Loading...
Measurement of the strange sea of the proton
Rutledge, Gary A.
Rutledge, Gary A.
Abstract
The differential cross section for elastic scattering of longitudinally-polarized electrons from protons exhibits a parity-violating asymmetry, due to the interference between weak and electromagnetic amplitudes. The asymmetry is extracted from the detector counting rates as APV = ( Dr - Dl)/(Dr + D l) where Drl are related to the right (left) differential cross sections sigmar, sigmal respectively. Thus APV = (sigmar - sigma l)/(sigmar + sigmal) for right-handed and left-handed electrons. This asymmetry is sensitive to the presence of strange sea quarks in the proton, in particular to the strange vector matrix elements GsE and GsM .;In an experiment performed in April--May 1998 and May 1999 in Hall A at the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab, data were obtained for a total of 179.6 Coulombs of incident electrons. Elastically-scattered electrons corresponding to an average Q 2 = 0.477(GeV/c)2 were detected in a pair of high-resolution spectrometers.;The excellent stability of the CEBAF beam led to negligible contribution from false asymmetries; Averaged over the experiment, the helicity-correlated beam position differences were less than 10nm and the helicity-correlated beam intensity asymmetries were less than 1 ppm.;The result APV = -15.05 +/- 0.98(stat) +/- 0.56(syst) ppm was measured at the kinematic point 〈thetalab〉 = 12.3?? and 〈 Q2〉 = 0.447 (GeV/c)2. Comparing the experimental asymmetry with the theoretical asymmetry, A th, allows extraction for the value of the strange form factor &parl0;GsE+ 0.392GsM&parr0;/&parl0;Gp M/mp&parr0; = 0.069 +/- 0.056 +/- 0.039, where the first error is experimental and the second arises from uncertainty in the electromagnetic form factors.
Description
Date
2001-01-01
Journal Title
Journal ISSN
Volume Title
Publisher
Collections
Download Dataset
Files
Loading...
3037193.pdf
Adobe PDF, 7.44 MB
Rights Holder
Usage License
Embargo
Research Projects
Organizational Units
Journal Issue
Keywords
Citation
Advisor
Department
Physics
DOI
https://dx.doi.org/doi:10.21220/s2-c0a3-5520