= Solution
The evidence tests several linked claims: a <weak neutral current>, massive charged and neutral mediators, their chiral couplings, and the non-Abelian interactions among those mediators. A theory must describe these with a common set of electroweak parameters.
The <Gargamelle neutral-current experiment> supplied a particularly direct early test. A neutrino beam crossed a heavy-liquid <bubble chamber>; charged reaction products made visible tracks, while incoming and outgoing neutrinos did not. Neutral-current candidates had a hadronic vertex without an accompanying charged lepton, or an isolated recoiling electron. The visible final state differs from a muon-neutrino charged-current event with an outgoing muon. Neutral hadrons entering from surrounding material could imitate a hadronic vertex, so background rejection was essential. The 1973 observations supported an interaction carried by a neutral weak mediator; they did not directly reconstruct an on-shell Z resonance.<Gargamelle by CERN>[Experimental description: neutrino beam, heavy-liquid chamber, hadronic and electron-scattering searches]{ref}
The <UA1 experiment> and <UA2 experiment> collider discoveries supplied complementary evidence in 1983. A proton–antiproton collider provided enough energy to produce the mediators. Charged W candidates used a high-transverse-momentum charged lepton and missing transverse momentum from an escaping neutrino; because its longitudinal momentum was not measured, a transverse-mass distribution was useful. Neutral Z candidates instead formed a charged-lepton pair with an invariant-mass peak. Observing both kinds of events and their masses tested the predicted mediator structure.<The Z boson by CERN>[History: 1983 W and Z discovery at the proton–antiproton collider]{ref}
The <Weinberg angle> connects independent measurements. At tree level, a <Higgs doublet> gives
$$
m_W=\frac{gv}{2},\qquad m_Z=\frac{v}{2}\sqrt{g^2+g'^2},\qquad e=g\sin\theta_W,
$$
so \b[$m_W=m_Z\cos\theta_W$]. Neutral-current scattering, the mediator masses and electromagnetic measurements must be consistent with one mixing angle after a common renormalization prescription and <radiative corrections> are included. Precise Z-resonance widths and asymmetries test the left- and right-chiral couplings; a mass peak alone would not establish those coupling assignments.
At higher collider energies, W-pair production tested the <electroweak triple gauge couplings>. Reconstructing hadronic jets or a charged lepton plus missing momentum identifies W decays; total rates and production/decay angles constrain the $WW\gamma$ and $WWZ$ vertices. Their non-Abelian relations are required for the characteristic interference with neutrino exchange. L3's 2004 analysis used these channels and found agreement with the Standard Model expectation.<Measurement of Triple-Gauge-Boson Couplings of the W Boson at LEP by L3 Collaboration>[Abstract: measured triple-gauge parameters and W-pair, single-W and single-photon samples]{ref}
Finally, the 2012 <Higgs boson discovery> and subsequent coupling tests address the symmetry-breaking sector, beyond the existence of gauge mediators. The initial observation was a new resonance in several decay channels; establishing all its properties requires further measurements. These are mutually supporting tests of the <electroweak interaction>, with distinct apparatus, observables and background controls, rather than a claim that any single event proves the entire theory.
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