Session L05: Intersections of Nuclear and Nucleon Structure

Preliminary results searching for the onset of color transparency in A(e,e'p) in Hall C at Jefferson Lab

Color transparency (CT) is a fundamental phenomenon of QCD postulating that at high momentum transfer, one can preferentially measure hadrons that fluctuate to a small color neutral transverse size in the nucleus, and final state interactions within the nuclear medium are sup- pressed. CT is observed experimentally as a rise in the measured nuclear transparency as a function of the momentum transferred. While CT has been observed for mesons, it remains unconfirmed in baryons. Observation of CT in baryons would provide a new means to study the nuclear strong force and would be the first clear observation of hadrons fluctuating to a small size in the nucleus. An enhancement in the nuclear transparency was observed in A(p,2p) reactions at Brookhaven. This experiment, E1206107, seeks to confirm the measurement of pro- ton transparency as well as to measure the onset. During the spring of 2018, this experiment was the first to run in Hall C at Jefferson Lab using the recently upgraded 12 GeV electron beam and obtained four kinematic points at momentum transfer Q^2 from 8-14.3 GeV^2, overlapping the same region where Brookhaven previously observed an enhancement. This ex- periment used the High Momentum Spectrometer (HMS) and Super High Momentum Spectrometer (SHMS) in coincidence to measure A(e,e'p) on a carbon target. This talk will summarize the motivation to measure the onset of color transparency in baryons and will present preliminary results from this experiment. DOE Grant Number: DE-FG02-07ER41528   

Bound Nucleon Structure in QCD and Quark Confinement

The reasons for believing that nucleons that are bound in nuclei are different from those that move freely are discussed using examples from experiment and theory. These show that the structure of the nucleon must be modified by its presence in a nucleus, and that  the modifications must be small. Existing data regarding lepton-nucleus interactions and simple theory based on  electromagnetic current conservation and analytic properties of scattering amplitudes are used to display the importance of quark confinement in limiting the sizes of some of these modifications. Furthermore, quark confinement is shown to be an essential requirement in understanding   lepton-nucleus interactions and  the resulting derived nuclear properties to be as they are observed.