M_H=89⁺³⁸_-28 GeV,
m_t=172.7 ± 28.8 GeV,
S²_z = 0.23122 ± 0.00015,
&alpha_s(M_Z)=0.1216 ± 0.0017.

We used GAPP (Global Analysis of Particle Properties) for the first time for the 1997 off-year partial update of our contribution to the Particle Data Group in C. Caso et al, Eur. Phys. J. C3, 1 (1998). Important updates can be found in hep-ph/9809352 and in D.E. Groom et al, Eur. Phys. J. C15, 1 (2000). The Figure 1 below represents the status of the Standard Model.

Figura 1. One standard deviation (39.35 %) uncertaities in M_H as a funtion of m_t for the direct and indirect data, and the 90% CL region (Δχ² = 4.605) allowed by all data. The SM prediction as a funtion of M_H is also indicated. The widths of the M_H bands reflect the theoretical uncertainty from α(M_Z).

The most important result within the SM is presently the extraction of the Higgs boson mass,

and the resulting limits at 95 (90, 99)% confidence upper limit are M_H < 194 (176, 235) GeV respectively. The extracted M_H is strongly correlated with m_t as can be seen in the next figure, which shows the one standard deviation contours for the lineshape variables and cross section ratios, the Z pole asymmetries, deep inelastic neutrino scattering, M_W, the direct m_t constraint, and the 90% CL allowed region by all data.

Figure 2. One-standard-deviation (39.35%) uncertainties in M _H as a funtion of m_t for various inputs, and the 90% CL region (Δχ²=4.605) allowed by all data. &alpha(M_Z)=0.120 is assumed except for the fits including the Z-lineshape data. The 95% direct lower limit from LEP 2 is also known.

GAPP was also essential in a study of Bounds on Supersymmetry from Electroweak Precision Analysis, in collaboration with Damien Pierce, published in Nucl. Phys. B526, 53 (1998). Within the frameworks of supergravity and gauge mediated supersymmetry breaking we systematically investigated the allowed parameter spaces in these classes of models. Precision observables, direct limits on superparticles, as well as electroweak and unification scale boundary conditions, have all been considered simultaneously. New limits on superpartners and extra Higgs scalars could be set.

For results on extra Z bosons, see our paper Constraints on Extended Neutral Gauge Structures, Phys. Lett. B456, 68 (1999).

As for a more model independent parametrization of new physics we show the current constraints on the oblique parameters, S and T (with U = 0), in the following figure. The one standard deviation contours for the individual data sets are for a reference Higgs boson mass of 117 GeV. For the fits to all data we show the 90% CL contours.

Figure 3. 1 σ constraints (39.35%) on S and T from various inputs combined with M_Z. S and T represent the contributions of new physics only. (Uncertainties from m_t are included in the errors.) The contours assume M_H = 117 GeV except for the central and upper 90% CL contours allowed by all data, which are for M_H= 340 GeV and 1000 GeV, respectively. Data sets not involving M_W are insensitive to U. Due to higher order effects, however, U=0 has to be assumed in all fits. α_s is constrained using the τ lifetime as additional input in all fits.