Observation of nuclear scaling in the A(e,e′) reaction at xB>1 -: art. no. 014313

The ratios of inclusive electron scattering cross sections of He-4, C-12, and Fe-56 to He-3 have been measured for the first time. It is shown that these ratios are independent of x(B) at Q(2)>1.4 GeV2 for x(B)>1.5, 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)>1.4 GeV2 and x(B)>1.5 is consistent with the kinematical expectation that two-nucleon short range correlations (SRC) dominate the nuclear wave function at p(m)greater than or similar to300 MeV/c. The values of these ratios in the scaling region can be related to the relative probabilities of SRC in nuclei with Agreater than or equal to3. Our data, combined with calculations and other measurements of the He-3/deuterium ratio, demonstrate that for nuclei with Agreater than or equal to12 these probabilities are 4.9-5.9 times larger than in deuterium, while for He-4 it is larger by a factor of about 3.8.