Physics Research Works
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Item Longitudinal Electroproduction of Charged Pions from 1H, 2H, and 3He(American Physical Society, 2001-11-12) 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.; DeSchepper, 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.; Kyle, G.; 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.Separated longitudinal and transverse cross sections for charged pion electroproduction from 1H, 2H, and 3He were measured at Q2 = 0.4(GeV/c)2 for two values of the invariant mass, W = 1.15GeV and W = 1.60GeV, in a search for a mass dependence which would signal the effect of nuclear pions. This is the first such study that includes recoil momenta significantly above the Fermi surface. The longitudinal cross section, if dominated by the pion-pole process, should be sensitive to nuclear pion currents. Comparisons of the longitudinal cross section target ratios to a quasifree calculation reveal a significant suppression in 3He at W = 1.60GeV. The W = 1.15GeV results are consistent with simple estimates of the effect of nuclear pion currents, but are also consistent with pure quasifree production.Item Measurements of Deuteron Photodisintegration up to 4.0 GeV(American Physical Society, 1998-11-23) Bochna, C.; Terburg, B.P.; Abbott, D.J.; Ahmidouch, A.; Armstrong, C.S.; Arrington, J.; Assamagan, K.A.; Baker, O.K.; Barrow, S.P.; Beatty, D.P.; Beck, D.H.; Beedoe, S.Y.; Beise, E.J.; Belz, J.E.; Bosted, P.E.; Brash, E.J.; Breuer, H.; Cadman, R.V.; Cardman, L.; Carlini, R.D.; Cha, J.; Chant, N.S.; Collins, G.; Cothran, C.; Cummings, W.J.; Danagoulian, S.; Duncan, F.A.; Dunne, J.A.; Dutta, D.; Eden, T.; Ent, R.; Filippone, B.W.; Forest, T.A.; Fortune, H.T.; Frolov, V.V.; Gao, H.; Geesaman, D.F.; Gilman, R.; Gueye, P.L.J.; Gustafsson, K.K.; Hansen, J.-O.; Harvey, M.; Hinton, W.; Holt, R.J.; Jackson, H.E.; Keppel, C.E.; Khandaker, M.A.; Kinney, E.R.; Klein, A.; Koltenuk, D.M.; Kumbartzki, G.; Lung, A.F.; Mack, D.J.; Madey, R.; Markwoitz, P.; McFarlane, K.W.; McKeown, R.D.; Meekins, D.G.; Meziani, Z.-E.; Miller, M.A.; Mitchell, J.H.; Mkrtchyan, H.G.; Mohring, R.M.; Napolitano, J.; Nathan, A.M.; Niculescu, G.; Niculescu, I.; O'Neill, T.G.; Owen, B.R.; Pate, S.F.; Potterveld, D.H.; Price, J.W.; Rakness, G.L.; Ransome, R.; Reinhold, J.; Rutt, P.M.; Salgado, C.W.; Savage, G.; Segel, R.; Simicevic, N.; Stoler, P.; Suleiman, R.; Tang, L.; van Westrum, D.; Vulcan, W.F.; Williamson, S.; Witkowski, M.T.; Wood, S.A.; Yan, C.; Zeidman, B.The first measurements of the differential cross section for the d(γ,p)n reaction up to 4.0 GeV were performed at the Continuous Electron Beam Accelerator Facility (CEBAF) at Thomas Jefferson Laboratory. We report the cross sections at the proton center-of-mass angles of 36°, 52°, 69°, and 89°. These results are in reasonable agreement with previous measurements at lower energy. The 89° and 69° data show constituent-counting-rule behavior up to 4.0 GeV photon energy. The 52° and 36° data disagree with the counting-rule behavior. The quantum chromodynamics (QCD) model of nuclear reactions involving reduced amplitudes disagrees with the present data.Item Quasifree (e,e′p) Reactions and Proton Propagation in Nuclei(American Physical Society, 1998-06-08) Abbott, D.; Ahmidouch, A.; Amatuni, Ts. 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.; Breuer, H.; Bruins, E.E.W.; Carlini, R.; Cha, J.; Chant, N.; Cothran, C.; Cummings, W.J.; Danagoulian, S.; Day, D.; DeSchepper, D.; Ducret, J.-E.; Duncan, F.; Dunne, J.; Dutta, D.; Eden, T.; Ent, R.; Fortune, H.T.; Frolov, V.; Geesaman, D.F.; Gao, H.; Gilman, R.; Gueye, P.; Hansen, J.O.; Hinton, W.; Holt, R.J.; Jackson, C.; Jackson, H.E.; Jones, C.E.; 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.; 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.O.; Segel, R.E.; Stoler, P.; Suleiman, R.; Tadevosyan, V.; Tang, L.; Terburg, B.; van Westrum, D.; Welch, P.; Williamson, C.; Wood, S.; Yan, C.; Yang, Jae-Choon; Yu, J.; Zeidman, B.; Zhao, W.; Zihlmann, B.The ( e,e′p) reaction was studied on targets of C, Fe, and Au at momentum transfers squared Q2 of 0.6, 1.3, 1.8, and 3.3 GeV2 in a region of kinematics dominated by quasifree electron-proton scattering. Missing energy and missing momentum distributions are reasonably well described by plane wave impulse approximation calculations with Q2 and A dependent corrections that measure the attenuation of the final state protons.Item Exclusive Electron Scattering from Deuterium at High Momentum Transfer(American Physical Society, 1995-06-12) Bulten, H.J.; Anthony, P.L.; Arnold, R.G.; Arrington, J.; Beise, E.J.; Belz, E.; van Bibber, K.; Bosted, P.E.; van den Brand, J.F.J.; Chapman, M.S.; Coulter, K.P.; Dietrich, F.S.; Ent, R.; Epstein, M.; Filippone, B.W.; Gao, H.; Gearhart, R.A.; Geesaman, D.F.; Holt, R.J.; Jackson, H.E.; Jones, C.E.; Keppel, C.E.; Kinney, E.; Kuhn, S.E.; Lee, K.; Lorenzon, W.; Lung, A.; Makins, N.C.R.; Margaziotis, D.J.; McKeown, R.D.; Milner, R.G.; Mueller, B.; Napolitano, J.; Nelson, J.; O'Neill, T.G.; Papavassiliou, V.; Petratos, G.G.; Rock, S.E.; Spengos, M.; Szalata, Z.M.; Tao, L.H.; White, J.L.; Zeidman, B.Cross sections are presented for the reaction 2H(e,e′p)n for momentum transfers in the range 1.2≤Q2≤6.8(GeV/c)2 and for missing momenta from 0 to 250 MeV/c. The longitudinal-transverse interference structure function has been separated at Q2 = 1.2(GeV/c)2. The observables are compared to calculations performed in nonrelativistic and relativistic frameworks. The data are best described by a fully relativistic calculation.Item Two-Body Photodisintegration of the Deuteron up to 2.8 GeV(The American Physical Society, 1995-01) Belz, J.E.; Potterveld, D.H.; Anthony, P.; Arnold, R.G.; Arrington, J.; Beck, D.; Beise, E.J.; Bosted, P.E.; Bulten, H.-J.; Chapman, M.S.; Coulter, K.P.; Dietrich, F.; Ent, R.; Epstein, M.; Filippone, B.W.; Gao, H.; Gearhart, R.A.; Geesaman, D.F.; Hansen, J.-O.; Holt, R.J.; Jackson, H.E.; Jones, C.E.; Keppel, C.E.; Kinney, E.R.; Kuhn, S.; Lee, K.; Lorenzon, W.; Makins, N.C.R.; Lung, A.; Margaziotis, D.J.; McKeown, R.D.; Meziani, Z.E.; Milner, R.G.; Mueller, B.; Napolitano, J.; Nelson, J.; O'Neill, T.G.; Papavassiliou, V.; Petratos, G.G.; Rock, S.E.; Segel, R.E.; Spengos, M.; Szalta, Z.M.; Tao, L.H.; van Bibber, K.; van der Brand, F.J.; White, J.L.; Zeidman, B.Measurements were performed for the photodisintegration cross section of the deuteron for photon energies from 1.6 to 2.8 GeV and center-of-mass angles from 37° to 90°. The measured energy dependence of the cross section at θc.m.=90° is in agreement with the constituent counting rules.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 Quasielastic (e,e′p) reaction on 12C,56Fe, and 197Au(2003-12) 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.; 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.; Gueye, 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, A.; Klein, A.; Koltenuk, D.; Kramer, L.; Lorenzon, W.; Lung, A.; McFarlane, K.; Mack, D.J.; Madey, R.; Markowitz, P.; Martin, J.; Mateos, A.; Meekins, D.; 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.; Tadevosyan, V.; Tang, L.; Terburg, B.; Welch, T.P.; Williamson, C.; Wood, S.; Yan, C.; Yang, J.-C.; Yu, J.; Zeidman, B.; Zhao, W.; Zihlmann, B.We report the results from a systematic study of the quasielastic (e,e′p) reaction on 12C, 56Fe, and 197Au performed at Jefferson Lab. We have measured nuclear transparency and extracted spectral functions (corrected for radiation) over a Q2 range of 0.64–3.25 (GeV∕c)2 for all three nuclei. In addition, we have extracted separated longitudinal and transverse spectral functions at Q2 of 0.64 and 1.8 (GeV∕c)2 for these three nuclei (except for 197Au at the higher Q2). The spectral functions are compared to a number of theoretical calculations. The measured spectral functions differ in detail but not in overall shape from most of the theoretical models. In all three targets the measured spectral functions show considerable excess transverse strength at Q2=0.64 (GeV∕c)2, which is much reduced at 1.8 (GeV∕c)2.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.