John Dowell has made important contributions to experimental particle physics. He made, by measuring forward proton–proton cross sections, one of the first tests of dispersion relations in particle scattering. His measurement of meson–nucleon total cross sections provided data at a crucial period in establishing the SU(3) scheme, and his K+ nucleon scattering studies gave definitive phase shifts, in particular showing that there are no resonant states in the K+ nucleon system as expected in the quark model.
He published the first results from CERN’s SPS accelerator, measuring dimuon production, which included the first observation in Europe of the J/psi particle, which consists of charmed quarks. The experiment consolidated the evidence that matter is composed of quarks. The Nobel Prize-winning discovery of W and Z weak bosons followed in 1983 at the CERN proton–antiproton collider, in which he had a strong role. After research at HERA at DESY, he devoted his attention to developing detectors for the LHC and had a key role in designing the ATLAS detector, which discovered the Higgs boson.