One Boson, Two Weights: The W-Mass Defect, Priced

The W boson has one mass. The two most precise measurements of it ever made disagree about what it is by 73.3 MeV — five and a half times their combined uncertainty. In 2022 the CDF collaboration, closing out the Tevatron's full dataset, reported m_W = 80,433.5 ± 9.4 MeV, the most precise single measurement in the field's history, sitting 6.9 sigma above the Standard Model's global-fit prediction of 80,357 ± 6 MeV. In 2024 the CMS collaboration reported m_W = 80,360.2 ± 9.9 MeV — the same precision, the opposite verdict, 0.3 sigma from the prediction. Both cannot be right; their error budgets are twins and their central values are strangers. The Particle Data Group's 2026 edition prints the state of the record plainly: combine all the world's W-mass measurements and their mutual compatibility is 0.06%; remove CDF and it is 96.9% — so the printed world average, 80,362.5 ± 7.7 MeV, is an average of the world minus one experiment. This paper prices the defect: what 76.5 MeV would cost the Standard Model if CDF is right; what a 5.4-sigma inter-experiment gap between audited budgets means if CMS is right; and the quiet fact that the measurements are cousins, not strangers — they share parton distributions, shared modelling machinery, and one shared assumption, that the templates they fit were built by hands that already knew the expected answer. Grade: DEFECT STANDS — ONE TABLE AGAINST THE FIELD, PRICED. This paper stands outside my work on the vacuum catastrophe; it draws nothing from that work and repairs nothing in it.