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The Fermilab Muon g-2 Collaboration reported its first measurement of the positive muon's anomalous magnetic moment with 0.46 ppm precision. The result was consistent with the earlier Brookhaven measurement, and the combined experimental value showed a tension of about 4.2 sigma with the Standard Model theoretical prediction. This hinted at possible physics beyond the Standard Model.
The CMS Collaboration at the CERN LHC reported the observation of the Standard Model Higgs boson decaying to a pair of bottom quarks, the dominant predicted decay channel. The analysis focused on Higgs bosons produced in association with a W or Z boson (VH) in 13 TeV proton-proton collision data from 2017. Combined with earlier 7, 8, and 13 TeV measurements, the result yielded an excess at 125 GeV exceeding 5 standard deviations, establishing the decay.
The LHCb collaboration at CERN's Large Hadron Collider reported the observation of exotic structures in the J/ψp invariant-mass spectrum of Λ_b^0 baryon decays, interpreted as hidden-charm pentaquark states. Two resonant states, labelled Pc(4380)+ and Pc(4450)+, were identified with high statistical significance. The result provided the first compelling evidence for pentaquarks, baryon-like states composed of five quarks.
The ATLAS Collaboration reported the observation of a new neutral boson in searches for the Standard Model Higgs boson, using proton-proton collision data from the LHC corresponding to about 4.8 fb⁻¹ at √s = 7 TeV (2011) and 5.8 fb⁻¹ at √s = 8 TeV (2012). Combining sensitive decay channels, the analysis found an excess at a mass of about 126.0 GeV with a local significance of 5.9 standard deviations, consistent with the production and decay of a Standard Model Higgs boson. The result, announced jointly with a companion CMS measurement, provided experimental confirmation of the boson associated with the Brout–Englert–Higgs mechanism of electroweak symmetry breaking.