4,325 research outputs found

    Implications of Non-universal Soft Masses on Gauge Coupling Unification

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    We study the gauge coupling unification of the minimal supersymmetric standard model with non-universal soft scalar and gaugino masses. The unification scale of the gauge couplings is estimated for non-universal cases. It is sensitive to the non-universality. It turns out that these cases can be combined with the assumption of string unification, which leads to a prediction of sin2θW(MZ)\sin^2 \theta_W(M_Z) and k1k_1, the normalisation of the U(1)YU(1)_Y generator. String unification predicts k1=1.31.4k_1=1.3 - 1.4. These values have non-trivial implications on string model building. Two-loop corrections are also calculated. Some of these cases exhibit a large discrepancy between experiment and string unification. We calculate string threshold corrections to explain the discrepancy.Comment: 25 pages, Latex, 4 figures (not included

    Probing SO(10) symmetry breaking patterns through sfermion mass relations

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    We consider supersymmetric SO(10) grand unification where the unified gauge group can break to the Standard Model gauge group through different chains. The breaking of SO(10) necessarily involves the reduction of the rank, and consequent generation of non-universal supersymmetry breaking scalar mass terms. We derive squark and slepton mass relations, taking into account these non-universal contributions to the sfermion masses, which can help distinguish between the different chains through which the SO(10) gauge group breaks to the Standard Model gauge group. We then study some implications of these non-universal supersymmetry breaking scalar masses for the low energy phenomenology.Comment: 13 pages, latex using revtex4, contains 2 figures, replaced with version accepted for publicatio

    Implications of non-universality of soft terms in supersymmetric grand unified theories

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    Most discussions of supersymmetric grand unified theories assume universality of the soft supersymmetry breaking terms at the grand scale. We point out that the behaviour of these theories might change significantly in the presence of non--universal soft terms. Particularly in SO(10)--like models with a large value of tanβ\beta we observe a decisive change of predictions, allowing the presence of relatively light gauginos as well as small supersymmetric corrections to the b--quark mass. Some results remain rather stable, including the μ\mu--M1/2M_{1/2} correlation. Models with small tanβ\beta seem to be less affected by non--universality which mainly leads to the new possibility of small m0m_{0} (i.e. the squark and slepton soft mass parameter), excluded in the universal case.Comment: 15 pages (Latex) plus 5 figures (uuencoded postscript file). TUM-HEP 201/9

    Crosschecks for Unification at the LHC

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    Experiments at the Large Hadron Collider (LHC) might test the picture of supersymmetric Grand Unification in particle physics. We argue that the identification of gaugino masses is the most promising step in this direction. Mass predictions for gauginos are pretty robust and often related to the values of the gauge couplings constants. They might allow a meaningful crosscheck for grand unification, at least in simple schemes like gravity, anomaly or mirage mediation.Comment: 23 pages, 8 figure

    Sparticle Mass Spectrum in Grand Unified Theories

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    We carry out a detailed analysis of sparticle mass spectrum in supersymmetric grand unified theories. We consider the spectroscopy of the squarks and sleptons in SU(5) and SO(10) grand unified theories, and show how the underlying supersymmetry breaking parameters of these theories can be determined from a measurement of different sparticle masses. This analysis is done analytically by integrating the one-loop renormalization group equations with appropriate boundary conditions implied by the underlying grand unified gauge group. We also consider the impact of non-universal gaugino masses on the sparticle spectrum, especially the neutralino and chargino masses which arise in supersymmetric grand unified theories with non-minimal gauge kinetic function. In particular, we study the interrelationships between the squark and slepton masses which arise in grand unified theories at the one-loop level, which can be used to distinguish between the different underlying gauge groups and their breaking pattern to the Standard Model gauge group. We also comment on the corrections that can affect these one-loop results.Comment: 19 pages, 6 figure

    Non-Universal Gaugino Masses in Supersymmetric SO(10)

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    We consider SUSY SO(10) models in which SUSY breaking occurs via an F-term which does not transform as an SO(10) singlet. This results in non-universal GUT-scale gaugino masses leading to a different pattern of sparticle masses from what is expected in the minimal supergravity model (mSUGRA). We study three breaking chains of SO(10) down to the standard model through SU(4)\timesSU(2)\timesSU(2), SU(2)×\timesSO(7) and `flipped' SU(5) achieved by the representations 54 and 210 which appear in the symmetric product of two SO(10) adjoints. We examine the phenomenological implications of the different boundary conditions corresponding to the different breaking chains and present the sparticle spectrum.Comment: 23 pages, 3 figures, 2 tables, corrected typos, discussion and references added, final version accepted for publication on NP

    Supergravity Unified Models

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    The development of supergravity unified models and their implications for current and future experiments are discussed.Comment: Latex, 21 pages, to appear in book "Perspectives on Supergravity", World Scientific, Editor G. Kane; reference numbers and minor typos correcte

    Prospects for the direct detection of neutralino dark matter in orbifold scenarios

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    We analyse the phenomenology of orbifold scenarios from the heterotic superstring, and the resulting theoretical predictions for the direct detection of neutralino dark matter. In particular, we study the parameter space of these constructions, computing the low-energy spectrum and taking into account the most recent experimental and astrophysical constraints, as well as imposing the absence of dangerous charge and colour breaking minima. In the remaining allowed regions the spin-independent part of the neutralino-proton cross section is calculated and compared with the sensitivity of dark matter detectors. In addition to the usual non universalities of the soft terms in orbifold scenarios due to the modular weight dependence, we also consider D-term contributions to scalar masses. These are generated by the presence of an anomalous U(1), providing more flexibility in the resulting soft terms, and are crucial in order to avoid charge and colour breaking minima. Thanks to the D-term contribution, large neutralino detection cross sections can be found, within the reach of projected dark matter detectors.Comment: 51 pages, 25 figure

    Higgs and Supersymmetric Particle Signals at the Infrared Fixed Point of the Top Quark Mass

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    We study the properties of the Higgs and supersymmetric particle spectrum associated with the infrared fixed point solution of the top quark mass in the MSSM. We concentrate on the possible detection of these particles, analysing the deviations from the Standard Model predictions for the leptonic and hadronic variables measured at LEP and for the decay rate bsγb\rightarrow s\gamma. We consider the low and moderate tanβ\tan \beta regime, and we study both, the cases of universal and non--universal soft supersymmetry breaking parameters at high energies. In the first case, for any given value of the top quark mass, the Higgs and sparticle spectra are completely determined as a function of two soft supersymmetry breaking parameters. In the case of non--universality, instead, the strong correlations between the sparticle masses are relaxed, allowing a richer structure for the precision data variables. We show, however, that the requirement that the low energy theory proceeds from a grand unified theory with a local symmetry group including SU(5)SU(5), strongly constrains the set of possible indirect experimental signatures. As a general feature, whenever a significant deviation from the Standard Model value of the precision data variables is predicted, a light sparticle, visible at LEP2, appears in the spectrum.Comment: 42 pages, 16 figures (not included), CERN-TH.7393/9
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