93 research outputs found

    Predictions for Higgs and SUSY spectra from SO(10) Yukawa Unification with mu > 0

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    We use t,b,τt, b, \tau Yukawa unification to constrain SUSY parameter space. We find a narrow region survives for μ>0\mu > 0 (suggested by \bsgam and the anomalous magnetic moment of the muon) with A01.9m16A_0 \sim - 1.9 m_{16}, m101.4m16m_{10} \sim 1.4 m_{16}, m1612003000m_{16} \sim 1200 -3000 \gev and μ,M1/2100500\mu, M_{1/2} \sim 100 - 500 \gev. Demanding Yukawa unification thus makes definite predictions for Higgs and sparticle masses.Comment: 10 pages, 3 figures, revised version to be published in PR

    Sparticle mass spectra from SU(5) SUSY GUT models with bτb-\tau Yukawa coupling unification

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    Supersymmetric grand unified models based on the gauge group SU(5) often require in addition to gauge coupling unification, the unification of b-quark and τ\tau-lepton Yukawa couplings. We examine SU(5) SUSY GUT parameter space under the condition of bτb-\tau Yukawa coupling unification using 2-loop MSSM RGEs including full 1-loop threshold effects. The Yukawa-unified solutions break down into two classes. Solutions with low tan\beta ~3-11 are characterized by gluino mass ~1-4 TeV and squark mass ~1-5 TeV. Many of these solutions would be beyond LHC reach, although they contain a light Higgs scalar with mass <123 GeV and so may be excluded should the LHC Higgs hint persist. The second class of solutions occurs at large tan\beta ~35-60, and are a subset of tbτt-b-\tau unified solutions. Constraining only bτb-\tau unification to ~5% favors a rather light gluino with mass ~0.5-2 TeV, which should ultimately be accessible to LHC searches. While our bτb-\tau unified solutions can be consistent with a picture of neutralino-only cold dark matter, invoking additional moduli or Peccei-Quinn superfields can allow for all of our Yukawa-unified solutions to be consistent with the measured dark matter abundance.Comment: 19 pages, 5 figures, 1 table, PDFLate

    Neutrino Masses and Lepton-Flavor Violation in Supersymmetric Models with lopsided Froggatt-Nielsen charges

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    We analyze in detail lepton-flavor violation (LFV) in the charged-lepton sector such as μeγ\mu \to e \gamma, τμγ\tau \to \mu \gamma, μeee\mu \to eee and the μe\mu \to e conversion in nuclei, within the framework of supersymmetric models with lopsided Froggatt--Nielsen charges, in which the large mixing in the neutrino sector as well as small mixings in the quark sector can be naturally accommodated. We show that the present experimental limits on the LFV processes already exclude some of the models. The future proposed search for LFV, especially in muon processes, can provide a significant probe to this framework. We also stress the importance of the measurement of Ue3MNSU^{MNS}_{e3} in neutrino experiments, and the fact that the KamLAND experiment could play a significant role to test a certain class of models.Comment: 33 pages, 20 figure

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    Particle Physics Approach to Dark Matter

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    We review the main proposals of particle physics for the composition of the cold dark matter in the universe. Strong axion contribution to cold dark matter is not favored if the Peccei-Quinn field emerges with non-zero value at the end of inflation and the inflationary scale is superheavy since, under these circumstances, it leads to unacceptably large isocurvature perturbations. The lightest neutralino is the most popular candidate constituent of cold dark matter. Its relic abundance in the constrained minimal supersymmetric standard model can be reduced to acceptable values by pole annihilation of neutralinos or neutralino-stau coannihilation. Axinos can also contribute to cold dark matter provided that the reheat temperature is adequately low. Gravitinos can constitute the cold dark matter only in limited regions of the parameter space. We present a supersymmetric grand unified model leading to violation of Yukawa unification and, thus, allowing an acceptable b-quark mass within the constrained minimal supersymmetric standard model with mu>0. The model possesses a wide range of parameters consistent with the data on the cold dark matter abundance as well as other phenomenological constraints. Also, it leads to a new version of shifted hybrid inflation.Comment: 32 pages including 6 figures, uses svmult.cls, some clarifications added, lectures given at the Third Aegean Summer School "The Invisible Universe: Dark Matter and Dark Energy", 26 September-1 October 2005, Karfas, Island of Chios, Greece (to appear in the proceedings

    Higgs-Mediated B0>μ+μB^0 -> \mu^+ \mu^- in Minimal Supersymmetry

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    In this letter we demonstrate a new source for large flavor-changing neutral currents within the minimal supersymmetric standard model. At moderate to large tan(beta), it is no longer possible to diagonalize the masses of the quarks in the same basis as their Yukawa couplings. This generates large flavor-violating couplings of the form bˉRdLH\bar b_R d_L H and bˉRsLH\bar b_R s_L H where H is any of the three neutral, physical Higgs bosons. These new couplings lead to rare processes in the B system such as B0>μ+μB^0 -> \mu^+ \mu^- decay and B-Bbar mixing. We show that the latter is anomalously suppressed, while the former is in the experimentally interesting range. Current limits on B0>μ+μB^0 -> \mu^+ \mu^- already provide nontrivial constraints on models of moderate to large tan(beta), with an observable signal possible at Run II of the Tevatron if m_A < 400-600 GeV, extending to the TeV range if a proposed Run III of 30/fb were to occur.Comment: 9 pages LaTeX, 1 figure. Small numerical improvement and comment on b->X_s l+l- adde

    More Model-Independent Analysis of b->s Processes

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    We study model-independently the implications of non-standard scalar and pseudoscalar interactions for the decays b ->s gamma, b -> s g, b -> s l^+l^- (l=e,mu) and B_s -> mu^+ mu^-. We find sizeable renormalization effects from scalar and pseudoscalar four-quark operators in the radiative decays and at O(alpha_s) in hadronic b decays. Constraints on the Wilson coefficients of an extended operator basis are worked out. Further, the ratios R_H = BR(B -> H mu^+ mu^-)/BR(B -> H e^+ e^-), for H=K^(*), X_s, and their correlations with B_s -> mu^+ mu^- decay are investigated. We show that the Standard Model prediction for these ratios defined with the same cut on the dilepton mass for electron and muon modes, R_H= 1 + O(m^2_mu/m^2_b), has a much smaller theoretical uncertainty (<1%) than the one for the individual branching fractions. The present experimental limit R_K < 1.2 puts constraints on scalar and pseudoscalar couplings, which are similar to the ones from current data on BR(B_s -> mu^+ mu^-). We find that new physics corrections to R_{K*} and R_{X_s} can reach 13% and 10%, respectively.Comment: 28 pages, 6 figures; Table 1 updated, two refs added (to appear in PRD

    Yukawa Unification as a Window into the Soft Supersymmetry Breaking Lagrangian

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    We study Yukawa unification, including the effects of a physical neutrino mass consistent with the Superkamiokande observations, in a string/DD-brane inspired Pati-Salam model which allows the most general non-universal scalar and gaugino masses, including the usual DD-term contributions which arise in SO(10). We investigate how the tight constraints from rare decays such as bsγb \to s \gamma and τμγ\tau \to \mu \gamma can provide information about the family dependent supersymmetry breaking soft Lagrangian, for example the trilinears associated with the second and third family. Many of our results also apply to SO(10) to which the model approximately reduces in a limiting case. In both models we find that Yukawa unification is perfectly viable providing the non-universal soft masses have particular patterns. In this sense Yukawa unification acts as a window into the soft supersymmetry breaking Lagrangian.Comment: References added. 82 pages, 57 figures, Late

    Finite Supersymmetric Threshold Corrections to CKM Matrix Elements in the Large tanβtan\beta Regime

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    We evaluate the finite 1-loop threshold corrections, proportional to tanβtan\beta, to the down quark mass matrix. These result in corrections to down quark masses and to Cabibbo-Kobayashi-Maskawa [CKM] matrix elements. The corrections to CKM matrix elements are the novel feature of this paper. For grand unified theories with large tanβ\tan\beta these corrections may significantly alter the low energy predictions of four of the CKM matrix elements and the Jarlskog parameter J, a measure of CP violation. The angles α,β\alpha,\: \beta and γ\gamma of the unitarity triangle and the ratio VubVcb|{V_{ub} \over V_{cb}}|, however, are not corrected to this order. We also discuss these corrections in the light of recent models for fermion masses. Here the corrections may be useful in selecting among the various models. Moreover, if one model fits the data, it will only do so for a particular range of SUSY parameters.Comment: 15 pages, 3 figures not included; hard copy of the figures may be obtained upon reques
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