D. Dominici

Effective Weak Interaction Theory with Possible New Vector Resonance from a Strong Higgs Sector

Abstract We consider the effective lagrangian for electroweak interactions in the limit of a strong interacting Higgs sector ( m H → ∞). We assume that the appearing SU(2) v hidden local symmetry is realized through a new dynamical vector boson resonance V. We derive the physical admixtures and masses of W, Z and V bosons and calculate the couplings of the physical bosons to fermions. No physical Higgs remains in the spectrum. We find that the standard low energy phenomenology of weak interactions, as well as the W-, Z-masses and properties, may be rather closely reproduced in our effective theory, even for low values of the mass of the new vector resonance, within presently accessible energies.

Non-Linear realization of supersymmetry algebra from supersymmetric constraint

Abstract We discuss spontaneous symmetry breaking of global supersymmetry for a single scalar superfield in an arbitrary Kahler manifold. We show that when the curvature of the manifold goes to infinity (or, equivalently, the masses of the scalar partners of the goldstino go to infinity) a non-linear realization of supersymmetry is obtained. The model can be described, in perfect analogy to the ordinary σ-models, by means of a supersymmetric constraint on the superfield Φ, of the form Φ2=0. The non-linear realization we obtain is different from that of Volkov and Akulov. The differences among the two realizations are discussed.

Physical implications of possible J = 1 bound states from strong Higgs

Abstract A strongly interacting Higgs sector could give rise to new bound states. Among them, spin-1 bosonic states would, through their mixing with γ, W and Z, significantly modify some phenomenological predictions. For a first attempt at describing such a situation we have employed the local hidden symmetry formulation of the non-linear σ-model, used as a simulation of the strong Higgs sector, and have conjectured the appearance of the boson kinetic term. The relatively simple description that we obtain allows for a calculation of the mixing and couplings, for a fit of all the low-energy phenomenology, and for a discussion of the experimental predictions. In particular, we find that accurate measurements of the W and Z masses could permit a test of these ideas.

Testing for heavier vector bosons in e+e− at Z peak. A comparative study of different models

Abstract We have analyzed the experimental consequences which the existence of a heavy neutral gauge vector boson may produce in e + e − measurements made at energies around the Z mass. The analysis has been made as model independent as possible and it is mainly based upon the classification of the various models according to the transformation properties of the extra neutral gauge field under U(1) em . As specific examples we consider extra U(1) and left-right (LR) models, as well as a model with electroweak symmetry broken by a strongly interacting sector (BESS). For the analysis we have used the new data from CDF, UA2 and SLC/LEP1 on W and Z masses. We give analytical expressions for the deviations from the standard model (SM) of the observables relevant at LSC/LEP1 energies, such as widths and asymmetries. The range of the allowed deviations from the SM is explicitly evaluated for each of the models discussed. Small deviations are generally expected in the Z line-shape parameters; for extra U(1) and LR models the most sensitive observables are the leptonic peak cross section and width. Potentially large effects might show up in asymmetry measurements with a pattern distinguishing BESS from the other models. Larger deviations are favoured in BESS by a larger top mass and the contrary holds for the other models.

Low energy strong electroweak sector with decoupling.

We discuss possible symmetries of effective theories describing spinless and spin 1 bosons, mainly to concentrate on an intriguing phenomenological possibility: that of a hardly noticeable strong electroweak sector at relatively low energies. Specifically, a model with both vector and axial vector strong interacting bosons may possess a discrete symmetry imposing degeneracy of the two sets of bosons (degenerate BESS model). In such a case its effects at low energies become almost invisible and the model easily passes all low energy precision tests. The reason lies essentially in the fact that the model automatically satisfies decoupling, contrary to models with only vectors. For large mass of the degenerate spin one bosons the model becomes identical at the classical level to the standard model taken in the limit of infinite Higgs mass. For these reasons we have thought it worthwhile to fully develop the model, together with its possible generalizations, and to study the expected phenomenology. For instance, just because of its invisibility at low energy, it is conceivable that degenerate BESS has low mass spin one states and gives quite visible signals at existing or forthcoming accelerators.

A gravitino-goldstino high-energy equivalence theorem

Abstract We show that in spontaneously broken supergravity S-matrix elements with longitudinally polarized gravitinos are asymptotically equal, to order m 3 2 s , to corresponding matrix elements where each longitudinally polarized gravitino is replaced by the corresponding goldstino.

Moose models with vanishing S parameter

In the linear moose framework, which naturally emerges in deconstruction models, we show that there is a unique solution for the vanishing of the S parameter at the lowest order in the weak interactions. We consider an effective gauge theory based on K SU(2) gauge groups, K+1 chiral fields, and electroweak groups SU(2){sub L} and U(1){sub Y} at the ends of the chain of the moose. S vanishes when a link in the moose chain is cut. As a consequence one has to introduce a dynamical nonlocal field connecting the two ends of the moose. Then the model acquires an additional custodial symmetry which protects this result. We examine also the possibility of a strong suppression of S through an exponential behavior of the link couplings as suggested by the Randall Sundrum metric.

Military use of depleted uranium: assessment of prolonged population exposure

This work is an exposure assessment for a population living in an area contaminated by the use of depleted uranium (DU) weapons. RESRAD 5.91 code was used to evaluate the average effective dose at depths of 1, 10, 20 cm of contaminated soil, in a residential farming scenario. Critical pathways and groups are identified in soil inhalation and ingestion; critical group is identified in children playing with the soil. From the available information on DU released at targeted sites, both critical and average exposure can produce toxicological hazards. The annual dose limit for the population can be exceeded within a few years from DU deposition for soil inhalation. As a result, clean up at targeted sites must be planned on the basis of measured concentration, when available, while special measures must be adopted anyway to reduce unaware exposures.

Playing with fermion couplings in Higgsless models

We discuss the fermion couplings in a four dimensional SU(2) linear moose model by allowing for direct couplings between the left-handed fermions on the boundary and the gauge fields in the internal sites. This is realized by means of a product of nonlinear {sigma}-model scalar fields which, in the continuum limit, is equivalent to a Wilson line. The effect of these new nonlocal couplings is a contribution to the {epsilon}{sub 3} parameter which can be of opposite sign with respect to the one coming from the gauge fields along the string. Therefore, with some fine-tuning, it is possible to satisfy the constraints from the electroweak data.

Effective Lagrangian Description of the Possible Strong Sector of the Standard Model

Abstract We discuss the effective lagrangian of the scalar and longitudinal sector of the standard SU(2) × U(1) model and derive the corresponding Feyman rules. Such a sector becomes strong when the Higgs mass parameter m H is large. Scalar propagation, in this case, is conveniently described by a degenerate 2 × 2 matrix. We apply the Feyman rules to calculate scattering amplitudes among longitudinally polarized W and Z, which now satisfy partial wave-unitarity also at large m H . We also calculate production amplitudes among such states and find that they are no longer depressed, when m H is large.