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Now showing items 1 - 16 of 59083

  • Mass-dependent cuts in longitudinal phase space

    Pauli, P.   Glazier, D. I.   Battaglieri, M.   Celentano, A.   De Vita, R.   Diehl, S.   Filippi, A.   Londergan, J. T.   Mathieu, V.   Szczepaniak, A. P.  

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  • photoproduction from threshold to

    Goetz, J. T.   Hicks, K.   Kunkel, M. C.   Price, J. W.   Weygand, D. P.   Adhikari, S.   Anefalos Pereira, S.   Battaglieri, M.   Bedlinskiy, I.   Biselli, A. S.   Boiarinov, S.   Bookwalter, C.   Briscoe, W. J.   Brooks, W. K.   Burkert, V. D.   Cao, F.   Carman, D. S.   Celentano, A.   Chandavar, S.   Chatagnon, P.   Chetry, T.   Ciullo, G.   Cole, P. L.   Contalbrigo, M.   Crede, V.   D'Angelo, A.   Dashyan, N.   De Vita, R.   Defurne, M.   Deur, A.   Diehl, S.   Djalali, C.   Dugger, M.   Dupre, R.   Egiyan, H.   Ehrhart, M.   El Alaoui, A.   El Fassi, L.   Elouadrhiri, L.   Eugenio, P.   Fedotov, G.   Filippi, A.   Gevorgyan, N.   Ghandilyan, Y.   Girod, F. X.   Glazier, D. I.   Golovatch, E.   Gothe, R. W.   Griffioen, K. A.   Guidal, M.   Guo, L.   Hafidi, K.   Hakobyan, H.   Harrison, N.   Hattawy, M.   Heddle, D.   Holtrop, M.   Ireland, D. G.   Ishkhanov, B. S.   Isupov, E. L.   Jo, H. S.   Joosten, S.   Kabir, M. L.   Keller, D.   Khachatryan, G.   Khachatryan, M.   Khandaker, M.   Kim, A.   Kim, W.   Klein, F. J.   Kubarovsky, V.   Lanza, L.   Livingston, K.   MacGregor, I. J. D.   McKinnon, B.   Meyer, C. A.   Mirazita, M.   Mokeev, V.   Movsisyan, A.   Munoz Camacho, C.   Nadel-Turonski, P.   Niccolai, S.   Niculescu, G.   Osipenko, M.   Ostrovidov, A. I.   Paolone, M.   Paremuzyan, R.   Park, K.   Pasyuk, E.   Pogorelko, O.   Prok, Y.   Protopopescu, D.   Raue, B. A.   Ripani, M.   Riser, D.   Rizzo, A.   Rosner, G.   Sabatié, F.   Saini, M. S.   Salgado, C.   Schott, D.   Schumacher, R. A.   Sharabian, Y. G.   Skorodumina, Iu.   Sober, D. I.   Sokhan, D.   Sparveris, N.   Strakovsky, I. I.   Strauch, S.   Taiuti, M.   Tan, J. A.   Ungaro, M.   Voskanyan, H.   Voutier, E.   Wang, R.   Wei, X.   Wood, M. H.   Zachariou, N.   Zhang, J.   Zhao, Z. W.  

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  • Threshold pi(0) photoproduction on transverse polarised protons at MAMI

    Schumann, S.   Otte, P. B.   Akondi, C. S.   Annand, J. R. M.   Arends, H. -J.   Beck, R.   Bernstein, A. M.   Borisov, N.   Braghieri, A.   Briscoe, W. J.   Cherepnya, S.   Collicott, C.   Costanza, S.   Downie, E. J.   Dieterle, M.   Fernandez-Ramirez, C.   Fix, A.   Fil'kov, L. V.   Garni, S.   Glazier, D. I.   Gradl, W.   Gurevich, G.   Hall-Barrientos, P.   Hamilton, D.   Hornidge, D.   Howdle, D.   Huber, G. M.   Kashevarov, V. L.   Keshelashvili, I.   Kondratiev, R.   Korolija, M.   Krusche, B.   Lazarev, A.   Lisin, V.   Livingston, K.   MacGregor, I. J. D.   Mancel, J.   Manley, D. M.   Martel, P. P.   McNicoll, E. F.   Meyer, W.   Middleton, D.   Miskimen, R.   Mushkarenkov, A.   Nefkens, B. M. K.   Neganov, A.   Nikolaev, A.   Oberle, M.   Ostrick, M.   Ortega, H.   Ott, P.   Oussena, B.   Paudyal, D.   Pedroni, P.   Polonski, A.   Polyanski, V. V.   Prakhov, S.   Reicherz, G.   Rostomyan, T.   Sarty, A.   Sikora, M. H.   Sokhoyan, V.   Steffen, O.   Strakovsky, I. I.   Strub, Th.   Supek, I.   Tiator, L.   Thomas, A.   Unverzagt, M.   Usov, Yu. A.   Watts, D. P.   Werthmueller, D.   Witthauer, L.   Wolfes, M.  

    Polarisation-dependent differential cross sections sigma(T) associated with the target asymmetry T have been measured for the reaction gamma (p)over arrow -> p pi(0) with transverse target polarisation from pi(0) threshold to photon energies of 190 MeV. The data were obtained using a frozen-spin butanol target with the Crystal Ball/TAPS detector set-up and the Glasgow photon tagging system at the Mainz Microtron MAMI. Results for sigma(T) have been used in combination with our previous measurements of the unpolarised cross section sigma(0) and the beam asymmetry Sigma for a model-independent determination of S- and P-wave multipoles in the pi(0) threshold region, which includes for the first time a direct determination of the imaginary part of the E0+ multipole. (C) 2015 The Authors. Published by Elsevier B.V.
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  • Photoproduction of pi(0)-pairs off protons and off neutrons

    Dieterle, M.   Oberle, M.   Ahrens, J.   Annand, J. R. M.   Arends, H. J.   Bantawa, K.   Bartolome, P. A.   Beck, R.   Bekrenev, V.   Berghaeuser, H.   Braghieri, A.   Branford, D.   Briscoe, W. J.   Brudvik, J.   Cherepnya, S.   Costanza, S.   Demissie, B.   Downie, E. J.   Drexler, P.   Fil'kov, L. V.   Fix, A.   Garni, S.   Glazier, D. I.   Hamilton, D.   Heid, E.   Hornidge, D.   Howdle, D.   Huber, G. M.   Jahn, O.   Jude, T. C.   Kaeser, A.   Kashevarov, V. L.   Keshelashvili, I.   Kondratiev, R.   Korolija, M.   Krusche, B.   Lisin, V.   Livingston, K.   MacGregor, I. J. D.   Maghrbi, Y.   Mancell, J.   Manley, D. M.   Marinides, Z.   McGeorge, J. C.   McNicoll, E.   Mekterovic, D.   Metag, V.   Micanovic, S.   Middleton, D. G.   Mushkarenkov, A.   Nikolaev, A.   Novotny, R.   Ostrick, M.   Otte, P.   Oussena, B.   Pedroni, P.   Pheron, F.   Polonski, A.   Prakhov, S.   Robinson, J.   Rostomyan, T.   Schumann, S.   Sikora, M. H.   Sober, D. I.   Starostin, A.   Strub, Th.   Supek, I.   Thiel, M.   Thomas, A.   Unverzagt, M.   Walford, N. K.   Watts, D. P.   Werthmueller, D.   Witthauer, L.  

    Total cross sections, angular distributions, and invariant-mass distributions have been measured for the photoproduction of pairs off free protons and off nucleons bound in the deuteron. The experiments were performed at the MAMI accelerator facility in Mainz using the Glasgow photon tagging spectrometer and the Crystal Ball/TAPS detector. The accelerator delivered electron beams of 1508 and 1557MeV, which produced bremsstrahlung in thin radiator foils. The tagged photon beam covered energies up to 1400MeV. The data from the free proton target are in good agreement with previous measurements and were only used to test the analysis procedures. The results for differential cross sections (angular distributions and invariant-mass distributions) for free and quasi-free protons are almost identical in shape, but differ in absolute magnitude up to 15%. Thus, moderate final-state interaction effects are present. The data for quasi-free neutrons are similar to the proton data in the second resonance region (final-state invariant masses up to MeV), where both reactions are dominated by the decay. At higher energies, angular and invariant-mass distributions are different. A simple analysis of the shapes of the invariant-mass distributions in the third resonance region is consistent with strong contributions of an decay for the proton, while the reaction is dominated by a sequential decay via a intermediate state for the neutron. The data are compared to predictions from the Two-Pion-MAID model and the Bonn-Gatchina coupled-channel analysis.
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  • Photon beam asymmetry Sigma for eta and eta ' photoproduction from the proton

    Collins, P.   Ritchie, B. G.   Dugger, M.   Anisovich, A. V.   Doering, M.   Klempt, E.   Nikonov, V. A.   Roenchen, D.   Sadasivan, D.   Sarantsev, A.   Adhikari, K. P.   Akbar, Z.   Amaryan, M. J.   Pereira, S. Anefalos   Avakian, H.   Ball, J.   Balossino, I.   Bashkanov, M.   Battaglieri, M.   Bedlinskiy, I.   Biselli, A. S.   Briscoe, W. J.   Brooks, W. K.   Burkert, V. D.   Cao, Frank Thanh   Carman, D. S.   Celentano, A.   Chandavar, S.   Charles, G.   Chetry, T.   Ciullo, G.   Clark, L.   Colaneri, L.   Cole, P. L.   Compton, N.   Contalbrigo, M.   Cortes, O.   Crede, V.   D'Angelo, A.   Dashyan, N.   De Vita, R.   De Sanctis, E.   Deur, A.   Djalali, C.   Dupre, R.   Egiyan, H.   El Alaoui, A.   El Fassi, L.   Elouadrhiri, L.   Eugenio, P.   Fanchini, E.   Fedotov, G.   Filippi, A.   Fleming, J. A.   Ghandilyan, Y.   Gilfoyle, G. P.   Giovanetti, K. L.   Girod, F. X.   Glazier, D. I.   Gleason, C.   Golovatch, E.   Gothe, R. W.   Griffioen, K. A.   Guo, L.   Hafidi, K.   Hakobyan, H.   Hanretty, C.   Harrison, N.   Heddle, D.   Hicks, K.   Holtrop, M.   Hughes, S. M.   Ilieva, Y.   Ireland, D. G.   Ishkhanov, B. S.   Isupov, E. L.   Jenkins, D.   Jo, H. S.   Joosten, S.   Keller, D.   Khachatryan, G.   Khachatryan, M.   Khandaker, M.   Kim, A.   Kim, W.   Klein, A.   Klein, F. J.   Kubarovsky, V.   Lanza, L.   Lenisa, P.   Livingston, K.   MacGregor, I. J. D.   Markov, N.   McKinnon, B.   Meyer, C. A.   Mirazita, M.   Mokeev, V.   Montgomery, R. A.   Movsisyan, A.   Camacho, C. Munoz   Murdoch, G.   Nadel-Turonski, P.   Niccolai, S.   Niculescu, G.   Niculescu, I.   Osipenko, M.   Ostrovidov, A. I.   Paolone, M.   Paremuzyan, R.   Park, K.   Pasyuk, E.   Phelps, W.   Pisano, S.   Pogorelko, O.   Price, J. W.   Prok, Y.   Protopopescu, D.   Raue, B. A.   Ripani, M.   Rizzo, A.   Rosner, G.   Roy, P.   Sabatie, F.   Salgado, C.   Schumacher, R. A.   Sharabian, Y. G.   Skorodumina, Iu.   Smith, G. D.   Sokhan, D.   Sparveris, N.   Stepanyan, S.   Strakovsky, I. I.   Strauch, S.   Taiuti, M.   Tian, Ye   Torayev, B.   Ungaro, M.   Voskanyan, H.   Voutier, E.   Walford, N. K.   Wei, X.   Zachariou, N.   Zhang, J.  

    Measurements of the linearly-polarized photon beam asymmetry Sigma for photoproduction from the proton of eta and eta ' mesons are reported. A linearly-polarized tagged photon beam produced by coherent bremsstrahlung was incident on a cryogenic hydrogen target within the CEBAF Large Acceptance Spectrometer. Results are presented for the gamma p -> eta p reaction for incident photon energies from 1.070 to 1.876 GeV, and from 1.516 to 1.836 GeV for the gamma p -> eta ' p reaction. For gamma p -> eta p, the data reported here considerably extend the range of measurements to higher energies, and are consistent with the few previously published measurements for this observable near threshold. For gamma p -> eta ' p, the results obtained are consistent with the few previously published measurements for this observable near threshold, but also greatly expand the incident photon energy coverage for that reaction. Initial analysis of the data reported here with the Bonn-Gatchina model strengthens the evidence for four nucleon resonances - the N(1895)1/2(-), N(1900)3/2(+), N(2100)1/2(+) and N(2120)3/2(-) resonances which presently lack the "four-star" status in the current Particle Data Group compilation, providing examples of how these new measurements help refine models of the photoproduction process. (C) 2017 The Authors. Published by Elsevier B.V.
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  • Coherent photoproduction of pi(0)- and eta-mesons off Li-7

    Maghrbi, Y.   Krusche, B.   Ahrens, J.   Annand, J. R. M.   Arends, H. J.   Beck, R.   Bekrenev, V.   Boillat, B.   Braghieri, A.   Branford, D.   Briscoe, W. J.   Brudvik, J.   Cherepnya, S.   Codling, R. F. B.   Downie, E. J.   Drexler, P.   Fil'kov, L. V.   Fix, A.   Glazier, D. I.   Gregor, R.   Heid, E.   Hornidge, D.   Jaegle, I.   Jahn, O.   Kashevarov, V. L.   Keshelashvili, I.   Knezevic, A.   Kondratiev, R.   Korolija, M.   Krambrich, D.   Lang, M.   Lisin, V.   Livingston, K.   Lugert, S.   MacGregor, I. J. D.   Manley, D. M.   Martinez, M.   McGeorge, J. C.   Mekterovic, D.   Metag, V.   Nefkens, B. M. K.   Nikolaev, A.   Novotny, R.   Ostrick, M.   Pedroni, P.   Pheron, F.   Polonski, A.   Prakhov, S.   Price, J. W.   Rosner, G.   Rost, M.   Rostomyan, T.   Schadmand, S.   Schumann, S.   Sober, D.   Starostin, A.   Supek, I.   Tarbert, C. M.   Thomas, A.   Unverzagt, M.   Watts, D. P.   Werthmueller, D.   Zehr, F.  

    Coherent photoproduction of pi(0)-mesons from threshold (E-th approximate to 136 MeV) throughout the Delta-resonance region and of eta-mesons close to the production threshold (E-th approximate to 570 MeV for eta) has been measured for Li-7 nuclei. The experiment was performed using the tagged-photon beam of the Mainz MAMI accelerator with the Crystal Ball and TAPS detectors combined to give an almost 4 pi solid-angle electromagnetic calorimeter. The reactions were identified by a combined invariant-mass and missing-energy analysis. A comparison of the pion data to plane-wave impulse modelling tests the nuclear mass form factor. So far coherent eta production had been only identified for the lightest nuclear systems (H-2 and He-3). For He-3 a large enhancement of the cross section above plane-wave approximations had been reported, indicating the formation of a quasi-bound state. The present Li data for eta production agree with a plane-wave approximation. Contrary to He-3, neither a threshold enhancement of the total cross section nor a deviation of the angular distributions from the expected form factor dependence were observed.
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  • Quasi-free photoproduction of eta-mesons off He-3 nuclei

    Witthauer, L.   Werthmueller, D.   Keshelashvili, I.   Aguar-Bartolome, P.   Ahrens, J.   Annand, J. R. M.   Arends, H. J.   Bantawa, K.   Beck, R.   Bekrenev, V.   Braghieri, A.   Branford, D.   Briscoe, W. J.   Brudvik, J.   Cherepnya, S.   Demissie, B.   Dieterle, M.   Downie, E. J.   Drexler, P.   Fil'kov, L. V.   Fix, A.   Glazier, D. I.   Hamilton, D.   Heid, E.   Hornidge, D.   Howdle, D.   Huber, G. M.   Jaegle, I.   Jahn, O.   Jude, T. C.   Kaeser, A.   Kashevarov, V. L.   Kondratiev, R.   Korolija, M.   Kruglov, S. P.   Krusche, B.   Kulbardis, A.   Lisin, V.   Livingston, K.   MacGregor, I. J. D.   Maghrbi, Y.   Mancell, J.   Manley, D. M.   Marinides, Z.   Martinez, M.   McGeorge, J. C.   McNicoll, E.   Metag, V.   Middleton, D. G.   Mushkarenkov, A.   Nefkens, B. M. K.   Nikolaev, A.   Novotny, R.   Oberle, M.   Ostrick, M.   Oussena, B.   Pedroni, P.   Pheron, F.   Polonski, A.   Prakhov, S.   Robinson, J.   Rosner, G.   Rost, M.   Rostomyan, T.   Schumann, S.   Sikora, M. H.   Sober, D.   Starostin, A.   Supek, I.   Thiel, M.   Thomas, A.   Unverzagt, M.   Watts, D. P.  

    Quasi-free photoproduction of eta-mesons has been measured off nucleons bound in He-3 nuclei for incident photon energies from the threshold region up to 1.4 GeV. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with an almost 4 pi covering electromagnetic calorimeter, combining the TAPS and Crystal Ball detectors. The eta-mesons were detected in coincidence with the recoil nucleons. This allowed a comparison of the production cross section off quasi-free protons and quasi-free neutrons and a full kinematic reconstruction of the final state, eliminating effects from nuclear Fermi motion. In the S-11(1535) resonance peak, the data agree with the neutron/proton cross section ratio extracted from measurements with deuteron targets. More importantly, the prominent structure observed in photoproduction off quasi-free neutrons bound in the deuteron is also clearly observed. Its parameters (width, strength) are consistent with the expectations from the deuteron results. On an absolute scale the cross sections for both quasi-free protons and neutrons are suppressed with respect to the deuteron target pointing to significant nuclear final-state interaction effects.
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  • Systematic studies of micro-channel plate PMTs

    Lehmann, A.   Britting, A.   Cowie, E.   Dodokhof, V. Kh.   Dueren, M.   Dutta, D.   Eyrich, W.   Foehl, K.   Glazier, D. I.   Hayrapetyan, A.   Hoek, M.   Hohler, R.   Kaiser, R.   Keri, T.   Koch, P.   Kroeck, B.   Lehmann, D.   Marton, J.   Merle, O.   Montgomery, R.   Peters, K.   Reinicke, S.   Rosner, G.   Roy, B.   Schepers, G.   Schmitt, L.   Schwarz, C.   Schwiening, J.   Seitz, B.   Sfientie, C.   Suzuki, K.   Uhlig, F.   Vodopianov, A. S.   Watts, D. P.   Yu, W.  

    DIRC Cherenkov detectors will be the main devices for pi/K separation at the PANDA experiment at FAIR. Due to their advantageous properties in terms of time resolution and especially inside magnetic fields micro-channel plate photo multipliers (MCP-PMTs) are very attractive sensor candidates. In this paper we present the investigation of several types of multi-anode MCP-PMTs. The darkcount rate, the behavior inside a magnetic field of up to 2T, the time resolution, the gain homogeneity and crosstalk of multi-pixel MCP-PMTs were found to be well suitable for the PANDA requirements. Even the rate capability of the latest models from Burle-Photonis and Hamamatsu is satisfactory. Although a big step forward was accomplished with these recently available MCP-PMTs, the lifetime is still not sufficient for the photon densities expected for the PANDA DIRCs. (C) 2010 Elsevier B.V. All rights reserved.
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  • Particle identification for the PANDA detector

    Schwarz, C.   Ahmed, G.   Britting, A.   Buehler, P.   Cowie, E.   Dodokhov, V. Kh.   Dueren, M.   Dutta, D.   Eyrich, W.   Foehl, K.   Glazier, D. I.   Hayrapetyan, A.   Hoek, M.   Hohler, R.   Lehmann, A.   Lehmann, D.   Kaiser, R.   Keri, T.   Koch, P.   Kroeck, B.   Marton, J.   Merle, O.   Montgomery, R.   Peters, K.   Reinicke, S.   Rosner, G.   Roy, B.   Schepers, G.   Schmitt, L.   Schwiening, J.   Seitz, B.   Sfienti, C.   Suzuki, K.   Uhlig, F.   Vodopianov, A. S.   Watts, D. P.   Yu, W.  

    Cooled antiproton beams of unprecedented intensities in the momentum range of 1.5-15 GeV/c will be used for the PANDA experiment at FAIR to perform high precision experiments in the charmed quark sector. The proposed PANDA detector is a 4 pi internal target spectrometer at the HESR allowing the detection and identification of neutral and charged particles generated within the total energy range of the antiproton annihilation products. The detector is divided in a forward spectrometer and a target spectrometer. The charged particle identification in the latter is performed by ring imaging Cherenkov counters employing the DIRC principle. (C) 2010 Elsevier B.V. All rights reserved.
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  • A quasi-real photon tagger for CLAS12

    Glazier, D. I.  

    The planned energy upgrade of the Jefferson Lab electron beam to 12 GeV will enable a host of different physics topics to be explored. The CLAS detector will undergo a corresponding upgrade to focus the detector systems in the forward angle region. As part of this CLAS12 project, a forward "quasi-real" photon tagger is being developed. This device will measure the scattered electrons with kinematics consistent with low Q(2) virtual photons. Such a system will enable a full reconstruction of the photoproduction of many poorly understood hadronic states, for example hybrid meson, cascade and Omega(-) states. Investigation of these states will provide a much needed examination of our understanding of QCD in the nonpeturbative regime.
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  • Photoproduction of pi(0)eta on protons and the Delta(1700)D(33)-resonance

    Kashevarov, V. L.   Fix, A.   Aguar-Bartolome, P.   Akasoy, L. K.   Annand, J. R. M.   Arends, H. J.   Bantawa, K.   Beck, R.   Bekrenev, V.   Berghaeuser, H.   Boillat, B.   Braghieri, A.   Branford, D.   Briscoe, W. J.   Brudvik, J.   Cherepnya, S.   Downie, E. J.   Drexler, P.   Fil'kov, L. V.   Glazier, D. I.   Gregor, R.   Heid, E.   Hornidge, D.   Jahn, O.   Jude, T. C.   Knezevic, A.   Kondratiev, R.   Korolija, M.   Kotulla, M.   Koulbardis, A.   Kruglov, S.   Krusche, B.   Lisin, V.   Livingston, K.   MacGregor, I. J. D.   Maghrbi, Y.   Manley, D. M.   Martinez-Fabregate, M.   McGeorge, J. C.   McNicoll, E. F.   Mekterovic, D.   Metag, V.   Micanovic, S.   Nefkens, B. M. K.   Nikolaev, A.   Novotny, R.   Ostrick, M.   Owens, R. O.   Pedroni, P.   Pheron, F.   Polonski, A.   Robinson, J.   Prakhov, S. N.   Rosner, G.   Rostomyan, T.   Schumann, S.   Sober, D.   Starostin, A.   Suarez, I. M.   Supek, I.   Tarbert, C. M.   Thiel, M.   Thomas, A.   Unverzagt, M.   Watts, D. P.   Zamboni, I.   Zehr, F.  

    Total and differential cross-sections for the reaction gamma p -> pi(0)eta p have been measured with the Crystal Ball/TAPS detector using the tagged photon facility at the MAMI C accelerator in Mainz. In the energy range E(gamma) = 0.95-1.4 GeV the reaction is dominated by the excitation and sequential decay of the Delta(1700)D(33)-resonance. Angular distributions measured with high statistics allow us to determine the ratio of hadronic decay widths Gamma(eta Delta)/Gamma pi S(11) and the ratio of the helicity amplitudes A(3/2)/A(1/2) for this resonance.
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  • (3)He(e,e'pp) and (3)He(e,e'pn) reactions at AmPS and MAMI RID D-4072-2011

    Middleton, D. G.   Annand, J. R. M.   Antelo, M. Ases   Ayerbe, C.   Barneo, P.   Baumann, D.   Bermuth, J.   Bernauer, J.   Blok, H. P.   Boehm, R.   Bosnar, D.   Ding, M.   Distler, M. O.   Friedrich, J.   Llongo, J. Garcia   Glazier, D. I.   Grabmayr, P.   Hehl, T.   Heim, J.   Hesselink, W. H. A.   Jans, E.   Manas, G. Jover   Kohl, M.   Lapikas, L.   MacGregor, I. J. D.   Martin, I.   McGeorge, J. C.   Merkel, H.   Merle, P.   Monstad, K.   Moschini, F.   Mueller, U.   Benito, R. Perez   Pospischil, Th.   Potokar, M.   Rosner, G.   Seimitz, M.   de Vries, H.   Walcher, Th.   Watts, D. P.   Weinriefer, M.   Weiss, M.   Zihlmann, B.  

    This paper reports on measurements of the (3)He(e,e'pp) reaction measured at AmPS and the (3)He(e,e'pn) reaction measured at MAMI. The measurements were performed in similar kinematics to allow a comparison to be made between the cross sections of the two reactions. Results are shown for both reactions together with a comparison for the (3)He(e,e'pp) data with continuum Faddeev calculations.
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  • First measurements of the (16)O(e, e ' pn)(14)N reaction RID D-4072-2011

    Middleton, D. G.   Annand, J. R. M.   Barbieri, C.   Barneo, P.   Blok, H. P.   Boehm, R.   Distler, M. O.   Friedrich, J.   Giusti, C.   Glazier, D. I.   Grabmayr, P.   Hehl, T.   Heim, J.   Hesselink, W. H. A.   Jans, E.   Kohl, M.   Lapikas, L.   MacGregor, I. J. D.   Martin, I.   McGeorge, J. C.   Merkel, H.   Moschini, F.   Rosner, G.   Seimetz, M.   de Vries, H.   Walcher, Th.   Watts, D. P.   Zihlmann, B.  

    This paper reports on the first measurement of the (16)O(e, e'pn)(14)N reaction. Data were measured in kinematics centred on a super-parallel geometry at energy and momentum transfers of 215MeV and 316MeV/c. The experimental resolution was sufficient to distinguish groups of states in the residual nucleus but not good enough to separate individual states. The data show a strong dependence on missing momentum and this dependence appears to be different for two groups of states in the residual nucleus. Theoretical calculations of the reaction using the Pavia code do not reproduce the shape or the magnitude of the data.
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  • First results on nucleon resonance photocouplings from the gamma p -> pi(+)pi(-) p reaction

    Golovatch, E.   Burkert, V. D.   Carman, D. S.   Gothe, R. W.   Hicks, K.   Ishkhanov, B. S.   Mokeev, V. I.   Pasyuk, E.   Adhikari, S.   Akbar, Z.   Amaryan, M. J.   Avakian, H.   Ball, J.   Barion, L.   Bashkanov, M.   Battaglieri, M.   Bedlinskiy, I.   Biselli, A. S.   Boiarinov, S.   Briscoe, W. J.   Cao, F.   Celentano, A.   Chatagnon, P.   Chetry, T.   Ciullo, G.   Clark, L.   Clary, B. A.   Cole, P. L.   Contalbrigo, M.   Crede, V.   D'Angelo, A.   Dashyan, N.   DeVita, R.   DeSanctis, E.   Defurne, M.   Deur, A.   Diehl, S.   Djalali, C.   Dugger, M.   Dupre, R.   Egiyan, H.   Ehrhart, M.   ElAlaoui, A.   ElFassi, L.   Elouadrhiri, L.   Eugenio, P.   Fedotov, G.   Fersch, R.   Filippi, A.   Ghandilyan, Y.   Gilfoyle, G. P.   Giovanetti, K. L.   Girod, F. X.   Glazier, D. I.   Griffioen, K. A.   Guidal, M.   Guo, L.   Hafidi, K.   Hakobyan, H.   Harrison, N.   Hattawy, M.   Heddle, D.   Holtrop, M.   Ilieva, Y.   Ireland, D. G.   Isupov, E. L.   Jenkins, D.   Jo, H. S.   Johnston, S.   Joo, K.   Kabir, M. L.   Keller, D.   Khachatryan, G.   Khachatryan, M.   Khandaker, M.   Kim, W.   Klein, A.   Klein, F. J.   Kubarovsky, V.   Lanza, L.   Lenisa, P.   Livingston, K.   MacGregor, I. J. D.   Marchand, D.   Markov, N.   McKinnon, B.   Meyer, C. A.   Montgomery, R. A.   Movsisyan, A.   Munoz Camacho, C.   Nadel-Turonski, P.   Niccolai, S.   Niculescu, G.   Osipenko, M.   Ostrovidov, A. I.   Paolone, M.   Paremuzyan, R.   Park, K.   Pogorelko, O.   Price, J. W.   Prok, Y.   Protopopescu, D.   Ripani, M.   Riser, D.   Rizzo, A.   Rosner, G.   Sabatie, F.   Salgado, C.   Schumacher, R. A.   Sharabian, Y. G.   Skorodumina, Iu.   Smith, G. D.   Sober, D. I.   Sokhan, D.   Sparveris, N.   Strakovsky, I. I.   Strauch, S.   Taiuti, M.   Tan, J. A.   Tyler, N.   Ungaro, M.   Voskanyan, H.   Voutier, E.   Wang, R.   Wei, X.   Wood, M. H.   Zachariou, N.   Zhang, J.   Zhao, Z. W.  

    We report the first experimental measurements of the nine 1-fold differential cross sections for the gamma p ->pi(+)pi(-) p reaction, obtained with the CLAS detector at Jefferson Laboratory. The measurements cover the invariant mass range of the final state hadrons from 1.6 GeV < W < 2.0 GeV. For the first time the photocouplings of all prominent nucleon resonances in this mass range have been extracted from this exclusive channel. Photoproduction of two charged pions is of particular importance for the evaluation of the photocouplings for the Delta(1620)1/2(-) , Delta(1700)3/2(-) , N(1720)3/2(+), and Delta(1905)5/2(+) resonances, which have dominant decays into the pi pi N final states rather than the more extensively studied single meson decay channels. (C) 2018 The Author. Published by Elsevier B.V.
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  • Radiative pi(0) photoproduction on protons in the Delta(+)(1232) region RID D-4072-2011

    Schumann, S.   Boillat, B.   Downie, E. J.   Aguar-Bartolome, P.   Ahrens, J.   Annand, J. R. M.   Arends, H. J.   Beck, R.   Bekrenev, V.   Braghieri, A.   Branford, D.   Briscoe, W. J.   Brudvik, J. W.   Cherepnya, S.   Codling, R.   Drexler, P.   Fil'kov, L. V.   Glazier, D. I.   Gregor, R.   Heid, E.   Hornidge, D.   Jahn, O.   Kashevarov, V. L.   Kondratiev, R.   Korolija, M.   Kotulla, M.   Krambrich, D.   Krusche, B.   Lang, M.   Lisin, V.   Livingston, K.   Lugert, S.   MacGregor, I. J. D.   Manley, D. M.   Martinez-Fabregate, M.   McGeorge, J. C.   Mekterovic, D.   Metag, V.   Nefkens, B. M. K.   Nikolaev, A.   Novotny, R.   Ostrick, M.   Owens, R. O.   Pedroni, P.   Polonski, A.   Prakhov, S. N.   Price, J. W.   Rosner, G.   Rost, M.   Rostomyan, T.   Sober, D.   Starostin, A.   Supek, I.   Tarbert, C. M.   Thomas, A.   Unverzagt, M.   Walcher, Th.   Watts, D. P.   Zehr, F.  

    The reaction gamma p -> p pi(0)gamma' has been measured with the Crystal Ball/TAPS detectors using the energy-tagged photon beam at the electron accelerator facility MAMI-B. Energy and angular differential cross-sections for the emitted photon gamma' and angular differential cross-sections for the pi(0) have been determined with high statistics in the energy range of the Delta(+)(1232)-resonance. Cross-sections and the ratio of the cross-section to the nonradiative process gamma p -> p pi(0) are compared to theoretical reaction models, having the anomalous magnetic moment kappa(Delta+) as free parameter. As the shape of the experimental distributions is not reproduced in detail by the model calculations, currently no extraction of kappa(Delta+) is feasible.
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  • Helicity dependence of the gamma He-3 -> pi X reactions in the Delta(1232) resonance region

    Costanza, S.   Mushkarenkov, A.   Rigamonti, F.   Romaniuk, M.   Bartolome, P. Aguar   Ahrens, J.   Annand, J. R. M.   Arends, H. -J.   Beck, R.   Braghieri, A.   Bekrenev, V.   Berghaeuser, H.   Briscoe, W. J.   Cherepnya, S. N.   Collicott, C.   Downie, E. J.   Drexler, P.   Fil'kov, L. V.   Fix, A.   Glazier, D. I.   Hamilton, D.   Heid, E.   Heil, W.   Hornidge, D.   Howdle, D.   Jaegle, I.   Huber, G. M.   Jahn, O.   Jude, T.   Kashevarov, V. L.   Keshelashvili, I.   Kondratiev, R.   Korolija, M.   Krimmer, J.   Krusche, B.   Kruglov, S.   Kulbardis, A.   Lisin, V.   Livingston, K.   MacGregor, I. J. D.   Mancell, J.   Mandaglio, G.   Manley, D. M.   McGeorge, J. C.   Middleton, D. G.   Metag, V.   Nefkens, B. M. K.   Nikolaev, A.   Oberle, M.   Ostrick, M.   Ortega, H.   Otte, P. B.   Oussena, B.   Pedroni, P.   Pheron, F.   Polonski, A.   Prakhov, S.   Rosner, G.   Rostomyan, T.   Sarty, A. J.   Schumann, S.   Starostin, A.   Supek, I.   Thiel, M.   Thomas, A.   Unverzagt, M.   Watts, D. P.   Werthmueller, D.  

    The helicity dependences of the differential cross sections for the semi- inclusive gamma He-3 -> pi(0) X and gamma He-3 -> pi(+/-) X reactions have been measured for the first time in the energy region 200 < E-gamma < 450 MeV. The experiment was performed at the tagged photon beam facility of the MAMI accelerator in Mainz using a longitudinally polarised high-pressure He-3 gas target. Hadronic products were measured with the large-acceptance Crystal Ball detector complemented with additional devices for charged-particle tracking and identification. Unpolarised differential cross sections and their helicity dependence are compared with theoretical calculations using the Fix-Arenhovel model. The effect of the intermediate excitation of the Delta(1232) resonance can be clearly seen from this comparison, especially for the polarised case, where nuclear effects are relatively small. The model provides a better theoretical description of the unpolarised charged pion photoproduction data than the neutral pion channel. It does significantly better in describing the helicity-dependent data in both channels. These comparisons provide new information on the mechanisms involved in pion photoproduction on He-3 and suggest that a polarised He-3 target can provide valuable information on the corresponding polarised quasi-free neutron reactions.
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