Lisa L. Everett

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.

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.

Icosahedral (A5) Family Symmetry and the Golden Ratio Prediction for Solar Neutrino Mixing

We investigate the possibility of using icosahedral symmetry as a family symmetry group in the lepton sector. The rotational icosahedral group, which is isomorphic to A{sub 5}, the alternating group of five elements, provides a natural context in which to explore (among other possibilities) the intriguing hypothesis that the solar neutrino mixing angle is governed by the golden ratio, {phi}=(1+{radical}(5))/2. We present a basic toolbox for model building using icosahedral symmetry, including explicit representation matrices and tensor product rules. As a simple application, we construct a minimal model at tree level in which the solar angle is related to the golden ratio, the atmospheric angle is maximal, and the reactor angle vanishes to leading order. The approach provides a rich setting in which to investigate the flavor puzzle of the standard model.

RESOLUTION TO THE SUPERSYMMETRIC CP PROBLEM WITH LARGE SOFT PHASES VIA D-BRANES

We examine the soft supersymmetry breaking parameters that result from various ways of embedding the standard model (SM) on D-branes within the type I string picture, allowing the parameters to have large CP -violating phases. One embedding naturally provides the relations among soft parameters to satisfy the electron and neutron electric dipole moment constraints even with large phases, while with other embeddings large phases are not allowed. The results generally suggest how low energy data might teach us about Planck scale physics. {copyright} {ital 1999} {ital The American Physical Society}

Classification of Flat Directions in Perturbative Heterotic Superstring Vacua with Anomalous U(1)

Abstract We develop techniques to classify D - and F -flat directions for N = 1 supersymmetric string vacua of the perturbative heterotic string theory, which possess an anomalous U (1) gauge group at the tree level. Genus-one corrections generate a Fayet-Iliopoulos term for the D-term of U (1) A , which is cancelled by non-zero vacuum expectation values (VEVs) of certain massless multiplets, in such a way that the anomalous U (1) is broken, while maintaining the D - and F -flatness of the effective field theory. A systematic analysis of flat directions is given for non-zero VEVs of non-Abelian singlets, and the techniques are illustrated for a specific model. The approach sets the stage to classify the D - and F -flat directions for a large class of perturbative string vacua. This classification is a prerequisite to systematically addressing the phenomenological consequences of these models.

Golden ratio neutrino mixing and A5 flavor symmetry

We provide a systematic and thorough exploration of lepton flavor models in which the solar mixing angle is related to the golden ratio. For scenarios in which the solar mixing angle is given by the inverse cotangent of the golden ratio, we demonstrate that A5 is the smallest non-Abelian finite group that contains all of the symmetries necessary to enforce this specific lepton mixing pattern. Within this context, we propose two lepton flavor models that yield this mixing pattern through the breaking of A5 at leading order to the Klein four subgroup in the neutrino sector. Both models have triplet embeddings of the lepton doublets as well as the charged lepton singlets. In the charged lepton sector, the residual symmetry is Z5 in the first model, while in the second model, A5 is broken completely at leading order. For the second model, the reactor mixing angle vanishes at leading order and is of the order of the square of the Cabibbo angle at next-to-leading order, which is allowed by the global analysis of current lepton data.

Implications of Muon g 2 for Supersymmetry and for Discovering Superpartners Directly

We study the implications of interpreting the recent muon g(mu) -- 2 deviation from the standard model prediction as evidence for virtual superpartners, with very general calculations that include effects of phases and are consistent with all relevant constraints. Assuming that the central value is confirmed with smaller errors, there are upper limits on masses: at 1.5 sigma, at least one superpartner mass is below about 450 GeV (550 GeV) for tan beta = 35 (50) and may be produced at the Fermilab Tevatron in the upcoming run.

Higgs-Pair Production and Measurement of the Triscalar Coupling at LHC(8,14)

Abstract We simulate the measurement of the triscalar Higgs coupling at LHC ( 8 , 14 ) via pair production of h (125 GeV). We find that the most promising hh final state is b b ¯ γ γ . We account for deviations of the triscalar coupling from its SM value and study the effects of this coupling on the hh cross-section and distributions with cut-based and multivariate methods. Our fit to the hh production matrix element at LHC(14) with 3 ab − 1 yields a 30% uncertainty on this coupling in the SM and a range of 20–60% uncertainties for non-SM values.

Intermediate scales, {mu} parameter, and fermion masses from string models

We address intermediate scales within a class of string models. The intermediate scales occur due to the SM singlets S{sub i} acquiring non-zero VEVs due to radiative breaking; the mass squared m{sub i}{sup 2} of S{sub i} is driven negative at {mu}{sub rad} due to O(1) Yukawa couplings of S{sub i} to exotic particles (calculable in a class of string models). The actual VEV of S{sub i} depends on the relative magnitude of the non-renormalizable terms of the type {cflx S}{sub i}{sup K+3}/M{sup K} in the superpotential. We mainly consider the case in which the S{sub i} are charged under an additional non-anomalous U(1){sup {prime}} gauge symmetry and the VEVs occur along F- and D-flat directions. We explore various scenarios in detail, depending on the type of Yukawa couplings to the exotic particles and on the initial boundary values of the soft SUSY breaking parameters. We then address the implications of these scenarios for the {mu} parameter and the fermionic masses of the standard model. {copyright} {ital 1998} {ital The American Physical Society}

Scrutinizing the 125 GeV Higgs boson in two Higgs doublet models at the LHC, ILC, and Muon Collider

The discovery at the LHC of a scalar particle with properties that are so far consistent with the SM Higgs boson is one of the most important advances in the history of particle physics. The challenge of future collider experiments is to determine whether its couplings will show deviations from the SM Higgs, as this would indicate new physics at the TeV scale, and also to probe the flavor structure of the Yukawa couplings. As a benchmark alternative to the SM Higgs, we consider a generic two Higgs doublet model (2HDM) and analyze the precision to which the LHC14, an ILC250, 500, 1000 GeV and a 125 GeV Muon Collider (MC) can determine the gauge and Yukawa couplings. We allow for correlations among the couplings. We include the impact of a Higgs total width measurement, indirectly at the LHC and ILC and by a direct scan at the MC. We also discuss pattern relations among the couplings that can test for singlet or doublet Higgs extensions of 2HDMs.