Eur. Phys. J. A (2007) 32: 451-455
https://doi.org/10.1140/epja/i2006-10394-y

PAVI 2006

New results from the HAPPEX Experiments at Q² = 0.1GeV/c²

Department of Physics, College of William & Mary, 23187-8795, Williamsburg, VA, USA

^* e-mail: armd@jlab.org

Received: 31 August 2006
Accepted: 18 March 2007
Published online: 11 June 2007

Abstract

The nucleon's strange electric and magnetic form factors G _E ^s and G _M ^s can be probed via parity-violating electron scattering. The HAPPEX Collaboration has made new measurements of the parity-violating asymmetry A _PV in elastic scattering of 3GeV electrons off hydrogen and ⁴He targets with 〈θ_lab〉 ≈ 6.0^° . For ⁴He the preliminary result is A _PV = (+ 6.43±0.23(stat)±0.22(syst))×10^-6 . For hydrogen the preliminary result is A _PV = (- 1.60±0.12(stat)±0.05(syst))×10^-6 . From these values we extract G ^s _E = 0.004±0.014±0.013 at 〈Q ²〉 = 0.077 GeV/c^2 , and G ^s _E +0.09G ^s _M = 0.004±0.011±0.005 at 〈Q ²〉 = 0.109 GeV/c^2 , both consistent with zero, providing stringent new limits on the role of strange quarks in the vector structure of the nucleon.