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  1. Book ; Online ; Thesis: Measurement of polarization observables in the reaction gamma p ->p pi0 pi0 using linearly polarized photons with the CBELSA/TAPS experiment

    Sokhoyan, Vahe

    2012  

    Author's details Vahe Sokhoyan
    Keywords Medizin, Gesundheit ; Medicine, Health
    Subject code sg610
    Language English
    Publisher Universitäts- und Landesbibliothek Bonn
    Publishing place Bonn
    Document type Book ; Online ; Thesis
    Database Digital theses on the web

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

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

    Physical review letters

    2024  Volume 132, Issue 12, Page(s) 121902

    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. ... ...

    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.
    Language English
    Publishing date 2024-04-05
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.132.121902
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Measurement of Compton Scattering at MAMI for the Extraction of the Electric and Magnetic Polarizabilities of the Proton.

    Mornacchi, E / Martel, P P / Abt, S / Achenbach, P / Adlarson, P / Afzal, F / Ahmed, Z / Annand, J R M / Arends, H J / Bashkanov, M / Beck, R / Biroth, M / Borisov, N / Braghieri, A / Briscoe, W J / Cividini, F / Collicott, C / Costanza, S / Denig, A /
    Dolzhikov, A S / Downie, E J / Drexler, P / Fegan, S / Gardner, S / Ghosal, D / Glazier, D I / Gorodnov, I / Gradl, W / Günther, M / Gurevich, D / Heijkenskjöld, L / Hornidge, D / Huber, G M / Käser, A / Kashevarov, V L / Kay, S J D / Korolija, M / Krusche, B / Lazarev, A / Livingston, K / Lutterer, S / MacGregor, I J D / Manley, D M / Miskimen, R / Mocanu, M / Mullen, C / Neganov, A / Neiser, A / Ostrick, M / Paudyal, D / Pedroni, P / Powell, A / Rostomyan, T / Sokhoyan, V / Spieker, K / Steffen, O / Strakovsky, I / Strub, T / Thiel, M / Thomas, A / Usov, Yu A / Wagner, S / Watts, D P / Werthmüller, D / Wettig, J / Wolfes, M / Zachariou, N

    Physical review letters

    2022  Volume 128, Issue 13, Page(s) 132503

    Abstract: A precise measurement of the differential cross sections dσ/dΩ and the linearly polarized photon beam asymmetry Σ_{3} for Compton scattering on the proton below pion threshold has been performed with a tagged photon beam and almost 4π detector at the ... ...

    Abstract A precise measurement of the differential cross sections dσ/dΩ and the linearly polarized photon beam asymmetry Σ_{3} for Compton scattering on the proton below pion threshold has been performed with a tagged photon beam and almost 4π detector at the Mainz Microtron. The incident photons were produced by the recently upgraded Glasgow-Mainz photon tagging facility and impinged on a cryogenic liquid hydrogen target, with the scattered photons detected in the Crystal Ball/TAPS setup. Using the highest statistics Compton scattering data ever measured on the proton along with two effective field theories (both covariant baryon and heavy-baryon) and one fixed-t dispersion relation model, constraining the fits with the Baldin sum rule, we have obtained the proton electric and magnetic polarizabilities with unprecedented precision: α_{E1}=10.99±0.16±0.47±0.17±0.34, β_{M1}=3.14±0.21±0.24±0.20±0.35; in units of 10^{-4}  fm^{3} where the errors are statistical, systematic, spin polarizability dependent, and model dependent.
    Language English
    Publishing date 2022-04-15
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.128.132503
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Measurement of the helicity asymmetry

    Gottschall, M / Afzal, F / Anisovich, A V / Bayadilov, D / Beck, R / Bichow, M / Brinkmann, K Th / Crede, V / Dieterle, M / Dietz, F / Dutz, H / Eberhardt, H / Elsner, D / Ewald, R / Fornet-Ponse, K / Friedrich, St / Frommberger, F / Gridnev, A / Grüner, M /
    Gutz, E / Hammann, Ch / Hannappel, J / Hartmann, J / Hillert, W / Hoffmeister, Ph / Honisch, Ch / Jude, T / Kammer, S / Kalinowsky, H / Keshelashvili, I / Klassen, P / Klein, F / Klempt, E / Koop, K / Krusche, B / Kube, M / Lang, M / Lopatin, I / Mahlberg, P / Makonyi, K / Metag, V / Meyer, W / Müller, J / Müllers, J / Nanova, M / Nikonov, V / Novotny, R / Piontek, D / Reicherz, G / Rostomyan, T / Sarantsev, A / Schmidt, Ch / Schmieden, H / Seifen, T / Sokhoyan, V / Spieker, K / Thiel, A / Thoma, U / Urban, M / Pee, H van / Walther, D / Wendel, Ch / Werthmüller, D / Wiedner, U / Wilson, A / Winnebeck, A / Witthauer, L / Wunderlich, Y

    The European physical journal. A, Hadrons and nuclei

    2021  Volume 57, Issue 1, Page(s) 40

    Abstract: A measurement of the double-polarization ... ...

    Abstract A measurement of the double-polarization observable
    Language English
    Publishing date 2021-01-28
    Publishing country France
    Document type Journal Article
    ZDB-ID 1459066-9
    ISSN 1434-601X ; 1434-6001
    ISSN (online) 1434-601X
    ISSN 1434-6001
    DOI 10.1140/epja/s10050-020-00334-2
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Measurement of the helicity dependence for single π0 photoproduction from the deuteron

    Cividini, Federico / Dieterle, Michael / Abt, S. / Achenbach, Patrik / Adlarson, P. / Afzal, F. / Ahmed, Zafar / Annand, John R.M. / Arends, Hans Jürgen / Bashkanov, Mikhail / Beck, Reinhard / M. Biroth / Borisov, N. / Braghieri, A. / Briscoe, W.J. / Collicott, Cristina / Costanza, Susanna / Denig, A. / Dolzhikov, A.S. /
    Downie, E.J. / Drexler, P. / Fegan, Suzanne / Fix, A. / Gardner, S. / Ghosal, D. / Glazier, D.I. / Gorodnov, I. / Gradl, W. / Günther, M. / Gurevich, D. / Heijkenskjöld, L. / Hornidge, D. / Huber, G.M. / Käser, A. / Kashevarov, V.L. / Kay, S.J.D. / Korolija, M. / Krusche, B. / Lazarev, A. / Livingston, K. / Lutterer, S. / MacGregor, I.J.D. / Manley, D.M. / Martel, P.P. / Miskimen, R. / Mocanu, M. / Mornacchi, E. / Mullen, C. / Neganov, A. / Neiser, A. / Ostrick, M. / Paudyal, D. / Pedroni, P. / Powell, A. / Rostomyan, T. / Sokhoyan, V. / Spieker, K. / Steffen, O. / Strakovsky, I. / Strub, T. / Thiel, A. / Thiel, M. / Thomas, A. / Usov, Yu.A. / Wagner, S. / Watts, D.P. / Werthmüller, D. / Wettig, J. / Witthauer, L. / Wolfes, M. / Zachariou, N.

    2022  

    Abstract: The helicity-dependent single π0 photoproduction cross section on the deuteron and the angular dependence of the double polarisation observable E for the quasi-free single π0 production off the proton and the neutron have been measured, for the first ... ...

    Abstract The helicity-dependent single π0 photoproduction cross section on the deuteron and the angular dependence of the double polarisation observable E for the quasi-free single π0 production off the proton and the neutron have been measured, for the first time, from the threshold region up to the photon energy 1.4 GeV. The experiment was performed at the tagged photon facility of the MAMI accelerator and used a circularly polarised photon beam and longitudinally polarised deuteron target. The reaction products were detected using the large acceptance Crystal Ball/TAPS calorimeter, which covered 97% of the full solid angle. Comparing the cross section from the deuteron with the sum of free nucleon cross sections provides a quantitative estimate of the effects of the nuclear medium on pion production. In contrast, comparison of the E helicity asymmetry data from quasi-free protons off deuterium with data from a free proton target indicates that nuclear effects do not significantly affect this observable. As a consequence, it is deduced that the helicity asymmetry E on a free neutron can be reliably extracted from measurements on a deuteron in quasi-free kinematics.

    58

    6
    Keywords DDC::500 Naturwissenschaften und Mathematik::530 Physik
    Subject code 530
    Language English
    Publishing country de
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: Measurement of Compton Scattering at MAMI for the Extraction of the Electric and Magnetic Polarizabilities of the Proton

    Mornacchi, E. / Martel, P. P. / Abt, S. / Achenbach, Patrick / Adlarson, P. / Afzal, Farah Noreen / Ahmed, Zafar / Annand, John R.M. / Arends, Hans-Juergen / Bashkanov, Mikhail / Beck, Reinhard / Biroth, M. / Borisov, N. / Braghieri, A. / Briscoe, W. J. / Cividini, Federico / Collicott, C. / Costanza, S. / Denig, A. /
    Dolzhikov, A.S. / Downie, E.J. / Drexler, P. / Fegan, S. / Gardner, S. / Ghosal, D. / Glazier, D.I. / Gorodnov, I. / Gradl, W. / Günther, M. / Gurevich, D. / Heijkenskjöld, L. / Hornidge, D. / Huber, G.M. / Käser, A. / Kashevarov, V.L. / Kay, S.J.D. / Korolija, M. / Krusche, B. / Alexander, Lazarev / Livingston, K. / Lutterer, S. / MacGregor, I.J.D. / Manley, D.M. / Miskimen, R. / Mocanu, Ana M. / Mullen, Claudius C. / Neganov, A. / Neiser, A. / Ostrick, M. / Paudyal, D. / Pedroni, P. / Powell, A. / Rostomyan, T. / Sokhoyan, V. / K. Spieker / Wirth, Steffen / Strakovsky, I. / Strub, T. / Thiel, M. / Thomas, A. / Usov, Yu.A. / Wagner, S. / Watts, D.P. / Werthmüller, D. / Wettig, J. / Wolfes, M. / Zachariou, N.

    2022  

    Abstract: A precise measurement of the differential cross sections dσ/dΩ and the linearly polarized photon beam asymmetry Σ_{3} for Compton scattering on the proton below pion threshold has been performed with a tagged photon beam and almost 4π detector at the ... ...

    Abstract A precise measurement of the differential cross sections dσ/dΩ and the linearly polarized photon beam asymmetry Σ_{3} for Compton scattering on the proton below pion threshold has been performed with a tagged photon beam and almost 4π detector at the Mainz Microtron. The incident photons were produced by the recently upgraded Glasgow-Mainz photon tagging facility and impinged on a cryogenic liquid hydrogen target, with the scattered photons detected in the Crystal Ball/TAPS setup. Using the highest statistics Compton scattering data ever measured on the proton along with two effective field theories (both covariant baryon and heavy-baryon) and one fixed-t dispersion relation model, constraining the fits with the Baldin sum rule, we have obtained the proton electric and magnetic polarizabilities with unprecedented precision: α_{E1}=10.99±0.16±0.47±0.17±0.34, β_{M1}=3.14±0.21±0.24±0.20±0.35; in units of 10^{-4} fm^{3} where the errors are statistical, systematic, spin polarizability dependent, and model dependent.

    128

    13
    Keywords Electromagnetic transitions ; Nuclear reactions ; Nuclear structure & decays ; Photonuclear reactions ; DDC::500 Naturwissenschaften und Mathematik
    Subject code 530
    Language English
    Publishing country de
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  7. Article ; Online: Observation of the pη^{'} Cusp in the New Precise Beam Asymmetry Σ Data for γp→pη.

    Afzal, F / Wunderlich, Y / Anisovich, A V / Bayadilov, D / Beck, R / Becker, M / Blanke, E / Brinkmann, K-Th / Ciupka, S / Crede, V / Dieterle, M / Dutz, H / Elsner, D / Friedrich, S / Frommberger, F / Gridnev, A / Gottschall, M / Grüner, M / Gutz, E /
    Hammann, C / Hannappel, J / Hartmann, J / Hillert, W / Hoff, J / Hoffmeister, P / Honisch, C / Jude, T / Kalinowsky, H / Kalischewski, F / Keshelashvili, I / Klassen, P / Klein, F / Klempt, E / Koop, K / Kroenert, P / Krusche, B / Lang, M / Lopatin, I / Mahlberg, P / Meißner, U-G / Messi, F / Metag, V / Meyer, W / Mitlasóczki, B / Müller, J / Müllers, J / Nanova, M / Nikonov, K / Nikonov, V / Novinskiy, V / Novotny, R / Piontek, D / Reicherz, G / Richter, L / Rönchen, D / Rostomyan, T / Salisbury, B / Sarantsev, A / Schaab, D / Schmidt, C / Schmieden, H / Schultes, J / Seifen, T / Sokhoyan, V / Sowa, C / Spieker, K / Stausberg, N / Thiel, A / Thoma, U / Triffterer, T / Urban, M / Urff, G / van Pee, H / Walther, D / Wendel, Ch / Wiedner, U / Wilson, A / Winnebeck, A / Witthauer, L

    Physical review letters

    2020  Volume 125, Issue 15, Page(s) 152002

    Abstract: Data on the beam asymmetry Σ in the photoproduction of η mesons off protons are reported for tagged photon energies from 1130 to 1790 MeV (mass range from W=1748  MeV to W=2045  MeV). The data cover the full solid angle that allows for a precise moment ... ...

    Abstract Data on the beam asymmetry Σ in the photoproduction of η mesons off protons are reported for tagged photon energies from 1130 to 1790 MeV (mass range from W=1748  MeV to W=2045  MeV). The data cover the full solid angle that allows for a precise moment analysis. For the first time, a strong cusp effect in a polarization observable has been observed that is an effect of a branch-point singularity at the pη^{'} threshold [E_{γ}=1447  MeV (W=1896  MeV)]. The latest BnGa partial wave analysis includes the new beam asymmetry data and yields a strong indication for the N(1895)1/2^{-} nucleon resonance, demonstrating the importance of including all singularities for a correct determination of partial waves and resonance parameters.
    Language English
    Publishing date 2020-10-22
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.125.152002
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Signatures of the d^{*}(2380) Hexaquark in d(γ,pn[over →]).

    Bashkanov, M / Watts, D P / Kay, S J D / Abt, S / Achenbach, P / Adlarson, P / Afzal, F / Ahmed, Z / Akondi, C S / Annand, J R M / Arends, H J / 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 / Günther, M / Gurevich, D / Heijkenskjöld, L / Hornidge, D / Huber, G M / Käser, A / 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 / Powell, A / Prakhov, S N / Ron, G / Sarty, A / Sfienti, C / Sokhoyan, V / Spieker, K / Steffen, O / Strakovsky, I I / Strub, T / Supek, I / Thiel, A / Thiel, M / Thomas, A / Usov, Yu A / Wagner, S / Walford, N K / Werthmüller, D / Wettig, J / Wolfes, M / Zachariou, N / Zana, L A

    Physical review letters

    2020  Volume 124, Issue 13, Page(s) 132001

    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 ... ...

    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_{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.
    Language English
    Publishing date 2020-04-17
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.124.132001
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Single

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

    The European physical journal. A, Hadrons and nuclei

    2021  Volume 57, Issue 6, Page(s) 205

    Abstract: ... The ... ...

    Abstract The quasifree
    Language English
    Publishing date 2021-06-26
    Publishing country France
    Document type Journal Article
    ZDB-ID 1459066-9
    ISSN 1434-601X ; 1434-6001
    ISSN (online) 1434-601X
    ISSN 1434-6001
    DOI 10.1140/epja/s10050-021-00521-9
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Helicity-Dependent Cross Sections for the Photoproduction of π^{0} Pairs from Nucleons.

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

    Physical review letters

    2020  Volume 125, Issue 6, Page(s) 62001

    Abstract: The double-polarization observable E and helicity-dependent cross sections σ_{1/2}, σ_{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 ... ...

    Abstract The double-polarization observable E and helicity-dependent cross sections σ_{1/2}, σ_{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.
    Language English
    Publishing date 2020-08-26
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.125.062001
    Database MEDical Literature Analysis and Retrieval System OnLINE

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