Particle physics is at a turning point
et's tentatively agree that the Large Hadron Collider (LHC) detectors ATLAS and the Compact Muon Solenoid have discovered a Higgs boson, with a mass of about 125 gigaelectronvolts (GeV). Although standard statistical measures might not consider the situation settled, it seems very likely that there has indeed been a discovery at CERN, Europe's high-energy physics lab near Geneva, Switzerland, given that two quite different detectors both see a signal of some significance at about the same mass, and that both see the expected signals in two or more channels. This is a profound turning point in the quest for a fundamental unified theory of the physical world. The properties and mass of the LHC's Higgs boson suggest that physicists will soon find superpartners for particles , and that we have begun to connect string theory to the real world. The Higgs boson, an as-yet-unknown kind of matter thought to generate mass in other particles , is the final ingredient needed to complete and confirm the standard model of particle physics. This amazing theory describes the particles (quarks and leptons) and the strong, weak and electromagnetic forces that interact to make our world (with the addition of the theory of gravity). Quarks combine to make protons and neutrons; protons and neutrons to make nuclei; nuclei and electrons (a type of lepton) to make atoms, then molecules and chocolate and people and planets and stars and so on. The standard model has no puzzles or problems, and incorporates at a fundamental level everything from condensed-matter physics to astrophysics. It achieves the goals of four centuries of physics. The Higgs itself has been sought for decades: the main route through which its signal was reported at the LHC was the particle's decay into two photons. Collaborators and I first studied this signal in the mid 1980s, as a possible method for detecting the Higgs boson at the Super-conducting Super Collider, which was to be built at Waxahachie in Texas but was cancelled in 1993. Besides completing the standard model, the discovery of the Higgs tells us that a future, deeper underlying theory of the law(s) of nature must include and account for fundamental Higgs bosons. (Physicists have suggested alternative theories that include oddities such as composite Higgs bosons, but the CERN discovery essentially excludes them.) That will extend the standard model, and go beyond it to illuminate issues such as supersymmetry and the …