I. Mardor

Nuclear transparency in 90°c.m. quasielastic A(p, 2p) reactions

nuclear transparency deuterons were studied. Second, we review the techniques used in an earlier experiment, E834, and show that the two experiments are consistent for the carbon data. E834 also determines the nuclear transparencies for lithium, aluminum, copper, and lead nuclei as well as for carbon. A determination of the sp + , p + pd transparencies is also reported. We find for both E850 and E834 that the Asp ,2 pd nuclear transparency, unlike that for Ase , e8pd nuclear transparency, is incompatible with a constant value versus energy as predicted by Glauber calculations. The Asp ,2 pd nuclear transparency for carbon and aluminum increases by a factor of two between 5.9 and 9.5 GeV/c incident proton momentum. At its peak the Asp ,2 pd nuclear transparency is ,80% of the constant Ase , e8pd nuclear transparency. Then the nuclear transparency falls back to a value at least as small as that at 5.9 GeV/ c, and is compatible with the Glauber level again. This oscillating behavior is generally interpreted as an interplay between two components of the pN scattering amplitude; one short ranged and perturbative, and the other long ranged and strongly absorbed in the nuclear medium. A study of the A dependent nuclear transparency indicates that the effective cross section varies with incident momentum and is considerably smaller than the free pN cross section. We suggest a number of experiments for further studies of nuclear transparency effects.

The influence of the nuclear medium on K+ total cross sections

Abstract The study of the K+ total cross sections on a wide range of nuclei has revealed important modifications of the free-space K+-nucleon interaction when the nucleon is embedded in a nucleus. Data indicating such an effect were first obtained in a comparison of the total cross sections on carbon and deuterium. In this letter we report new measurements on 6Li, silicon, and calcium, and demonstrate that the previously reported modifications occur quite generally.

The large momentum transfer reaction 12C(p,2p + n) as a new method for measuring short range NN correlations in nuclei

Abstract The reaction 12 C( p ,2 p + n ) was measured for momentum transfers of 4.8 and 6.2 (GeV/c) 2 at beam momenta of 5.9 and 7.5 GeV/c. We measured the quasi-elastic reaction ( p ,2 p ) at θ cm ⋍ 90°, in a kinematically complete measurement. The neutron momentum was measured in triple coincidence with the two emerging high momentum protons. We present the correlation between the momenta of the struck target proton and the neutron. The events are associated with the high momentum components of the nuclear wave function. We present sparse data which, combined with a quasi elastic description of the ( p ,2 p ) reaction and kinematical arguments, point to a novel way for isolating two-nucleon short range correlations.

Measurement of polarization-transfer to bound protons in carbon and its virtuality dependence

Abstract We measured the ratio P x / P z of the transverse to longitudinal components of polarization transferred from electrons to bound protons in C 12 by the C 12 ( e → , e ′ p → ) process at the Mainz Microtron (MAMI). We observed consistent deviations from unity of this ratio normalized to the free-proton ratio, ( P x / P z ) C 12 / ( P x / P z ) H 1 , for both s- and p-shell knocked out protons, even though they are embedded in averaged local densities that differ by about a factor of two. The dependence of the double ratio on proton virtuality is similar to the one for knocked out protons from H 2 and He 4 , suggesting a universal behavior. It further implies no dependence on average local nuclear density.

Components of polarization-transfer to a bound proton in a deuteron measured by quasi-elastic electron scattering

Abstract We report the first measurements of the transverse ( P x and P y ) and longitudinal ( P z ) components of the polarization transfer to a bound proton in the deuteron via the H 2 ( e → , e ′ p → ) reaction, over a wide range of missing momentum. A precise determination of the electron beam polarization reduces the systematic uncertainties on the individual components to a level that enables a detailed comparison to a state-of-the-art calculation of the deuteron using free-proton electromagnetic form factors. We observe very good agreement between the measured and the calculated P x / P z ratios, but deviations of the individual components. Our results cannot be explained by medium modified electromagnetic form factors. They point to an incomplete description of the nuclear reaction mechanism in the calculation.

Transparency in hadronic reactions at high momentum transfers

In this article, experimental results about color transparency of hadrons in nuclei will be briefly reviewed. The current progress of a new experiment, EVA, will also be reported.