We discuss here diffraction scattering of hadrons in a field-theoretic model with quark field operators. We first note that a nonrelativistic model qualitatively describes correct baryon-baryon and baryon-meson slopes in terms of harmonic-oscillator wave functions. Next, for a relativistic description, we apply a Lorentzboosting scheme proposed earlier. It then becomes apparent that a current-current type of interaction in quark space can possibly reproduce baryon-baryon diffraction scattering. When we consider baryon-meson diffraction scattering, a change in the usual form of the current-current interaction becomes necessary to reproduce the quark additivity rule for hadron-hadron scattering; but even with this there is some mismatch with the pion charge radius. An alternative scheme of Lorentz boosting is discussed which has some similarity with the quasipotential approach. This field-theoretic analysis indicates the necessity of assumptions which are at present difficult to understand.

ZЈ bosons are known to naturally exist in well-motivated extensions of the standard model. The leptophobic ZЈ gauge boson can appear in models with E 6 gauge symmetry due to the mixing of the gauge-boson kinetic terms. We show that flavor-changing neutral currents can be generated in some of these models due to the mixing of the ordinary d R , s R , and b R quark fields with the exotic h R , where exotic h R means an exotic vector-singlet charge Ϫ1/3 quark h. Since the ZЈ boson does not couple to charged leptons, the constraints on the flavor-changing couplings U db ZЈ and U sb ZЈ are relatively weak. B q 0 -B q 0 mixing (qϭd,s) can be dominated by ZЈ-mediated flavor-changing neutral currents.

A string in four dimensions is constructed by supplementing it with forty four Majorana fermions. The later are represented by eleven vectors in the bosonic representation SO(D − 1, 1). The central charge is 26. The fermions are grouped in such a way that the resulting action is world sheet supersymmetric. The energy momentum and current generators satisfy the super-Virasoro algebra. GSO projections are necessary for proving modular invariance. Space-time supersymmetry algebra is deduced and is substantiated for specific modes of zero mass. The symmetry group of the model can descend to the low energy standard model group SU (3) × SUL(2) × UY (1) through the Pati-Salam group.

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In the Left–Right Symmetric Model, [Formula: see text] and [Formula: see text] mass differences are considered, taking the effect of the triplet Higgs, WR and Z′ bosons in the effective Hamiltonian in Vacuum Insertion Method and in Heavy Quark Effective Theory. It is observed that the masses MR, MH, and MZ′ are well within the experimental search in the forthcoming accelerators.