Distinguishability of superstring E6-inspired low-energy models and SU(5)c color model.
We calculate the asymmetry parameters [ital A], [ital B], [ital C][sub [ital L],][ital R] in the deep-inelastic [ital e]-[ital d] and [ital e]-[ital p] scattering processes in the four effective low-energy models (referred to as [chi], [psi], [eta], and alternative left-right-symmetric models) resulting from the breaking of the superstring-inspired E[sub 6] model and the SU(5)[sub [ital c]] model, and compared with those in the standard model. It is seen that [chi] and [eta] models can be discriminated through the measurement of [ital A] and [ital B] parameters while [ital C][sub [ital L]] can differentiate the [chi] model only from the standard model. However, the alternative left-right-symmetric model and the SU(5)[sub [ital c]] model cannot be distinguished from the standard model through measurement of [ital A], [ital B], and [ital C][sub [ital L]] parameters. Interestingly, all the models can be markedly distinguished from the standard model through the measurement of [ital C][sub [ital R]] for values of [ital y] in the range 0.38[le][ital y][le]0.42.

title: HERA constraints on warped quantum gravity
abstract: We study recent data on deep inelastic e+p scattering at HERA to constrain the parameters of the Randall-Sundrum scenario of quantum gravity with a small extra dimension and a non-factorizable geometry.

title: SPONTANEOUS CP VIOLATION IN A TWO-GENERATION LEFT-RIGHT SYMMETRIC MODEL WITH TWO HIGGS BI-DOUBLETS
abstract: We discuss a two-generation left-right symmetric model with two Higgs bi-doublets and a discrete symmetry to show that spontaneous CP violation arises as a result of soft breaking of the discrete symmetry. The contributions to the CP violation parameter e in the transition come from the box diagrams due to WL-WR exchanges as well as from the mixing of the real and imaginary parts of the flavor changing neutral Higgs at the tree level and both contributions depend on the relative phase difference between the vacuum expectation values (vevs) of the relevant neutral Higgs scalars. Other CP violating effects in the model are consistent with their experimental values for the appropriate choice of the model parameters. The extension of the model to the realistic case of three generations of fermions does not appreciably change the phenomenology of the model.

title: CONSTRAINTS ON THE SU(5)C × SU(2)L × U(1)′ MODEL FROM LEP DATA
abstract: We have determined constraints on the SU(5)C × SU(2)L × U(1)′ model in terms of the extra mixing angle ϕ in the neutral gauge boson sector and ΔρM, the deviation of the Standard Model ρ parameter from unity at the tree level, using the recent precision measurements at LEP on electroweak parameters at the Z peak. The lower bound of the extra Z′ boson mass has also been determined.

title: Using Invisible Graviton Radiation to Detect Heavy Electroweak Resonances at a 500 GeV e+e- Collider
abstract: The process e+e- --> mu+ mu- + missing E_T, where the missing energy is due to the production of a tower of invisible graviton states in a model with large extra dimensions, is considered. We focus on the scenario when this process is used to detect a heavy dileptonic resonance in the electroweak sector of the model, taking as example some models with an extra Z' boson. It turns out that at a 500 GeV machine with 1000 inverse fb of luminosity, it may be possible to use this process to such detect resonances if there are two large extra dimensions and the string scale is not too far above a TeV.

title: Almost degenerate neutrinos in a left-right symmetric model with discrete symmetries

title: Proton decay and related processes in unified models with gauged baryon number.
abstract: In unification models based on SU(15) or SU(16), baryon number is part of the gauge symmetry, broken spontaneously. In such models we discuss various scenarios of important baryon-number-violating processes such as proton decay and neutron-antineutron oscillation. Our analysis depends on the effective operator method, and covers many variations of symmetry breaking, including different intermediate groups and different Higgs-boson content. We discuss processes mediated by gauge bosons and Higgs bosons in parallel. We show how accidental global or discrete symmetries present in the full gauge invariant Lagrangian restrict baryon-number-violating processes in these models. In all cases we find that baryon-number-violating interactions are sufficiently suppressed to allow grand unification at energies much lower than the usual 10[sup 16] GeV.

title: Isospin breaking in superstring-inspired E6 model.
abstract: It is shown that in superstring-inspired E/sub 6/ models spontaneous left-right-symmetry breaking can naturally lead to isospin-symmetry breaking via the seesaw mechanism in the down-quark sector. This can also explain why /ital m//sub /ital u///lt/m/sub d/, whereas /ital m//sub /ital c///gt/m/sub s/ and /ital m//sub /ital t///gt/m/sub b/. The Kobayashi-Maskawa matrix and /ital CP/ violation in this model are discussed.