Measurement of strange quark contributions to the vector form factors of the proton at Q2 = 0.22 (GeV / c)2.
/ Authors
S. Baunack, K. Aulenbacher, D. B. Ríos, L. Capozza, J. Diefenbach, B. Gläser, D. Harrach, Y. Imai, E. Kabuß, R. Kothe
and 18 more authors
J. Lee, H. Merkel, M. C. M. Espi, U. Müller, E. Schilling, G. Stephan, C. Weinrich, J. Arvieux, M. El-Yakoubi, R. Frascaria, R. Kunne, F. Maas, M. Morlet, S. Ong, J. Wiele, S. Kowalski, Y. Prok, S. Taylor
/ Abstract
A new measurement of the parity violating asymmetry in elastic electron scattering on hydrogen at backward angles and at a four momentum transfer of Q;{2} = 0.22 (Ge V / c);{2} is reported here. The measured asymmetry is A_{LR} = (-17.23 +/- 0.82_{stat} +/- 0.89_{syst}) x 10;{-6}. The standard model prediction assuming no strangeness is A_{0} = (-15.87 +/- 1.22) x 10;{-6}. In combination with previous results from measurements at forward angles, it is possible to disentangle for the first time the strange form factors at this momentum transfer, G_{E};{s} = 0.050 +/- 0.038 +/- 0.019 and G_{M};{s} = -0.14 +/- 0.11 +/- 0.11.
Journal: Physical review letters