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Register a new userSusy Seesaw Inflation and NMSO(10)GUT
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Charanjit S. Aulakh
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We show that Supersymmetric models with Type I seesaw neutrino masses support slow roll inflection point inflation. The inflaton is the D-flat direction labelled by the chiral invariant HLN composed of the Higgs(H), slepton(L) and conjugate sneutrino(N) superfields. The scale of inflation and fine tuning is set by the conjugate neutrino Majorana mass $M_{ u^c} sim 10^6-10^{12}$ GeV. The cubic term in the (quartic) inflaton potential is dominantly from superpotential (not soft Susy breaking) couplings. The tuning conditions are thus insensitive to soft supersymmetry breaking parameters and are generically much less stringent than for previous `A-term inflation scenarios controlled by mass scales $sim TeV$. WMAP limits on the ratio of tensor to scalar perturbations limit the scale $M$ controlling inflection point inflation: $M <7.9 times 10^{13}$ GeV. `Instant preheating is operative and dumps the inflaton energy into MSSM modes giving a high reheat temperature : $T_{rh} approx M_{ u^c}^{3/4}, 10^{6}$ GeV $sim 10^{11}- 10^{15} $ GeV. A large gravitino mass $> 50 $ TeV is therefore required to avoid over closure by reheat produced gravitinos. `Instant preheating and NLH inflaton facilitate production of right handed neutrinos during inflaton decay and thus non-thermal leptogenesis in addition to thermal leptogenesis. We show that the embedding in the fully realistic New Minimal Supersymmetric SO(10) GUT requires use of the heaviest righthanded neutrino mass as the controlling scale but the possibility of a measurable tensor scalar perturbation ratio seems marginal. We examine the parametric difficulties remaining.
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SO(10) GUT models with only small Higgs fields use higher-dimensional operators to generate realistic fermion mass matrices. In particular, a Higgs field in the spinor representation, 16^d_H, acquires a weak scale vev. We include the weak vev of the corresponding field bar{16}^u_H and investigate the effect on two successful models, one by Albright and Barr (AB) and another by Babu, Pati and Wilczek (BPW). We find that the BPW model is a particular case within a class of models with identical fermion masses and mixings. In contrast, we expect corrections to the parameters of AB-type models.
Supersymmetric $SO(10)$ grand unified models with renormalizable Yukawa couplings involving only ${bf 10}$ and $overline{bf 126}$ Higgs fields have been shown to realize the fermion masses and mixings economically. In previous works, the sum rule of the fermion mass matrices are given by inputting the quark matrices, and the neutrino mixings are predicted in this framework. Now the three neutrino mixings have been measured, and in this paper, we give the sum rule by inputting the lepton mass matrices, which makes clear certain features of the solution, especially if the vacuum expectation values of ${bf 126}+ overline{bf126}$ ($v_R$) are large and the right-handed neutrinos are heavy. We perform the $chi^2$ analyses to fit the fermion masses and mixings using the sum rule. In previous works, the best fit appears at $v_R sim 10^{13}$ GeV, and the fit at the large $v_R$ scale ($sim 10^{16}$ GeV) has been less investigated. Our expression of the sum rule has a benefit to understand the flavor structure in the large $v_R$ solution. Using the fit results, we perform the calculation of the $mu to egamma$ process and the electric dipole moment of electron, and the importance of $v_R$ dependence emerges in low energy phenomena. We also show the prediction of the CP phase in the neutrino oscillations, which can be tested in the near future.
Till today lepton flavor violation has not been observed in processes involving charged leptons. Hence, a search for it is under hot pursuit both in theories and experiments. In our current work, we investigate the rates of rare decay processes such as $tau rightarrow mu gamma$ in SU(5) SUSY GUT and found that it satisfies the current bound and is one order below the projected sensitivity. This gives a corroborative argument for the influence of the large top-Yukawa coupling at the GUT scale ($lambda_{tG}$) on flavor violating decay rates of leptons which are investigable at low energy electroweak scale $M_Z$. Secondly, we discuss the decay rates of $mu rightarrow e gamma$ & $tau rightarrow mu gamma$ in MSSM with added right handed neutrino superfields. From this, we set bounds on $tan beta$ and further, we investigate the mass of $tilde{chi}^0 _1$, the LSP, using the rates of LFV decays. In the calculations, the latest updated data from LHC, neutrino oscillation experiments and constraints on branching ratios from the MEG experiment have been used.
Proton decay is one of the most important predictions of the grand unified theory (GUT). In the supersymmetric (SUSY) GUT, proton decays via the dimension-five operators need to be suppressed. In the $SO(10)$ model where ${bf 10}+overline{bf 126}$ Higgs fields couple to fermions, neutrino oscillation parameters including the CP-violating Pontecorvo-Maki-Nakagawa-Sakata (PMNS) phase can be related to the Yukawa couplings to generate the dimension-five operators in the unified framework. We show how the suppressed proton decay depends on the PMNS phase, and stress the importance of the precise measurements of the PMNS phase as well as the neutrino 23-mixing angle. These become especially important if the SUSY particles are found around less than a few TeV at LHC and proton decays are observed at Hyper-Kamiokande and DUNE experiments in the near future.
We build explicit supersymmetric unification models where grand unified gauge symmetry breaking and supersymmetry (SUSY) breaking are caused by the same sector. Besides, the SM-charged particles are also predicted by the symmetry breaking sector, and they give the soft SUSY breaking terms through the so-called gauge mediation. We investigate the mass spectrums in an explicit model with SU(5) and additional gauge groups, and discuss its phenomenological aspects. Especially, nonzero A-term and B-term are generated at one-loop level according to the mediation via the vector superfields, so that the electro-weak symmetry breaking and 125 GeV Higgs mass may be achieved by the large B-term and A-term even if the stop mass is around 1 TeV.
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