S. F. King

The soft supersymmetry-breaking Lagrangian: theory and applications

After an introduction recalling the theoretical motivation for low energy (100 GeV to TeV scale) supersymmetry, this review describes the theory and experimental implications of the soft supersymmetry-breaking Lagrangian of the general minimal supersymmetric standard model (MSSM). Extensions to include neutrino masses and nonminimal theories are also discussed. Topics covered include models of supersymmetry breaking, phenomenological constraints from electroweak symmetry breaking, flavor/CP violation, collider searches, and cosmological constraints including dark matter and implications for baryogenesis and inflation.

Flavor physics of leptons and dipole moments

This chapter of the report of the “Flavor in the era of the LHC” Workshop discusses the theoretical, phenomenological and experimental issues related to flavor phenomena in the charged lepton sector and in flavor conserving CP-violating processes. We review the current experimental limits and the main theoretical models for the flavor 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.

Physics at a future Neutrino Factory and super-beam facility

The conclusions of the Physics Working Group of the International Scoping Study of a future Neutrino Factory and super-beam facility (the ISS) are presented. The ISS was carried out by the international community between NuFact05, (the 7th International Workshop on Neutrino Factories and Super-beams, Laboratori Nazionali di Frascati, Rome, 21–26 June 2005) and NuFact06 (Ivine, CA, 24–30 August 2006). The physics case for an extensive experimental programme to understand the properties of the neutrino is presented and the role of high-precision measurements of neutrino oscillations within this programme is discussed in detail. The performance of second-generation super-beam experiments, beta-beam facilities and the Neutrino Factory are evaluated and a quantitative comparison of the discovery potential of the three classes of facility is presented. High-precision studies of the properties of the muon are complementary to the study of neutrino oscillations. The Neutrino Factory has the potential to provide extremely intense muon beams and the physics potential of such beams is discussed in the final section of the report.The conclusions of the Physics Working Group of the International Scoping Study of a future Neutrino Factory and super-beam facility (the ISS) are presented. The ISS was carried out by the international community between NuFact05, (the 7th International Workshop on Neutrino Factories and Superbeams, Laboratori Nazionali di Frascati, Rome, June 21-26, 2005) and NuFact06 (Irvine, California, 2430 August 2006). The physics case for an extensive experimental programme to understand the properties of the neutrino is presented and the role of high-precision measurements of neutrino oscillations within this programme is discussed in detail. The performance of second generation super-beam experiments, beta-beam facilities, and the Neutrino Factory are evaluated and a quantitative comparison of the discovery potential of the three classes of facility is presented. High-precision studies of the properties of the muon are complementary to the study of neutrino oscillations. The Neutrino Factory has the potential to provide extremely intense muon beams and the physics potential of such beams is discussed in the final section of the report. The ISS Physics Working Group Editors: S.F. King1, K. Long2, Y. Nagashima3, B.L. Roberts4, and O. Yasuda5.

Fermion masses and mixing angles from SU(3) family symmetry

Abstract 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 ∼| V ub |. The SU (3) symmetry can also ensure the near degeneracy of squarks and sleptons needed to avoid large flavour changing neutral currents.

Large mixing angle MSW and atmospheric neutrinos from single right-handed neutrino dominance and U(1) family symmetry

Abstract Single right-handed neutrino dominance (SRHND) in the 23 sector of the light effective neutrino mass matrix has been proposed as a natural explanation for the concurrent large 23 mixing angle and large 23 mass hierarchy. In this paper we show how large 12 mixing angles, suitable for the large mixing angle (LMA) MSW solution to the solar neutrino problem, may arise from SRHND. In order to understand the conditions for SRHND and LMA MSW we first consider the case of one and two right-handed neutrinos, and obtain simple analytic conditions which are then extended to the case of three right-handed neutrinos. We then introduce a single U (1) family symmetry and show how these analytic conditions may be translated into U (1) charge assignments and perform a systematic search for the simplest examples.

NMSSM Higgs Benchmarks Near 125 GeV

The recent LHC indications of a SM-like Higgs boson near 125 GeV are consistent not only with the Standard Model (SM) but also with Supersymmetry (SUSY). However naturalness arguments disfavour the Minimal Supersymmetric Standard Model (MSSM). We consider the Next-to-Minimal Supersymmetric Standard Model (NMSSM) with a SM-like Higgs boson near 125 GeV involving relatively light stops and gluinos below 1 TeV in order to satisfy naturalness requirements. We are careful to ensure that the chosen values of couplings do not become non-perturbative below the grand unification (GUT) scale, although we also examine how these limits may be extended by the addition of extra matter to the NMSSM at the two-loop level. We then propose four sets of benchmark points corresponding to the SM-like Higgs boson being the lightest or the second lightest Higgs state in the NMSSM or the NMSSM-with-extra-matter. With the aid of these benchmark points we discuss how the NMSSM Higgs boson near 125 GeV may be distinguished from the SM Higgs boson in future LHC searches.

Charged lepton corrections to neutrino mixing angles and CP phases revisited

Abstract We re-analyze charged lepton corrections to neutrino mixing angles and CP phases, carefully including CP phases from the charged lepton sector. We present simple analytical formulae for including the charged lepton corrections and derive compact new results for small neutrino and charged lepton mixings θ 13 ν and θ 13 e . We find a generic relation θ 12 + 1 2 θ 12 e cos ( δ − π ) ≈ θ 12 ν , which relates the prediction from the neutrino sector θ 12 ν to the charged lepton mixing θ 12 e and to the MNS neutrino oscillation phase δ. We apply our formula to the examples of bimaximal or tri-bimaximal neutrino mixing. One implication is that the so-called quark–lepton complementarity relation θ 12 + θ C = 45 ° can only hold for δ = π and it gets modified in the presence of leptonic CP violation. On the other hand, the lepton mixing θ 13 generated from the charged lepton correction θ 12 e is independent of CP phases and given by θ 13 = 1 2 θ 12 e . Combining these results leads to a model-independent sum rule: θ 12 + θ 13 cos ( δ − π ) ≈ θ 12 ν where θ 12 ν = ( 35.26 ° ) 45 ° in the case of (tri-)bimaximal neutrino mixing, for example.

Tri-bimaximal neutrino mixing from discrete subgroups of SU(3) and SO(3) family symmetry

It has recently been shown how tri-bimaximal neutrino mixing can be achieved, using the see-saw mechanism with constrained sequential dominance, through the vacuum alignment of a broken non-Abelian gauged family symmetry such as SO(3) or SU(3). Generalising the approach of Altarelli and Feruglio developed for an A4 model we show how the reduction of the underlying symmetry to a discrete subgroup of SO(3) or SU(3) renders this alignment a generic property of such models. This means near tri-bimaximal mixing can be quite naturally accommodated in a complete unified theory of quark and lepton masses.

Theory and phenomenology of an exceptional supersymmetric standard model

We make a comprehensive study of the theory and phenomenology of a low-energy supersymmetric standard model originating from a string-inspired E6 grand unified gauge group. The exceptional supersymmetric standard model (ESSM) considered here is based on the low-energy standard model gauge group together with an extra Z[prime] corresponding to an extra U(1)N gauge symmetry under which right-handed neutrinos have zero charge. The low-energy matter content of the ESSM corresponds to three 27 representations of the E6 symmetry group, to ensure anomaly cancellation, plus an additional pair of Higgs-like doublets as required for high-energy gauge coupling unification. The ESSM is therefore a low-energy alternative to the minimal supersymmetric standard model (MSSM) or next-to-minimal supersymmetric standard model (NMSSM). The ESSM involves extra matter beyond the MSSM contained in three 5+5* representations of SU(5), plus three SU(5) singlets which carry U(1)N charges, one of which develops a vacuum expectation value, providing the effective µ term for the Higgs doublets, as well as the necessary exotic fermion masses. We explore the renormalization group flow of the ESSM and examine theoretical restrictions on the values of new Yukawa couplings caused by the validity of perturbation theory up to the grand unification scale. We then discuss electroweak symmetry breaking and Higgs phenomenology and establish an upper limit on the mass of the lightest Higgs particle which can be significantly heavier than in the MSSM and NMSSM, in leading two-loop approximation. We also discuss the phenomenology of the Z[prime] and the extra matter, whose discovery will provide a smoking gun signal of the model.

Fermion masses and mixing angles from SU (3) family symmetry and unification

We develop a bottom–up approach to constructing a theory of fermion masses and mixing angles based on the gauge group SU(3)×G where SU(3) is a family symmetry and G contains a unified group such as SO(10) or its Pati–Salam subgroup, together with other discrete symmetries. We construct a realistic model and show that it can provide an excellent description of quark and lepton masses and mixing angles, including almost maximal atmospheric mixing and the LMA MSW solar neutrino solution. We predict a neutrino mixing angle ?13 near the current limit. The model provides the basis for a new solution to the flavour problem with a characteristic soft SUSY breaking mass spectrum.