A phenomenological profile of the Higgs boson
A discussion is given of the production, decay and observability of the scalar Higgs boson H expected in gauge theories of the weak and electromagnetic interactions such as the Weinberg-Salam model. After reviewing previous experimental limits on the mass of the Higgs boson, we give a speculative cosmological argument for a small mass. If its mass is similar to that of the pion, the Higgs boson may be visible in the reactions Ï−p → Hn or Î³p → Hp near threshold. If its mass is â²300 MeV, the Higgs boson may be present in the decays of kaons with a branching ratio O(10−7), or in the decays of one of the new particles: 3.7 → 3.1 + H with a branching ratio O(10−4). If its mass is â©½4 GeV, the Higgs boson may be visible in the reaction pp → H + X, H → Î¼+Î¼−. If the Higgs boson has a mass â©½2mÎ¼, the decays H → e+e− and H → Î³Î³ dominate, and the lifetime is O(6 × 10−4 to 2 × 10−12) seconds. As thresholds for heavier particles (pions, strange particles, new particles) are crossed, decays into them become dominant, and the lifetime decreases rapidly to O(10−20) sec for a Higgs boson of mass 10 GeV. Decay branching ratios in principle enable the quark masses to be determined.