Collaboration, A;
Maas, FE;
Achenbach, P;
Aulenbacher, K;
Baunack, S;
Capozza, L;
Diefenbach, J;
... Taylor, S; + view all
(2004)
Measurement of Strange Quark Contributions to the Nucleon's Form Factors at Q^2=0.230 (GeV/c)^2.
Physical Review Letters
, 93
(2)
10.1103/PhysRevLett.93.022002.
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Abstract
We report on a measurement of the parity-violating asymmetry in the scattering of longitudinally polarized electrons on unpolarized protons at a $Q^2$ of 0.230 (GeV/c)^2 and a scattering angle of \theta_e = 30^o - 40^o. Using a large acceptance fast PbF_2 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} +- 0.27_{\rm sys}) 10^{-6}. The Standard Model expectation assuming no strangeness contributions to the vector form factors is $A_0=(-6.30 +- 0.43) 10^{-6}$. 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 + 0.225 G^s_M = 0.039 +- 0.034 or F^s_1 + 0.130 F^s_2 = 0.032 +- 0.028.
| Type: | Article |
|---|---|
| Title: | Measurement of Strange Quark Contributions to the Nucleon's Form Factors at Q^2=0.230 (GeV/c)^2 |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1103/PhysRevLett.93.022002 |
| Publisher version: | http://dx.doi.org/10.1103/PhysRevLett.93.022002 |
| Language: | English |
| Additional information: | © 2004 The American Physical Society |
| URI: | https://discovery.ucl.ac.uk/id/eprint/1375195 |
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