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1. Measurement of the helicity asymmetry e in ω→π+π-π0 photoproduction

Author

Akbar, Z, Roy, P, Park, S, Crede, V, Anisovich, Av, Denisenko, I, Klempt, E, Nikonov, Va, Sarantsev, Av, Adhikari, Kp, Adhikari, S, Amaryan, Mj, Anefalos Pereira, S, Avakian, H, Ball, J, Battaglieri, M, Batourine, V, Bedlinskiy, I, Boiarinov, S, Briscoe, Wj, Brock, J, Brooks, Wk, Burkert, Vd, Cao, Ft, Carlin, C, Carman, Ds, Celentano, A, Charles, G, Chetry, T, Ciullo, G, Clark, L, Cole, Pl, Contalbrigo, M, Cortes, O, D'Angelo, A, Dashyan, N, De Vita, R, De Sanctis, E, Deur, A, Djalali, C, Dugger, M, Dupre, R, Egiyan, H, El Fassi, L, Eugenio, P, Fedotov, G, Fersch, R, Filippi, A, Fradi, A, Garcon, M, Gevorgyan, N, Giovanetti, Kl, Girod, Fx, Gleason, C, Gohn, W, Golovatch, E, Gothe, Rw, Griffioen, Ka, Guidal, M, Guo, L, Hafidi, K, Hakobyan, H, Hanretty, C, Harrison, N, Hattawy, M, Heddle, D, Hicks, K, Hollis, G, Holtrop, M, Ireland, Dg, Ishkhanov, Bs, Isupov, El, Jenkins, D, Joosten, S, Keith, Cd, Keller, D, Khachatryan, G, Khachatryan, M, Khandaker, M, Kim, A, Kim, W, Klein, A, Klein, Fj, Kubarovsky, V, Lanza, L, Livingston, K, Macgregor, Ijd, Markov, N, Mckinnon, B, Meekins, Dg, Mineeva, T, Mokeev, V, Movsisyan, A, Munoz Camacho, C, Nadel-Turonski, P, Niccolai, S, Osipenko, M, Ostrovidov, Ai, Paolone, M, Paremuzyan, R, Park, K, Pasyuk, E, Phelps, W, Pogorelko, O, Price, Jw, Prok, Y, Protopopescu, D, Raue, Ba, Ripani, M, Ritchie, Bg, Rizzo, A, Rosner, G, Sabatie, F, Salgado, C, Schumacher, Ra, Sharabian, Yg, Skorodumina, I, Smith, Gd, Sober, Di, Sokhan, D, Sparveris, N, Stepanyan, S, Strakovsky, Ii, Strauch, S, Taiuti, M, Ungaro, M, Voskanyan, H, Voutier, E, Wei, X, Wood, Mh, Zachariou, N, Zana, L, Zhang, J, and Zhao, Zw

Subjects
Settore FIS/04 - Fisica Nucleare e Subnucleare
Published
2017

2. Measurement of the helicity asymmetry E for the reaction γ p → π 0 p : The CBELSA/TAPS Collaboration.

Author

Gottschall M, Afzal F, Anisovich AV, Bayadilov D, Beck R, Bichow M, Brinkmann KT, Crede V, Dieterle M, Dietz F, Dutz H, Eberhardt H, Elsner D, Ewald R, Fornet-Ponse K, Friedrich S, Frommberger F, Gridnev A, Grüner M, Gutz E, Hammann C, Hannappel J, Hartmann J, Hillert W, Hoffmeister P, Honisch C, 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 C, Schmieden H, Seifen T, Sokhoyan V, Spieker K, Thiel A, Thoma U, Urban M, Pee HV, Walther D, Wendel C, Werthmüller D, Wiedner U, Wilson A, Winnebeck A, Witthauer L, and Wunderlich Y

Abstract

A measurement of the double-polarization observable E for the reaction γ p → π 0 p is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin butanol (C 4 H 9 OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from E γ = 600 to 2310 MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses., (© The Author(s) 2021.)

Published
2021
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3. Observation of the pη^{'} Cusp in the New Precise Beam Asymmetry Σ Data for γp→pη.

Author

Afzal F, Wunderlich Y, Anisovich AV, Bayadilov D, Beck R, Becker M, Blanke E, Brinkmann KT, 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 UG, 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 C, Wiedner U, Wilson A, Winnebeck A, and Witthauer L

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.

Published
2020
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4. First Measurements of the Double-Polarization Observables F, P, and H in ω Photoproduction off Transversely Polarized Protons in the N^{*} Resonance Region.

Author

Roy P, Park S, Crede V, Anisovich AV, Klempt E, Nikonov VA, Sarantsev AV, Wei NC, Huang F, Nakayama K, Adhikari KP, Adhikari S, Angelini G, Avakian H, Barion L, Battaglieri M, Bedlinskiy I, Biselli AS, Boiarinov S, Briscoe WJ, Brock J, Brooks WK, Burkert VD, Cao F, Carlin C, Carman DS, Celentano A, Chatagnon P, Chetry T, Ciullo G, Cole PL, Contalbrigo M, Cortes O, D'Angelo A, Dashyan N, De Vita R, De Sanctis E, Deur A, Diehl S, Djalali C, Dugger M, Dupre R, Duran B, Egiyan H, Ehrhart M, El Alaoui A, El Fassi L, Eugenio P, Fegan S, Filippi A, Fradi A, Gilfoyle GP, Girod FX, Golovatch E, Gothe RW, Griffioen KA, Guidal M, Guo L, Hafidi K, Hanretty C, Harrison N, Hattawy M, Hayward TB, Heddle D, Hicks K, Holtrop M, Ilieva Y, Ireland DG, Ishkhanov BS, Isupov EL, Jenkins D, Jo HS, Johnston S, Joosten S, Kabir ML, Keith CD, Keller D, Khachatryan G, Khachatryan M, Khanal A, Khandaker M, Kim A, Kim W, Klein FJ, Kubarovsky V, Kuleshov SV, Kunkel MC, Lanza L, Lenisa P, Livingston K, MacGregor IJD, Marchand D, McKinnon B, Meekins DG, Meyer CA, Mineeva T, Mokeev V, Montgomery RA, Movsisyan A, Munoz Camacho C, Nadel-Turonski P, Niccolai S, Niculescu G, Osipenko M, Ostrovidov AI, Paolone M, Pappalardo LL, Paremuzyan R, Pasyuk E, Payette D, Phelps W, Pierce J, Pogorelko O, Prok Y, Protopopescu D, Raue BA, Ripani M, Riser D, Ritchie BG, Rizzo A, Rosner G, Sabatié F, Salgado C, Schumacher RA, Seely ML, Sharabian YG, Shrestha U, Skorodumina I, Sokhan D, Soto O, Sparveris N, Strakovsky II, Strauch S, Taiuti M, Tan JA, Torayev B, Tyler N, Ungaro M, Voskanyan H, Voutier E, Walford NK, Wang R, Watts DP, Wei X, Wood MH, Zachariou N, Zhang J, and Zhao ZW

Abstract

First measurements of double-polarization observables in ω photoproduction off the proton are presented using transverse target polarization and data from the CEBAF Large Acceptance Spectrometer (CLAS) FROST experiment at Jefferson Lab. The beam-target asymmetry F has been measured using circularly polarized, tagged photons in the energy range 1200-2700 MeV, and the beam-target asymmetries H and P have been measured using linearly polarized, tagged photons in the energy range 1200-2000 MeV. These measurements significantly increase the database on polarization observables. The results are included in two partial-wave analyses and reveal significant contributions from several nucleon (N^{*}) resonances. In particular, contributions from new N^{*} resonances listed in the Review of Particle Properties are observed, which aid in reaching the goal of mapping out the nucleon resonance spectrum.

Published
2019
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5. Strong Evidence for Nucleon Resonances near 1900 MeV.

Author

Anisovich AV, Burkert V, Hadžimehmedović M, Ireland DG, Klempt E, Nikonov VA, Omerović R, Osmanović H, Sarantsev AV, Stahov J, Švarc A, and Thoma U

Abstract

Data on the reaction γp→K^{+}Λ from the CLAS experiments are used to derive the leading multipoles, E_{0+}, M_{1-}, E_{1+}, and M_{1+}, from the production threshold to 2180 MeV in 24 slices of the invariant mass. The four multipoles are determined without any constraints. The multipoles are fitted using a multichannel L+P model that allows us to search for singularities and to extract the positions of poles on the complex energy plane in an almost model-independent method. The multipoles are also used as additional constraints in an energy-dependent analysis of a large body of pion and photoinduced reactions within the Bonn-Gatchina partial wave analysis. The study confirms the existence of poles due to nucleon resonances with spin parity J^{P}=1/2^{-}, 1/2^{+}, and 3/2^{+} in the region at about 1.9 GeV.

Published
2017
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6. Three-body nature of N(*) and Δ(*) resonances from sequential decay chains.

Author

Thiel A, Sokhoyan V, Gutz E, van Pee H, Anisovich AV, Bacelar JC, Bantes B, Bartholomy O, Bayadilov D, Beck R, Beloglazov Y, Castelijns R, Crede V, Dutz H, Elsner D, Ewald R, Frommberger F, Fuchs M, Funke Ch, Gregor R, Gridnev A, Hillert W, Hoffmeister P, Horn I, Jaegle I, Junkersfeld J, Kalinowsky H, Kammer S, Kleber V, Klein F, Klein F, Klempt E, Kotulla M, Krusche B, Lang M, Löhner H, Lopatin I, Lugert S, Mertens T, Messchendorp JG, Metag V, Metsch B, Nanova M, Nikonov V, Novinski D, Novotny R, Ostrick M, Pant L, Pfeiffer M, Piontek D, Roy A, Sarantsev AV, Schmidt Ch, Schmieden H, Shende S, Süle A, Sumachev VV, Szczepanek T, Thoma U, Trnka D, Varma R, Walther D, Wendel Ch, and Wilson A

Abstract

The Nπ^{0}π^{0} decays of positive-parity N^{*} and Δ^{*} resonances at about 2 GeV are studied at ELSA by photoproduction of two neutral pions off protons. The data reveal clear evidence for several intermediate resonances: Δ(1232), N(1520)3/2^{-}, and N(1680)5/2^{+}, with spin parities J^{P}=3/2^{+}, 3/2^{-}, and 5/2^{+}. The partial wave analysis (within the Bonn-Gatchina approach) identifies N(1440)1/2^{+} and the N(ππ)_{S wave} (abbreviated as Nσ here) as further isobars and assigns the final states to the formation of nucleon and Δ resonances and to nonresonant contributions. We observe the known Δ(1232)π decays of Δ(1910)1/2^{+}, Δ(1920)3/2^{+}, Δ(1905)5/2^{+}, Δ(1950)7/2^{+}, and of the corresponding spin-parity series in the nucleon sector, N(1880)1/2^{+}, N(1900)3/2^{+}, N(2000)5/2^{+}, and N(1990)7/2^{+}. For the nucleon resonances, these decay modes are reported here for the first time. Further new decay modes proceed via N(1440)1/2^{+}π, N(1520)3/2^{-}π, N(1680)5/2^{+}π, and Nσ. The latter decay modes are observed in the decay of N^{*} resonances and at most weakly in Δ^{*} decays. It is argued that these decay modes provide evidence for a 3-quark nature of N^{*} resonances rather than a quark-diquark structure.

Published
2015
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7. N(1520) 3/2(-) helicity amplitudes from an energy-independent multipole analysis based on new polarization data on photoproduction of neutral pions.

Author

Hartmann J, Dutz H, Anisovich AV, Bayadilov D, Beck R, Becker M, Beloglazov Y, Berlin A, Bichow M, Böse S, Brinkmann KT, Crede V, Dieterle M, Eberhardt H, Elsner D, Fornet-Ponse K, Friedrich S, Frommberger F, Funke Ch, Gottschall M, Gridnev A, Grüner M, Gutz E, Hammann Ch, Hannappel J, Hannen V, Herick J, Hillert W, Hoffmeister P, Honisch Ch, Jahn O, Jude T, Käser A, Kaiser D, Kalinowsky H, Kalischewski F, Klassen P, Keshelashvili I, Klein F, Klempt E, Koop K, Krusche B, Kube M, Lang M, Lopatin I, Makonyi K, Messi F, Metag V, Meyer W, Müller J, Nanova M, Nikonov V, Novinski D, Novotny R, Piontek D, Rosenbaum C, Roth B, Reicherz G, Rostomyan T, Sarantsev A, Schmidt Ch, Schmieden H, Schmitz R, Seifen T, Sokhoyan V, Thämer P, Thiel A, Thoma U, Urban M, van Pee H, Walther D, Wendel Ch, Wiedner U, Wilson A, Winnebeck A, Witthauer L, and Wunderlich Y

Abstract

New data on the polarization observables T, P, and H for the reaction γp→pπ(0) are reported. The results are extracted from azimuthal asymmetries when a transversely polarized butanol target and a linearly polarized photon beam are used. The data were taken at the Bonn electron stretcher accelerator ELSA using the CBELSA/TAPS detector. These and earlier data are used to perform a truncated energy-independent partial wave analysis in sliced-energy bins. This energy-independent analysis is compared to the results from energy-dependent partial wave analyses.

Published
2014
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8. First measurement of the helicity asymmetry for γp → pπ0 in the resonance region.

Author

Gottschall M, Anisovich AV, Bantes B, Bayadilov D, Beck R, Bichow M, Böse S, Brinkmann KT, Challand T, Crede V, Dietz F, Dutz H, Eberhardt H, Elsner D, Ewald R, Fornet-Ponse K, Friedrich S, Frommberger F, Funke Ch, Gridnev A, Grüner M, Gutz E, Hammann Ch, Hannappel J, Hartmann J, Hillert W, Hoffmeister P, Honisch Ch, Jaegle I, Kaiser D, Kalinowsky H, Kammer S, Keshelashvili I, Klein F, Klempt E, Koop K, Krusche B, Kube M, Lang M, Lopatin I, Maghrbi Y, Makonyi K, Metag V, Meyer W, Müller J, Nanova M, Nikonov V, Novotny R, Piontek D, Reicherz G, Rostomyan T, Sarantsev A, Schaepe S, Schmidt Ch, Schmieden H, Schmitz R, Seifen T, Sokhoyan V, Thiel A, Thoma U, Urban M, van Pee H, Walther D, Wendel Ch, Wiedner U, Wilson A, and Winnebeck A

Abstract

The first measurement of the helicity dependence of the photoproduction cross section of single neutral pions off protons is reported for photon energies from 600 to 2300 MeV, covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, and BnGa partial wave analyses. Strikingly large differences between data and predictions are observed, which are traced to differences in the helicity amplitudes of well-known and established resonances. Precise values for the helicity amplitudes of several resonances are reported.

Published
2014
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9. Thiel et al. reply:.

Author

Thiel A, Anisovich AV, Bayadilov D, Bantes B, Beck R, Beloglazov Y, Bichow M, Böse S, Brinkmann KT, Challand T, Crede V, Dietz F, Drexler P, Dutz H, Eberhardt H, Elsner D, Ewald R, Fornet-Ponse K, Friedrich S, Frommberger F, Funke Ch, Gottschall M, Grüner M, Gutz E, Hammann Ch, Hannappel J, Hartmann J, Hillert W, Hoffmeister P, Honisch Ch, Jaegle I, Jürgensen I, Kaiser D, Kalinowsky H, Kalischewski F, Kammer S, Keshelashvili I, Kleber V, Klein F, Klempt E, Krusche B, Lang M, Lopatin I, Maghrbi Y, Makonyi K, Metag V, Meyer W, Müller J, Nanova M, Nikonov V, Novotny R, Piontek D, Reicherz G, Sarantsev A, Schmidt Ch, Schmieden H, Seifen T, Sokhoyan V, Sumachev V, Thoma U, vanPee H, Walther D, Wendel Ch, Wiedner U, Wilson A, Winnebeck A, and Wunderlich Y

Published
2013
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10. Well-established nucleon resonances revisited by double-polarization measurements.

Author

Thiel A, Anisovich AV, Bayadilov D, Bantes B, Beck R, Beloglazov Y, Bichow M, Böse S, Brinkmann KT, Challand T, Crede V, Dietz F, Drexler P, Dutz H, Eberhardt H, Elsner D, Ewald R, Fornet-Ponse K, Friedrich S, Frommberger F, Funke Ch, Gottschall M, Grüner M, Gutz E, Hammann Ch, Hannappel J, Hartmann J, Hillert W, Hoffmeister P, Honisch Ch, Jaegle I, Jürgensen I, Kaiser D, Kalinowsky H, Kalischewski F, Kammer S, Keshelashvili I, Kleber V, Klein F, Klempt E, Krusche B, Lang M, Lopatin I, Maghrbi Y, Makonyi K, Metag V, Meyer W, Müller J, Nanova M, Nikonov V, Novotny R, Piontek D, Reicherz G, Sarantsev A, Schmidt Ch, Schmieden H, Seifen T, Sokhoyan V, Sumachev V, Thoma U, Vanpee H, Walther D, Wendel Ch, Wiedner U, Wilson A, Winnebeck A, and Wunderlich Y

Abstract

The first measurement is reported of the double-polarization observable G in the photoproduction of neutral pions off protons, covering the photon energy range from 620 to 1120 MeV and the full solid angle. G describes the correlation between the photon polarization plane and the scattering plane for protons polarized along the direction of the incoming photon. The observable is highly sensitive to contributions from baryon resonances. The new results are compared to the predictions from SAID, MAID, and BnGa partial wave analyses. In spite of the long-lasting efforts to understand γp→pπ(0) as the simplest photoproduction reaction, surprisingly large differences between the new data and the latest predictions are observed which are traced to different contributions of the N(1535) resonance with spin parity J(P)=1/2(-) and N(1520) with J(P)=3/2(-). In the third resonance region, where N(1680) with J(P)=5/2(+) production dominates, the new data are reasonably close to the predictions.

Published
2012
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11. Evidence for a parity doublet Delta(1920)P33 and Delta(1940)D33 from gammap-->ppi;{0}eta.

Author

Horn I, Anisovich AV, Anton G, Bantes R, Bartholomy O, Beck R, Beloglazov Y, Bogendörfer R, Castelijns R, Crede V, Ehmanns A, Ernst J, Fabry I, Flemming H, Fösel A, Fuchs M, Funke C, Gothe R, Gridnev A, Gutz E, Höffgen S, Hössl J, Junkersfeld J, Kalinowsky H, Klein F, Klempt E, Koch H, Konrad M, Kopf B, Krusche B, Langheinrich J, Löhner H, Lopatin I, Lotz J, Matthäy H, Menze D, Messchendorp J, Metag V, Nikonov VA, Novinski D, Ostrick M, van Pee H, Sarantsev AV, Schmidt C, Schmieden H, Schoch B, Suft G, Sumachev V, Szczepanek T, Thoma U, Walther D, and Weinheimer C

Abstract

Evidence is reported for the existence of a parity doublet of Delta resonances with total angular momentum J=3/2 from photoproduction of the ppi;{0}eta final state. The two parity partners Delta(1920)P33 and Delta(1940)D33 make significant contributions to the reaction. Cascades of resonances into Delta(1232)eta, N(1535)pi, and Na0(980) are clearly observed.

Published
2008
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12. Quasifree photoproduction of eta mesons off the neutron.

Author

Jaegle I, Mertens T, Anisovich AV, Bacelar JC, Bantes B, Bartholomy O, Bayadilov D, Beck R, Beloglazov YA, Castelijns R, Crede V, Dutz H, Ehmanns A, Elsner D, Essig K, Ewald R, Fabry I, Fuchs M, Funke Ch, Gothe R, Gregor R, Gridnev AB, Gutz E, Höffgen S, Hoffmeister P, Horn I, Junkersfeld J, Kalinowsky H, Kammer S, Kleber V, Klein F, Klein F, Klempt E, Konrad M, Kotulla M, Krusche B, Lang M, Langheinrich J, Löhner H, Lopatin IV, Lotz J, Lugert S, Menze D, Messchendorp JG, Metag V, Morales C, Nanova M, Nikonov VA, Novinski D, Novotny R, Ostrick M, Pant LM, van Pee H, Pfeiffer M, Radkov A, Roy A, Sarantsev AV, Schadmand S, Schmidt C, Schmieden H, Schoch B, Shende SV, Sokhoyan V, Süle A, Sumachev VV, Szczepanek T, Thoma U, Trnka D, Varma R, Walther D, Weinheimer Ch, and Wendel Ch

Abstract

Quasifree photoproduction of eta mesons off nucleons bound in the deuteron has been measured with the CBELSA/TAPS detector for incident photon energies up to 2.5 GeV at the Bonn ELSA accelerator. The eta mesons have been detected in coincidence with recoil protons and recoil neutrons, which allows a detailed comparison of the quasifree n(gamma,eta)n and p(gamma,eta)p reactions. The excitation function for eta production off the neutron shows a pronounced bumplike structure at W=1.68 GeV (E{gamma} approximately 1 GeV), which is absent for the proton.

Published
2008
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13. Photoproduction of eta mesons off protons for 0.75 GeV<E(gamma)<3 GeV.

Author

Credé V, Bartholomy O, Anisovich AV, Anton G, Bantes R, Beloglazov Y, Bogendörfer R, Castelijns R, Ehmanns A, Ernst J, Fabry I, Flemming H, Fösel A, Freiesleben H, Fuchs M, Funke Ch, Gothe R, Gridnev A, Gutz E, Höffgen SK, Horn I, Hössl J, Joosten R, Junkersfeld J, Kalinowsky H, Klein F, Klempt E, Koch H, Konrad M, Kopf B, Krusche B, Langheinrich J, Löhner H, Lopatin I, Lotz J, Matthäy H, Menze D, Messchendorp J, Morales C, Novinski D, Ostrick M, van Pee H, Radkov A, Reinnarth J, Sarantsev AV, Schadmand S, Schmidt Ch, Schmieden H, Schoch B, Suft G, Sumachev V, Szczepanek T, Thoma U, Walther D, and Weinheimer Ch

Abstract

Total and differential cross sections for the reaction p(gamma,eta)p have been measured for photon energies in the range from 750 MeV to 3 GeV. The low-energy data are dominated by the S11 wave which has two poles in the energy region below 2 GeV. Eleven nucleon resonances are observed in their decay into peta. At medium energies we find evidence for a new resonance N(2070)D15 with (M,Gamma)=(2068+/-22, 295+/-40) MeV. At gamma energies above 1.5 GeV, a strong peak in the forward direction develops, signaling the exchange of vector mesons in the t channel.

Published
2005
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14. Neutral-pion photoproduction off protons in the energy range 0.3 GeV<E(gamma)<3 GeV.

Author

Bartholomy O, Credé V, van Pee H, Anisovich AV, Anton G, Bantes R, Beloglazov Y, Bogendörfer R, Castelijns R, Ehmanns A, Ernst J, Fabry I, Flemming H, Fösel A, Freiesleben H, Fuchs M, Funke Ch, Gothe R, Gridnev A, Gutz E, Höffgen SK, Horn I, Hössl J, Joosten R, Junkersfeld J, Kalinowsky H, Klein F, Klempt E, Koch H, Konrad M, Kopf B, Krusche B, Langheinrich J, Löhner H, Lopatin I, Lotz J, Matthäy H, Menze D, Messchendorp J, Morales C, Novinski D, Ostrick M, Radkov A, Reinnarth J, Sarantsev AV, Schadmand S, Schmidt Ch, Schmieden H, Schoch B, Suft G, Sumachev V, Szczepanek T, Thoma U, Walther D, and Weinheimer Ch

Abstract

Single pi(0) photoproduction has been studied with the CB-ELSA experiment at Bonn using tagged photon energies between 0.3 and 3.0 GeV. The experimental setup covers a very large solid angle of approximately 98% of 4pi. Differential cross sections dsigma/dOmega have been measured. Complicated structures in the angular distributions indicate a variety of different resonances being produced in the s channel intermediate state gammap-->N(*)(Delta(*))-->ppi(0). A combined analysis including the data presented in this letter along with other data sets reveals contributions from known resonances and evidence for a new resonance N(2070)D15.

Published
2005
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