arXiv subjects
Publications and source records attributed to S. F. King.
We analyze the phenomenology of the Higgs sector in a 5D model compactified on an $S_1/Z_2$ orbifold with a compactification scale $M_C \sim {\mathcal O}(TeV)$ where supersymmetry breaking is localized on a brane at one of the fixed points. We show that the conventional MSSM Higgs boson mass bounds in 4D can be violated when we allow the gauge sector, Higgs and third family multiplets to live in the fifth extra dimension.
I discuss the cosmological implications of neutrino mass including the cosmological relic density and dark matter, the galaxy structure limits on neutrino mass, nucleosynthesis, supernovae, cosmic rays and gamma ray bursts.
I discuss the implications of neutrino oscillations for neutrino mass patterns and mass matrices, and for neutrinoless double beta decay. I then go on to discuss the implications for cosmological relic density and dark matter, the galaxy structure limits on neutrino mass, nucleosynthesis, supernovae, cosmic rays and gamma ray bursts.
Recent SNO results strongly favour the large mixing angle (LMA) MSW solar solution. We argue that there are only two technically natural low energy neutrino mass matrix structures consistent with the LMA MSW solution, corresponding to either a hierarchy or an inverted hierarchy with pseudo-Dirac neutrinos. We first present a model-independent analysis in which we diagonalise each of these two mass matrix structures to leading order in $θ_{13}$ and extract the neutrino masses, mixing angles and phases. In this analysis we express the MNS matrix to leading order in the small angle $θ_{13}$ including the neutrino {\em and} charged lepton mixing angles and phases, the latter playing a crucial rôle for allowing the inverted hierarchy case to be consistent with the LMA MSW solution. We then consider the see-saw mechanism with right-handed neutrino dominance and show how the successful neutrino mass matrix structures may be constructed with no tuning and with small radiative corrections, leading to a full, partial or inverted neutrino mass hierarchy. In each case we derive approximate analytic relations between the input see-saw parameters and the resulting neutrino masses, mixing angles and phases, which will provide a useful guide for unified model building. For the hierarchical cases the LMA MSW solution gives a soft lower bound $|U_{e3}|\simgt 0.1$, just below the current CHOOZ limit. Both hierarchical and inverted hierarchical cases predict small $ββ_{0ν}$ with $|m_{ee}|\sim 0.01$ eV within the sensitivity of future proposals such as GENIUS. Successful leptogenesis is possible if the dominant right-handed neutrino is the heaviest one, but the leptogenesis phase is unrelated to the MNS phases.
I review promising approaches to neutrino mass models, focussing on three neutrino patterns of neutrino masses and mixing angles, and the corresponding Majorana mass matrices. I discuss the see-saw mechanism, and show how it may be applied in a very natural way to give a neutrino mass hierarchy with large atmospheric and solar angles by assuming single right-handed neutrino dominance. A theoretical framework for understanding quark and lepton (including neutrino) masses and mixing angles based on SUSY, GUTs and Family symmetry is then described, and sample models which involve single right-handed neutrino dominance are discussed.
I discuss a class of hierarchical neutrino mass models based on the see-saw mechanism with single right-handed neutrino dominance. I apply this mechanism to a string inspired SUSY Pati-Salam model and indicate how it may emerge from intersecting D-branes.
We consider twisted moduli contributions to supersymmetry breaking in effective type I string constructions involving intersecting D5_i and D9-branes using Goldstino angles to parametrise the supersymmetry breaking. It is well known that twisted moduli enter at tree-level into the gauge kinetic functions, and can provide new sources of gaugino mass if they develop F-term vacuum expectation values. It is generally assumed that string states which are sequestered from the twisted moduli receive a zero soft mass in the twisted modulus domination limit, however the standard form of Kahler potential does not reproduce this expectation. We therefore propose a new form of the Kahler potential which is consistent at leading order with the sequestered form proposed by Randall and Sundrum, and show that it leads to exponentially suppressed sequestered soft masses. Including the effects of Green-Schwarz mixing, we write down the soft scalar masses and trilinears arising from a type I string construction involving intersecting D5_i and D9-branes in the presence of untwisted and twisted moduli. If the squarks and sleptons are identified with sequestered states then in the twisted moduli dominated limit this corresponds to gaugino mediated supersymmetry breaking, and we discuss two different scenarios for this. The general results will be useful for phenomenological studies involving a combination of gravity and gaugino mediated SUSY breaking due to the dilaton, untwisted and twisted moduli contributions, and enable the soft masses to be studied as a function of the different compactification radii.
We analyze the phenomenology of the Higgs sector in a 5D model compactified on an $S_1/Z_2$ orbifold where the compactification scale $M_C$ is around the TeV scale. We show that the conventional MSSM Higgs boson mass bounds in 4D can be violated when we allow the gauge sector, Higgs and third family multiplets to live in the fifth extra dimension. Supersymmetry is broken at an orbifold fixed point which is spatially separated from the Yukawa brane where two chiral families are localized. When the brane-localized supersymmetry breaking term for the stop sector is arbitrarily large, we find that the stop KK-mode mass spectrum is completely independent of the Higgs fields. Hence, the Higgs masses only receive radiative contributions from the top KK-modes. The 1-loop effective potential is insensitive to the cutoff scale of the theory and yields a negative Higgs squared-mass contribution that triggers electroweak symmetry breaking in the range $1.5\simlt\tanβ\simlt 20$, where bottom/sbottom loop effects can be ignored. The recent LEP Higgs bound at $m_{h^{0}} > 114.1$ GeV, in conjunction with naturalness arguments, allows us to bracket the compactification scale $1.5 \simlt M_{C} \simlt 4$ TeV. Within this parameter space, we find that the lightest Higgs boson mass has an upper bound $m_{h^{0}} \simlt 160$ GeV with the magnitude of the $μ$-parameter restricted to the range $33 \simlt | μ| \simlt 347$ GeV.
We explore supersymmetric Type I string-motivated three-family scenarios in which the Standard Model is embedded within two sets of intersecting D branes with U(1)-extended Pati-Salam gauge groups. We study a model inspired by the Shiu-Tye Type IIB orientifold, in which a three-family scenario is obtained by assuming that the gauge symmetry breaking takes place in two stages; the Pati-Salam group arises from diagonal breaking of the U(N) gauge groups, which is then broken to the SM gauge group. We investigate the diagonal breaking scenario in detail and find that generically there are difficulties involved in decoupling the exotic Higgs remnants. On the phenomenological side, proper low energy gauge coupling predictions effectively lead to a ``single brane'' scenario for M_string of order 10^16 GeV. The soft parameters in this limit are constrained by a well-known sum rule, leading to a distinctive phenomenological pattern for the low energy mass spectrum.
We consider the problem of supersymmetry and electroweak breaking in a 5d theory compactified on an $S^{1}/Z_{2}$ orbifold, where the extra dimension may be large or small. We consider the case of a supersymmetry breaking 4d brane located at one of the orbifold fixed points with the Standard Model gauge sector, third family and Higgs fields in the 5d bulk, and the first two families on a parallel 4d matter brane located at the other fixed point. We compute the Kaluza-Klein mass spectrum in this theory using a matrix technique which allows us to interpolate between large and small extra dimensions. We also consider the problem of electroweak symmetry breaking in this theory and localize the Yukawa couplings on the 4d matter brane spatially separated from the brane where supersymmetry is broken. We calculate the 1-loop effective potential using a zeta-function regularization technique, and find that the dominant top and stop contributions are separately finite. Using this result we find consistent electroweak symmetry breaking for a compactification scale {$ 1/R \approx 830$ GeV} and a lightest Higgs boson mass $m_{h} \approx 170$ GeV.
In this talk, based on \cite{Kane:2001rb}, we emphasise that intermediate scale supersymmetric inflation models are particularly attractive since inflation, baryogenesis and the relic abundance of cold dark matter (CDM) are all related by a set of parameters which also affect particle physics collider phenomena, neutrino masses and the strong CP problem. We also point out that the present day relic abundances of different forms of matter are (in principle) calculable from the supersymmetric inflation model together with a measurement of the CMB temperature and the Hubble constant. From these relic abundances one can deduce the amount of the present day dark energy (DE) density.
We consider supersymmetric inflation models in which inflation occurs at an intermediate scale and which provide a solution to the $μ$ problem and the strong CP problem. Such models are particularly attractive since inflation, baryogenesis and the relic abundance of cold dark matter are all related by a set of parameters which also affect particle physics collider phenomena, neutrino masses and the strong CP problem. For such models the natural situation is a universe containing matter composed of baryons, massive neutrinos, lightest superpartner cold dark matter, and axions. The present day relic abundances of these different forms of matter are (in principle) calculable from the supersymmetric inflation model together with a measurement of the CMB temperature and the Hubble constant. From these relic abundances one can deduce the amount of the present day dark energy density.
We consider the Standard Models of particle physics and hot big bang cosmology, and review the theoretical and experimental motivations for extending these models to include supersymmetry and inflation. An obvious extension would be to unite these two models into a single all-encompassing theory. We identify a list of theoretical challenges that such a theory must address, which we illustrate with a simple model - a variant of the next-to-minimal supersymmetric Standard Model - that addresses these challenges.
We propose a model based on SU(3) family symmetry which leads to a successful description of quark and lepton masses and mixing angles including approximate bi-maximal mixing in the neutrino sector suitable for the LOW or quasi-vacuum solar solutions, with the atmospheric angle predicted to be accurately maximal due to the SU(3) symmetry. The model predicts a CHOOZ angle $θ_{13}\sim |V_{ub}|.$ The SU(3) symmetry can also ensure the near degeneracy of squarks and sleptons needed to avoid large flavour changing neutral currents.
We consider how well current theories can predict neutrino mass and mixing parameters, and construct a statistical discriminator which allows us to compare different models to each other. As an example we consider see-saw models based on family symmetry, and single right-handed neutrino dominance, and compare them to each other and to the case of neutrino anarchy with random entries in the neutrino Yukawa and Majorana mass matrices. The predictions depend crucially on the range of the undetermined coefficients over which we scan, and we speculate on how future theories might lead to more precise predictions for the coefficients and hence for neutrino observables. Our results indicate how accurately neutrino masses and mixing angles need to be measured by future experiments in order to discriminate between current models.
We make an analytic and numerical study of leptogenesis in the framework of the (Supersymmetric) Standard Model plus the see-saw mechanism with a U(1) family symmetry and single right-handed neutrino dominance. In presenting our analytic and numerical results we make a clear distinction between the theoretically clean asymmetry parameter $ε_1$ and the baryon asymmetry $Y_B$. In calculating $Y_B$ we propose and use a fit to the solutions to the Boltzmann equations which gives substantially more reliable results than parametrisations previously used in the literature. Our results show that there is a decoupling between the low energy neutrino observables and the leptogenesis predictions, but that nevertheless leptogenesis is capable of resolving ambiguities within classes of models which would otherwise lead to similar neutrino observables. For example we show that models where the dominant right-handed neutrino is the heaviest are preferred to models where it is the lightest and study an explicit example of a unified model of this type.
We review the current status of neutrino oscillations after 1258 days of Super-Kamiokande, assess their future prospects over the next 10 years as the next generation of experiments come on-line, and discuss the longer-term opportunities presented by a Neutrino Factory. We also give an introduction to the see-saw mechanism and its application to atmospheric and solar neutrinos.
We discuss the lepton sector of a realistic string-inspired model based on the Pati-Salam $SU(4)\times SU(2)_L \times SU(2)_R$ gauge group supplemented by a U(1) family symmetry. The model involves third family Yukawa unification, predicts large $\tan β\sim 50$, and describes all fermion masses and mixing angles, including approximate bi-maximal mixing in the neutrino sector. Atmospheric neutrino mixing is achieved via a large 23 entry in the neutrino Yukawa matrix which can have important phenomenological effects. We find that the recent BNL result on the muon ($g-2$) can be easily accommodated in a large portion of the SUSY parameter space of this model. Over this region of parameter space the model predicts a CP-even Higgs mass near 115 GeV, and a rate for $τ\to μγ$ which is close to its current experimental limit.