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Physical Review Letters 102 (2009) 151803
Measurement of Strange Quark Contributions to the Vector Form Factors of the Proton at Q2=0.22 (GeV/c)2
S. Baunack, K. Aulenbacher, D. Balaguer Ríos, L. Capozza, J. Diefenbach, B. Gläser, D. von Harrach, Y. Imai, E.-M. Kabuß, R. Kothe, J. H. Lee, H. Merkel, M. C. Mora Espí, U. Müller, E. Schilling, G. Stephan, C. Weinrich, J. Arvieux1, M. A. El-Yakoubi1, R. Frascaria1, R. Kunne1, F. E. Maas1, M. Morlet1, S. Ong1, J. Van de Wiele1, S. Kowalski, Y. Prok, S. Taylor

A new measurement of the parity violating asymmetry in elastic electron scattering on hydrogen at backward angles and at a four momentum transfer of Q2=0.22 (GeV/c)2 is reported here. The measured asymmetry is ALR=(-17.23±0.82stat±0.89syst)×10-6. The standard model prediction assuming no strangeness is A0=(-15.87±1.22)×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, GEs=0.050±0.038±0.019 and GMs=-0.14±0.11±0.11.
1 :  IPNO - Institut de Physique Nucléaire d'Orsay
Physique/Physique Nucléaire Expérimentale