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287 results on '"Supek, I."'

251. π±Elastic and inelastic scattering from 3H and 3He

Author

Briscoe, W.J., Barlow, D.B., Berman, B.L., Caress, R.W., Dhuga, K.S., Dragic, S.N., Greene, S.J., Isenhower, D., Knowles, D., Macek, D., Matthews, S.K., Mokhtari, A., Nefkens, B.M.K., Nicholas, N.J., Pillai, C., Price, J.W., Sadler, M.E., Slaus, Ivo, Supek, I., and Taragin, M.F.

Abstract

We have measured the differential cross sections for the scattering of π±from 3H and 3He. The dσ's are normalized to π±d elastic scattering measured under the same experimental conditions. Our newest measurements were performed at incident pion energies from 142 to 256 MeV and angles between 140° and 180°. The momentum-transfer dependence of the cross sections was measured up to 11 fm−2, making it possible to explore differences in the matter form factors of 3H and 3He.

Published
1993
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252. Measurement of the π-→3π0n total cross section from threshold to 0.75 GeV/c

Author

Starostin, A., Nefkens, B. M. K., Manley, D. M., Abaev, V. V., Allgower, C. E., Bekrenev, V., Briscoe, W. J., Clajus, M., Comfort, J. R., Craig, K., Grosnick, D., Isenhower, D., Knecht, N., Koetke, D. D., Koulbardis, A. A., Nikolai Kozlenko, Kruglov, S., Lolos, G., Lopatin, I. V., Manweiler, R., Marušić, A., Mcdonald, S., Olmsted, J., Papandreou, Z., Peaslee, D. C., Phaisangittisakul, N., Prakhov, S., Price, J. W., Ramirez, A. F., Sadler, M., Shafi, A., Spinka, H., Stanislaus, T. D. S., Staudenmaier, H. M., Supek, I., and Tippens, W. B.

253. Neutron polarisation transfer, $C_{x'}^n$, in $\pi^+$ photoproduction off the proton

Author

Bashkanov, M., Watts, D. P., Kay, S. J. D., Abt, S., Patrick Achenbach, Adlarson, P., Afzal, F., Ahmed, Z., Akondi, C. S., Annand, J. R. M., Beck, R., Biroth, M., Borisov, N., Braghieri, A., Briscoe, W. J., Cividini, F., Collicott, C., Costanza, S., Denig, A., Downie, E. J., Drexler, P., Fegan, S., Fix, A., Gardner, S., Ghosal, D., Glazier, D. I., Gorodnov, I., Gradl, W., Gurevich, D., Heijkenskjöld, L., Hornidge, D., Huber, G. M., Kashevarov, V. L., Korolija, M., Krusche, B., Lazarev, A., Livingston, K., Lutterer, S., Macgregor, I. J. D., Manley, D. M., Martel, P. P., Miskimen, R., Mornacchi, E., Mullen, C., Neganov, A., Neiser, A., Ostrick, M., Otte, P. B., Paudyal, D., Pedroni, P., Rostomya, T., Sokhoyan, V., Spieker, K., Steffen, O., Strakovsky, I. I., Strub, T., Supek, I., Thiel, A., Thiel, M., Thomasf, A., Usov, Yu A., Wagner, S., Walford, N. K., Wettig, J., Wolfes, M., and Zachariou, N.

Subjects
Nuclear Experiment
Abstract

We report a first measurement of the double-polarisation observable, $C_{x'}$, in $\pi^+$ photoproduction off the proton. The $C_{x'}$ double-polarisation observable represents the transfer of polarisation from a circularly polarised photon beam to the recoiling neutron. The MAMI circularly polarised photon beam impinged on a liquid deuterium target cell, with reaction products detected in the Crystal Ball calorimeter. Ancillary apparatus surrounding the target provided tracking, particle identification and determination of recoil nucleon polarisation. The $C_{x'}$ observable is determined for photon energies 800-1400 MeV, providing new constraints on models aiming to elucidate the spectrum and properties of nucleon resonances. This is the first determination of any polarisation observable from the beam-recoil group of observables for this reaction, providing a valuable constraint and systematic check of the current solutions of partial wave analysis based theoretical models.

254. Dynamics of the π-p → π0π0n Reaction for pπ- < 750 MeV/c

Author

Craig, K., Comfort, J. R., Allgower, C. E., Bekrenev, V., Berger, E., Briscoe, W. J., Clajus, M., Draper, B., Grosnick, D., Isenhower, D., Knecht, N., Koetke, D., Koulbardis, A., Kozlenko, N., Kruglov, S., Lolos, G. J., Lopatin, I., Manley, D. M., Manweiler, R., Marušić, A., Mcdonald, S., Nefkens, B. M. K., Olmsted, J., Zisis Papandreou, Peaslee, D., Phaisangittisakul, N., Prakhov, S., Price, J. W., Pulver, M., Ramirez, A. F., Sadler, M. E., Shafi, A., Spinka, H., Stanislaus, S., Starostin, A., Supek, I., Staudenmaier, H. M., and Tippens, W. B.

255. Photoproduction of π0π0 - and π0π+ -pairs off the proton from threshold to the second resonance region

Author

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

Abstract

Precise total cross-sections and invariant-mass distributions have been measured for photoproduction of pion pairs off the proton producing $\ensuremath p\pi^0\pi^0$ and $\ensuremath n\pi^+\pi^0$ final states from the threshold region up to 800MeV incident photon energy. Additionally, beam helicity asymmetries have been measured in the second resonance region (550MeV-820MeV). The experiment was performed at 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 results are much more precise than any previous measurements and confirm the chiral perturbation theory predictions for the threshold behavior of these reactions. In the second resonance region, the invariant-mass distributions of meson-meson and meson-nucleon pairs are in reasonable agreement with model predictions, but none of the models reproduce the asymmetries for the mixed-charge channel

256. Quasi-free photoproduction of η -mesons off 3He nuclei

Author

Witthauer, L., Werthmüller, D., Keshelashvili, I., Aguar-Bartolomé, P., Ahrens, J., Annand, J., Arends, H., Bantawa, K., Beck, R., Bekrenev, V., Braghieri, A., Branford, D., Briscoe, W., Brudvik, J., Cherepnya, S., Demissie, B., Dieterle, M., Downie, E., Drexler, P., Fil'kov, L., Fix, A., Glazier, D., Hamilton, D., Heid, E., Hornidge, D., Howdle, D., Huber, G., Jaegle, I., Jahn, O., Jude, T., Käser, A., Kashevarov, V., Kondratiev, R., Korolija, M., Kruglov, S., Krusche, B., Kulbardis, A., Lisin, V., Livingston, K., MacGregor, I., Maghrbi, Y., Mancell, J., Manley, D., Marinides, Z., Martinez, M., McGeorge, J., McNicoll, E., Metag, V., Middleton, D., Mushkarenkov, A., Nefkens, B., 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., Sober, D., Starostin, A., Supek, I., Thiel, M., Thomas, A., Unverzagt, M., Watts, D., Witthauer, L., Werthmüller, D., Keshelashvili, I., Aguar-Bartolomé, P., Ahrens, J., Annand, J., Arends, H., Bantawa, K., Beck, R., Bekrenev, V., Braghieri, A., Branford, D., Briscoe, W., Brudvik, J., Cherepnya, S., Demissie, B., Dieterle, M., Downie, E., Drexler, P., Fil'kov, L., Fix, A., Glazier, D., Hamilton, D., Heid, E., Hornidge, D., Howdle, D., Huber, G., Jaegle, I., Jahn, O., Jude, T., Käser, A., Kashevarov, V., Kondratiev, R., Korolija, M., Kruglov, S., Krusche, B., Kulbardis, A., Lisin, V., Livingston, K., MacGregor, I., Maghrbi, Y., Mancell, J., Manley, D., Marinides, Z., Martinez, M., McGeorge, J., McNicoll, E., Metag, V., Middleton, D., Mushkarenkov, A., Nefkens, B., 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., Sober, D., Starostin, A., Supek, I., Thiel, M., Thomas, A., Unverzagt, M., and Watts, D.

Abstract

Quasi-free photoproduction of η-mesons has been measured off nucleons bound in 3He 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 4π covering electromagnetic calorimeter, combining the TAPS and Crystal Ball detectors. The η-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 S11(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

257. Coherent photoproduction of π0- and η-mesons off 7Li

Author

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

Abstract

Coherent photoproduction of π0-mesons from threshold (E th ≈ 136 MeV) throughout the Δ-resonance region and of η-mesons close to the production threshold (E th ≈ 570 MeV for η has been measured for 7Li 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 4π 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 η production had been only identified for the lightest nuclear systems (2H and 3He . For 3He 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 η production agree with a plane-wave approximation. Contrary to 3He , neither a threshold enhancement of the total cross section nor a deviation of the angular distributions from the expected form factor dependence were observed

258. Photoproduction of $ \pi^{0}$ -pairs off protons and off neutrons

Author

Dieterle, M., Oberle, M., Ahrens, J., Annand, J., Arends, H., Bantawa, K., Bartolome, P., Beck, R., Bekrenev, V., Berghäuser, H., Braghieri, A., Branford, D., Briscoe, W., Brudvik, J., Cherepnya, S., Costanza, S., Demissie, B., Downie, E., Drexler, P., Fil'kov, L., Fix, A., Garni, S., Glazier, D., Hamilton, D., Heid, E., Hornidge, D., Howdle, D., Huber, G., Jahn, O., Jude, T., Käser, A., Kashevarov, V., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lisin, V., Livingston, K., MacGregor, I., Maghrbi, Y., Mancell, J., Manley, D., Marinides, Z., McGeorge, J., McNicoll, E., Mekterovic, D., Metag, V., Micanovic, S., Middleton, D., 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., Sober, D., Starostin, A., Strub, Th, Supek, I., Thiel, M., Thomas, A., Unverzagt, M., Walford, N., Watts, D., Werthmüller, D., Witthauer, L., Dieterle, M., Oberle, M., Ahrens, J., Annand, J., Arends, H., Bantawa, K., Bartolome, P., Beck, R., Bekrenev, V., Berghäuser, H., Braghieri, A., Branford, D., Briscoe, W., Brudvik, J., Cherepnya, S., Costanza, S., Demissie, B., Downie, E., Drexler, P., Fil'kov, L., Fix, A., Garni, S., Glazier, D., Hamilton, D., Heid, E., Hornidge, D., Howdle, D., Huber, G., Jahn, O., Jude, T., Käser, A., Kashevarov, V., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lisin, V., Livingston, K., MacGregor, I., Maghrbi, Y., Mancell, J., Manley, D., Marinides, Z., McGeorge, J., McNicoll, E., Mekterovic, D., Metag, V., Micanovic, S., Middleton, D., 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., Sober, D., Starostin, A., Strub, Th, Supek, I., Thiel, M., Thomas, A., Unverzagt, M., Walford, N., Watts, D., Werthmüller, D., and Witthauer, L.

Abstract

Total cross sections, angular distributions, and invariant-mass distributions have been measured for the photoproduction of $ \pi^{0}\pi^{0}$ 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 $ \approx 1550$ MeV), where both reactions are dominated by the $ N(1520)3/2^{-} \rightarrow \Delta(1232)3/2^{+}\pi$ 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 $ N^{\star}\rightarrow N\sigma$ decay for the proton, while the reaction is dominated by a sequential decay via a $ \Delta\pi$ intermediate state for the neutron. The data are compared to predictions from the Two-Pion-MAID model and the Bonn-Gatchina coupled-channel analysis.

259. Measurement of the beam-helicity asymmetry I⊙ in the photoproduction of $ \pi^{0}$ $ \pi^{\pm}$ pairs off protons and off neutrons

Author

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

Abstract

Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of mixed-charge pion pairs in the reactions $ \gamma p\rightarrow n\pi^{0}\pi^{+}$ off free protons and $ \gamma d \rightarrow (p)p\pi^{0}\pi^{-}$ and $ \gamma d\rightarrow (n)n\pi^{0}\pi^{+}$ off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow-Mainz magnetic spectrometer. The charged pions, recoil protons, recoil neutrons, and decay photons from $ \pi^{0}$ mesons were detected in the $ 4\pi$ electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. Using a complete kinematic reconstruction of the final state, excellent agreement was found between the results for free and quasi-free protons, suggesting that the quasi-free neutron results are also a close approximation of the free-neutron asymmetries. A comparison of the results to the predictions of the Two-Pion-MAID reaction model shows that the reaction mechanisms are still not well understood, in particular at low incident photon energies in the second nucleon-resonance region.

260. Measurement of the spin-rotation parametersAandRforπ+p→π+p andπ−p→π−p scattering from 471 to 625 MeV/c

Author

Barlow, D. B., primary, Kessler, R. S., additional, Kim, G. J., additional, Nefkens, B. M. K., additional, Pillai, C., additional, Price, J. W., additional, Wightman, J. A., additional, Hall, S., additional, Lane, D. W., additional, Loe, S. R., additional, Morton, L. K., additional, Sadler, M. E., additional, Adrian, S. D., additional, Briscoe, W. J., additional, Kramer, L. H., additional, Mokhtari, A., additional, Petrov, A. M., additional, Seftor, C. J., additional, Taragin, M. F., additional, Davis, J. F., additional, and Supek, I., additional

Published
1989
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263. Pionska apsorpcija u 4He

Author

Planinić, Mirko, Androić, Darko, Backenstoss, Gerhard, Bosnar, Damir, Dooling, Tom, Furić, Miroslav, Gram, Peter, Gregory, Nick, Hoffart, Arnim, Ingram, Quentin, Klein, Andew, Koch, Klaus, Koehler, Joerg, Kotlinski, Boghdan, Kroedel, Mathias, Kyle, Gary, Lehmann, Albert, Mateos, Arthu, Michaelian, Karo, Petković, Tomislav, Redwine, Robert, Rowntree, David, Šimičević, Neven, Trezeciak, Ralf, Ullrich, Horst, Weyer, Heinz, Wildi, Markus, Wilson, Kewin, K.Ilakovac, K., Martinis, M., and Supek, I.

Subjects
(ppp)n, (ppn)p, positive pion absorption in 4He, cross-sections of partial channels, multinucleon channels: (pp)d/pn, (pn)pp, (pd)p, (ppd), (pppn), Nuclear Theory, NATURAL SCIENCES. Physics, PRIRODNE ZNANOSTI. Fizika, CEBAF, Jlab, cross sections of partial channels, (pp)d/pn [multinucleon channels], Nuclear Experiment
Abstract

This paper presents a large solid angle measurement of the positive pion absorption cross-section on 4He and its decomposition into partial channels. A large fraction of the absorption cross-section at incident pion kinetic energies of Tπ+ =70, 118, 162, 239, and 330 MeV is due to multinucleon channels., Daju se ishodi mjerenja pod velikim prostornim kutom udarnog presjeka za apsorpciju pozitivnih piona u He4 i razdjela na pojedine kanale. Velik dio apsorpcijskog udarnog presjeka za energije upadnih piona od Tπ+ =70, 118, 162, 239 i 330 MeV je posljedica višenukleonskih kanala.

Published
1999

264. First Measurement Using Elliptically Polarized Photons of the Double-Polarization Observable E for γp→pπ^{0} and γp→nπ^{+}.

Author

Afzal F, Spieker K, Hurck P, Abt S, Achenbach P, Adlarson P, Ahmed Z, Akondi CS, Annand JRM, Arends HJ, Bashkanov M, Beck R, Biroth M, Borisov N, Braghieri A, Briscoe WJ, Cividini F, Collicott C, Costanza S, Denig A, Dieterle M, Downie EJ, Drexler P, Fegan S, Gardner S, Ghosal D, Glazier DI, Gorodnov I, Gradl W, Gurevich D, Heijkenskjöld L, Hornidge D, Huber GM, Kashevarov VL, Kay SJD, Korolija M, Krusche B, Lazarev A, Livingston K, Lutterer S, MacGregor IJD, Macrae RG, Manley DM, Martel PP, Miskimen R, Mocanu M, Mornacchi E, Mullen C, Neganov A, Neiser A, Oberle M, Ostrick M, Otte PB, Paudyal D, Pedroni P, Powell A, Reicherz G, Rostomyan T, Sfienti C, Sokhoyan V, Steffen O, Strakovsky II, Strub T, Supek I, Thiel A, Thiel M, Thomas A, Usov YA, Wagner S, Walford NK, Watts DP, Werthmüller D, Wettig J, Witthauer L, Wolfes M, and Zachariou N

Abstract

We report the measurement of the helicity asymmetry E for the pπ^{0} and nπ^{+} final states using, for the first time, an elliptically polarized photon beam in combination with a longitudinally polarized target at the Crystal Ball experiment at MAMI. The results agree very well with data that were taken with a circularly polarized photon beam, showing that it is possible to simultaneously measure polarization observables that require linearly (e.g., G) and circularly polarized photons (e.g., E) and a longitudinally polarized target. The new data cover a photon energy range 270-1400 MeV for the pπ^{0} final state (230-842 MeV for the nπ^{+} final state) and the full range of pion polar angles, θ, providing the most precise measurement of the observable E. A moment analysis gives a clear observation of the pη cusp in the pπ^{0} final state.

Published
2024
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265. Single π 0 production off neutrons bound in deuteron with linearly polarized photons.

Author

Mullen C, Gardner S, Glazier DI, Kay SJD, Livingston K, Strakovsky II, Workman RL, Abt S, Achenbach P, Afzal F, Ahmed Z, Akondi CS, Annand JRM, Bashkanov M, Beck R, Biroth M, Borisov NS, Braghieri A, Briscoe WJ, Cividini F, Collicott C, Costanza S, Denig A, Dieterle M, Downie EJ, Drexler P, Fegan S, Ferretti-Bondy MI, Ghosal D, Gorodnov I, Gradl W, Günther M, Gurevic G, Heijkenskjöld L, Hornidge D, Huber GM, Jermann N, Kaeser A, Korolija M, Kashevarov VL, Krusche B, Kulikov VV, Lazarev A, Lutterer S, MacGregor IJD, Manley DM, Martel PP, Martemianov MA, Meier C, Miskimen R, Mocanu M, Mornacchi E, Neganov A, Oberle M, Ostrick M, Otte P, Paudyal D, Pedroni P, Powell A, Prakhov SN, Reicherz G, Ron G, Rostomyan T, Sfienti C, Sokhoyan V, Spieker K, Steffen O, Strub T, Supek I, Thiel A, Thiel M, Thomas A, Unverzagt M, Usov YA, Wagner S, Walford NK, Watts DP, Werthmüller D, Wettig J, Witthauer L, Wolfes M, and Zachariou N

Abstract

The quasifree γ → d → π 0 n ( p ) photon beam asymmetry, Σ , has been measured at photon energies, E γ , from 390 to 610 MeV, corresponding to center of mass energy from 1.271 to 1.424 GeV, for the first time. The data were collected in the A2 hall of the MAMI electron beam facility with the Crystal Ball and TAPS calorimeters covering pion center-of-mass angles from 49 ∘ to 148 ∘ . In this kinematic region, polarization observables are sensitive to contributions from the Δ ( 1232 ) and N (1440) resonances. The extracted values of Σ have been compared to predictions based on partial-wave analyses (PWAs) of the existing pion photoproduction database. Our comparison includes the SAID, MAID and Bonn-Gatchina analyses; while a revised SAID fit, including the new Σ measurements, has also been performed. In addition, isospin symmetry is examined as a way to predict π 0 n photoproduction observables, based on fits to published data in the channels π 0 p , π + n and π - p ., (© The Author(s) 2021.)

Published
2021
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266. Helicity-Dependent Cross Sections for the Photoproduction of π^{0} Pairs from Nucleons.

Author

Dieterle M, Witthauer L, Fix A, Abt S, Achenbach P, Adlarson P, Afzal F, Aguar Bartolome P, Ahmed Z, Annand JRM, Arends HJ, Bashkanov M, Beck R, Biroth M, Borisov N, Braghieri A, Briscoe WJ, Cividini F, Collicott C, Costanza S, Denig A, Dolzhikov AS, Downie EJ, Drexler P, Gardner S, Ghosal D, Glazier DI, Gorodnov I, Gradl W, Günther M, Gurevich D, Heijkenskjöld L, Hornidge D, Huber GM, Käser A, Kashevarov VL, Kay S, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Lazarev A, Lisin V, Livingston K, Lutterer S, MacGregor IJD, Manley DM, Martel PP, Metag V, Meyer W, Middleton DG, Miskimen R, Mornacchi E, Mullen C, Mushkarenkov A, Neganov A, Neiser A, Oberle M, Ostrick M, Otte PB, Paudyal D, Pedroni P, Polonski A, Powell A, Prakhov SN, Reicherz G, Ron G, Rostomyan T, Sarty A, Sfienti C, Sokhoyan V, Spieker K, Steffen O, Strakovsky II, Strub T, Supek I, Thiel A, Thiel M, Thomas A, Unverzagt M, Usov YA, Wagner S, Walford NK, Watts DP, Werthmüller D, Wettig J, Wolfes M, and Zana LA

Abstract

The double-polarization observable E and helicity-dependent cross sections σ&#95;{1/2}, σ&#95;{3/2} have been measured for the photoproduction of π^{0} pairs off quasifree protons and neutrons at the Mainz MAMI accelerator with the Crystal Ball/TAPS setup. A circularly polarized photon beam was produced by bremsstrahlung from longitudinally polarized electrons and impinged on a longitudinally polarized deuterated butanol target. The reaction products were detected with an almost 4π covering calorimeter. The results reveal for the first time the helicity- and isospin-dependent structure of the γN→Nπ^{0}π^{0} reaction. They are compared to predictions from reaction models in view of nucleon resonance contributions and also to a refit of one model that predicted results for the proton and for the neutron target. The comparison of the prediction and the refit demonstrates the large impact of the new data.

Published
2020
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267. Signatures of the d^{*}(2380) Hexaquark in d(γ,pn[over →]).

Author

Bashkanov M, Watts DP, Kay SJD, Abt S, Achenbach P, Adlarson P, Afzal F, Ahmed Z, Akondi CS, Annand JRM, Arends HJ, Beck R, Biroth M, Borisov N, Braghieri A, Briscoe WJ, Cividini F, Collicott C, Costanza S, Denig A, Downie EJ, Drexler P, Fegan S, Fix A, Gardner S, Ghosal D, Glazier DI, Gorodnov I, Gradl W, Günther M, Gurevich D, Heijkenskjöld L, Hornidge D, Huber GM, Käser A, Kashevarov VL, Korolija M, Krusche B, Lazarev A, Livingston K, Lutterer S, MacGregor IJD, Manley DM, Martel PP, Miskimen R, Mornacchi E, Mullen C, Neganov A, Neiser A, Ostrick M, Otte PB, Paudyal D, Pedroni P, Powell A, Prakhov SN, Ron G, Sarty A, Sfienti C, Sokhoyan V, Spieker K, Steffen O, Strakovsky II, Strub T, Supek I, Thiel A, Thiel M, Thomas A, Usov YA, Wagner S, Walford NK, Werthmüller D, Wettig J, Wolfes M, Zachariou N, and Zana LA

Abstract

We report a measurement of the spin polarization of the recoiling neutron in deuterium photodisintegration, utilizing a new large acceptance polarimeter within the Crystal Ball at MAMI. The measured photon energy range of 300-700 MeV provides the first measurement of recoil neutron polarization at photon energies where the quark substructure of the deuteron plays a role, thereby providing important new constraints on photodisintegration mechanisms. A very high neutron polarization in a narrow structure centered around E&#95;{γ}∼570  MeV is observed, which is inconsistent with current theoretical predictions employing nucleon resonance degrees of freedom. A Legendre polynomial decomposition suggests this behavior could be related to the excitation of the d^{*}(2380) hexaquark.

Published
2020
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268. Study of η and η' Photoproduction at MAMI.

Author

Kashevarov VL, Ott P, Prakhov S, Adlarson P, Afzal F, Ahmed Z, Akondi CS, Annand JRM, Arends HJ, Beck R, Braghieri A, Briscoe WJ, Cividini F, Codling R, Collicott C, Costanza S, Denig A, Downie EJ, Dieterle M, Ferretti Bondy MI, Fil'kov LV, Fix A, Gardner S, Garni S, Glazier DI, Glowa D, Gradl W, Gurevich G, Hamilton DJ, Hornidge D, Howdle D, Huber GM, Käser A, Kay S, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Linturi J, Lisin V, Livingston K, MacGregor IJD, MacRae R, Mancell J, Manley DM, Martel PP, McGeorge JC, McNicol E, Middleton DG, Miskimen R, Mornacchi E, Mullen C, Mushkarenkov A, Neiser A, Oberle M, Ostrick M, Otte PB, Oussena B, Paudyal D, Pedroni P, Polyanski VV, Rajabi A, Reicherz G, Robinson J, Rosner G, Rostomyan T, Sarty A, Schott DM, Schumann S, Sfienti C, Sokhoyan V, Spieker K, Steffen O, Strandberg B, Strakovsky II, Strub T, Supek I, Taragin MF, Thiel A, Thiel M, Tiator L, Thomas A, Unverzagt M, Wagner S, Watts DP, Werthmüller D, Wettig J, Witthauer L, Wolfes M, Workman RL, and Zana L

Abstract

The reactions γp→ηp and γp→η^{'}p are measured from their thresholds up to the center-of-mass energy W=1.96  GeV with the tagged-photon facilities at the Mainz Microtron, MAMI. Differential cross sections are obtained with unprecedented statistical accuracy, providing fine energy binning and full production-angle coverage. A strong cusp is observed in the total cross section for η photoproduction at the energies in the vicinity of the η^{'} threshold, W=1896  MeV (E&#95;{γ}=1447  MeV). Within the framework of a revised ηMAID isobar model, the cusp, in connection with a steep rise of the η^{'} total cross section from its threshold, can only be explained by a strong coupling of the poorly known N(1895)1/2^{-} state to both ηp and η^{'}p. Including the new high-accuracy results in the ηMAID fit to available η and η^{'} photoproduction data allows the determination of the N(1895)1/2^{-} properties.

Published
2017
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269. Measurements of double-polarized compton scattering asymmetries and extraction of the proton spin polarizabilities.

Author

Martel PP, Miskimen R, Aguar-Bartolome P, Ahrens J, Akondi CS, Annand JR, Arends HJ, Barnes W, Beck R, Bernstein A, Borisov N, Braghieri A, Briscoe WJ, Cherepnya S, Collicott C, Costanza S, Denig A, Dieterle M, Downie EJ, Fil'kov LV, Garni S, Glazier DI, Gradl W, Gurevich G, Hall Barrientos P, Hamilton D, Hornidge D, Howdle D, Huber GM, Jude TC, Kaeser A, Kashevarov VL, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Lazarev A, Lisin V, Livingston K, MacGregor IJ, Mancell J, Manley DM, Meyer W, Middleton DG, Mushkarenkov A, Nefkens BM, Neganov A, Nikolaev A, Oberle M, Ortega Spina H, Ostrick M, Ott P, Otte PB, Oussena B, Pedroni P, Polonski A, Polyansky V, Prakhov S, Rajabi A, Reicherz G, Rostomyan T, Sarty A, Schrauf S, Schumann S, Sikora MH, Starostin A, Steffen O, Strakovsky II, Strub T, Supek I, Thiel M, Tiator L, Thomas A, Unverzagt M, Usov Y, Watts DP, Witthauer L, Werthmüller D, and Wolfes M

Abstract

The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to extract the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the Δ(1232) region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields γ(E1E1)=-3.5±1.2, γ(M1M1)=3.16±0.85, γ(E1M2)=-0.7±1.2, and γ(M1E2)=1.99±0.29, in units of 10(-4)  fm(4).

Published
2015
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270. Measurement of the transverse target and beam-target asymmetries in η meson photoproduction at MAMI.

Author

Akondi CS, Annand JR, Arends HJ, Beck R, Bernstein A, Borisov N, Braghieri A, Briscoe WJ, Cherepnya S, Collicott C, Costanza S, Downie EJ, Dieterle M, Fix A, Fil'kov LV, Garni S, Glazier DI, Gradl W, Gurevich G, Hall Barrientos P, Hamilton D, Hornidge D, Howdle D, Huber GM, Kashevarov VL, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Lazarev A, Lisin V, Livingston K, MacGregor IJ, Mancel J, Manley DM, Martel P, McNicoll EF, Meyer W, Middleton D, Miskimen R, Mushkarenkov A, Nefkens BM, Neganov A, Nikolaev A, Oberle M, Ostrick M, Ortega H, Ott P, Otte PB, Oussena B, Pedroni P, Polonski A, Polyanski VV, Prakhov S, Reicherz G, Rostomyan T, Sarty A, Schumann S, Steffen O, Strakovsky II, Strub T, Supek I, Tiator L, Thomas A, Unverzagt M, Usov YA, Watts DP, Werthmüller D, Witthauer L, and Wolfes M

Abstract

We present new data for the transverse target asymmetry T and the very first data for the beam-target asymmetry F in the γ[over →]p[over →]→ηp reaction up to a center-of-mass energy of W=1.9  GeV. The data were obtained with the Crystal-Ball/TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. All existing model predictions fail to reproduce the new data indicating a significant impact on our understanding of the underlying dynamics of η meson photoproduction. The peculiar nodal structure observed in existing T data close to threshold is not confirmed.

Published
2014
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271. Neutron skin of (208)pb from coherent pion photoproduction.

Author

Tarbert CM, Watts DP, Glazier DI, Aguar P, Ahrens J, Annand JR, Arends HJ, Beck R, Bekrenev V, Boillat B, Braghieri A, Branford D, Briscoe WJ, Brudvik J, Cherepnya S, Codling R, Downie EJ, Foehl K, Grabmayr P, Gregor R, Heid E, Hornidge D, Jahn O, Kashevarov VL, Knezevic A, Kondratiev R, Korolija M, Kotulla M, Krambrich D, Krusche B, Lang M, Lisin V, Livingston K, Lugert S, MacGregor IJ, Manley DM, Martinez M, McGeorge JC, Mekterovic D, Metag V, Nefkens BM, Nikolaev A, Novotny R, Owens RO, Pedroni P, Polonski A, Prakhov SN, Price JW, Rosner G, Rost M, Rostomyan T, Schadmand S, Schumann S, Sober D, Starostin A, Supek I, Thomas A, Unverzagt M, Walcher T, Zana L, and Zehr F

Abstract

Information on the size and shape of the neutron skin on (208)Pb is extracted from coherent pion photoproduction cross sections measured using the Crystal Ball detector together with the Glasgow tagger at the MAMI electron beam facility. On exploitation of an interpolated fit of a theoretical model to the measured cross sections, the half-height radius and diffuseness of the neutron distribution are found to be c(n)=6.70±0.03(stat.)  fm and a(n)=0.55±0.01(stat.)(-0.03)(+0.02)(sys.)  fm, respectively, corresponding to a neutron skin thickness Δr(np)=0.15±0.03(stat.)(-0.03)(+0.01)(sys.)  fm. The results give the first successful extraction of a neutron skin thickness with an electromagnetic probe and indicate that the skin of (208)Pb has a halo character. The measurement provides valuable new constraints on both the structure of nuclei and the equation of state for neutron-rich matter.

Published
2014
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272. Photoproduction of π0 mesons off neutrons in the nucleon resonance region.

Author

Dieterle M, Keshelashvili I, Ahrens J, Annand JR, Arends HJ, Bantawa K, Bartolome PA, Beck R, Bekrenev V, Braghieri A, Branford D, Briscoe WJ, Brudvik J, Cherepnya S, Demissie B, Downie EJ, Drexler P, Fil'kov LV, Fix A, Glazier DI, Hamilton D, Heid E, Hornidge D, Howdle D, Huber GM, Jaegle I, Jahn O, Jude TC, Käser A, Kashevarov VL, Kondratiev R, Korolija M, Kruglov SP, Krusche B, Kulbardis A, Lisin V, Livingston K, MacGregor IJ, Maghrbi Y, Mancell J, Manley DM, Marinides Z, Martinez M, McGeorge JC, McNicoll E, Mekterovic D, Metag V, Micanovic S, Middleton DG, Mushkarenkov A, Nefkens BM, Nikolaev A, Novotny R, Oberle M, Ostrick M, Oussena B, Pedroni P, Pheron F, Polonski A, Prakhov SN, Robinson J, Rosner G, Rostomyan T, Schumann S, Sikora MH, Sober D, Starostin A, Supek I, Thiel M, Thomas A, Unverzagt M, Watts DP, Werthmüller D, and Witthauer L

Abstract

Precise angular distributions have been measured for the first time for the photoproduction of π0 mesons off neutrons bound in the deuteron. The effects from nuclear Fermi motion have been eliminated by a complete kinematic reconstruction of the final state. The influence of final-state-interaction effects has been estimated by a comparison of the reaction cross section for quasifree protons bound in the deuteron to the results for free protons and then applied as a correction to the quasifree neutron data. The experiment was performed at the tagged photon facility of the Mainz Microtron MAMI with the Crystal Ball and TAPS detector setup for incident photon energies between 0.45 and 1.4 GeV. The results are compared to the predictions from reaction models and partial-wave analyses based on data from other isospin channels. The model predictions show large discrepancies among each other and the present data will provide much tighter constraints. This is demonstrated by the results of a new analysis in the framework of the Bonn-Gatchina coupled-channel analysis which included the present data.

Published
2014
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273. Measurement of the 1H(γ, p)π0 reaction using a novel nucleon spin polarimeter.

Author

Sikora MH, Watts DP, Glazier DI, Aguar-Bartolomé P, Akasoy LK, Annand JR, Arends HJ, Bantawa K, Beck R, Bekrenev VS, Berghäuser H, Braghieri A, Branford D, Briscoe WJ, Brudvik J, Cherepnya S, Codling RF, Demissie BT, Downie EJ, Drexler P, Fil'kov LV, Freehart B, Gregor R, Hamilton D, Heid E, Hornidge D, Howdle DA, Jaegle I, Jahn O, Jude TC, Kashevarov VL, Keshelashvili I, Kondratiev R, Korolija M, Kotulla M, Koulbardis AA, Kruglov SP, Krusche B, Lisin V, Livingston K, MacGregor IJ, Maghrbi Y, Manley DM, Marinides Z, Martinez M, McGeorge JC, McKinnon B, McNicoll EF, Mekterovic D, Metag V, Micanovic S, Middleton DG, Mushkarenkov A, Nefkens BM, Nikolaev A, Novotny R, Ostrick M, Otte PB, Oussena B, Pedroni P, Pheron F, Polonski A, Prakhov S, Robinson J, Rosner G, Rostomyan T, Schumann S, Sober DI, Starostin A, Strakovsky II, Suarez IM, Supek I, Thiel M, Thomas A, Unverzagt M, Werthmüller D, Workman RL, Zamboni I, and Zehr F

Abstract

We report the first large-acceptance measurement of polarization transfer from a polarized photon beam to a recoiling nucleon. The measurement pioneers a novel polarimetry technique, which can be applied to many other nuclear and hadron physics experiments. The commissioning reaction of 1H(γ, p)π0 in the range 0.4

Published
2014
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274. Narrow structure in the excitation function of η photoproduction off the neutron.

Author

Werthmüller D, Witthauer L, Keshelashvili I, Aguar-Bartolomé P, Ahrens J, Annand JR, Arends HJ, Bantawa K, Beck R, Bekrenev V, Braghieri A, Branford D, Briscoe WJ, Brudvik J, Cherepnya S, Demissie B, Dieterle M, Downie EJ, Drexler P, Fil'kov LV, Fix A, Glazier DI, Hamilton D, Heid E, Hornidge D, Howdle D, Huber GM, Jaegle I, Jahn O, Jude TC, Käser A, Kashevarov VL, Kondratiev R, Korolija M, Kruglov SP, Krusche B, Kulbardis A, Lisin V, Livingston K, MacGregor IJ, Maghrbi Y, Mancell J, Manley DM, Marinides Z, Martinez M, McGeorge JC, McNicoll EF, Metag V, Middleton DG, Mushkarenkov A, Nefkens BM, Nikolaev A, Novotny R, Oberle M, Ostrick M, Oussena B, Pedroni P, Pheron F, Polonski A, Prakhov SN, Robinson J, Rosner G, Rostomyan T, Schumann S, Sikora MH, Sober D, Starostin A, Supek I, Thiel M, Thomas A, Unverzagt M, and Watts DP

Abstract

The photoproduction of η mesons off nucleons bound in 2H and 3He has been measured in coincidence with recoil protons and recoil neutrons for incident photon energies from threshold up to 1.4 GeV. The experiments were performed at the Mainz MAMI accelerator, using the Glasgow tagged photon facility. Decay photons from the η→2γ and η→3π0 decays and the recoil nucleons were detected with an almost 4π electromagnetic calorimeter combining the Crystal Ball and TAPS detectors. The data from both targets are of excellent statistical quality and show a narrow structure in the excitation function of γn→nη. The results from the two measurements are consistent, taking into account the expected effects from nuclear Fermi motion. The best estimates for position and intrinsic width of the structure are W=(1670±5)  MeV and Γ=(30±15)  MeV. For the first time precise results for the angular dependence of this structure have been extracted.

Published
2013
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275. Accurate test of chiral dynamics in the γp→π0p reaction.

Author

Hornidge D, Aguar Bartolomé P, Annand JR, Arends HJ, Beck R, Bekrenev V, Berghäuser H, Bernstein AM, Braghieri A, Briscoe WJ, Cherepnya S, Dieterle M, Downie EJ, Drexler P, Fernández-Ramírez C, Filkov LV, Glazier DI, Hall Barrientos P, Heid E, Hilt M, Jaegle I, Jahn O, Jude TC, Kashevarov VL, Keshelashvili I, Kondratiev R, Korolija M, Koulbardis A, Krambrich D, Kruglov S, Krusche B, Laffoley AT, Lisin V, Livingston K, MacGregor IJ, Mancell J, Manley DM, McNicoll EF, Mekterovic D, Metag V, Micanovic S, Middleton DG, Moores KW, Mushkarenkov A, Nefkens BM, Oberle M, Ostrick M, Otte PB, Oussena B, Pedroni P, Pheron F, Polonski A, Prakhov S, Robinson J, Rostomyan T, Scherer S, Schumann S, Sikora MH, Starostin A, Supek I, Thiel M, Thomas A, Tiator L, Unverzagt M, Watts DP, Werthmüller D, and Witthauer L

Abstract

A precision measurement of the differential cross sections dσ/dΩ and the linearly polarized photon asymmetry Σ≡(dσ⊥-dσ∥)/(dσ⊥+dσ∥) for the γp→π0p reaction in the near-threshold region has been performed with a tagged photon beam and almost 4π detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multiphoton detector system and a cryogenic liquid hydrogen target were used. These data allowed for a precise determination of the energy dependence of the real parts of the S- and all three P-wave amplitudes for the first time and provide the most stringent test to date of the predictions of chiral perturbation theory and its energy region of agreement with experiment.

Published
2013
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276. Precise measurement of the pi+-->pi0 e+nu branching ratio.

Author

Pocanić D, Frlez E, Baranov VA, Bertl W, Brönnimann Ch, Bychkov M, Crawford JF, Daum M, Khomutov NV, Korenchenko AS, Korenchenko SM, Kozlowski T, Kravchuk NP, Kuchinsky NA, Li W, Minehart RC, Mzhavia D, Ritchie BG, Ritt S, Rozhdestvensky AM, Sidorkin VV, Smith LC, Supek I, Tsamalaidze Z, VanDevender BA, Wang Y, Wirtz HP, and Ziock KO

Abstract

Using a large acceptance calorimeter and a stopped pion beam we have made a precise measurement of the rare pi(+)-->pi(0)e(+)nu (pi(beta)) decay branching ratio. We have evaluated the branching ratio by normalizing the number of observed pi(beta) decays to the number of observed pi(+)-->e(+)nu (pi(e2)) decays. We find the value of Gamma(pi(+)-->pi(0)e(+)nu)/Gamma(total)=[1.036+/-0.004(stat)+/-0.004(syst)+/-0.003(pi(e2))]x10(-8), where the first uncertainty is statistical, the second systematic, and the third is the pi(e2) branching ratio uncertainty. Our result agrees well with the standard model prediction.

Published
2004
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277. Dynamics of the pi(-)p-->pi(0)pi(0)n reaction for p(pi(-))<750 MeV/c.

Author

Craig K, Comfort JR, Allgower CE, Bekrenev V, Berger E, Briscoe WJ, Clajus M, Draper B, Grosnick D, Isenhower D, Knecht N, Koetke D, Koulbardis A, Kozlenko N, Kruglov S, Lolos GJ, Lopatin I, Manley DM, Manweiler R, Marusić A, McDonald S, Nefkens BM, Olmsted J, Papandreou Z, Peaslee D, Phaisangittisakul N, Prakhov S, Price JW, Pulver M, Ramirez AF, Sadler ME, Shafi A, Spinka H, Stanislaus S, Starostin A, Supek I, Staudenmaier HM, and Tippens WB

Abstract

Data are presented for the reaction pi(-)p-->pi(0)pi(0)n in the range from threshold to p(pi(-))=750 MeV/c. The systematics of the data and multipole analyses are examined for sensitivity to a f(0)(600) ("sigma") meson. A one-pion-exchange mechanism is found to be very weak, or absent. The reaction appears to become dominated by sequential pi(0) decays through the Delta(1232) resonance as the beam momentum increases, along with substantial interference effects from several competing mechanisms.

Published
2003
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278. Properties of the Lambda(1670)(1-)/2 resonance.

Author

Manley DM, Abaev VV, Allgower CE, Bekrenev V, Briscoe WJ, Clajus M, Comfort JR, Craig K, Grosnick D, Isenhower D, Knecht N, Koetke DD, Kulbardis AA, Kozlenko NG, Kruglov S, Lolos G, Lopatin IV, Manweiler R, Marusić A, McDonald S, Nefkens BM, Olmsted J, Papandreou Z, Peaslee DC, Phaisangittisakul N, Prakhov S, Price JW, Ramirez AF, Sadler M, Shafi A, Spinka H, Stanislaus TD, Starostin A, Staudenmaier HM, Strakovsky II, Supek I, and Tippens WB

Abstract

Recently the Crystal Ball Collaboration measured precise new data for the near-threshold reaction K(-)p-->etaLambda, which is dominated by formation of the Lambda(1670)1 / 2(-). In this Letter, we present results of a unitary, multichannel analysis that incorporates the new Crystal Ball data. For our preferred fit, we obtain mass M = 1673+/-2 MeV, width Gamma = 23+/-6 MeV, and elasticity x = 0.37+/-0.07. This elasticity is significantly larger than previously recognized. Resonance parameters of our preferred fit are in striking agreement with the quark-model predictions of Koniuk and Isgur.

Published
2002
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279. Measurement of pi(0)pi(0) production in the nuclear medium by pi(-) interactions at 0.408 GeV/c.

Author

Starostin A, Staudenmaier HM, Allgower CE, Bekrenev V, Berger E, Briscoe WJ, Clajus M, Comfort JR, Craig K, Grosnick D, Isenhower D, Knecht N, Koetke D, Koulbardis A, Kozlenko N, Kruglov S, Kycia T, Lolos G, Lopatin I, Manley DM, Manweiler B, Marusić A, McDonald S, Nefkens BM, Olmsted J, Papandreou Z, Peaslee D, Peterson RJ, Phaisangittisakul N, Prakhov S, Pulver M, Ramirez AF, Sadler M, Shafi A, Slaus I, Spinka H, Stanislaus S, Supek I, and Tippens WB

Abstract

We report on an investigation of the (pi(-),pi(0)pi(0)) reaction by means of measurements of the pi(0)pi(0) invariant mass distributions from pi(-) interactions on H, D, C, Al, and Cu targets at p(pi(-)) = 0.408 GeV/c. The sharp, strong peak in the pi(+)pi(-) invariant mass near 2m(pi) reported by the CHAOS Collaboration is not seen in our pi(0)pi(0) data. However, we do observe a change in the shape of the pi(0)pi(0) invariant mass spectrum for the different targets, indicating that the pi(0)pi(0) interaction diminishes in the nuclear medium as represented by nuclei D, C, Al, and Cu, compared to hydrogen.

Published
2000
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285. 2H(p,n)2p spin transfer from 305 to 788 MeV.

Author

McNaughton MW, Koch K, Supek I I, Tanaka N, Ambrose DA, Coffey P, Johnston K, McNaughton KH, Riley PJ, Glass G, Hiebert JC, Northcliffe LC, Simon AJ, Mercer DJ, Adams DL, Spinka H, Jeppesen RH, Tripard GE, and Woolverton H

Published
1992
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