R.D. Peccei

ARE THERE REAL GOLDSTONE BOSONS ASSOCIATED WITH BROKEN LEPTON NUMBER

We consider, in the context of simple gauge models, the possibility that lepton number is a spontaneously broken global symmetry, leading to massive Majorana neutrinos. We find that the usual objections associated with global symmetry breakdown may be moot in this case since the Goldstone boson associated with lepton number breakdown - the majoron - is so weakly coupled to matter that it may have well escaped detection.

Rare decays of the Z0

We study radiative and Higgs decay modes of the Z0 into hypothetical heavy quark bound states (onia). In general, we find that the rates for these decays are extremely small. However, in some cases, there is some enhancement if the onia are rather near in mass to the Z0. We examine the experimental prospects for detecting, by these means, spin-parity onium states which are otherwise difficult to reach or discovering Higgs mesons. We conclude, unfortunately, that these prospects are not very bright.

Quantum chromodynamic effects and CP violation in the Kobayashi-Maskawa model

We study, in the context of the Kobayashi-Maskawa model, the effects that quantum chromodynamics has on the predictions for CP violation in kaon decays. We derive an effective hamiltonian for ΔS = 1 transitions in which all-order corrections in the strong coupling constant αs are incorporated, including those arising from penguin diagrams. We examine, in particular, the predictions of this hamiltonian for the ratio of the CP-violating parameters |ϵ′/ϵ|. Our results for this ratio are well within the present experimental bound, but are considerably smaller than the recent calculation of Gilman and Wise. The discrepancy between our results and those of Gilman and Wise arises because of the different way we have estimated the amplitude for K0 decay. A discussion of the reliability of both our estimate and that of Gilman and Wise is included.

Quarks and leptons as quasi Nambu-Goldstone Fermions

Abstract We discuss a new idea for constructing composite quarks and leptons which have (approximately) vanishing mass. They are associated with fermionic partners of Goldstone bosons arising from the spontaneous breakdown of an internal symmetry G f in a supersymmetric preon theory. For G f = SU(5) being broken to SU(3) × U(1) em there arise as quasi Goldstone fermions, naturally and unequivocally, precisely the quarks and leptons of one family. The dynamics of these quasi Goldstone fermions is explored by constructing a general supersymmetric nonlinear effective lagrangian. By means of a reduced model, we show that the first nontrivial interactions of the quasi Goldstone fermions can give rise, in an effective way, to the weak interactions. Issues connected with the incorporation of families in the scheme and the generation of masses, as well as the possible structure of the underlying preon theory are briefly discussed.

Quasi goldstone fermions

Abstract We discuss a mechanism by which, in theories with an explicitly broken supersymmetry, we can obtain calculable fermion masses, provided certain softly broken R symmetries are incorporated. The corresponding fermion representations are determined by the pattern of internal symmetry breakdown. This mechanism is explicitly studied in a simple U(1) model. Prospects and limitations of this idea for constructing realistic fermion spectra are discussed.

Quasi nambu-goldstone fermions

The Fermi-Bose symmetry, namely supersymmetry is presumably the only way of combining internal symmetries with Lorentz invariance in our 4 dimensional space-time, and is also expected to be useful for understanding the existence of massless fermions in terms of a well-defined geometry.1) Although there has not been observed any experimental evidence on such a symmetry yet, our feeling is that the super-Poincare algebra is so elegant and beautiful that it must be relevant at some underlying level.

Radiative Z0 decays — a composite scenario

Abstract A speculative analysis of the recently observed radiative Z 0 decays is presented based on a composite scenario. The large radiative branching ratio occurs because of a strong γ transition of the Z 0 to a pair of parity doublet spin-0 states near 50 GeV. Constraints and possible interesting experimental signatures are indicated.

Quarkonium sum rules: A critical reappraisal

Abstract We reanalyze the ITEP charmonium sum rules incorporating experimental errors and allowing for variations in input parameters. The necessity of a gluon condensate term is apparent for the ratio sum rules, but the presence or absence of this term cannot be established using the moment sum rules. Plausibility arguments are given for trusting the results of the ratio sum rules and the advantages of mass-independent double ratio sum rules are stressed. Sum rules for the bottomonium system are also analyzed and the results are shown to be consistent with what is obtained in the charmonium sector.

Fermion - Fermion Condensates and {CP} Violation

We discuss some theoretical difficulties of the standard Kobayashi-Maskawa scheme for CP violation and present an alternative scenario where CP violation arises through non-vanishing phases in fermion-fermion condensates. We illustrate our ideas in the context of a left-right symmetric model with a hierarchy of mass scales (MWR⪢MWL). We show that the mass scale hierarchy leads naturally to a negligible θ-parameter at tree level, θtree∼(MWLMWR)2, with this result being preserved in higher order. The resulting theory of CP violation in the kaon sector is of the superweak type and the electric dipole moment of the neutron is essentially determined by θ. There is no direct connection in the model between the phases responsible for the universs baryon asymmetry and those responsible for CP violation in the kaon system — a result we claim is a general feature of gauge theory models of unified interactions.

Horizontal symmetries, dynamical symmetry breaking and neutrino masses

Abstract We study experimental and theoretical constraints which can prevent the introduction of horizontal gauge ssymmetries. To allow for the possibility of dynamical symmetry breaking, we restrict the symmetry breaking interactions to have the quantum numbers of spin-zero bound states of the fermions in the theory. Under these circumstances we find that horizontal interactions, which do not violete any of the present bounds on flavor changing processes, are only allowed if the symmetry breakdown introduces a large Majorana mass for the neutrinos. Some phenomenological consequences of this result are discussed.