We measured simultaneously pp elastic and quasielastic ͑ p, 2p͒ scattering in hydrogen, deuterium, and carbon for momentum transfers of 4.8 to 6.2 ͑GeV͞c͒ 2 at incoming momenta of 5.9 and 7.5 GeV͞c and center-of-mass scattering angles in the range u c.m. 83.7 ± 90 ± . The nuclear transparency is defined as the ratio of the quasielastic cross section to the free pp cross section. At incoming momentum of 5.9 GeV͞c, the transparency of carbon decreases by a factor of 2 from u c.m. Ӎ 85 ± to u c.m. Ӎ 89 ± . At the largest angle the transparency of carbon increases from 5.9 to 7.5 GeV͞c by more than 50%. The transparency in deuterium does not depend on incoming momentum nor on u c.m. . [S0031-9007 (98)07818-1] PACS numbers: 24.85. + p, 25.40. -h, 24.10. -iNuclear transparency is a measure of the initial and final state interactions that the incoming and outgoing protons undergo before and after the main ͑p, 2p͒ reaction. Conventional theoretical calculations of the nuclear transparency within the Glauber picture [1,2] predict that above an incident momentum of approximately 5 GeV͞c the nuclear transparency does not depend on the incoming momentum nor on the pp c.m. scattering angle, u c.m. . The expectation from QCD based models of proton dynamics in hard exclusive interactions is that the initial and final state scattering may be smaller than the Glauber theory would predict. It is also expected that nuclear transparency should increase with incoming momentum reaching an asymptotic value of 1. These QCD phenomena have been referred to as color transparency [3].

We report results on a precision measurement of the ratio R = uLIUT in deep inelastic electronnucleon scattering in the kinematic range 0.2 ~ x ~ 0.5 and 1 ~ Q 2 ~ 10 ( Ge VIc ) 2 • Our results show, for the first time, a clear falloff of R with increasing Q 2 • Our R results are in agreement with QCD predictions only when corrections for target mass effects and some additional higher twist effects are included. At small x, the data on R favor structure functions with a large gluon contribution. We also report results on the differences RA -RD and the cross section ratio uA I uD between Fe and Au nuclei and the deuteron. Our results for RA -RD are consistent with zero for all x, Q 2 indicating that possible contributions to R from nuclear higher twist effects and spin-0 constituents in nuclei are not different from those in nucleons. The ratios uA I uD from all recent experiments, at all x, Q 2 values, are now in agreement.

Quasielastic e-d cross sections have been measured at forward and backward angles. Rosenbluth separations were done to obtain RL and R T at Q 2 = \.15, 2.50, 3.25, and 4.00 (GeV/c) 2 . The neutron form factors GEH and G\fn have been extracted using a nonrelativistic model. The sensitivity to deuteron wave function, relativistic corrections, and models of the inelastic background are reported. The results for GMn are consistent with the dipole form, while GEH is consistent with zero. Comparisons are made to theoretical models based on vector meson dominance, perturbative QCD, and QCD sum rules, as well as constituent quarks.

Abstract. Recently, a new technique for measuring short-range NN correlations in nuclei (NN SRCs) was reported by the E850 collaboration, using data from the EVA spectrometer at the AGS at Brookhaven Nat. Lab. In this talk, we will report on a larger set of data from new measurement by the collaboration, utilizing the same technique. This technique is based on a very simple kinematic approach. For quasielastic knockout of protons from a nucleus ( 12 C(p,2p) was used for the current work), we can reconstruct the momentum p f of the struck proton in the nucleus before the reaction, from the three momenta of the two detected protons, p 1 and p 2 and the three momentum of the incident proton, p 0 :If there are significant n-p SRCs, then we would expect to find a neutron with momentum -p f in coincidence with the two protons, provided p f is larger than the Fermi momentum k F for the nucleus (∼220 MeV/c for 12 C). Our results reported here confirm the earlier results from the E850 collaboration.

Measurements of the deuteron elastic magnetic structure function B(Q') are reported at squared four-momentum transfer values 1.20~Qi~2.77 (GeV/c)'. Also reported are values for the proton magnetic form factor Gstr(Q2) at 11 Q values between 0.49 and 1.75 (GeV/c) . The data were obtained using an electron beam of 0.5 to 1.3 GeV. Electrons backscattered near 180' were detected in coincidence with deuterons or protons recoiling near 0 in a large solid-angle double-arm spectrometer system. The data for B(Q ) are found to decrease rapidly from Q =1.2 to 2 (GeV/c), and then rise to a secondary maximum around Q'=2. 5 (GeV/c)'. Reasonable agreement is found with several different models, including those in the relativistic impulse approximation, nonrelativistic calculations that include meson-exchange currents, isobar configurations, and six-quark configurations, and one calculation based on the Skyrme model. All calculations are very sensitive to the choice of deuteron wave function and nucleon form factor parametrization. The data for GMr(Q') are in good agreement with the empirical dipole fit.

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