Physics
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Item Momentum transfer dependence of nuclear transparency from the quasielastic 12C(e,e’p) reaction(1994-03) Makins, N.C.R.; Ent, R.; Chapman, M.S.; Hansen, J.-O.; Lee, K.; Milner, R.G.; Nelson, J.; Bosted, P.E.; Keppel, C.E.; Lung, A.; Rock, S.E.; Spengos, M.; Szalata, Z.M.; Tao, L.H.; White, J.L.; Coulter, K.P.; Geesaman, D.F.; Holt, R.J.; Jackson, H.E.; Papavassiliou, V.; Potterveld, D.H.; Zeidman, B.; Arrington, J.; Beise, E.J.; Belz, E.; Filippone, B.W.; Gao, H.; Lorenzon, W.; Mueller, B.; McKeown, R.D.; O'Neill, T.G.; Epstein, M.; Margaziotis, D.J.; Napolitano, J.; Anthony, P.L.; van Bibber, K.; Dietrich, F.S.; Gearhart, R.A.; Petratos, G.G.; Kuhn, S.E.The cross section for quasielastic 12C(e,e’p) scattering has been measured at momentum transfer Q2=1, 3, 5, and 6.8 (GeV/c)2. The results are consistent with scattering from a single nucleon as the dominant process. The nuclear transparency is obtained and compared with theoretical calculations that incorporate color transparency effects. No significant rise of the transparency with Q2 is observed.Item Evidence for virtual Compton scattering from the proton(1995-11) van der Brand, J.F.J.; Ent, R.; Anthony, P.L.; Arnold, R.G.; Arrington, J.; Beise, E.J.; Belz, J.E.; Bosted, P.E.; Bulten, H.-J.; Chapman, M.S.; Coulter, K.P.; Dietrich, F.S.; Epstein, M.; Filippone, B.W.; Gao, H.; Gearheat, R.A.; Geesaman, D.F.; Hansen, J.-O.; Holt, R.J.; Jackson, H.E.; Jones, C.E.; Margaziotis, D.J.; McKeown, R.D.; Milner, R.G.; Mueller, B.; Napolitano, J.; Nelson, J.; Keppel, C.E.; Kinney, R.D.; Kuhn, S.; Lee, K.; Lorenzon, W.; Lung, A.; Makins, N.C.R.; O'Neill, T.G.; Papavassiliou, V.; Petratos, G.; Potterveld, D.H.; Rock, S.E.; Spengos, M.; Szalata, Z.M.; Tao, L.H.; van Bibber, K.; Wasson, D.A.; White, J.L.; Zeidman, B.In virtual Compton scattering an electron is scattered off a nucleon such that the nucleon emits a photon. We show that these events can be selected experimentally, and present the first evidence for virtual Compton scattering from the proton in data obtained at the Stanford Linear Accelerator Center. The angular and energy dependence of the data is well described by a calculation that includes the coherent sum of electron and proton radiation.Item Measurement of longitudinal and transverse cross sections in the 3He(e,e′π+)3H reaction at W=1.6 GeV(2001-12) Gaskell, D.; Ahmidouch, A.; Ambrozewicz, P.; Anklin, H.; Arrington, J.; Assamagan, K.; Avery, S.; Bailey, K.; Baker, O.K.; Beedoe, S.; Beise, B.; Breuer, H.; Brown, D.S.; Carlini, R.; Cha, J.; Chant, N.; Cowley, A.; Danagoulian, S.; De Schepper, D.; Dunne, J.; Dutta, D.; Ent, R.; Gan, L.; Gasparian, A.; Geesaman, D.F.; Gilman, R.; Glashausser, C.; Gueye, P.; Harvey, M.; Hashimoto, O.; Hinton, W.; Hofman, G.; Jackson, C.; Jackson, H.E.; Keppel, C.; Kinney, E.; Koltenuk, D.; Lung, A.; Mack, D.; McKee, D.; Mitchell, J.; Mkrtchyan, H.; Mueller, B.; Niculescu, G.; Niculescu, I.; O'Neill, T.G.; Papavassiliou, V.; Potterveld, D.; Reinhold, J.; Roos, P.; Sawafta, R.; Segel, R.; Stepanyan, S.; Tadevosyan, V.; Takahashi, T.; Tang, L.; Terburg, B.; Van Westrum, D.; Volmer, J.; Welch, T.P.; Wood, S.; Yuan, L.; Zeidman, B.; Zihlmann, B.The coherent 3He(e,e′π+)3H reaction was measured at Q2=0.4 (GeV/c)2 and W=1.6 GeV for two values of the virtual photon polarization, ε, allowing the separation of longitudinal and transverse cross sections. The results from the coherent process on 3He were compared to H(e,e′π+)n data taken at the same kinematics. This marks the first direct comparison of these processes. At these kinematics (pπ=1.1 GeV/c), pion rescattering from the spectator nucleons in the 3He(e,e′π+)3H process is expected to be small, simplifying the comparison to π+ production from the free proton.Item Separated spectral functions for the quasifree 12C(e,e′p) reaction(2000-05) Dutta, D.; van Westrum, D.; Abbott, D.; Ahmidouch, A.; Amatuni, A.; Armstrong, C.; Arrington, J.; Assamagan, K.A.; Bailey, K.; Baker, O.K.; Barrow, S.; Beard, K.; Beatty, D.; Beedoe, S.; Beise, E.; Belz, E.; Bochna, C.; Bosted, P.E.; Breuer, H.; Bruins, E.E.W.; Carlini, R.; Cha, J.; Chant, N.; Chrien, R.E.; Cothran, C.; Cummings, W.J.; Danagoulian, S.; Day, D.; DeSchepper, D.; Ducret, J.-E.; Duncan, F.; Dunne, J.; Eden, T.; Ent, R.; Fortune, H.T.; Frolov, V.; Geesaman, D.F.; Gao, H.; Gilman, R.; Gue`ye, P.; Hansen, J.O.; Hinton, W.; Holt, R.J.; Jackson, C.; Jackson, H.E.; Jones, C.; Kaufman, S.; Kelly, J.J.; Keppel, C.; Khandaker, M.; Kim, W.; Kinney, E.; Klein, A.; Koltenuk, D.; Kramer, L.; Lorenzon, W.; McFarlane, K.; Mack, D.J.; Madey, R.; Markowitz, P.; Martin, J.; Mateos, A.; Meekins, D.; Meier, E.; Miller, M.A.; Milner, R.; Mitchell, J.; Mohring, R.; Mkrtchyan, H.; Nathan, A.M.; Niculescu, G.; Niculescu, I.; O'Neill, T.G.; Potterveld, D.; Price, J.W.; Reinhold, J.; Salgado, C.; Schiffer, J.P.; Segel, R.E.; Stoler, P.; Suleiman, R.; Sawafta, R.; Sutter, R.J.; Tadevosyan, V.; Tang, L.; Terburg, B.; Welch, T.P.; Williamson, C.; Wood, S.; Yan, C.; Jae-Choon, Yang; Yu, J.; Zeidman, B.; Zhao, W.; Zihlmann, B.A separation of the longitudinal and transverse 12C(e,e′p) cross sections in the quasifree region has been performed in parallel kinematics at Q2 of 0.64 and 1.8 GeV2 for initial proton momentum <80 MeV. The separated transverse and longitudinal spectral functions at Q2=0.64GeV2 show significant differences for missing energy between 25 and 60 MeV indicating a breakdown in the single nucleon knockout picture. The transverse spectral functions exhibit definite momentum transfer dependence.