7 research outputs found
Parity-Violating Electron Scattering from 4He and the Strange Electric Form Factor of the Nucleon
We have measured the parity-violating electroweak asymmetry in the elastic
scattering of polarized electrons from ^4He at an average scattering angle
= 5.7 degrees and a four-momentum transfer Q^2 = 0.091 GeV^2. From
these data, for the first time, the strange electric form factor of the nucleon
G^s_E can be isolated. The measured asymmetry of A_PV = (6.72 +/- 0.84 (stat)
+/- 0.21 (syst) parts per million yields a value of G^s_E = -0.038 +/- 0.042
(stat) +/- 0.010 (syst), consistent with zero
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Constraints on the nucleon strange form factors at Q(2)similar to 0.1 GeV2
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 ă Ξlab ă = 6.0â, with the result APV = ( - 1.14 ± 0.24 ( stat ) ± 0.06 ( syst ) ) Ă 10-6. From this we extract, at Q2 = 0.099  GeV2, the strange form factor combination {Mathematical expression} 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 GEs and GMs at Q2 ⌠0.1  GeV2. A consistent picture emerges when several measurements at about the same Q2 value are combined: GEs is consistent with zero while positive values are favored for GMs, though GEs = GMs = 0 is compatible with the data at 95% C.L. © 2006 Elsevier B.V. All rights reserved
Precision measurements of the nucleon strange form factors at Q(2)similar to 0.1 GeV2
We report new measurements of the parity-violating asymmetry A(PV) in elastic scattering of 3 GeV electrons off hydrogen and 4He targets with approximately 6.0 degrees . The 4He result is A(PV)=(+6.40+/-0.23(stat)+/-0.12(syst))x10(-6). The hydrogen result is A(PV)=(-1.58+/-0.12(stat)+/-0.04(syst))x10(-6). These results significantly improve constraints on the electric and magnetic strange form factors G(E)(s) and G(M)(s). We extract G(E)(s)=0.002+/-0.014+/-0.007 at =0.077 GeV2, and G(E)(s)+0.09G(M)(s)=0.007+/-0.011+/-0.006 at =0.109 GeV2, providing new limits on the role of strange quarks in the nucleon charge and magnetization distributions
Precision measurements of the nucleon strange form factors at Q(2)similar to 0.1 GeV2 RID A-2969-2011
We report new measurements of the parity-violating asymmetry APV in elastic scattering of 3 GeV
electrons off hydrogen and 4He targets with h-lab=6deg. The 4He result is APV=(+6.40+-0.23stat+0.04syst)x10**6. The hydrogen result is APV=
(1.58+-0.12stat+-0.04syst)*10**6. These results
significantly improve constraints on the electric and magnetic strange form factors GsE and GsM. We
extract GsE=0.002+-0.014+-0.007 at Q**2=0.077 GeV2, and GsE+0.09GsM=0.007+-0.011+-0.006 at Q2=0.109 GeV2, providing new limits on the role of strange quarks in the nucleon charge
and magnetization distributions