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

Constraints on the Nucleon Strange Form Factors at Q^2 ~ 0.1 GeV^2

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 =6 degrees, with the result A_PV = -1.14 +/- 0.24 (stat) +/- 0.06 (syst) parts per million. From this we extract, at Q^2 = 0.099 GeV^2, the strange form factor combination G_E^s + 0.080 G_M^s = 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 G_E^s and G_M^s at Q^2 ~0.1 GeV^2. A consistent picture emerges when several measurements at about the same Q^2 value are combined: G_E^s is consistent with zero while G_M^s prefers positive values though G_E^s=G_M^s=0 is compatible with the data at 95% C.L.Comment: minor wording changes for clarity, updated references, dropped one figure to improve focu

Constraints on the nucleon strange form factors at Q2 ∼ 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 〈 θlab 〉 = 6.0○, with the result APV = ( - 1.14 ± 0.24 ( stat ) ± 0.06 ( syst ) ) × 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 Q2∼0.1 GeV^2

We report new measurements of the parity-violating asymmetry APV in elastic scattering of 3 GeV electrons off hydrogen and He4 targets with ⟨θlab⟩≈6.0°. The He4 result is APV=(+6.40±0.23(stat)±0.12(syst))×10−6. The hydrogen result is APV=(−1.58±0.12(stat)±0.04(syst))×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 ⟨Q2⟩=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

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 〈 θlab 〉 = 6.0○, with the result APV = ( - 1.14 ± 0.24 ( stat ) ± 0.06 ( syst ) ) × 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

Measurement of the 3He spin-structure functions and of neutron (3He) spin-dependent sum rules at 0.035 ≤ Q2 ≤ 0.24 GeV2

International audienceThe spin-structure functions g1 and g2, and the spin-dependent partial cross-section σTT have been extracted from the polarized cross-sections differences, Δσ∥(ν,Q2) and Δσ⊥(ν,Q2) measured for the He3→(e→,e′)X reaction, in the E97-110 experiment at Jefferson Lab. Polarized electrons with energies from 1.147 to 4.404 GeV were scattered at angles of 6∘ and 9∘ from a longitudinally or transversely polarized 3He target. The data cover the kinematic regions of the quasi-elastic, resonance production and beyond. From the extracted spin-structure functions, the first moments Γ1‾(Q2), Γ2(Q2) and ITT(Q2) are evaluated with high precision for the neutron in the Q2 range from 0.035 to 0.24GeV2. The comparison of the data and the chiral effective field theory predictions reveals the importance of proper treatment of the Δ degree of freedom for spin observables