ar X iv : n uc l - ex / 0 50 60 11 v 2 2 3 D ec 2 00 5 Constraints on theNucleonStrangeFormFactors at Q 2 ∼ 0 . 1 GeV 2 The HAPPEXCollaboration
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چکیده
We report the most precise measurement to date of a parity-violating asymmetry in elastic electron-proton scattering. The measurement was carried out with a beam energy of 3.03 GeV and a scattering angle 〈θlab〉 = 6.0 ◦, with the result APV = (−1.14 ± 0.24 (stat) ± 0.06 (syst)) × 10. From this we extract, at Q = 0.099GeV, the strange form factor combination GsE + 0.080G s M = 0.030 ± 0.025 (stat) ± 0.006 (syst) ± 0.012 (FF) where the first two errors are experimental and the last error is due to the uncertainty in the neutron electromagnetic form factor. This result significantly improves current knowledge of GsE and G s M at Q 2 ∼ 0.1GeV. A consistent picture emerges when several measurements at about the same Q value are combined: GsE is consistent with zero while G s M prefers positive values though G s E = G s M = 0 is compatible with the data at 95% C.L.
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تاریخ انتشار 2006