Measurement of the x- and Q² -Dependence of the Asymmetry A1 on the Nucleon

Authors

K. V. Dharmawardane, Old Dominion University
S. E. Kuhn, Old Dominion UniversityFollow
P. Bosted
Y. Prok
G. Adams
P. Ambrozewicz
M. Anghinolfi
G. Asryan
H. Avakian
H. Bagdasaryan, Old Dominion University
M. Bektasoglu, Old Dominion University
S. Bültmann, Old Dominion UniversityFollow
S. L. Careccia, Old Dominion University
G. E. Dodge, Old Dominion UniversityFollow
T. A. Forest, Old Dominion University
G. Gavalian, Old Dominion University
N. Guler, Old Dominion University
C. E. Hyde-Wright, Old Dominion UniversityFollow
H. G. Juengst, Old Dominion University
A. Klein, Old Dominion University
J. Lachniet, Old Dominion University
M. R. Niroula, Old Dominion University
R. A. Niyazov, Old Dominion University
L. M. Qin, Old Dominion University
F. Sabatié, Old Dominion University
S. Tkachenko, Old Dominion University
L. B. Weinstein, Old Dominion UniversityFollow
J. Zhang, Old Dominion University

Document Type

Article

Publication Date

2006

DOI

10.1016/j.physletb.2006.08.011

Publication Title

Physics Letters B

Volume

641

Issue

1

Pages

11-17

Abstract

We report results for the virtual photon asymmetry A₁ on the nucleon from new Jefferson Lab measurements. The experiment, which used the CEBAF Large Acceptance Spectrometer and longitudinally polarized proton (¹⁵NH₃) and deuteron (¹⁵ND₃) targets, collected data with a longitudinally polarized electron beam at energies between 1.6 GeV and 5.7 GeV. In the present Letter, we concentrate on our results for A₁ ( x , Q² ) and the related ratio g1 / F₁ ( x , Q² ) in the resonance and the deep inelastic regions for our lowest and highest beam energies, covering a range in momentum transfer Q² from 0.05 to 5.0 ( GeV /c )² and in final-state invariant mass W up to about 3 GeV. Our data show detailed structure in the resonance region, which leads to a strong Q² -dependence of A₁ (x, Q²) for W below 2 GeV. At higher W, a smooth approach to the scaling limit, established by earlier experiments, can be seen, but A₁ ( x, Q²) is not strictly Q² -independent. We add significantly to the world data set at high x, up to x = 0.6 . Our data exceed the SU ( 6 ) -symmetric quark model expectation for both the proton and the deuteron while being consistent with a negative d-quark polarization up to our highest x. This data set should improve next-to-leading order (NLO) pQCD fits of the parton polarization distributions.

Comments

Open access under CC BY license.

Original Publication Citation

Dharmawardane, K. V., Kuhn, S. E., Bosted, P., Prok, Y., Adams, G., Ambrozewicz, P., . . . Zhao, Z. (2006). Measurement of the x- and Q²-dependence of the asymmetry A₁ on the nucleon. Physics Letters B, 641(1), 11-17. doi:https://doi.org/10.1016/j.physletb.2006.08.011

ORCID

0000-0003-2243-6836 (Kuhn), 0000-0002-5680-1814 (Bültmann), 0000-0003-1582-237 (Dodge), 0000-0001-7282-8120 (Hyde), 0000-0001-5416-2900 (weinstein)

Repository Citation

Dharmawardane, K. V.; Kuhn, S. E.; Bosted, P.; Prok, Y.; Adams, G.; Ambrozewicz, P.; Anghinolfi, M.; Asryan, G.; Avakian, H.; Bagdasaryan, H.; Bektasoglu, M.; Bültmann, S.; Careccia, S. L.; Dodge, G. E.; Forest, T. A.; Gavalian, G.; Guler, N.; Hyde-Wright, C. E.; Juengst, H. G.; Klein, A.; Lachniet, J.; Niroula, M. R.; Niyazov, R. A.; Qin, L. M.; Sabatié, F.; Tkachenko, S.; Weinstein, L. B.; and Zhang, J., "Measurement of the x- and Q² -Dependence of the Asymmetry A1 on the Nucleon" (2006). Physics Faculty Publications. 109.
https://digitalcommons.odu.edu/physics_fac_pubs/109