Armstrong, D.S.
FORMFAC
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Measurement of the neutral weak form factors of the proton.

The HAPPEX collaboration Aniol, K.A. ; Armstrong, D.S. ; Baylac, M. ; et al.
Phys.Rev.Lett. 82 (1999) 1096-1100, 1999.
Inspire Record 478059 DOI 10.17182/hepdata.31319

We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from the proton. The kinematic point (theta_lab = 12.3 degrees and Q^2=0.48 (GeV/c)^2) is chosen to provide sensitivity, at a level that is of theoretical interest, to the strange electric form factor G_E^s. The result, A=-14.5 +- 2.2 ppm, is consistent with the electroweak Standard Model and no additional contributions from strange quarks. In particular, the measurement implies G_E^s + 0.39G_M^s = 0.023 +- 0.034 (stat) +- 0.022 (syst) +- 0.026 (delta G_E^n), where the last uncertainty arises from the estimated uncertainty in the neutron electric form factor.

1 data table
Table 1

Longitudinally polarized beam. C=L and C=R means left- and right polarization. The second systematic uncertainty arises from the estimated uncertainty inthe neutron electromagnetic from factor.


Electroproduction of the Delta Resonance at High Momentum Transfer

Frolov, V.V. ; Adams, G.S. ; Ahmidouch, A. ; et al.
Phys.Rev.Lett. 82 (1999) 45-48, 1999.
Inspire Record 475116 DOI 10.17182/hepdata.41616

We studied the electroproduction of the Delta(1232) resonance via the reaction p(e,e'p)\pi0 at four-momentum transfers Qsq = 2.8 and 4.0 GeV^2. This is the highest Qsq for which exclusive resonance electroproduction has ever been observed. Decay angular distributions for Delta to p-pi0$ were measured over a wide range of barycentric energies covering the resonance. The $N-\Delta$ transition form factor G*_M and ratios of resonant multipoles E{1+}/M{1+} and S{1+}/M{1+} were extracted from the decay angular distributions. These ratios remain small, indicating that perturbative QCD is not applicable for this reaction at these momentum transfers.

4 data tables
Table 1

CONST(NAME=E1+/M1+) and CONST(NAME=S1+/M1+) are the ratios of the electric quadrupole moment to magnetic dipole moment and Coulomb quadrupole moment to magnetic dipole moment, respectively (see paper). Resonance only.

Table 2

CONST(NAME=E1+/M1+) and CONST(NAME=S1+/M1+) are the ratios of the electric quadrupole moment to magnetic dipole moment and Coulomb quadrupole moment to magnetic dipole moment, respectively (see paper). Resonance only.

Table 3

CONST(NAME=E1+/M1+) and CONST(NAME=S1+/M1+) are the ratios of the electric quadrupole moment to magnetic dipole moment and Coulomb quadrupole moment to ma gnetic dipole moment, respectively (see paper). Resonance + background.

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A measurement of the electric form-factor of the neutron through d(pol.)(e(pol.),e' n)p at Q**2 = 0.5-(GeV/c)**2.

The E93026 collaboration Zhu, H. ; Ahmidouch, A. ; Anklin, H. ; et al.
Phys.Rev.Lett. 87 (2001) 081801, 2001.
Inspire Record 556212 DOI 10.17182/hepdata.31418

We report the first measurement of the neutron electric form factor $G_E^n$ via $\vec{d}(\vec{e},e'n)p$ using a solid polarized target. $G_E^n$ was determined from the beam-target asymmetry in the scattering of longitudinally polarized electrons from polarized deuterated ammonia, $^{15}$ND$_3$. The measurement was performed in Hall C at Thomas Jefferson National Accelerator Facility (TJNAF) in quasi free kinematics with the target polarization perpendicular to the momentum transfer. The electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle segmented detector. We find $G_E^n = 0.04632\pm0.00616 (stat.) \pm0.00341 (syst.)$ at $Q^2 = 0.495$ (GeV/c)$^2$.

1 data table
Table 1

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