Details

Autor(en) / Beteiligte

• Maas, F E
• Achenbach, P
• Aulenbacher, K
• Baunack, S
• Capozza, L
• Diefenbach, J
• Grimm, K
• Imai, Y
• Hammel, T
• von Harrach, D
• Kabuss, E M
• Kothe, R
• Lee, J H
• Lorente, A
• Lopes Ginja, A
• Nungesser, L
• Schilling, E
• Stephan, G
• Weinrich, C
• Altarev, I
• Arvieux, J
• Collin, B
• Frascaria, R
• Guidal, M
• Kunne, R
• Marchand, D
• Morlet, M
• Ong, S
• van de Wiele, J
• Kowalski, S
• Plaster, B
• Suleiman, R
• Taylor, S

Titel

Measurement of strange-quark contributions to the nucleon's form factors at Q(2) = 0.230 (GeV/c)(2)

Ist Teil von

• Physical review letters, 2004-07, Vol.93 (2), p.022002-022002

Ort / Verlag

United States

Erscheinungsjahr

2004

Quelle

American Physical Society Journals

Beschreibungen/Notizen

• We report on a measurement of the parity-violating asymmetry in the scattering of longitudinally polarized electrons on unpolarized protons at a Q2 of 0.230 (GeV/c)(2) and a scattering angle of theta (e) = 30 degrees - 40 degrees. Using a large acceptance fast PbF2 calorimeter with a solid angle of delta omega = 0.62 sr, the A4 experiment is the first parity violation experiment to count individual scattering events. The measured asymmetry is A(phys)=(-5.44+/-0.54(stat)+/-0.26(sys))x10(-6). The standard model expectation assuming no strangeness contributions to the vector form factors is A(0) = (-6.30+/-0.43) x 10(-6). The difference is a direct measurement of the strangeness contribution to the vector form factors of the proton. The extracted value is G(s)(E) + 0.225G(s)(M) = 0.039+/-0.034 or F(s)(1) + 0.130F(s)(2) = 0.032+/-0.028.