Graham G. Ross

Cosmological problems for the polonyi potential

We study the cosmological implications of N = 1 supergravity with the Polonyi potential. We find that for typical values of the gravitino mass (102-103 GeV) the universe goes through a late period of reheating (i.e., from a temperature of about 10 -7 MeV to 10 -2 MeV). Any baryon-to-photon ratio is thus diluted by an unacceptable 15 orders of magnitude, with no hope of regeneration.

The Anomalous Gluon Contribution to Polarized Leptoproduction

Abstract We show that, due to the anomaly, the gluon contribution to the first moment of the polarized proton structure function, as measured in deep inelastic scattering, is not suppressed by a power of the strong coupling evaluated at a large scale. As a result, the EMC result for the first moment of polarized proton electroproduction is consistent with a large quark spin component.

SU(2)L × U(1) symmetry breaking as a radiative effect of supersymmetry breaking in GUTs

Abstract It is shown how in a globally supersymmetric SU(3) × SU(2) × U(1) model supersymmetry breaking can, via radiative corrections, induce an effective Higgs potential which spontaneously breaks SU(2) × U(1) Q . We discuss the spectrum of the resulting theory particularly the many new fermions and scalar particles which should be produced by the next generation of accelerator. The inclusion of the model in supersymmetric GUTs is considered and a model is constructed in which no unnatural adjustment of parameters is required.

Discrete gauge symmetries and the origin of baryon and lepton number conservation in supersymmetric versions of the standard model

In the supersymmetric standard model operators of dimension 4 and 5 generically violate B and L number. One usually assumes the presence of some discrete symmetry (“matter parities”) in order to forbid dangerous operators which may lead otherwise to unacceptable violations of B and L. We give a general classification of such discrete ZN symmetries (and R-symmetries) and show that the number of independent possibilities is substantially reduced by equivalences. We argue that normal discrete symmetries may be expected to be violated by quantum gravity effects and hence are not enough to inhibit nucleon decay. On the other hand, gauge (either discrete or continuous) symmetries are stable under quantum gravity effects and we discuss how such symmetries may eliminate the dangerous B- or L-violating operators. We find that the massless fermion content of modeld with discrete “gauge” symmetries is strongly constrained by the cancellation of “discrete gauge anomalies”. We show that there are two preferred ZN symmetries which are discrete anomaly free with the minimal light matter content. One of them is the standard R-parity whereas the other is a unique Z3 symmetry allowing for lepton number violation. We argue that from the point of view of arranging for proton stability without fine-tuning the second option should be preferred. The differences in the phenomenology of the various sypersymmetric models dictated by the different symmetries are discussed.

Fermion masses and mixing angles from gauge symmetries

Abstract The structure of the quark and lepton masses and mixing angles provides one of the few windows we have on the underlying physics generating the Standard Model. In an attempt to identify the underlying symmetric group we look for the simplest gauge extension of the SUSY standard model capable of generating the observed structure. We show that the texture structure and hierarchical form found in the (symmetric) quark and lepton mass matrices follows if one extends the gauge group of the standard model to include an horizontal U(1) gauge factor, constrained by the need for anomaly cancellation. This U(1) symmetry is spontaneously broken slightly below the unification/string scale leaving as its only remnant the observed structure of masses and mixings. Anomaly cancellation is possible only in the context of superstring theories via the Green-Schwarz mechanism with sin 2 (θ W ) = 3 8 .

Low-energy predictions in supersymmetric grand unified theories

Abstract Globally supersymmetric theories provide a solution to the gauge hierarchy problem without the need for a strongly interacting sector. We consider various such theories which generalise the standard SU(3) × SU(2) × U(1) model and compute their predictions for the unification scale M X , sin 2 θ W and fermion mass ratios.

Supersymmetric models without R parity

Abstract We show that many supersymmetric models may spontaneously break R parity through scalar neutrinos acquiring a vacuum expectation value (vev). These models allow supersymmetric particles to be produced singly and to decay to non-supersymmetric states. This leads to a new pattern of supersymmetric phenomenology. We discuss the lepton number violation to be expected in this class of models.

Mass and mixing angle predictions from infra-red fixed points

Abstract It is argued that low energy parameters, such as masses and mixing angles, may be related by the infra-red fixed points of the underlying field theory. For the Kobayashi-Maskawa 6 quark model the infra-red fixed points predicts the top quark mass m t = 135 GeV and the Higgs mass m H = 72 GeV. The implications for the mixing angles and phase are discussed and we also show that grand unification predictions should not be significantly affected.

Search for gluons in e+e− annihilation

Abstract We study the deviations to be expected at high energies from the recently observed two-jet structure of hadronic final states in e + e − annihilation. Motivated by the approximate validity of the naive parton model and by asymptotic freedom, we suggest that hard gluon bremsstrahlung may be the dominant source of hadrons with large momenta transverse to the main jet axes. This process should give rise to three-jet final states. These may be observable at the highest SPEAR or DORIS energies, and should be important at the higher PETRA or PEP energies.

Stitching the Yukawa quilt

Abstract We develop a systematic analysis of quark mass matrices which, starting with the measured values of quark masses and mixing angles, allows for a model-independent search for all possible (symmetric or hermitian) mass matrices having texture zeroes at the unification scale. A survey of all six and five texture zero structures yields a total of five possible solutions which may be distinguished by improved measurements of the CKM matrix elements and which may readily be extended to include lepton masses with the GeorgiJarskog texture. The solutions naturally suggest a parameterisation for the mass matrices based on a perturbative expansion and we present some speculations concerning the origin of such structure.