2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009;
Denver, Colorado
Session L4: Nucleon Microscopy
3:30 PM–5:18 PM,
Sunday, May 3, 2009
Room: Plaza F
Sponsoring
Unit:
DNP
Chair: Kees De Jager, Thomas Jefferson National National Accelerator Facility
Abstract ID: BAPS.2009.APR.L4.2
Abstract: L4.00002 : The Elastic Electromagnetic Form Factors of the Proton
4:06 PM–4:42 PM
Preview Abstract
Abstract
Author:
Edward Brash
(Christopher Newport University and Jefferson Laboratory)
In many senses, the internal structure of the nucleon is the defining
problem of QCD, the fundamental theory of the strong interaction.
The internal structure of the nucleon defines its mass, spin, and its
interactions. The nucleon is the fundamental building block of the
nucleus, and indeed it is the residual nucleon-nucleon interaction
that governs all nuclear structure, in much the same way that residual
interactions between atoms governs molecular structure. As such, a
full and detailed quantitative understanding of the internal structure
of the nucleon is a necessary precursor to extending our understanding
of nuclear physics.
A fundamental test of the QCD in the confinement region
is the electromagnetic structure of the nucleon.
In particular, measurements of the elastic electric and magnetic form
factors of the proton, $G_{Ep}$ and $G_{Mp}$, respectively, at
large momentum transfer, $Q^2$, shed new light on its internal
nonperturbative structure.
The ratio, $R_p = \mu_p G_{Ep}/G_{Mp}$, where $\mu_p$ is the
proton magnetic moment, has been measured extensively over the last
decade at the Jefferson Laboratory, using the polarization transfer
method, where one measures $R_p$ directly by measuring the ratio of transverse
to longitudinal polarizations of the recoiling proton in elastic electron-proton
scattering. These data have revealed
that the ratio decreases approximately linearly with increasing $Q^2$ above
a $Q^2$ $\sim$ 1~GeV$^2$.
The polarization transfer results are
of unprecedented high precision and accuracy, due in large part to the
small systematic uncertainties associated with the experimental
technique. Most recently, the Gep-III Experiment was completed in June of 2008 in
Hall C at Jefferson Laboratory. It extends the Q$^2$-range from 5.6 to 8.54
GeV$^2$.
In this presentation, I will review the status of the proton elastic electromagnetic
form factor data, including
the latest results from the Gep-III experiment, and discuss a number of theoretical
approaches to describing nucleon form factors.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.APR.L4.2