Measurement of two-and three-nucleon shortrange correlation probabilities in nuclei KS The ratios of inclusive electron scattering cross sections of 4 He, 12 C, and 56 Fe to 3 He have been measured at 1 < x B < 3. At Q 2 > 1:4 GeV 2 , the ratios exhibit two separate plateaus, at 1:5 < x B < 2 and at x B > 2:25. This pattern is predicted by models that include 2-and 3-nucleon short-range correlations (SRC). Relative to A 3, the per-nucleon probabilities of 3-nucleon SRC are 2.3, 3.1, and 4.4 times larger for A 4, 12, and 56. This is the first measurement of 3-nucleon SRC probabilities in nuclei.

The ratios of inclusive electron scattering cross sections of 4 He, 12 C, and 56 Fe to 3 He have been measured for the first time. It is shown that these ratios are independent of x B at Q 2 Ͼ1.4 GeV 2 for x B Ͼ1.5, where the inclusive cross section depends primarily on the high momentum components of the nuclear wave function. The observed scaling shows that the momentum distributions at high-momenta have the same shape for all nuclei and differ only by a scale factor. The observed onset of the scaling at Q 2 Ͼ1.4 GeV 2 and x B Ͼ1.5 is consistent with the kinematical expectation that two-nucleon short range correlations ͑SRC͒ dominate the nuclear wave function at p m տ300 MeV/c. The values of these ratios in the scaling region can be related to the relative probabilities of SRC in nuclei with Aу3. Our data, combined with calculations and other measurements of the 3 He/deuterium ratio, demonstrate that for nuclei with Aу12 these probabilities are 4.9-5.9 times larger than in deuterium, while for 4 He it is larger by a factor of about 3.8.

We measured the inclusive electron-proton cross section in the nucleon resonance region (WϽ2.5 GeV) at momentum transfers Q 2 below 4.5 (GeV/c) 2 with the CLAS detector. The large acceptance of CLAS allowed the measurement of the cross section in a large, contiguous two-dimensional range of Q 2 and x, making it possible to perform an integration of the data at fixed Q 2 over the significant x interval. From these data we extracted the structure function F 2 and, by including other world data, we studied the Q 2 evolution of its moments, M n (Q 2 ), in order to estimate higher twist contributions. The small statistical and systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and will require significant improvements in theoretical predictions if a meaningful comparison with these new experimental results is to be made.

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