Recent results from the G⁰ experiment

¹ Department of Physics, University of Zagreb, Zagreb HR-41001 Croatia
² Department of Physics, College of William and Mary, Williamsburg, VA 23187 USA
³ Institut de Physique Nucléaire d’Orsay, Universite Paris-Sud, F-91406 Orsay Cedex FRANCE
⁴ Loomis Laboratory of Physics, University of Illinois, Urbana, IL 61801 USA
⁵ Physics Department, University of Maryland, College Park, MD 20742 USA
⁶ Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 USA
⁷ Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 USA
⁸ Department of Physics, University of Manitoba, Winnipeg, MB R3T 2N2 CANADA
⁹ TRIUMF, Vancouver, BC V6T 2A3 CANADA
¹⁰ Physics Department, New Mexico State University, Las Cruces, NM 88003 USA
¹¹ LPSC, Universite Joseph Fourier Grenoble 1, CNRS/IN2P3, Institut Polytechnique de Grenoble, Grenoble, FRANCE
¹² Department of Physics and Astronomy, Ohio University, Athens, OH 45701 USA
¹³ Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 USA
¹⁴ Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125 USA
¹⁵ Department of Physics, Virginia Tech, Blacksburg, VA 24061 USA
¹⁶ Department of Physics, University of Winnipeg, Winnipeg, MB R3B 2E9 CANADA
¹⁷ Jozef Stefan Institute, 1000 Ljubljana, SLOVENIA
¹⁸ Yerevan Physics Institute, Yerevan 375036 ARMENIA
¹⁹ Department of Physics, Louisiana Tech University, Ruston, LA 71272 USA
²⁰ Department of Physics, Hendrix College, Conway, AR 72032 USA

^a e-mail: real@in2p3.fr
^b Deceased

Abstract

We have measured parity violating asymmetries in elastic electron-proton and quasi-elastic electrondeuteron scattering at backward electron angle. These measurements have been done at two momentum transfers : Q² = 0.22 and 0.63 (GeV/c)² . Together with our previous forward angle measurement [1], we can extract strange quark contributions to the electromagnetic form factors of the nucleon, as well as nucleon axial form factor coming from the neutral weak interaction. The results indicate a strange quark magnetic contribution close to zero at these Q² , and a possible non zero strange quark electric contribution for the high Q² . The first Q² behavior measurement of the nucleon axial form factor in elastic electron scattering shows a good agreement with radiative corrections calculated at Q² = 0 and with a dipole form using the axial mass determined in neutrino scattering.