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].
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.
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