Nature’s four fundamental interactions are gravity, electromagnetism, the strong force, and the weak force. The weak force governs phenomena such as radioactive decay, and its carriers, the W and Z bosons, were long-predicted but unseen. Rubbia proposed converting CERN’s Super Proton Synchrotron (SPS) into a proton–antiproton collider for the UA1 experiment. Van der Meer invented stochastic cooling, a technique to accumulate and cool antiproton beams, enabling high-density collisions. Combining these innovations, scientists observed the W and Z bosons in 1983, providing key evidence for the Standard Model. Accelerator technology born from this work now benefits society through PET scanners and cancer therapy.

Electroweak theory unifies weak and electromagnetic interactions and predicts massive gauge bosons (W±, Z0) with masses around 80–90 GeV/c², beyond the reach of fixed-target machines of the 1970s. Rubbia spearheaded a plan to convert CERN’s SPS into a counter-rotating proton–antiproton collider, delivering a center-of-mass energy of 640 GeV for the UA1/UA2 program. Van der Meer’s stochastic cooling compressed the phase space of sparse antiproton beams produced in a source ring, boosting luminosity by more than an order of magnitude. The UA1 detector combined muon chambers and fine-grained calorimetry, allowing the extraction of W→eν candidates from transverse-mass spectra and a clear Z→e⁺e⁻ peak. Statistical significance exceeded 7σ, and measured gauge couplings and decay widths matched Standard Model expectations. The success paved the way for LEP and the LHC, underpinning later discoveries such as the Higgs boson and ongoing searches for physics beyond the Standard Model.

In the UA1/UA2 program, the SPS was operated as a 3.5 + 3.5 TeV m⁻¹ bending proton–antiproton collider with E_cm = 540 GeV. Van der Meer’s feedback-based stochastic cooling compressed the antiproton beam to Δp/p≈10⁻⁴; ≈1×10¹¹ p̄ were accumulated, achieving instantaneous luminosities of 2×10³⁰ cm⁻² s⁻¹. UA1’s 4π calorimetry and multi-layer tracking identified events with isolated e/μ of E_T≈40 GeV and Missing E_T≈40 GeV, extracting M_W = 80.0 ± 2.5 GeV/c² from the Jacobian peak. Z detection via e⁺e⁻/μ⁺μ⁻ channels yielded M_Z = 91.9 ± 1.3 GeV/c² and Γ_Z = 2.5 ± 0.5 GeV, strongly supporting the SU(2)_L×U(1)_Y symmetry-breaking model and giving ρ = 1.09 ± 0.15. The experimental techniques influenced later developments such as b-tagging, trigger farms, and online data reduction, establishing a prototype for modern hadron-collider experiments.