Strukturfunktionsmessungen in der tiefinelastischen Myon-Nukleon-Streuung

Measurements of deep inelastic scattering events on a combined copper and deuterium target were performed by the European Muon Collaboration (EMC) using a muon beam at CERN's SPS with energies at 100 GeV and 280GeV. The data are analysed and compared with a detailed Monte-Carlo simulation and allow the determination of structure functions from both targets. In the light of the present discrepancy between EMC's and BCDMS's structure functions, stringend cuts were applied to the data. The results confirm the EMC structure function measurements on unbound nucleons. The comparison between the copper structure function from this experiment and the NA2 iron structure function shows a trend to lower values at low $x_Bj$. Thus the ratio of the structure functions from this experiment, well known as the EMC-effect, agree with data from recent measurements of EMC and other experiments. The concept of this experiment also allows a direct measurement of the EMC-effect with high statistics (~ 245.000 events) and small systematic errors over a large region in $x_Bj$ and $Q^2$. Eight years after the discovery of the EMC-effect a very coherent picture emerges from all experimental data where four regions can be distinguished: shadowing at very small $x_Bj$, antishadowing at $0.1 \leq x_Bj \leq 0.3$, a linear fall at $0.3 \leq x_Bj \leq 10.7$ and again a rise of the ratio due to Fermi smearing al $x_Bj \geq 0.7. \textrm{A}$ "second generation" of models describing the EMC-effect in a self-consistent way over a large $x_Bj$-region begins to settle, the comparison to experimental data joins this coherent outlook. Several investigations using data from this experiment and combinations with other data lead all to the same indication of a - small - $Q^2$-dependence of the EMC-effect: the structure function ratio rise at small $x_Bj$; with increasing $Q^2$ and falls at high $x_Bj$. At $x_Bj \geq 0.4$ all data from muon-scattering experiments which measure at high $Q^2$ show a stronger $Q^2$-dependence as observed when combining these data with SLAC-experiments performed at lower $Q^2$.