Quasi-fixed point scenario in the modified NMSSM

The simplest extension of the MSSM that does not contradict LEP II experimental bound on the lightest Higgs boson mass at $\tan\beta\sim 1$ is the modified Next-to-Minimal Supersymmetric Standard Model (MNSSM). We investigate the renormalization of Yukawa couplings and soft SUSY breaking terms in this model. The possibility of $b$-quark and $\tau$-lepton Yukawa coupling unification at the Grand Unification scale $M_X$ is studied. The particle spectrum is analysed in the vicinity of the quasi-fixed point where the solutions of renormalization group equations are concentrated at the electroweak scale.Comment: 19 pages, 3 figures, LaTeX2

Impaired mentalizing in depression and the effects of borderline personality disorder on this relationship

Background: Mentalizing, the ability to understand the self and others as well as behaviour in terms of intentional mental states, is impaired in Borderline Personality Disorder (BPD). Evidence for mentalizing deficits in other mental disorders, such as depression, is less robust and these links have never been explored while accounting for the effects of BPD on mentalizing. Additionally, it is unknown whether BPD symptoms might moderate any relationship between depressive symptoms and mentalizing. / Methods: Using multivariate regression modelling on cross-sectional data obtained from a sample of 274 participants recruited from clinical settings, we investigated the association between mentalizing impairment and depression and examined whether this was moderated by the presence and number of concurrent BPD symptoms, while adjusting for socio-demographic confounders. / Results: Impaired mentalizing was associated with depressive symptoms, after adjustment for socio-demographic confounders and BPD symptoms (p = 0.002, β = − 0.18). BPD symptoms significantly moderated the association between impaired mentalizing and depressive symptoms (p = 0.003), with more severe borderline symptoms associated with a stronger effect of poor mentalization on increased depressive symptoms. / Conclusion: Mentalizing impairments occur in depression even after adjusting for the effect of BPD symptoms. Our findings help further characterise mentalizing impairments in depression, as well as the moderating effect of BPD symptoms on this association.. Further longitudinal work is required to investigate the direction of association

Type II See-Saw Mechanism, Deviations from Bimaximal Neutrino Mixing and Leptogenesis

A possible interplay of both terms in the type II see-saw formula is illustrated by presenting a novel way to generate deviations from exact bimaximal neutrino mixing. In type II see-saw mechanism with dominance of the non-canonical SU(2)_L triplet term, the conventional see-saw term can give a small contribution to the neutrino mass matrix. If the triplet term corresponds to the bimaximal mixing scheme in the normal hierarchy, the small contribution of the conventional see-saw term naturally generates non-maximal solar neutrino mixing. Atmospheric neutrino mixing is also reduced from maximal, corresponding to 1 - \sin^2 2 \theta_{23} of order 0.01. Also, small but non-vanishing U_{e3} of order 0.001 is obtained. It is also possible that the \Delta m^2 responsible for solar neutrino oscillations is induced by the small conventional see-saw term. Larger deviations from zero U_{e3} and from maximal atmospheric neutrino mixing are then expected. This scenario links the small ratio of the solar and atmospheric \Delta m^2 with the deviation from maximal solar neutrino mixing. We comment on leptogenesis in this scenario and compare the contributions to the decay asymmetry of the heavy Majorana neutrinos as induced by themselves and by the triplet.Comment: 22 pages, 3 figures. Final corrections, matches version in PR

Infrared quasi-fixed solutions in the NMSSM

The considerable part of the parameter space in the MSSM corresponding to the infrared quasi fixed point scenario is almost excluded by LEP II bounds on the lightest Higgs boson mass. In the NMSSM the mass of the lightest Higgs boson reaches its maximum value in the strong Yukawa coupling limit when Yukawa couplings are essentially larger than gauge ones at the Grand Unification scale. In this limit the solutions of the renormalisation group equations are attracted to the infrared and Hill type effective fixed lines or surfaces in the Yukawa coupling parameter space. They are concentrated in the vicinity of quasi fixed points for $Y_i(0)\to\infty$. However the solutions are attracted to such points rather weakly. For this reason when all $Y_i(0)\sim 1$ the solutions of the renormalisation group equations are gathered near a line in the Hill type effective surface. In the paper the approximate solutions for the NMSSM Yukawa couplings are given. The possibility of $b$--quark and $\tau$--lepton Yukawa coupling unification at the scale $M_{X}$ is also discussed.Comment: 32 pages, 8 figures included, LaTeX 2

Higgs bosons in the simplest SUSY models

Nowadays in the MSSM the moderate values of $\tan\beta$ are almost excluded by LEP II lower bound on the lightest Higgs boson mass. In the Next-to-Minimal Supersymmetric Standard Model the theoretical upper bound on it increases and reaches maximal value in the strong Yukawa coupling limit when all solutions of renormalization group equations are concentrated near the quasi-fixed point. For calculation of Higgs boson spectrum the perturbation theory method can be applied. We investigate the particle spectrum in the framework of the modified NMSSM which leads to the self-consistent solution in the strong Yukawa coupling limit. This model allows one to get $m_h\sim 125$ GeV at values of $\tan\beta\ge 1.9$. In the investigated model the lightest Higgs boson mass does not exceed $130.5\pm 3.5$ GeV. The upper bound on the lightest CP-even Higgs boson mass in more complicated supersymmetric models is also discussed.Comment: 27 pages, 5 figures included, LaTeX 2e. Plenary talk at the Conference of RAS Nuclear Physics Department 2000 in ITEP, Moscow, Russia; to appear in Phys. Atom. Nuc

Neutrino Mass and Grand Unification

Seesaw mechanism appears to be the simplest and most appealing way to understand small neutrino masses observed in recent experiments. It introduces three right handed neutrinos with heavy masses to the standard model, with at least one mass required by data to be close to the scale of conventional grand unified theories. This may be a hint that the new physics scale implied by neutrino masses and grand unification of forces are one and the same. Taking this point of view seriously, I explore different ways to resolve the puzzle of large neutrino mixings in grand unified theories such as SO(10) and models based on its subgroup $SU(2)_L\times SU(2)_R\times SU(4)_c$.Comment: 17 pages, 5 figures; Invited talk at the Nobel Symposium 129 on Neutrinos at Haga Slott, Sweden, August, 200

Particle spectrum in the modified NMSSM in the strong Yukawa coupling limit

A theoretical analysis of solutions of renormalisation group equations in the MSSM corresponding to the quasi-fixed point conditions shows that the mass of the lightest Higgs boson in this case does not exceed $94\pm 5\text{GeV}$. It means that a substantial part of the parameter space of the MSSM is practically excluded by existing experimental data from LEP II. In the NMSSM the upper bound on the lightest Higgs boson mass reaches its maximum in the strong Yukawa coupling regime, when Yukawa constants are considerably larger the gauge ones on the Grand Unification scale. In this paper a particle spectrum in a simple modification of NMSSM which leads to a self-consistent solution in the considered region of the parameter space is studied. This model allows one to get $m_h\sim 125\text{GeV}$ even for comparatively low values of $\tan\beta\ge 1.9$. For an analysis of the Higgs boson spectrum and neutralino spectrum a method for diagonalisation of mass matrices proposed formerly is used. The mass of the lightest Higgs boson in this model does not exceed $130.5\pm 3.5\text{GeV}$.Comment: 34 pages, 5 figures included, LaTeX 2

Large Neutrino Mixing from Renormalization Group Evolution

The renormalization group evolution equation for two neutrino mixing is known to exhibit nontrivial fixed point structure corresponding to maximal mixing at the weak scale. The presence of the fixed point provides a natural explanation of the observed maximal mixing of $\nu_{\mu}-\nu_{\tau}$ if the $\nu_{\mu}$ and $\nu_{\tau}$ are assumed to be quasi-degenerate at the seesaw scale without constraining on the mixing angles at that scale. In particular, it allows them to be similar to the quark mixings as in generic grand unified theories. We discuss implementation of this program in the case of MSSM and find that the predicted mixing remains stable and close to its maximal value, for all energies below the $O$(TeV) SUSY scale. We also discuss how a particular realization of this idea can be tested in neutrinoless double beta decay experiments.Comment: Latex file, 21 pages and 4 ps figures include

Preheating in Supersymmetric Hybrid Inflation

We study preheating in a general class of supersymmetric hybrid inflation model. Supersymmetry leads to only one coupling constant in the potential and thus only one natural frequency of oscillation for the homogeneous fields, whose classical evolution consequently differs from that of a general (non-supersymmetric) hybrid model. We emphasise the importance of mixing effects in these models which can significantly change the rate of production of particles. We perform a general study of the rate of production of the particles associated with the homogeneous fields, and show how preheating is efficient in producing these quanta. Preheating of other particle species will be model dependent, and in order to investigate this we consider a realistic working model of supersymmetric hybrid inflation which solves the strong-CP problem via an approximate Peccei-Quinn symmetry, which was proposed by us previously. We study axion production in this model and show that properly taking into account the mixing between the fields suppresses the axion production, yet enhances the production of other particles. Finally we demonstrate the importance of backreaction effects in this model which have the effect of shutting off axion production, leaving the axion safely within experimental bounds.Comment: 37 pages, Latex, 11 eps figures, 14 ps (colour) figure