The conclusions from the combined experimental evidence were that: the effect had a universal shape was independent of the squared four-momentum transfer, Q 2 increased with nuclear mass number A and scaled with the average nuclear density. 1995) and the New Muon collaboration (NMC) at CERN (Amaudruz et al. This surprising result was confirmed by many groups, culminating with the high-precision electron- and muon-scattering data from SLAC (Gomez et al. This surprising result was confirmed by many groups What the EMC experiment discovered was an unexpected downwards slope to the ratio (figure 1) – as revealed in CERN Courier in November 1982 and then published in a refereed journal the following March (Aubert et al. The binding energies of nucleons in the nucleus are several orders of magnitude smaller than the momentum transfers of deep-inelastic scattering, so, naively, such a ratio should be unity except for small corrections for the Fermi motion of nucleons in the nucleus. The data were plotted as a function of Bjorken-x, which in deep-inelastic scattering is interpreted as the fraction of the nucleon’s momentum carried by the struck quark. This is what happened 30 years ago when the European Muon collaboration (EMC) at CERN looked at the ratio of their data on per-nucleon deep-inelastic muon scattering off iron and compared it with that of the much smaller nucleus of deuterium. Instead, they are about results that make a researcher say, “That’s strange”. 1983) because the editor argued that the data had already been published.Ĭontrary to the stereotype, advances in science are not typically about shouting “Eureka!”. This image nearly derailed the highly cited refereed publication (Aubert et al. A plot of the EMC data as it appeared in the November 1982 issue of CERN Courier.
There is renewed interest in an old surprise.
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