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Item Proton propagation in nuclei studied in the A dependence of the (e,e’p) reaction in the quasifree region(1989-08) Geesaman, D.F.; Gilman, R.; Green, M.C.; Holt, R.J.; Schiffer, J.P.; Zeidman, B.; Garino, G.; Saber, M.; Segel, R.E.; Beise, E.J.; Dodson, G.W.; Hoibraten, S.; Pham, L.D.; Redwine, R.P.; Sapp, W.W.; Williamson, C.F.; Wood, S.A.; Chant, N.S.; Roos, P.G.; Silk, J.D.; Deady, M.; Maruyama, X.K.The A dependence of the (e,e’p) reaction in the quasifree region has been measured at an average Q2 of 0.33 (GeV/c)2 for targets of 12C, 27Al, 58Ni, and 181Ta. The outgoing proton kinetic energy was 180±30 MeV. By comparing the ratio of (e,e’p) coincidence to (e,e’) singles yields, average proton transmissions are obtained for each target. The resulting ‘‘mean free path’’ or, more precisely, the attenuation length for protons in the nucleus is significantly longer than expectations based on the free nucleon-nucleon cross section.Item Charged pion form factor between Q2=0.60 and 2.45 GeV2. II. Determination of, and results for, the pion form factor(2008-10) Huber, G.M.; Blok, H.P.; Horn, T.; Beise, E.J.; Gaskell, D.; Mack, D.J.; Tadevosyan, V.; Volmer, J.; Abbott, D.; Aniol, K.; Anklin, H.; Armstrong, C.; Arrington, J.; Assamagan, K.; Avery, S.; Baker, O.K.; Barrett, B.; Bochna, C.; Boeglin, W.; Brash, E.J.; Breuer, H.; Chang, C.C.; Chant, N.; Christy, M.E.; Dunne, J.; Eden, T.; Ent, R.; Fenker, H.; Gibson, E.F.; Gilman, R.; Gustafsson, K.; Hinton, W.; Holt, J.; Jackson, H.; Jin, S.; Jones, M.K.; Keppel, C.E.; Kim, P.H.; Kim, W.; King, P.M.; Klein, A.; Koltenuk, D.; Kovaltchouk, V.; Liang, M.; Liu, J.; Lolos, G.J.; Lung, A.; Margaziotis, D.J.; Markowitz, P.; Matsumura, A.; McKee, D.; Meekins, D.; Mitchell, J.; Miyoshi, T.; Mkrtchyan, H.; Mueller, B.; Niculescu, G.; Niculescu, I.; Okayasu, Y.; Pentchev, L.; Perdrisat, C.; Pitz, D.; Potterveld, D.; Punjabi, V.; Qin, L.M.; Reimer, P.E.; Reinhold, J.; Roche, J.; Roos, P.G.; Sarty, A.; Shin, I.K.; Smith, G.R.; Stepanyan, S.; Tang, L.G.; Tvaskis, V.; van der Meer, R.L.J.; Vansyoc, K.; VanWestrum, D.; Vidakovic, S.; Vulcan, W.; Warren, G.; Wood, S.A.; Xu, C.; Yan, C.; Zhao, W.-X.; Zheng, X.; Zihlmann, B.; The Jefferson Lab Fπ CollaborationThe charged pion form factor, Fπ(Q2), is an important quantity that can be used to advance our knowledge of hadronic structure. However, the extraction of Fπ from data requires a model of the 1H(e,e'π+)n reaction and thus is inherently model dependent. Therefore, a detailed description of the extraction of the charged pion form factor from electroproduction data obtained recently at Jefferson Lab is presented, with particular focus given to the dominant uncertainties in this procedure. Results for Fπ are presented for Q2=0.60-2.45 GeV2. Above Q2=1.5 GeV2, the Fπ values are systematically below the monopole parametrization that describes the low Q2 data used to determine the pion charge radius. The pion form factor can be calculated in a wide variety of theoretical approaches, and the experimental results are compared to a number of calculations. This comparison is helpful in understanding the role of soft versus hard contributions to hadronic structure in the intermediate Q2 regime.Item Recoil polarization measurements for neutral pion electroproduction at Q2=1(GeV/c)2 near the Δ resonance(2007-02) Kelly, J.J.; Gayou, O.; Roche, R.E.; Chai, Z.; Jones, M.K.; Sarty, A.J.; Frullani, S.; Aniol, K.; Beise, E.J.; Benmokhtar, F.; Bertozzi, W.; Boeglin, W.U.; Botto, T.; Brash, E.J.; Breuer, H.; Brown, E.; Burtin, E.; Calarco, J.R.; Cavata, C.; Chang, C.C.; Chant, N.S.; Chen, J.-P.; Coman, M.; Crovelli, D.; De Leo, R.; Dieterich, S.; Escoffier, S.; Fissum, K.G.; Garde, V.; Garibaldi, F.; Georgakopoulos, S.; Gilad, S.; Gilman, R.; Glashausser, C.; Hansen, J.-O.; Higinbotham, D.W.; Hotta, A.; Huber, G.M.; Ibrahim, H.; Iodice, M.; de Jager, C.W.; Jiang, X.; Kimenko, A.; Kozlov, A.; Kumbartzki, G.; Kuss, M.; Lagamba, L.; Laveissiere, G.; LeRose, J.J.; Lindgren, R.A.; Liyange, N.; Lolos, G.J.; Lourie, R.W.; Margaziotis, D.J.; Marie, F.; Markowitz, P.; McAleer, S.; Meekins, D.; Michaels, R.; Milbrath, B.D.; Mitchell, J.; Nappa, J.; Neyret, D.; Perdrisat, C.F.; Potokar, M.; Punjabi, V.A.; Pussieux, T.; Ransome, R.D.; Roos, P.G.; Rvachev, M.; Saha, A.; Sirca, S.; Suleiman, R.; Strauch, S.; Templon, J.A.; Todor, L.; Ulmer, P.E.; Urciuoli, G.M.; Weinstein, L.B.; Wijsooriya, K.; Wojtsekhowski, B.; Zheng, X.; Zhu, L.; Jefferson Laboratory E91011 and Hall A CollaborationsWe measured angular distributions of differential cross section, beam analyzing power, and recoil polarization for neutral pion electroproduction at Q2=1.0 (GeV/c)2 in 10 bins of 1.17⩽W⩽1.35 GeV across the Δ resonance. A total of 16 independent response functions were extracted, of which 12 were observed for the first time. Comparisons with recent model calculations show that response functions governed by real parts of interference products are determined relatively well near the physical mass, W=MΔ≈1.232 GeV, but the variation among models is large for response functions governed by imaginary parts, and for both types of response functions, the variation increases rapidly with W>MΔ. We performed a multipole analysis that adjusts suitable subsets of ℓπ⩽2 amplitudes with higher partial waves constrained by baseline models. This analysis provides both real and imaginary parts. The fitted multipole amplitudes are nearly model independent—there is very little sensitivity to the choice of baseline model or truncation scheme. By contrast, truncation errors in the traditional Legendre analysis of N→Δ quadrupole ratios are not negligible. Parabolic fits to the W dependence around MΔ for the multiple analysis gives values for Re(S1+/M1+)=(-6.61±0.18)% and Re(E1+/M1+)=(-2.87±0.19)% for the pπ0 channel at W=1.232 GeV and Q2=1.0 (GeV/c)2 that are distinctly larger than those from the Legendre analysis of the same data. Similarly, the multipole analysis gives Re(S0+/M1+)=(+7.1±0.8)% at W=1.232 GeV, consistent with recent models, while the traditional Legendre analysis gives the opposite sign because its truncation errors are quite severe.Item Cross section measurements of charged pion photoproduction in hydrogen and deuterium from 1.1 to 5.5 GeV(2005-04) Zhu, L.Y.; Arrington, J.; Averett, T.; Beise, E.; Calarco, J.; Chang, T.; Chen, J.P.; Chudakov, E.; Coman, M.; Clasie, B.; Crawford, C.; Dieterich, S.; Dohrmann, F.; Dutta, D.; Fissum, K.; Frullani, S.; Gao, H.; Gilman, R.; Glashausser, C.; Gomez, J.; Hafidi, K.; Hansen, O.; Higinbotham, D.W.; Holt, R.J.; de Jager, C.W.; Jiang, X.; Kinney, E.; Kramer, K.; Kumbartzki, G.; LeRose, J.; Liyanage, N.; Mack, D.; Markowitz, P.; McCormick, K.; Meekins, D.; Meziani, Z.-E.; Michaels, R.; Mitchell, J.; Nanda, S.; Potterveld, D.; Ransome, R.; Reimer, P.E.; Reitz, B.; Saha, A.; Schulte, E.C.; Seely, J.; Sirca, S.; Strauch, S.; Sulkosky, V.; Vlahovic, B.; Weinstein, L.B.; Wijesooriya, K.; Williamson, C.; Wojtsekhowski, B.; Xiang, H.; Xiong, F.; Xu, W.; Zeng, J.; Zheng, X.; Jefferson Lab Hall A Collaboration; Jefferson Lab E94-104 CollaborationThe differential cross sections for the γn→π-p and the γp→π+n processes were measured at Jefferson Lab. The photon energies ranged from 1.1 to 5.5 GeV, corresponding to center-of-mass energies from 1.7 to 3.4 GeV. The pion center-of-mass angles varied from 50° to 110°. The π- and π+ photoproduction data both exhibit a global scaling behavior at high energies and high transverse momenta, consistent with the constituent counting rule prediction and the existing π+ data. The data suggest possible substructure of the scaling behavior, which might be oscillations around the scaling value. The data show an enhancement in the scaled cross section at center-of-mass energy near 2.2 GeV. The differential cross section ratios [dσ/dt(γn→π-p)/dσ/dt(γp→π+n)] at high energies and high transverse momenta can be described by calculations based on one-hard-gluon-exchange diagrams.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 Nuclear transparency with the γn⃗π-p process in 4He(2003-08) Dutta, D.; Xiong, F.; Zhu, L.Y.; Arrington, J.; Averett, T.; Beise, E.; Calarco, J.; Chang, T.; Chen, J.P.; Chudakov, E.; Coman, M.; Clasie, B.; Crawford, C.; Dieterich, S.; Dohrmann, F.; Fissum, K.; Frullani, S.; Gao, H.; Gilman, R.; Glashausser, C.; Gomez, J.; Hafidi, K.; Hansen, J.-O.; Higinbotham, D.W.; Holt, R.J.; de Jager, C.W.; Jiang, X.; Kinnery, E.; Kramer, K.; Kumbartzki, G.; LeRose, J.; Liyanage, N.; Mack, D.; Markowitz, P.; McCormick, K.; Meziani, Z.-E.; Michaels, R.; Nanda, S.; Potterveld, D.; Ransome, R.; Reimer, P.E.; Reitz, B.; Saha, A.; Schulte, E.C.; Seely, J.; Sirca, S.; Strauch, S.; Sulkosky, V.; Vlahovic, B.; Weinstein, L.B.; Wijesooriya, K.; Williamson, C.F.; Wojtsekhowski, B.; Xiang, H.; Xu, W.; Zeng, J.; Zheng, X.; Jefferson Lab E94104 CollaborationWe have measured the nuclear transparency of the fundamental process γn⃗π-p in 4He. These measurements were performed at Jefferson Lab in the photon energy range of 1.6–4.5 GeV and at θcmπ=70° and 90°. These measurements are the first of their kind in the study of nuclear transparency in photoreactions. They also provide a benchmark test of Glauber calculations based on traditional models of nuclear physics. The transparency results suggest deviations from the traditional nuclear physics picture. The momentum transfer dependence of the measured nuclear transparency is consistent with Glauber calculations that include the quantum chromodynamics phenomenon of color transparency.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.Item Coherent π0 photoproduction on the deuteron up to 4 GeV(1999-09) Meekins, D.G.; 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.; Bochna, C.; 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.; Markowitz, P.; McFarlane, K.W.; McKeown, R.D.; 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, D.; Reinhold, J.; Rutt, P.M; Salgado, C.W.; Savage, G.; Segel, R.E.; Simicevic, N.; Stoler, P.; Suleiman, R.; Tang, L.; Terburg, B.P.; van Westrum, D.; Vulcan, W.F.; Williamson, S.E.; Witkowski, M.T.; Wood, S.A.; Yan, C.; Zeidman, B.The differential cross section for 2H(γ,d)π0 has been measured at deuteron center-of-mass angles of 90° and 136°. This work reports the first data for this reaction above a photon energy of 1 GeV, and permits a test of the apparent constituent counting rule and reduced nuclear amplitude behavior as observed in elastic ed scattering. Measurements were performed up to a photon energy of 4.0 GeV, and are in good agreement with previous lower energy measurements. Overall, the data are inconsistent with both constituent-counting rule and reduced nuclear amplitude predictions.Item Proton propagation in nuclei studied in the (e,e’p) reaction(1992-02) Geesaman, D.F.; Gilman, R.; Green, M.C.; Holt, R.J.; Schiffer, J.P.; Zeidman, B.; Garino, G.; Saber, M.; Segel, R.E.; Beise, E.J.; Dodson, G.W.; Hoibraten, S.; Pham, L.D.; Redwine, R.P.; Sapp, W.W.; Williamson, C.F.; Wood, S.A.; Chant, N.S.; Roos, P.G.; Silk, J.D.; Deady, M.; Maruyama, X.K.Proton propagation in nuclei was studied using the (e,e’p) reaction in the quasifree region. The coincidence (e,e’p) cross sections were measured at an electron angle of 50.4° and proton angles of 50.1°, 58.2°, 67.9°, and 72.9° for 12C, 27Al, 58Ni, and 181Ta targets at a beam energy of 779.5 MeV. The average outgoing proton energy was 180 MeV. The ratio of the (e,e’p) yield to the simultaneously measured (e,e’) yield was compared to that calculated in the plane-wave impulse approximation and an experimental transmission defined. These experimental transmissions are considerably larger (a factor of ∼2 for 181Ta) than those one would calculate from the free N-N cross sections folded into the nuclear density distribution. A new calculation that includes medium effects (N-N correlations, density dependence of the N-N cross sections and Pauli suppression) accounts for this increase.