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S. F. King

Publications and source records attributed to S. F. King.

At least 55 records · Page 3Linked to original sources
arXiv2009

Phenomenological Consequences of the Constrained Exceptional Supersymmetric Standard Model

The Exceptional Supersymmetric Standard Model (E$_6$SSM) provides a low energy alternative to the MSSM, with an extra gauged U(1)$_N$ symmetry, solving the $μ$-problem of the MSSM. Inspired by the possible embedding into an E$_6$ GUT, the matter content fills three generations of E$_6$ multiplets, thus predicting exciting exotic matter such as diquarks or leptoquarks. We present predictions from a constrained version of the model (cE$_6$SSM), with a universal scalar mass $m_0$, trilinear mass $A$ and gaugino mass $M_{1/2}$. We reveal a large volume of the cE$_6$SSM parameter space where the correct breakdown of the gauge symmetry is achieved and all experimental constraints satisfied. We predict a hierarchical particle spectrum with heavy scalars and light gauginos, while the new exotic matter can be light or heavy depending on parameters. We present representative cE$_6$SSM scenarios, demonstrating that there could be light exotic particles, like leptoquarks and a U(1)$_N$ Z' boson, with spectacular signals at the LHC.

hep-ph↗
arXiv2009

Unification of Gauge Couplings in the E(6)SSM

We argue that in the two-loop approximation gauge coupling unification in the exceptional supersymmetric standard model can be achieved for any phenomenologically reasonable value of strong gauge coupling at the electroweak scale consistent with the experimentally measured central value.

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arXiv2009

The Constrained Exceptional Supersymmetric Standard Model

We propose and study a constrained version of the Exceptional Supersymmetric Standard Model (E6SSM), which we call the cE6SSM, based on a universal high energy scalar mass m_0, trilinear scalar coupling A_0 and gaugino mass M_{1/2}. We derive the Renormalisation Group (RG) Equations for the cE6SSM, including the extra U(1)_{N} gauge factor and the low energy matter content involving three 27 representations of E6. We perform a numerical RG analysis for the cE6SSM, imposing the usual low energy experimental constraints and successful Electro-Weak Symmetry Breaking (EWSB). Our analysis reveals that the sparticle spectrum of the cE6SSM involves a light gluino, two light neutralinos and a light chargino. Furthermore, although the squarks, sleptons and Z' boson are typically heavy, the exotic quarks and squarks can also be relatively light. We finally specify a set of benchmark points which correspond to particle spectra, production modes and decay patterns peculiar to the cE6SSM, altogether leading to spectacular new physics signals at the Large Hadron Collider (LHC).

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arXiv2009

Neutrino Mass Models and the Implications of a Non-Zero Reactor Angle

In this talk we survey some of the recent promising developments in the search for the theory behind neutrino mass and mixing, and indeed all fermion masses and mixing. The talk is organized in terms of a neutrino mass models decision tree according to which the answers to experimental questions provide sign posts to guide us through the maze of theoretical models eventually towards a complete theory of flavour and unification. We also discuss the theoretical implications of the measurement of a non-zero reactor angle, as hinted at by recent experimental measurements.

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arXiv2008

Dark Matter in the USSM

We discuss the neutralino dark matter within classes of extended supersymmetric models, referred to as the USSM, containing one additional SM singlet Higgs plus an extra Z', together with their superpartners the singlino and bino'.

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arXiv2008

The Fine-Tuning Price of Neutralino Dark Matter in Models with Non-Universal Higgs Masses

We study the amounts of fine-tuning of the parameters of the MSSM with non-universal soft supersymmetry-breaking contributions to the Higgs masses (the NUHM) that would be required for the relic neutralino density to lie within the range favoured by WMAP and other astrophysical and cosmological observations. Such dark matter fine-tuning is analogous to the commonly studied electroweak fine-tuning associated with satisfying the electroweak symmetry breaking conditions, which we also study for completeness. We identify several distinct regions of the NUHM parameter space: a bulk region, a $\stau-\neut$ coannihilation region, a pseudoscalar Higgs funnel region, a focus-point bino/higgsino region and a $\sneut-\neut$ coannihilation region. Within each region, we analyse specific representative points for which we provide breakdowns of the contributions to the dark matter fine-tuning associated with the different NUHM parameters. In general, the NUHM offers points with both both smaller and larger amounts of dark matter fine-tuning than points in the corresponding regions of the CMSSM. Lower amounts of dark matter fine-tuning typically arise at points where several different (co)annihilation processes contribute, e.g., at junctions between regions with different dominant processes. We comment on the prospects for using collider measurements to estimate the likely dark matter density within the NUHM framework.

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arXiv2008

Neutralino Dark Matter in the USSM

This paper provides a comprehensive discussion of neutralino dark matter within classes of extended supersymmetric models referred to as the USSM containing one additional SM singlet Higgs plus an extra $Z'$, together with their superpartners the singlino and bino'. These extra states of the USSM can significantly modify the nature and properties of neutralino dark matter relative to that of the minimal (or even next-to-minimal) supersymmetric standard models. We derive the Feynman rules for the USSM and calculate the dark matter relic abundance and direct detection rates for elastic scattering in the USSM for interesting regions of parameter space where the largest differences are expected.

hep-ph↗
arXiv2008

Exceptional Supersymmetric Standard Models with non-Abelian Discrete Family Symmetry

We introduce a non-Abelian discrete $Δ_{27}$ family symmetry into the recently proposed classes of Exceptional Supersymmetric Standard Model ($E_6$SSM) based on a broken $E_6$ Grand Unified Theory (GUT) in order to solve the flavour problem in these models and in particular to account for tri-bimaximal neutrino mixing. We consider both the minimal version of the model (the ME$_6$SSM) with gauge coupling unification at the string scale and the E$_6$SSM broken via the Pati-Salam chain with gauge coupling unification at the conventional GUT scale. In both models there are low energy exotic colour triplets with couplings suppressed by the symmetries of the model, including the family symmetry. This leads to suppressed proton decay and long lived TeV mass colour triplet states with striking signatures at the LHC. We also present a dynamical solution to the $μ'$ problem (where $μ'$ is the mass of the additional pair of electroweak doublets in the E$_6$SSM).

hep-ph↗
arXiv2008

Deviations from Tri-bimaximal Mixing: Charged Lepton Corrections and Renormalization Group Running

We analyze the effects of charged lepton corrections and renormalization group (RG) running on the low energy predictions of theories which accurately predict tri-bimaximal neutrino mixing at the high energy scale. In particular we focus on GUT inspired see-saw models with accurate tri-bimaximal neutrino mixing at the GUT scale, in which the charged lepton corrections are Cabibbo-like and give rise to sum rules valid at the GUT scale. We study numerically the RG corrections to a variety of such neutrino mixing sum rules in order to assess their accuracy and reliability when comparing them to future low energy neutrino oscillation experiments. Our results indicate that the RG corrections to neutrino mixing sum rules are typically small (less than one degree), at least in the examples studied with hierarchical neutrinos.

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arXiv2008

The Constrained E$_6$SSM

We present a self--consistent $E_6$ inspired supersymmetric model with an extra $U(1)_{N}$ gauge symmetry under which right-handed neutrinos have zero charge. We explore the particle spectrum within the constrained version of this exceptional supersymmetric standard model (E$_6$SSM) and discuss its possible collider signatures.

hep-ph↗
arXiv2008

Leptogenesis in the Exceptional Supersymmetric Standard Model: flavour dependent lepton asymmetries

We calculate flavour dependent lepton asymmetries within the $E_6$ inspired Supersymmetric Standard Model ($\rm E_6SSM$), which has an extra $U(1)_N$ symmetry. In this model, the right-handed neutrino doesn't participate in gauge interactions, allowing it to be used for both the see--saw mechanism and leptogenesis. Extra Higgs, leptons and leptoquarks predicted by the E$_6$SSM contribute to the ordinary lepton CP asymmetries induced by the decays of the lightest right--handed neutrino (and sneutrino) and give rise to a set of extra decay asymmetries. We find that the CP asymmetries can be relatively large, even when the lightest right--handed neutrino is as light as $10^6 {GeV}$.

hep-ph↗
arXiv2008

Neutrino Mass Models: a road map

In this talk we survey some of the recent promising developments in the search for the theory behind neutrino mass and mixing, and indeed all fermion masses and mixing. The talk is organized in terms of a neutrino mass models road map according to which the answers to experimental questions provide sign posts to guide us through the maze of theoretical models eventually towards a complete theory of flavour and unification.

hep-ph↗
arXiv2008

Leptogenesis in the E$_6$SSM: Flavour Dependent Lepton Asymmetries

We discuss flavour dependent lepton asymmetries in the Exceptional Supersymmetric Standard Model (E$_6$SSM). In the E$_6$SSM, the right-handed neutrinos do not participate in gauge interactions, and they decay into leptons and leptoquarks. Their Majorana nature allows violation of lepton number. New particles and interactions can result in substantial lepton asymmetries, even for scales as low as $10^6 {\rm GeV}$.

hep-ph↗
arXiv2008

Flavon Inflation

We propose an entirely new class of particle physics models of inflation based on the phase transition associated with the spontaneous breaking of family symmetry responsible for the generation of the effective quark and lepton Yukawa couplings. We show that the Higgs fields responsible for the breaking of family symmetry, called flavons, are natural candidates for the inflaton field in new inflation, or the waterfall fields in hybrid inflation. This opens up a rich vein of possibilities for inflation, all linked to the physics of flavour, with interesting cosmological and phenomenological implications. Out of these, we discuss two examples which realise flavon inflation: a model of new inflation based on the discrete non-Abelian family symmetry group A_{4} or Delta_{27}, and a model of hybrid inflation embedded in an existing flavour model with a continuous SU(3) family symmetry. With the inflation scale and family symmetry breaking scale below the Grand Unification Theory (GUT) scale, these classes of models are free of the monopole (and similar) problems which are often associated with the GUT phase transition.

hep-ph↗
arXiv2008

Benchmark scenarios for the NMSSM

We discuss constrained and semi--constrained versions of the next--to--minimal supersymmetric extension of the Standard Model (NMSSM) in which a singlet Higgs superfield is added to the two doublet superfields that are present in the minimal extension (MSSM). This leads to a richer Higgs and neutralino spectrum and allows for many interesting phenomena that are not present in the MSSM. In particular, light Higgs particles are still allowed by current constraints and could appear as decay products of the heavier Higgs states, rendering their search rather difficult at the LHC. We propose benchmark scenarios which address the new phenomenological features, consistent with present constraints from colliders and with the dark matter relic density, and with (semi--)universal soft terms at the GUT scale. We present the corresponding spectra for the Higgs particles, their couplings to gauge bosons and fermions and their most important decay branching ratios. A brief survey of the search strategies for these states at the LHC is given.

hep-ph↗
arXiv2008

Flavour physics of leptons and dipole moments

This chapter of the report of the ``Flavour in the era of the LHC'' Workshop discusses the theoretical, phenomenological and experimental issues related to flavour phenomena in the charged lepton sector and in flavour-conserving CP-violating processes. We review the current experimental limits and the main theoretical models for the flavour structure of fundamental particles. We analyze the phenomenological consequences of the available data, setting constraints on explicit models beyond the Standard Model, presenting benchmarks for the discovery potential of forthcoming measurements both at the LHC and at low energy, and exploring options for possible future experiments.

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