Top quark mass in supersymmetric SO(10) unification (original) (raw)
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Fermion masses, mixing angles, and supersymmetric SO(10) unification
Physical Review D, 1995
We reanalyse the problem of fermion masses in supersymmetric SO(10) grand unified models. In the minimal model, both low energy Higgs doublets belong to the same 10 representation of SO(10) implying the unification not only of the gauge but also of the third generation Yukawa couplings. These models predict large values of tan β ∼ 50. In this paper we study the effects of departing from the minimal conditions in order to see if we can find models with a reduced value of tan β. In order to maintain predictability, however, we try to do this with the addition of only one new parameter. We still assume that the fermion masses arise from interactions of the spinor representations with a single 10 representation, but this 10 now only contains a part of the two light Higgs doublets. This enables us to introduce one new parameter ω = λ b /λ t. For values of ω ≪ 1 we can in principle reduce the value of tan β. In fact, ω is an overall factor which multiplies the down quark and charged lepton Yukawa matrices. Thus the theory is still highly constrained. We show that the first generation quark masses and the CP-violation parameter ǫ K are sufficient to yield strong constraints on the phenomenologically allowed models. In the end, we find that large values of tan β are still preferred.
Third generation Yukawa couplings unification in supersymmetric SO(10) model
The European Physical Journal C, 1998
In the minimal supersymmetric standard model (MSSM) contained in SUSY SO(10), top-b-τ Yukawa unification is achieved at the intermediate mass scale MI 10 13.10 GeV using the recent world average experimental value of the top-quark mass, mtop = 175±6 GeV, which has been directly established by CDF and D0 experiments at the Tevatron Collider. It is also observed that the Yukawa couplings unification scale MI can be further decreased by taking lower input values of the top-quark mass. This trend indicates the possible existence of an intermediate symmetry breaking scale in SUSY SO(10). The present finding does not agree with the earlier notion that the third generation Yukawa couplings unification should occur at the GUT scale MU .
Physical Review D, 1994
We calculate the two loop contributions to the predictions of the mass scales in an SO(10) grand unified theory. We consider the modified unification scale boundary conditions due to the non-renormalizable higher dimensional terms arising from quantum gravity or spontaneous compactification of extra dimensions in Kaluza-Klein type theory. We find the range of these couplings which allows left-right symmetry to survive till very low energy (as low as ∼ TeV) and still be compatible with the latest values of sin 2 θ W and α s derived from LEP. We consider both the situation when the left-right parity is broken and conserved.We consider both supersymmetric and nonsupersymmertic versions of the SO(10) theory.Taking the D-conserved non-susy case as an example we calculate the effects of moderate threshold uncertainties at the heavy scale, due to the unknown higgs masses,on the gravity induced couplings.
Physical Review Letters, 1991
We run all the couplings of the minimal supersymmetric (SUSY) extension of the standard model, taking account of the Yukawa sector. After identifying the scale at which the gauge couplings unify, we place bounds on the top-quark mass by requiring equality of the bottom-quark and~Yukawa couplings at that scale. For M&Us&=1 TeV, MI, =4.6 GeV, we find 139~M~194 GeV, which remarkably satisfy the p-parameter bound. Furthermore, using the minimal SUSY boundary condition on the scalar quartic coupling, we obtain bounds for the mass of the Higgs boson, 44~M H;«s~120 GeV.
Supersymmetric SO(10) Grand Unified Models with Yukawa Unification and a Positive μ Term
Physical Review Letters, 2001
Supersymmetric grand unified models based on SO(10) gauge symmetry have many desireable features, including the unification of Yukawa couplings. Including D-term contributions to scalar masses arising from the breakdown of SO(10), Yukawa coupling unification only to 30% can be achieved in models with a positive superpotential Higgs mass. The superparticle mass spectrum is highly constrained, and yields relatively light top squarks and charginos. Surprisingly, the pattern of GUT scale soft SUSY breaking masses are close to those found in the context of inverted hierarchy models. Our analysis supports the idea that the low energy MSSM parameter space is an approximate SO(10) inspired fixed point.
Precise Predictions for the Masses and Couplings in the Minimal Supersymmetric Standard Model
1995
We present selected results of our program to determine the masses, gauge couplings, and Yukawa couplings of the minimal supersymmetric model in a full oneloop calculation. We focus on the precise prediction of the strong coupling α s (M Z ) in the context of supersymmetric unification. We discuss the importance of including the finite corrections and demonstrate that the leading-logarithmic approximation can significantly underestimate α s (M Z ) when some superpartner masses are light. We show that if GUT thresholds are ignored, and the superpartner masses are less than about 500 GeV, the prediction for α s (M Z ) is quite large. We impose constraints from nucleon decay experiments and find that minimal SU(5) GUT threshold corrections increase α s (M Z ) over most of the parameter space. We also consider the missing-doublet SU(5) model and find that it predicts preferred values for the strong coupling, even for a very light superpartner spectrum. We briefly discuss predictions for the bottom-quark mass in the small tan β region. * M 0 is the universal scalar mass, M 1/2 is the universal gaugino mass, and A 0 is the universal A-term. † See Ref.
Predictions for Higgs and Supersymmetry Spectra from SO(10) Yukawa Unification with μ > 0
Physical Review Letters, 2002
We use t, b, τ Yukawa unification to constrain SUSY parameter space. We find a narrow region survives for µ > 0 (suggested by b → sγ and the anomalous magnetic moment of the muon) with A 0 ∼ −1.9 m 16 , m 10 ∼ 1.4 m 16 , m 16 ∼ 1200−3000 GeV and µ, M 1/2 ∼ 100−500 GeV. Demanding Yukawa unification thus makes definite predictions for Higgs and sparticle masses.
Physical Review D, 2002
In simple SO(10) SUSY GUTs the top, bottom and tau Yukawa couplings unify at the GUT scale. A naive renormalization group analysis, neglecting weak scale threshold corrections, leads to moderate agreement with the low energy data. However it is known that intrinsically large threshold corrections proportional to tan β ∼ m t (M Z)/m b (M Z) ∼ 50 can nullify these t, b, τ mass predictions. In this paper we turn the argument around. Instead of predicting fermion masses, we use the constraint of Yukawa unification and the observed values M t , m b (m b), M τ to constrain SUSY parameter space. We find a narrow region survives for µ > 0 with µ, M 1/2 << m 16 , A 0 ≈ −1.9 m 16 and m 16 > 1200 GeV. Demanding Yukawa unification thus makes definite predictions for Higgs and sparticle masses. In particular we find a light higgs with mass m 0 h = 114 ± 5 ± 3 GeV and a light stop with (mt 1) M IN ∼ 450 GeV and mt 1 << mb 1. In addition, we find a light chargino and a neutralino LSP. It is also significant that in this region of parameter space the SUSY contribution to the muon anomalous magnetic moment a SU SY µ < 16 × 10 −10 .
Determining heavy mass parameters in supersymmetric SO(10) models
Physical Review D, 2008
Extrapolations of soft scalar mass parameters in supersymmetric theories can be used to explore elements of the physics scenario near the grand unification scale. We investigate the potential of this method in the lepton sector of SO(10) which incorporates right-handed neutrino superfields. The method is exemplified in two models by exploring limits on the precision that can be expected from coherent LHC and e + e − collider analyses in the reconstruction of the fundamental scalar mass parameters at the unification scale and of the D-terms related to the breaking of grand unification symmetries. In addition, the mass of the third-generation right-handed neutrino can be estimated in seesaw scenarios. Even though the models are simplified and not intended to account for all aspects of a final comprehensive SO(10) theory, they provide nevertheless a valid base for identifying essential elements that can be inferred on the fundamental high-scale theory from high-energy experiments. *