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  1. Article ; Online: Overview of baryon resonances

    Downie E.J.

    EPJ Web of Conferences, Vol 73, p

    2014  Volume 01003

    Abstract: The quest to understand the physics of any system cannot be said to be complete as long as one cannot predict and fully understand its resonance spectrum. Despite this, due to the experimental challenge of the required double polarization measurements ... ...

    Abstract The quest to understand the physics of any system cannot be said to be complete as long as one cannot predict and fully understand its resonance spectrum. Despite this, due to the experimental challenge of the required double polarization measurements and the difficulty in achieving unambiguous, model-independent extraction and interpretation of the nucleon resonance spectrum of many broad and overlapping resonances, understanding of the structure and dynamics of the nucleon has suffered. The recent improvement in statistical quality and kinematic range of the data made available by such full-solid-angle systems as the CB and TAPS constellation at MAMI, coupled with the high flux polarized photon beam provided by the Glasgow Photon Tagger, and the excellent properties of the Mainz Frozen Spin Target, when paired with new developments in Partial Wave Analysis (PWA) methodology make this a very exciting and fruitful time in nucleon resonance studies. Here the recent influx of data and PWA developments are summarized, and the requirements for a complete, unambiguous PWA solution over the first and second resonance region are briefly reviewed.
    Keywords Physics ; QC1-999 ; Science ; Q
    Subject code 535
    Language English
    Publishing date 2014-06-01T00:00:00Z
    Publisher EDP Sciences
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: The MUSE experiment

    Downie E. J.

    EPJ Web of Conferences, Vol 73, p

    2014  Volume 07005

    Abstract: The proton radius puzzle is the difference between the proton radius as measured with electron scattering and in the excitation spectrum of atomic hydrogen, and that measured with muonic hydrogen spectroscopy. The MUSE experiment seeks to resolve this ... ...

    Abstract The proton radius puzzle is the difference between the proton radius as measured with electron scattering and in the excitation spectrum of atomic hydrogen, and that measured with muonic hydrogen spectroscopy. The MUSE experiment seeks to resolve this puzzle by simultaneously measuring elastic electron and muon scattering on the proton, in both charge states, thereby providing new information to the puzzle. MUSE addresses issues of two-photon effects, lepton universality and, possibly, new physics, while providing simultaneous form factor, and therefore radius, measurements with both muons and electrons.
    Keywords Physics ; QC1-999 ; Science ; Q
    Language English
    Publishing date 2014-06-01T00:00:00Z
    Publisher EDP Sciences
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Proton Compton Scattering from Linearly Polarized Gamma Rays.

    Li, X / Ahmed, M W / Banu, A / Bartram, C / Crowe, B / Downie, E J / Emamian, M / Feldman, G / Gao, H / Godagama, D / Grießhammer, H W / Howell, C R / Karwowski, H J / Kendellen, D P / Kovash, M A / Leung, K K H / Markoff, D M / McGovern, J A / Mikhailov, S /
    Pywell, R E / Sikora, M H / Silano, J A / Sosa, R S / Spraker, M C / Swift, G / Wallace, P / Weller, H R / Whisnant, C S / Wu, Y K / Zhao, Z W

    Physical review letters

    2022  Volume 128, Issue 13, Page(s) 132502

    Abstract: Differential cross sections for Compton scattering from the proton have been measured at scattering angles of 55°, 90°, and 125° in the laboratory frame using quasimonoenergetic linearly (circularly) polarized photon beams with a weighted mean energy ... ...

    Abstract Differential cross sections for Compton scattering from the proton have been measured at scattering angles of 55°, 90°, and 125° in the laboratory frame using quasimonoenergetic linearly (circularly) polarized photon beams with a weighted mean energy value of 83.4 MeV (81.3 MeV). These measurements were performed at the High Intensity Gamma-Ray Source facility at the Triangle Universities Nuclear Laboratory. The results are compared to previous measurements and are interpreted in the chiral effective field theory framework to extract the electromagnetic dipole polarizabilities of the proton, which gives α_{E1}^{p}=13.8±1.2_{stat}±0.1_{BSR}±0.3_{theo},β_{M1}^{p}=0.2∓1.2_{stat}±0.1_{BSR}∓0.3_{theo} in units of 10^{-4}  fm^{3}.
    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.128.132502
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. 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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  5. 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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  6. Article ; Online: New Insight in the Q^{2} Dependence of Proton Generalized Polarizabilities.

    Beričič, J / Correa, L / Benali, M / Achenbach, P / Ayerbe Gayoso, C / Bernauer, J C / Blomberg, A / Böhm, R / Bosnar, D / Debenjak, L / Denig, A / Distler, M O / Downie, E J / Esser, A / Fonvieille, H / Friščić, I / Kegel, S / Kohl, Y / Makek, M /
    Merkel, H / Middleton, D G / Mihovilovič, M / Müller, U / Nungesser, L / Paolone, M / Pochodzalla, J / Sánchez Majos, S / Schlimme, B S / Schoth, M / Schulz, F / Sfienti, C / Širca, S / Sparveris, N / Štajner, S / Thiel, M / Tyukin, A / Weber, A / Weinriefer, M

    Physical review letters

    2019  Volume 123, Issue 19, Page(s) 192302

    Abstract: Virtual Compton scattering on the proton has been investigated at three yet unexplored values of the four-momentum transfer Q^{2}: 0.10, 0.20, and 0.45  GeV^{2}, at the Mainz Microtron. Fits performed using either the low-energy theorem or dispersion ... ...

    Abstract Virtual Compton scattering on the proton has been investigated at three yet unexplored values of the four-momentum transfer Q^{2}: 0.10, 0.20, and 0.45  GeV^{2}, at the Mainz Microtron. Fits performed using either the low-energy theorem or dispersion relations allowed the extraction of the structure functions P_{LL}-P_{TT}/ε and P_{LT}, as well as the electric and magnetic generalized polarizabilities α_{E1}(Q^{2}) and β_{M1}(Q^{2}). These new results show a smooth and rapid falloff of α_{E1}(Q^{2}), in contrast to previous measurements at Q^{2}=0.33  GeV^{2}, and provide for the first time a precise mapping of β_{M1}(Q^{2}) in the low-Q^{2} region.
    Language English
    Publishing date 2019-11-19
    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.123.192302
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. 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.

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    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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  8. 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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  9. Article: Nurse-midwifery prototypes: clinical practice and education featuring Cook County Hospital Nurse-Midwifery Service.

    Evison, L / Downie, E J

    Journal of nurse-midwifery

    1978  Volume 23, Page(s) 27–30

    MeSH term(s) Chicago ; Clinical Competence ; Education, Nursing, Continuing ; Hospitals, University ; Nurse Midwives
    Language English
    Publishing date 1978
    Publishing country United States
    Document type Journal Article
    ZDB-ID 603980-7
    ISSN 0091-2182
    ISSN 0091-2182
    DOI 10.1016/0091-2182(78)90025-3
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. 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
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