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Register a new userPinning down the New Minimal Supersymmetric GUT
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Charanjit S. Aulakh
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We show that generic $ {bf{10oplus 120oplus {bar {126}}}}$ fits of fermion masses and mixings, using real superpotential couplings but with complex `Higgs fractions leading to complex yukawa couplings in the effective MSSM, emph{overdetermine}(by one extra constraint) the superpotential parameters of the New Minimal Supersymmetric SO(10) GUTcite{nmsgut}. Therefore fits should properly be done by generating the 24 generic fit parameters from the 23 parameters of the NMSGUT superpotential, given $tanbeta$ as input. Each numerical fit then emph{fully specifies} the parameters of the NMSGUT. An analysis of all its implications, modulo only the residual uncertainty of supersymmetry breaking parameters, is now feasible. Thus the NMSGUT offers the possibility of a confrontation between the scale of gauge unification and the fit to fermion masses due to their extractable common dependence on the NMSGUT parameters. If and when `smoking gun discoveries of Supersymmetry and Proton decay occur they will find the NMSGUT fully vulnerable to falsification.
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Supersymmetric GUTs based on SO(10) gauge group are leading contenders to describe particle physics beyond the Standard Model. Among these the New minimal supersymmetric SO(10) grand unified theory (NMSGUT) based on Higgs system 10+120+210+126+$overline{126}$ has been developing since 1982. It now successfully fits the whole standard Model gauge coupling, symmetry breaking and fermion mass-mixing data as well as the neutrino mass and mixing data in terms of NMSGUT parameters and just 6 soft supersymmetry breaking parameters defined at the GUT scale. In this thesis we study the phenomenology of NMSGUT, its implications for inflationary and Cold Dark matter cosmology and develop Renormalization group(RG) equations for the flow of NMSGUT couplings in the extreme ultraviolet. In the first part we show that superheavy threshold effects can drastically lower the SO(10) yukawa couplings required for realistic unification and this cures the long standing problem of fast proton decay in Susy GUT. Then we propose a novel Supersymmetric Seesaw inflection(SSI) scenario based upon a SU(2)_L x U(1)_R x U(1)_{B-L} invariant model, where the inflation mass is controlled by the large conjugate sneutrino mass. We show that it is much less fine-tuned and more stable than Dirac sneutrino based MSSM inflation. NMSGUT can embed SSI, and even provide a large tensor scalar ratio, but obstacles in achieving enough inflation remain. The NMSGUT Bino LSP is a good dark matter candidate when it can co-annihilate with a nearly degenerate sfermion as in fits with a light smuon. We also calculate two loop NMSGUT gauge-Yukawa Renormalization Group(RG) beta functions and show that GUT scale negative Higgs mass squared parameters required by NMSGUT fits can arise by RG flows from positive values at the Planck scale.
For points in SUSY parameter space where the sneutrino is lighter than the lightest chargino and next-to-lightest neutralino, its direct mass determination from sneutrino pair production process at e+e- collider is impossible since it decays invisibly. In such a scenario the sneutrino can be discovered and its mass determined from measurements of two-body decays of charginos produced in pairs at the ILC. Using the event generator WHIZARD we study the prospects of measuring sneutrino properties in a realistic ILC environment. In our analysis we include beamstrahlung, initial state radiation, a complete account of reducible backgrounds from SM and SUSY processes, and a complete matrix-element calculation of the SUSY signal which encompasses all irreducible background and interference contributions. We also simulate photon induced background processes using exact matrix elements. Radiation effects and the cuts to reduce background strongly modify the edges of the lepton energy spectra from which the sneutrino and chargino mass are determined. We discuss possible approaches to measure the sneutrino mass with optimal precision.
The Supersymmetric SO(10) theory (NMSO(10)GUT) based on thehfilbreak ${bf{210+126 +oot}}$ Higgs system proposed in 1982 has evolved into a realistic theory capable of fitting the known low energy Particle Physics data besides providing a Dark matter candidate and embedding Inflationary Cosmology. It dynamically resolves longstanding issues such as fast dimension five operator mediated proton decay in Susy GUTs by allowing explicit and complete calculation of crucial threshold effects at $M_{Susy}$ and $M_{GUT}$ in terms of fundamental parameters. This shows that SO(10) Yukawas responsible for observed fermion masses as well as operator dimension 5 mediated proton decay can be highly suppressed on a Higgs dissolution edge in the parameter space of GUTs with rich superheavy spectra. This novel and generically relevant result highlights the need for every realistic UV completion model with a large/infinite number of heavy fields coupled to the light Higgs doublets to explicitly account for the large wave function renormalization effects on emergent light Higgs fields in order to be considered a quantitatively well defined candidate UV completion. The NMSGUT predicts large soft Susy breaking trilinear couplings and distinctive sparticle spectra. Measurable or near measurable level of tensor perturbations- and thus large Inflaton mass scale- may be accommodated by Supersymetric Seesaw inflation within the NMSGUT based on an LHN flat direction Inflaton if the Higgs component contains contributions from heavy Higgs components. Successful NMSGUT fits suggest a emph{renormalizable} Yukawon Ultra minimal gauged theory of flavor based upon the NMSGUT Higgs structure.
We examine the extent to which it is possible to realize the NMSSM ideal Higgs models espoused in several papers by Gunion et al in the context of partially universal GUT scale boundary conditions. To this end we use the powerful methodology of nested sampling. We pay particular attention to whether ideal-Higgs-like points not only pass LEP constraints but are also acceptable in terms of the numerous constraints now available, including those from the Tevatron and $B$-factory data, $(g-2)_mu$ and the relic density $Omega h^2$. In general for this particular methodology and range of parameters chosen, very few points corresponding to said previous studies were found, and those that were found were at best $2sigma$ away from the preferred relic density value. Instead, there exist a class of points, which combine a mostly singlet-like Higgs with a mostly singlino-like neutralino coannihilating with the lightest stau, that are able to effectively pass all implemented constraints in the region $80<m_h<100$. It seems that the spin-independent direct detection cross section acts as a key discriminator between ideal Higgs points and the hard to detect singlino-like points.
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