Physics
Permanent URI for this communityhttp://hdl.handle.net/1903/2269
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Item Measurement of the vector analyzing power in elastic electron-proton scattering as a probe of double photon exchange amplitudes(2001-05) Wells, S.P.; Averett, T.; Barkhuff, D.; Beck, D.H.; Beise, E.J.; Benson, C.; Breuer, H.; Carr, R.; Covrig, S.; DelCorso, J.; Dodson, G.; Eppstein, C.; Farkhondeh, M.; Filippone, B.W.; Forest, T.; Frasier, P.; Hasty, R.; Ito, T.M.; Jones, C.; Korsch, W.; Kowalski, S.; Lee, P.; Maneva, E.; McCarty, K.; McKeown, R.D.; Mikell, J.; Mueller, B.; Naik, P.; Pitt, M.L; Ritter, J.; Savu, V.; Spayde, D.T.; Sullivan, M.; Tieulent, R.; Tsentalovich, E.; Yang, B.; Zwart, T.; SAMPLE CollaborationWe report the first measurement of the vector analyzing power in inclusive transversely polarized elastic electron-proton scattering at Q2 = 0.1 (GeV/c)2 and large scattering angles. This quantity should vanish in the single virtual photon exchange, plane wave impulse approximation for this reaction, and can therefore provide information on double photon exchange amplitudes for electro- magnetic interactions with hadronic systems. We find a non-zero value of A=-15.4±5.4 ppm. No calculations of this observable for nuclei other than spin 0 have been carried out in these kinematics, and the calculation using the spin orbit interaction from a charged point nucleus of spin 0 cannot describe these data.Item Strange Quark Contributions to Parity-Violating Asymmetries in the Backward Angle G0 Electron Scattering Experiment(2005-08) Androic, D.; Armstrong, D.S.; Arvieux, J.; Bailey, S.L.; Beck, D.H.; Beise, E.J.; Benesch, J.; Benmokhtar, F.; Bimbot, L.; Birchall, J.; Bosted, P.; Breuer, H.; Capuano, C.L.; Chao, Y.C.; Coppens, A.; Davis, C.A.; Ellis, C.; Flores, G.; Franklin, G.; Furget, C.; Gaskell, D.; Gericke, M.T.W.; Grames, J.; Guillard, G.; Hansknecht, J.; Horn, T.; Jones, M.; King, P.M.; Korsch, W.; Kox, S.; Lee, L.; Liu, J.; Lung, A.; Mammei, J.; Martin, J.W.; McKeown, R.D.; Mihovilovic, M.; Micherdzinska, A.; Mkrtchyan, H.; Muether, M.; Page, S.A.; Papavassiliou, V.; Pate, S.F.; Phillips, S.K.; Pillot, P.; Pitt, M.L.; Poelker, M.; Quinn, B.; Ramsay, W.D.; Real, J.S.; Roche, J.; Roos, P.; Schaub, J.; Seva, T.; Simicevic, N.; Smith, G.R.; Spayde, D.T.; Stutzman, M.; Suleiman, R.; Tadevosyan, V.; van Oers, T.H.; Versteegen, M.; Voutier, E.; Vulcan, W.; Wells, S.P.; Williamson, S.E.; Wood, S.A.; G0 CollaborationWe have measured parity-violating asymmetries in elastic electron-proton and quasi-elastic electron-deuteron scattering at Q2 = 0.22 and 0.63 GeV2. They are sensitive to strange quark contributions to currents in the nucleon, and to the nucleon axial current. The results indicate strange quark contributions of <∼ 10% of the charge and magnetic nucleon form factors at these four-momentum transfers. We also present the first measurement of anapole moment effects in the axial current at these four-momentum transfers