Mary K. Gaillard

The TeV Physics of Strongly Interacting W's and Z's

Abstract There are two possibilities for electroweak symmetry breaking: either there is a scalar particle much lighter than 1 TeV or the longitudinal components of W and Z bosons interact strongly at center of mass energies of order 1 TeV or more. We study the general signatures of a strongly interacting W, Z system and conclude that these two possibilities can be unambiguously distinguished by a hadron collider facility capable of observing the enhanced production of WW, WZ and ZZ pairs that will occur if Ws and Zs have strong interactions. Detection of the enhanced signal over background requires hadron collisions at a center of mass energy of order √ s = 40 TeV and an integrated luminosity of order 10 40 cm −2 . With these parameters we predict 3800 to 6000 gauge boson pairs satisfying cuts for which only 2600 pairs would be produced in the absence of strong interactions. As our results draw on the global chiral SU(2) symmetry of the scalar sector of the standard SU(2) × U(1) model, we give an extended proof, to all orders in the generalized renormalizable gauge, that high-energy amplitudes of longitudinal Ws and Zs are well approximated by amplitudes of the corresponding unphysical scalars. The results are applicable to the broad class of strong interaction models that admit a global chiral SU(2) symmetry.

Duality Rotations for Interacting Fields

Abstract We study the properties of interacting field theories which are invariant under duality rotations which transform a vector field strength into its dual. We consider non-abelian duality groups and find that the largest group for n interacting field strengths is the non-compact Sp(2 n ,R), which has U( n ) as its maximal compact subgroup. We show that invariance of the equations of motion requires that the lagrangian change in a particular way under duality. We use this property to demonstrate the existence of conserved currents, the invariance of the energy-momentum tensor and the S -matrix, and also in the general construction of the lagrangian. Finally we comment on the existence of zero-mass spin-one bound states in N =8 supergravity, which possesses a non-compact E 7 dual invariance.

Fermion masses and Higgs representations in SU(5)

Abstract We argue that the observed pattern of fermion masses, including m d and m e , is consistent with the simplest SU(5) grand unified model with just a 24 and a 5 of Higgs fields, if one takes into account possible effective low-energy apparently non-renormalizable interactions scaled by inverse powers of the Planck mass. We give arguments in favour of the simplest possible structure of Higgs representations in SU(5).

Multiple Production of W and Z as a Signal of New Strong Interactions

Anomalously large cross sections for multi W and Z final states will occur at SSC energies if electroweak symmetry breaking is due to new strong interactions.

One Loop Soft Supersymmetry Breaking Terms in Superstring Effective Theories

We perform a systematic analysis of soft supersymmetry breaking terms at the one loop level in a large class of string effective field theories. This includes the so-called anomaly mediated contributions. We illustrate our results for several classes of orbifold models. In particular, we discuss a class of models where soft supersymmetry breaking terms are determined by quasi model independent anomaly mediated contributions, with possibly non-vanishing scalar masses at the one loop level. We show that the latter contribution depends on the detailed prescription of the regularization process which is assumed to represent the Planck scale physics of the underlying fundamental theory. The usual anomaly mediation case with vanishing scalar masses at one loop is not found to be generic. However gaugino masses and A-terms always vanish at tree level if supersymmetry breaking is moduli dominated with the moduli stabilized at self- dual points, whereas the vanishing of the B-term depends on the origin of the � -term in the underlying theory. We also discuss the supersymmetric spectrum of O-I and O-II models, as well as a model of gaugino condensation. For reference, explicit spectra corresponding to a Higgs mass of 114 GeV are given. Finally, we address general strategies for distinguishing among these models.

Preserving flat directions during inflation

Abstract Supersymmetry is generally broken by the non-vanishing vacuum energy density present during inflation. In supergravity models, such a source of supersymmetry breaking typically makes a contribution to scalar masses of order m 2 ∼ H 2 , where H 2 ∼ V M p 2 is the Hubble parameter during inflation. We show that in supergravity models which possess a Heisenberg symmetry, supersymmetry breaking makes no contribution to scalar masses, leaving supersymmetric flat directions flat at tree-level. One-loop corrections in general lift the flat directions, but naturally give small negative squared masses ∼ −g 2 H 2 (4π) 2 for all flat directions that do not involve the stop. No-scale supergravity of the SU(N,1) type and the untwisted sectors from orbifold compactifications are special cases of this general set of models. We point out the importance of the preservation of flat directions for baryogenesis.

A grand unified theory obtained from broken supergravity

Abstract We examine the possibility that the “fundamental” particles appearing in grand unified theories are a subset of the SU(8) bound states of preons belonging to the SO(8) extended supergravity, selected by the requirement that they form a renormalizable gauge theory. Analysis of the SU(8) Higgs potential given by supersymmetry suggests that the maximal grand unification symmetry is SU(5). A maximal subset of fermions free of SU(5) anomalies, and hence renormalizable, contains three generations of 5 +10 left-handed helicity states. The unbroken SU(5) theory may also contain 5 and 24 Higgs fields which are massless at the tree level.

DILATON STABILIZATION IN THE CONTEXT OF DYNAMICAL SUPERSYMMETRY BREAKING THROUGH GAUGINO CONDENSATION

Abstract We study gaugino condensation in the context of superstring effective theories using the linear multiplet formulation for the dilaton superfield. Including non-perturbative corrections to the Kahler potential for the dilaton may naturally achieve dilaton stabilization, with supersymmetry breaking and gaugino condensation; these three issues are interrelated in a very simple way. In a toy model with a single static condensate, a dilaton vev is found within a phenomenologically interesting range. The effective theory differs significantly from condensate models studied previously in the chiral formulation.

Neutrino Masses and Oscillations in SU(5)

The masslessness of neutrinos and B - L conservation are not fundamental in SU(5), but “accidental” reflexions of the choice of a simple Higgs system. We argue that a low energy effective two-fermion interaction with two 5s of Higgs field can violate B - L at a very low level and generate neutrino masses of order 10−5 eV. These may cause oscillations detectable in solar neutrino experiments.

Uncertainties in the proton lifetime

We discuss the masses of the leptoquark bosons mx and the proton lifetime in grand unified theories based principally on SU(5). It is emphasized that estimates of mx based on the QCD coupling and the fine structure constant are probably more reliable than those using the experimental value of sin2θw. Uncertainties in the QCD Λ parameter and the correct value of α are discussed. We estimate higher-order effects on the evolution of coupling constants in a momentum-space renormalization scheme. It is shown that increasing the number of generations of fermions beyond the minimal three increases mx by almost a factor of 2 per generation. Additional uncertainties exist for each generation of technifermions that may exist. We discuss and discount the possibility that proton decay could be “Cabibbo rotated” away, and a speculation that Lorentz invariance may be violated in proton decay at a detectable level. We estimate that in the absence of any substantial new physics beyond that in the minimal SU(5) model the proton lifetime is 8 × 1030±2 years.