Date Awarded

2005

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Physics

Advisor

Keith A Griffioen

Abstract

We present an analysis of data from experiment E94-019 using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility (TJNAF). The experiment ran in the spring of 2002 over the course of two months with 5.765 GeV unpolarized electron beam on a liquid deuterium target and collected a total of 4.5 x 109 triggers. These data cover a wide kinematic range from the quasi-elastic peak up to an invariant mass W ≈ 3 GeV of the final hadronic system for momentum transfer Q 2 from 1.5 to 6.0 GeV2. Using CLAS we tagged spectator protons released in quasielastic scattering from high-momentum neutrons in deuterium at large emission angles with respect to the momentum transfer direction. Using these data one can test the physics of small-sized wavepacket expansion inside the nucleus. The absorption of a high-momentum virtual photon on a nucleon leads to the production of a small-sized wavepacket (due to the suppression of long-range pion and gluon fields) which evolves rapidly in time until it reaches the nucleon size. We can investigate how such a wavepacket moves within a nucleus and how long-range fields are restored. This study could provide information about the quark-gluon degrees of freedom, internucleon forces in nuclei, and color coherence effects such as color screening (CS) and color transparency (CT). Color screening would allow a small-sized object to escape from the nucleus without further interaction. Measuring the evolution of FSIs with the momentum transfer Q2 could reveal whether or not nuclear transparency may occur in quasielastic reactions such as d(e,e'p)n. We computed the ratio of the experimental cross section for d(e,e'p)n measured for kinematics dominated by rescattering effects to the cross section measured for the kinematics dominated by screening effects (suppression of FSIs). We have extracted absolute cross sections for the inclusive d(e,e') channel. They are presented in two-dimension kinematic bins with Q2 = 1.7 - 6.7 GeV2 and x = 0.7--1.9. By mapping these cross sections we can extract the probabilities of finding short range nucleon-nucleon correlation (SRC) state in nucleus. Absolute cross section for the exclusive d(e,e'p)n channel are presented for spectator momenta ps from 250 to 1000 MeV/c and Q2 = 2--6 GeV 2. Experimental measurements suggest a strong contribution from meson exchange and Delta-isobar currents which dominate FSIs. This makes it difficult to observe color coherent effects. This picture is corroborated by new theoretical developments.

DOI

https://dx.doi.org/doi:10.21220/s2-1cq8-mc12

Rights

© The Author

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