpreted via the deconstruction of a 5D theory with unified symmetry broken on a boundary. Although the matter and Higgs sectors of the theory have no simple extra-dimensional analog, gauge unification retains features characteristic of the 5D theory. We determine possible assignments of the matter and Higgs fields to unified multiplets and present theories that are viable alternatives to minimal trinified GUTs.Comment: 21 pages LaTeX, 6 eps figure

    Staggered Heavy Baryon Chiral Perturbation Theory

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    Although taste violations significantly affect the results of staggered calculations of pseudoscalar and heavy-light mesonic quantities, those entering staggered calculations of baryonic quantities have not been quantified. Here I develop staggered chiral perturbation theory in the light-quark baryon sector by mapping the Symanzik action into heavy baryon chiral perturbation theory. For 2+1 dynamical quark flavors, the masses of flavor-symmetric nucleons are calculated to third order in partially quenched and fully dynamical staggered chiral perturbation theory. To this order the expansion includes the leading chiral logarithms, which come from loops with virtual decuplet-like states, as well as terms the order of the cubed pion mass, which come from loops with virtual octet-like states. Taste violations enter through the meson propagators in loops and tree-level terms the order of the squared lattice spacing. The pattern of taste symmetry breaking and the resulting degeneracies and mixings are discussed in detail. The resulting chiral forms are appropriate to lattice results obtained with operators already in use and could be used to study the restoration of taste symmetry in the continuum limit. I assume that the fourth root of the fermion determinant can be incorporated in staggered chiral perturbation theory using the replica method.Comment: 54 pages; v2: corrected discussion in Sec. III.C, conclusions unchange
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