Jefferson Lab Experiment E06-007 Homepage

Impulse Approximation limitations to the (e,e',p) reaction on ²⁰⁸Pb, identifying correlations and relativistic effects in the nulcear medium

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Abstract

This measurement will determine the TL asymmtery, A_TL, for protons emitted forward of the three momentum transfer q and backward of q as a function of missing momentum, p_miss for the reaction ²⁰⁸Pb(e,e',p)²⁰⁷Tl. The low lying states in ²⁰⁷Tl will be the focus of this study using the high resolution spectrometers of Hall A. In the range of missing momenta p_miss < 300 MeV/c a complex structure in A_TL is predicted within the impulse approximation. Relativistic mean field calculations predict values of A_TL that deviate substantially from the predictions that do not include the enhancement of the lower component of the wave function due to dynamically relativistic effects. Spectroscopic factors will also be extracted for these low lying states and they will be compared to the ones derived at a lower Q² and over a rane of Q² from 0.81 to 1.97 (GeV/c)² to establish a dependence, or lack thereof, on Q². Cross section measurements will also be extended out to 500 MeV/c in missing momentum. An excess of strength at high p_miss has been found in a former experiment, that has been alternately attributed to long range correlation using nonrelativistic analyses, or to relativistic effects from a full relativistic analysis. This measurement will be made in fixed q,ω kinematics, q=1 GeV/c, ω = 0.433 GeV, Q² = 0.81 (GeV/c)². This is the first measurement of the (e,e',p) reaction in lead done at constant (q,ω) and under quasielastic conditions, χ_B = 1. These data will provide observables for current and future theories of long range correlations and dynamical relativistic effects in the nulcear medium.