Theoretical Summary Lecture for EPS HEP99

TL;DR

Peskin's EPS HEP99 theoretical summary surveys five pivotal themes in high-energy physics: precision electroweak physics, CP violation, QCD, supersymmetry spectroscopy, and experimental studies of extra dimensions. It highlights how precision data validate the Standard Model, constrain new physics via the oblique parameters $S$ and $T$, and sharpen the CKM picture through multiple unitarity triangles, while outlining promising paths for future experiments (B-factories, Tevatron Run II, LHC, linear colliders). It also surveys supersymmetric spectra under gravity, gauge, and anomaly mediation, with testable predictions such as nearly degenerate winos and gravitino phenomenology, and discusses large extra dimensions and brane-world scenarios with collider-accessible signals like missing energy and KK resonances. The article emphasizes that new physics could appear at accessible scales, and urges continued experimental and theoretical efforts to uncover the mechanism of electroweak symmetry breaking and possible unification $M$-wise. $S$ and $T$-parameter constraints, CKM angles, and collider tests are central to the roadmap toward a deeper understanding of fundamental interactions.

Abstract

This is the proceedings article for the concluding lecture of the 1999 High Energy Physics Conference of the European Physical Society. In this article, I review a number of topics that were highlighted at the meeting and have more general importance in high energy physics. The major topics discussed include: (1) precision electroweak physics, (2) CP violation, (3) new directions in QCD, (4) supersymmetry spectroscopy, (5) the experimental physics of extra dimensions.

Figures (15)

• Figure 1: Constraints on $\sin^2\theta_w$ as a function of the top quark mass, shown by Altarelli at the 1989 Lepton-Photon conference [2]. The small dot marked 1999 shows our current knowledge.
• Figure 2: Fits of the corpus of precision electroweak data to the parameters $S$ and $T$, for the data available in the summer of 1989 and the summer of 1999 [11].
• Figure 3: Expected capability of the Run II Tevatron experiments to observe the minimal Standard Model Higgs boson, at various levels of integrated luminosity [23]. The lower curve shows a preliminary improved analysis based on neural network techniques.
• Figure 4: Four figures which display how the Standard Model works at the $Z^0$ resonance and at higher energy. See the text for more details.
• Figure 5: Diagrams contributing to $\epsilon'/\epsilon$ in $K^0$ decays: (a) strong penguin, (b) electroweak penguin.