Physics Research Works
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Item Cross-Section Measurement of Charged-Pion Photoproduction from Hydrogen and Deuterium(American Physical Society, 2003-06-11) 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, J.-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.F.; Wojtsekhowski, B.; Xiang, H.; Xiong, F.; Xu, W.; Zeng, J.; Zheng, X.; Jefferson Lab Hall A ColloborationWe have measured the differential cross section for the γn→π-p and γp→π+n reactions at θc.m.=90° in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at Eγ≳3.3 GeV exhibit a global scaling behavior for both π- and π+ photoproduction, consistent with the constituent counting rule and the existing π+ photoproduction data. Possible oscillations around the scaling value are suggested by these new data. The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive π- to π+ photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.Item Longitudinal and Transverse Cross Sections in the 1H(e,e′K+)Λ Reaction(American Physical Society, 1998-08-31) Niculsescu, G.; Mohring, R.M.; Gueye, P.; Abbott, D.; Ahmidouch, A.; Amatuni, Ts.A.; Ambrozewicz, P.; Angelescu, T.; Armstrong, C.S.; Assamagan, K.; Avery, S.; Bailey, K.; Baker, O.K.; Beard, K.; Beedoe, S.; Beise, E.; Breuer, H.; Carlini, R.; Cha, J.; Chang, C.C.; Chant, N.; Cisbani, E.; Collins, G.; Cummings, W.; Danagoulian, S.; DeLeo, R.; Duncan, F.; Dunne, J.; Dutta, D.; Eden, T.; Ent, R.; Eyraud, L.; Ewell, L.; Finn, M.; Fortune, T.; Frolov, V.; Frullani, S.; Furget, C.; Garibaldi, F.; Gaskell, D.; Geesaman, D.F.; Gustafsson, K.K.; Hansen, J.-O.; Harvey, M.; Hinton, W.; Hungerford, E.; Iodice, M.; Jackson, C.; Keppel, C.; Kim, W.; Kino, K.; Koltenuk, D.; Kox, S.; Kramer, L.; Leone, T.; Lolos, G.; Lung, A.; Mack, D.; Madey, R.; Maeda, M.; Majewski, S.; Markowitz, P.; Martoff, C.J.; Meekins, D.; Mihul, A.; Mitchell, J.; Mkrtchyan, H.; Mtingwa, S.; Niculescu, I.; Perrino, R.; Potterveld, D.; Price, J.W.; Raue, B.A.; Real, J.-S.; Reinhold, J.; Roos, P.; Saito, T.; Savage, G.; Sawafta, R.; Segel, R.; Stepanyan, S.; Stoler, P.; Tadevosian, V.; Tang, L.; Teodorescu, L.; Terasawa, T.; Tsubota, H.; Urciuoli, G.M.; Volmer, J.; Vulcan, W.; Welch, P.; Williams, R.; Wood, S.; Yan, C.; Zeidman, B.The 1H(e,e′K+)Λ reaction was studied as a function of the squared four-momentum transfer, Q2, and the virtual photon polarization, ɛ. For each of four Q2 settings, 0.52, 0.75, 1.00, and 2.00 (GeV/c)2, the longitudinal and transverse virtual photon cross sections were extracted in measurements at three virtual photon polarizations. The Q2 dependence of the σL/σT ratio differs significantly from current theoretical predictions. This, combined with the precision of the measurement, implies a need for revision of existing calculations.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 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 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.