E. Klempt - The CLAS Collaboration

E. Klempt
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E. Klempt
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The CLAS Collaboration
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Nuclear Experiment (37)
 
High Energy Physics - Phenomenology (12)
 
High Energy Physics - Experiment (9)
 
Nuclear Theory (8)

Publications Authored By E. Klempt

2017May
Authors: D. Ho, P. Peng, C. Bass, P. Collins, A. D'Angelo, A. Deur, J. Fleming, C. Hanretty, T. Kageya, M. Khandaker, F. J. Klein, E. Klempt, V. Laine, M. M. Lowry, H. Lu, C. Nepali, V. A. Nikonov, T. O'Connell, A. M. Sandorfi, A. V. Sarantsev, R. A. Schumacher, I. I. Strakovsky, A. Švarc, N. K. Walford, X. Wei, C. S. Whisnant, R. L. Workman, I. Zonta, K. P. Adhikari, D. Adikaram, Z. Akbar, M. J. Amaryan, S. Anefalos Pereira, H. Avakian, J. Ball, M. Bashkanov, M. Battaglieri, V. Batourine, I. Bedlinskiy, W. J. Briscoe, V. D. Burkert, D. S. Carman, A. Celentano, G. Charles, T. Chetry, G. Ciullo, L. Clark, L. Colaneri, P. L. Cole, M. Contalbrigo, V. Crede, N. Dashyan, E. De Sanctis, R. De Vita, C. Djalali, R. Dupre, A. El Alaoui, L. El Fassi, L. Elouadrhiri, G. Fedotov, S. Fegan, R. Fersch, A. Filippi, A. Fradi, Y. Ghandilyan, G. P. Gilfoyle, F. X. Girod, D. I. Glazier, C. Gleason, W. Gohn, E. Golovatch, R. W. Gothe, K. A. Griffioen, M. Guidal, L. Guo, H. Hakobyan, N. Harrison, K. Hicks, M. Holtrop, S. M. Hughes, Y. Ilieva, D. G. Ireland, B. S. Ishkhanov, E. L. Isupov, D. Jenkins, H. Jiang, H. S. Jo, K. Joo, S. Joosten, D. Keller, G. Khachatryan, A. Kim, W. Kim, A. Klein, V. Kubarovsky, S. V. Kuleshov, L. Lanza, P. Lenisa, K. Livingston, I . J . D. MacGregor, N. Markov, B. McKinnon, T. Mineeva, V. Mokeev, R. A. Montgomery, A Movsisyan, C. Munoz Camacho, G. Murdoch, S. Niccolai, G. Niculescu, M. Osipenko, M. Paolone, R. Paremuzyan, K. Park, E. Pasyuk, W. Phelps, O. Pogorelko, J. W. Price, S. Procureur, D. Protopopescu, M. Ripani, D. Riser, B. G. Ritchie, A. Rizzo, G. Rosner, F. Sabatié, C. Salgado, Y. G. Sharabian, Iu. Skorodumina, G. D. Smith, D. I. Sober, D. Sokhan, N. Sparveris, S. Strauch, Ye Tian, B. Torayev, M. Ungaro, H. Voskanyan, D. P. Watts, M. H. Wood, N. Zachariou, J. Zhang, Z. W. Zhao

We report the first beam-target double-polarization asymmetries in the $\gamma + n(p) \rightarrow \pi^- + p(p)$ reaction spanning the nucleon resonance region from invariant mass $W$= $1500$ to $2300$ MeV. Circularly polarized photons and longitudinally polarized deuterons in $H\!D$ have been used with the CLAS detector at Jefferson Lab. The exclusive final state has been extracted using three very different analyses that show excellent agreement, and these have been used to deduce the {\it{E}} polarization observable for an effective neutron target. Read More

2017Mar
Authors: P. Collins, B. G. Ritchie, M. Dugger, A. V. Anisovich, M. Döring, E. Klempt, V. A. Nikonov, D. Rönchen, D. Sadasivan, A. Sarantsev, K. P. Adhikaria, Z. Akbar, M. J. Amaryana, S. Anefalos Pereira, H. Avakiana, J. Ball, I. Balossino, M. Bashkanova, M. Battaglieri, I. Bedlinskiy, A. S. Bisellik, W. J. Briscoe, W. K. Brooks, V. D. Burkert, Frank Thanh Cao, D. S. Carman, A. Celentano, S. Chandavar, G. Charles, T. Chetry, G. Ciullo, L. Clark, L. Colaneri, P. L. Cole, N. Compton, M. Contalbrigo, O. Cortes, V. Crede, A. D'Angelo, N. Dashyan, R. De Vita, E. De Sanctis, A. Deur, C. Djalali, R. Dupre, H. Egiyan, A. El Alaoui, L. El Fassi, L. Elouadrhiri, P. Eugenio, E. Fanchini, G. Fedotov, A. Filippi, J. A. Fleming, Y. Ghandilyan, G. P. Gilfoyle, K. L. Giovanetti, F. X. Girod, D. I. Glazier, C. Gleason, E. Golovatch, R. W. Gothe, K. A. Griffioen, L. Guo, K. Hafidi, H. Hakobyan, C. Hanretty, N. Harrison, D. Heddle, K. Hicks, M. Holtrop, S. M. Hughes, Y. Ilieva, D. G. Ireland, B. S. Ishkhanov, E. L. Isupov, D. Jenkins, H. S. Jo, S. Joosten, D. Keller, G. Khachatryan, M. Khachatryan, M. Khandaker, A. Kim, W. Kim, A. Klein, F. J. Klein, V. Kubarovsky, L. Lanza, P. Lenisa, K. Livingston, I. J. D. MacGregor, N. Markov, B. McKinnon, C. A. Meyer, M. Mirazita, V. Mokeev, R. A. Montgomery, A Movsisyan, C. Munoz Camacho, G. Murdoch, P. Nadel-Turonski, S. Niccolai, G. Niculescu, I. Niculescu, M. Osipenko, A. I. Ostrovidov, M. Paolone, R. Paremuzyan, K. Park, E. Pasyuk, W. Phelps, S. Pisano, O. Pogorelko, J. W. Price, Y. Prok, D. Protopopescu, B. A. Raue, M. Ripani, A. Rizzo, G. Rosner, P. Roy, F. Sabatié, C. Salgado, R. A. Schumacher, Y. G. Sharabian, Iu. Skorodumina, G. D. Smith, D. Sokhan, N. Sparveris, S. Stepanyan, I. I. Strakovsky, S. Strauch, M. Taiuti, Ye Tian, B. Torayev, M. Ungaro, H. Voskanyan, E. Voutier, N. K. Walford, X. Wei, N. Zachariou, J. Zhang

Measurements of the linearly-polarized photon beam asymmetry $\Sigma$ for photoproduction from the proton of $\eta$ and $\eta^\prime$ mesons are reported. A linearly-polarized tagged photon beam produced by coherent bremsstrahlung was incident on a cryogenic hydrogen target within the CEBAF Large Acceptance Spectrometer. Results are presented for the $\gamma p \to \eta p$ reaction for incident photon energies from 1. Read More

The helicity-dependent observable $E$ for the reaction $\gamma d\to \eta n (p)$ with a spectator proton was recently measured by the A2 Collaboration at MAMI in Mainz. The data were interpreted as further evidence for a narrow resonance with spin and parity $J^P=1/2^+$ ($P_{11}$ wave). However, a full partial wave analysis without any narrow resonance leads to an excellent description of the data, imposing a narrow resonance with the properties suggested by the A2 Collaboration leads to a significant deterioration of the fit quality: there is no need for a narrow resonance. Read More

New data on pion-photoproduction off the proton have been included in the partial wave analyses Bonn-Gatchina and SAID and in the dynamical coupled-channel approach J\"ulich-Bonn. All reproduce the recent new data well: the double polarization data for E, G, H, P and T in $\gamma p \to \pi^0 p$ from ELSA, the beam asymmetry $\Sigma$ for $\gamma p \to \pi^0 p$ and $\pi^+ n$ from Jefferson Laboratory, and the precise new differential cross section and beam asymmetry data $\Sigma$ for $\gamma p \to \pi^0 p$ from MAMI. The new fit results for the multipoles are compared with predictions not taking into account the new data. Read More

Data on the reaction $\gamma p\to \omega p$ with $\omega\to\pi^0\gamma$, taken with unpolarized or polarized beams in combination with an unpolarized or polarized proton-target, were analyzed within the Bonn-Gatchina (BnGa) partial wave analysis. Differential cross sections, several spin density matrix elements, the beam asymmetry $\Sigma$, the normalized helicity difference $E$, and the correlation $G$ between linear photon and longitudinal target polarization were included in a large data base on pion and photo-induced reactions. The data on $\omega$ photoproduction are used to determine twelve $N^*\to N\omega$ branching ratios; most of these are determined for the first time. Read More

2015Jun
Affiliations: 1The CBELSA/TAPS Collaboration, 2The CBELSA/TAPS Collaboration, 3The CBELSA/TAPS Collaboration, 4The CBELSA/TAPS Collaboration, 5The CBELSA/TAPS Collaboration, 6The CBELSA/TAPS Collaboration, 7The CBELSA/TAPS Collaboration, 8The CBELSA/TAPS Collaboration, 9The CBELSA/TAPS Collaboration, 10The CBELSA/TAPS Collaboration, 11The CBELSA/TAPS Collaboration, 12The CBELSA/TAPS Collaboration, 13The CBELSA/TAPS Collaboration, 14The CBELSA/TAPS Collaboration, 15The CBELSA/TAPS Collaboration, 16The CBELSA/TAPS Collaboration, 17The CBELSA/TAPS Collaboration, 18The CBELSA/TAPS Collaboration, 19The CBELSA/TAPS Collaboration, 20The CBELSA/TAPS Collaboration, 21The CBELSA/TAPS Collaboration, 22The CBELSA/TAPS Collaboration, 23The CBELSA/TAPS Collaboration, 24The CBELSA/TAPS Collaboration, 25The CBELSA/TAPS Collaboration, 26The CBELSA/TAPS Collaboration, 27The CBELSA/TAPS Collaboration, 28The CBELSA/TAPS Collaboration, 29The CBELSA/TAPS Collaboration, 30The CBELSA/TAPS Collaboration, 31The CBELSA/TAPS Collaboration, 32The CBELSA/TAPS Collaboration, 33The CBELSA/TAPS Collaboration, 34The CBELSA/TAPS Collaboration, 35The CBELSA/TAPS Collaboration, 36The CBELSA/TAPS Collaboration, 37The CBELSA/TAPS Collaboration, 38The CBELSA/TAPS Collaboration, 39The CBELSA/TAPS Collaboration, 40The CBELSA/TAPS Collaboration, 41The CBELSA/TAPS Collaboration, 42The CBELSA/TAPS Collaboration, 43The CBELSA/TAPS Collaboration, 44The CBELSA/TAPS Collaboration, 45The CBELSA/TAPS Collaboration, 46The CBELSA/TAPS Collaboration, 47The CBELSA/TAPS Collaboration, 48The CBELSA/TAPS Collaboration, 49The CBELSA/TAPS Collaboration, 50The CBELSA/TAPS Collaboration, 51The CBELSA/TAPS Collaboration, 52The CBELSA/TAPS Collaboration, 53The CBELSA/TAPS Collaboration, 54The CBELSA/TAPS Collaboration, 55The CBELSA/TAPS Collaboration, 56The CBELSA/TAPS Collaboration, 57The CBELSA/TAPS Collaboration, 58The CBELSA/TAPS Collaboration, 59The CBELSA/TAPS Collaboration, 60The CBELSA/TAPS Collaboration, 61The CBELSA/TAPS Collaboration, 62The CBELSA/TAPS Collaboration, 63The CBELSA/TAPS Collaboration, 64The CBELSA/TAPS Collaboration, 65The CBELSA/TAPS Collaboration, 66The CBELSA/TAPS Collaboration, 67The CBELSA/TAPS Collaboration, 68The CBELSA/TAPS Collaboration, 69The CBELSA/TAPS Collaboration, 70The CBELSA/TAPS Collaboration, 71The CBELSA/TAPS Collaboration, 72The CBELSA/TAPS Collaboration, 73The CBELSA/TAPS Collaboration, 74The CBELSA/TAPS Collaboration, 75The CBELSA/TAPS Collaboration, 76The CBELSA/TAPS Collaboration, 77The CBELSA/TAPS Collaboration, 78The CBELSA/TAPS Collaboration, 79The CBELSA/TAPS Collaboration

Data on the polarization observables T, P, and H for the reaction $\gamma p\to p\pi^0$ are reported. Compared to earlier data from other experiments, our data are more precise and extend the covered range in energy and angle substantially. The results were extracted from azimuthal asymmetries measured using a transversely polarized target and linearly polarized photons. Read More

The first measurements of the beam-target-helicity-asymmetries $E$ and $G$ in the photoproduction of $\omega$-mesons off protons at the CBELSA/TAPS experiment are reported. $E$ ($G$) was measured using circularly (linearly) polarised photons and a longitudinally polarised target. $E$ was measured over the photon energy range from close to threshold ($E_\gamma = 1108$~MeV) to $E_\gamma = 2300$~MeV and $G$ at a single energy interval of $1108 < E_\gamma <1300$~MeV. Read More

We report a partial-wave analysis of new data on the double-polarization variable $E$ for the reactions $\gamma p\to \pi^+ n$ and $\gamma p\to \pi^0 p$ and of further data published earlier. The analysis within the Bonn-Gatchina (BnGa) formalism reveals evidence for a poorly known baryon resonance, the one-star $\Delta(2200)7/2^-$. This is the lowest-mass $\Delta^*$ resonance with spin-parity $J^P=7/2^-$. Read More

2015Mar
Authors: S. Strauch1, W. J. Briscoe2, M. Döring3, E. Klempt4, V. A. Nikonov5, E. Pasyuk6, D. Rönchen7, A. V. Sarantsev8, I. Strakovsky9, R. Workman10, K. P. Adhikari11, D. Adikaram12, M. D. Anderson13, S. Anefalos Pereira14, A. V. Anisovich15, R. A. Badui16, J. Ball17, V. Batourine18, M. Battaglieri19, I. Bedlinskiy20, N. Benmouna21, A. S. Biselli22, J. Brock23, W. K. Brooks24, V. D. Burkert25, T. Cao26, C. Carlin27, D. S. Carman28, A. Celentano29, S. Chandavar30, G. Charles31, L. Colaneri32, P. L. Cole33, N. Compton34, M. Contalbrigo35, O. Cortes36, V. Crede37, N. Dashyan38, A. D'Angelo39, R. De Vita40, E. De Sanctis41, A. Deur42, C. Djalali43, M. Dugger44, R. Dupre45, H. Egiyan46, A. El Alaoui47, L. El Fassi48, L. Elouadrhiri49, P. Eugenio50, G. Fedotov51, S. Fegan52, A. Filippi53, J. A. Fleming54, T. A. Forest55, A. Fradi56, N. Gevorgyan57, Y. Ghandilyan58, K. L. Giovanetti59, F. X. Girod60, D. I. Glazier61, W. Gohn62, E. Golovatch63, R. W. Gothe64, K. A. Griffioen65, M. Guidal66, L. Guo67, K. Hafidi68, H. Hakobyan69, C. Hanretty70, N. Harrison71, M. Hattawy72, K. Hicks73, D. Ho74, M. Holtrop75, S. M. Hughes76, Y. Ilieva77, D. G. Ireland78, B. S. Ishkhanov79, E. L. Isupov80, D. Jenkins81, H. Jiang82, H. S. Jo83, K. Joo84, S. Joosten85, C. D. Keith86, D. Keller87, G. Khachatryan88, M. Khandaker89, A. Kim90, W. Kim91, A. Klein92, F. J. Klein93, V. Kubarovsky94, S. E. Kuhn95, P. Lenisa96, K. Livingston97, H. Y. Lu98, I . J . D. MacGregor99, N. Markov100, B. McKinnon101, D. G. Meekins102, C. A. Meyer103, V. Mokeev104, R. A. Montgomery105, C. I. Moody106, H. Moutarde107, A Movsisyan108, E. Munevar109, C. Munoz Camacho110, P. Nadel-Turonski111, L. A. Net112, S. Niccolai113, G. Niculescu114, I. Niculescu115, M. Osipenko116, A. I. Ostrovidov117, K. Park118, P. Peng119, W. Phelps120, J. J. Phillips121, S. Pisano122, O. Pogorelko123, S. Pozdniakov124, J. W. Price125, S. Procureur126, Y. Prok127, D. Protopopescu128, A. J. R. Puckett129, B. A. Raue130, M. Ripani131, B. G. Ritchie132, A. Rizzo133, G. Rosner134, P. Roy135, F. Sabatié136, C. Salgado137, D. Schott138, R. A. Schumacher139, E. Seder140, M. L. Seely141, I Senderovich142, Y. G. Sharabian143, A. Simonyan144, Iu. Skorodumina145, G. D. Smith146, D. I. Sober147, D. Sokhan148, N. Sparveris149, P. Stoler150, S. Stepanyan151, V. Sytnik152, M. Taiuti153, Ye Tian154, A. Trivedi155, R. Tucker156, M. Ungaro157, H. Voskanyan158, E. Voutier159, N. K. Walford160, D. P. Watts161, X. Wei162, M. H. Wood163, N. Zachariou164, L. Zana165, J. Zhang166, Z. W. Zhao167, I. Zonta168
Affiliations: 1The CLAS Collaboration, 2The CLAS Collaboration, 3The CLAS Collaboration, 4The CLAS Collaboration, 5The CLAS Collaboration, 6The CLAS Collaboration, 7The CLAS Collaboration, 8The CLAS Collaboration, 9The CLAS Collaboration, 10The CLAS Collaboration, 11The CLAS Collaboration, 12The CLAS Collaboration, 13The CLAS Collaboration, 14The CLAS Collaboration, 15The CLAS Collaboration, 16The CLAS Collaboration, 17The CLAS Collaboration, 18The CLAS Collaboration, 19The CLAS Collaboration, 20The CLAS Collaboration, 21The CLAS Collaboration, 22The CLAS Collaboration, 23The CLAS Collaboration, 24The CLAS Collaboration, 25The CLAS Collaboration, 26The CLAS Collaboration, 27The CLAS Collaboration, 28The CLAS Collaboration, 29The CLAS Collaboration, 30The CLAS Collaboration, 31The CLAS Collaboration, 32The CLAS Collaboration, 33The CLAS Collaboration, 34The CLAS Collaboration, 35The CLAS Collaboration, 36The CLAS Collaboration, 37The CLAS Collaboration, 38The CLAS Collaboration, 39The CLAS Collaboration, 40The CLAS Collaboration, 41The CLAS Collaboration, 42The CLAS Collaboration, 43The CLAS Collaboration, 44The CLAS Collaboration, 45The CLAS Collaboration, 46The CLAS Collaboration, 47The CLAS Collaboration, 48The CLAS Collaboration, 49The CLAS Collaboration, 50The CLAS Collaboration, 51The CLAS Collaboration, 52The CLAS Collaboration, 53The CLAS Collaboration, 54The CLAS Collaboration, 55The CLAS Collaboration, 56The CLAS Collaboration, 57The CLAS Collaboration, 58The CLAS Collaboration, 59The CLAS Collaboration, 60The CLAS Collaboration, 61The CLAS Collaboration, 62The CLAS Collaboration, 63The CLAS Collaboration, 64The CLAS Collaboration, 65The CLAS Collaboration, 66The CLAS Collaboration, 67The CLAS Collaboration, 68The CLAS Collaboration, 69The CLAS Collaboration, 70The CLAS Collaboration, 71The CLAS Collaboration, 72The CLAS Collaboration, 73The CLAS Collaboration, 74The CLAS Collaboration, 75The CLAS Collaboration, 76The CLAS Collaboration, 77The CLAS Collaboration, 78The CLAS Collaboration, 79The CLAS Collaboration, 80The CLAS Collaboration, 81The CLAS Collaboration, 82The CLAS Collaboration, 83The CLAS Collaboration, 84The CLAS Collaboration, 85The CLAS Collaboration, 86The CLAS Collaboration, 87The CLAS Collaboration, 88The CLAS Collaboration, 89The CLAS Collaboration, 90The CLAS Collaboration, 91The CLAS Collaboration, 92The CLAS Collaboration, 93The CLAS Collaboration, 94The CLAS Collaboration, 95The CLAS Collaboration, 96The CLAS Collaboration, 97The CLAS Collaboration, 98The CLAS Collaboration, 99The CLAS Collaboration, 100The CLAS Collaboration, 101The CLAS Collaboration, 102The CLAS Collaboration, 103The CLAS Collaboration, 104The CLAS Collaboration, 105The CLAS Collaboration, 106The CLAS Collaboration, 107The CLAS Collaboration, 108The CLAS Collaboration, 109The CLAS Collaboration, 110The CLAS Collaboration, 111The CLAS Collaboration, 112The CLAS Collaboration, 113The CLAS Collaboration, 114The CLAS Collaboration, 115The CLAS Collaboration, 116The CLAS Collaboration, 117The CLAS Collaboration, 118The CLAS Collaboration, 119The CLAS Collaboration, 120The CLAS Collaboration, 121The CLAS Collaboration, 122The CLAS Collaboration, 123The CLAS Collaboration, 124The CLAS Collaboration, 125The CLAS Collaboration, 126The CLAS Collaboration, 127The CLAS Collaboration, 128The CLAS Collaboration, 129The CLAS Collaboration, 130The CLAS Collaboration, 131The CLAS Collaboration, 132The CLAS Collaboration, 133The CLAS Collaboration, 134The CLAS Collaboration, 135The CLAS Collaboration, 136The CLAS Collaboration, 137The CLAS Collaboration, 138The CLAS Collaboration, 139The CLAS Collaboration, 140The CLAS Collaboration, 141The CLAS Collaboration, 142The CLAS Collaboration, 143The CLAS Collaboration, 144The CLAS Collaboration, 145The CLAS Collaboration, 146The CLAS Collaboration, 147The CLAS Collaboration, 148The CLAS Collaboration, 149The CLAS Collaboration, 150The CLAS Collaboration, 151The CLAS Collaboration, 152The CLAS Collaboration, 153The CLAS Collaboration, 154The CLAS Collaboration, 155The CLAS Collaboration, 156The CLAS Collaboration, 157The CLAS Collaboration, 158The CLAS Collaboration, 159The CLAS Collaboration, 160The CLAS Collaboration, 161The CLAS Collaboration, 162The CLAS Collaboration, 163The CLAS Collaboration, 164The CLAS Collaboration, 165The CLAS Collaboration, 166The CLAS Collaboration, 167The CLAS Collaboration, 168The CLAS Collaboration

First results from the longitudinally polarized frozen-spin target (FROST) program are reported. The double-polarization observable E, for the reaction $\vec \gamma \vec p \to \pi^+n$, has been measured using a circularly polarized tagged-photon beam, with energies from 0.35 to 2. Read More

The recent precise experimental results for the photoproduction of $\eta$-mesons off the neutron measured with the Crystal Ball/TAPS calorimeter at the MAMI accelerator have been investigated in detail in the framework of the Bonn-Gatchina coupled channel model. The main result is that the narrow structure observed in the excitation function of $\gamma n \rightarrow n\eta$ can be reproduced fully with a particular interference pattern in the $J^P=1/2^-$ partial wave. Introduction of the narrow resonance $N(1685)$ with the properties reported in earlier publications deteriorates the quality of the fit. Read More

We analyze the current status of three P-wave baryon states $N(1710){1/ 2}^+$, $N(1900){3/2}^+$, and $\Delta(1600){3/2}^+$ as given in the Review of Particles Physics (RPP). Since the evidence for a particle's existence is linked to its RPP "star" rating, we discuss its subjective present definition. We also present the accumulating evidence supporting these states and give our new "star" rating recommendations. Read More

New data on the polarization observables T, P, and H for the reaction $\gamma p \to p\pi^0$ 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. Read More

The reaction $\gamma \, p \rightarrow K^0_S\,\Sigma^+$ is studied in the photon energy range from threshold. Linearly polarised photon beams from coherent bremsstrahlung enabled the first measurement of photon beam asymmetries in this reaction up to $E_\gamma = 2250$ MeV. In addition, the recoil hyperon polarisation was determined through the asymmetry in the weak decay $\Sigma^+ \rightarrow p \pi^0$ up to $E_\gamma = 1650$ MeV. Read More

Using all recent data on the differential cross sections and spin observables for the reaction $\gamma p \to K^+ \Lambda$, an energy-independent partial-wave analysis is performed. The analysis requires multipoles up to $L = 2$; there is no evidence that the fit requires multipoles with $L=3$. At present the available data allow us to extract the dominant multipoles only. Read More

It is shown that the narrow structure observed in the excitation function of $\eta$ photoproduction off the Neutron originates from the interference of the two $S_{11}$ resonances. Read More

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. Read More

2013Nov
Affiliations: 1The CBELSA/TAPS Collaboration, 2The CBELSA/TAPS Collaboration, 3The CBELSA/TAPS Collaboration, 4The CBELSA/TAPS Collaboration, 5The CBELSA/TAPS Collaboration, 6The CBELSA/TAPS Collaboration, 7The CBELSA/TAPS Collaboration, 8The CBELSA/TAPS Collaboration, 9The CBELSA/TAPS Collaboration, 10The CBELSA/TAPS Collaboration, 11The CBELSA/TAPS Collaboration, 12The CBELSA/TAPS Collaboration, 13The CBELSA/TAPS Collaboration, 14The CBELSA/TAPS Collaboration, 15The CBELSA/TAPS Collaboration, 16The CBELSA/TAPS Collaboration, 17The CBELSA/TAPS Collaboration, 18The CBELSA/TAPS Collaboration, 19The CBELSA/TAPS Collaboration, 20The CBELSA/TAPS Collaboration, 21The CBELSA/TAPS Collaboration, 22The CBELSA/TAPS Collaboration, 23The CBELSA/TAPS Collaboration, 24The CBELSA/TAPS Collaboration, 25The CBELSA/TAPS Collaboration, 26The CBELSA/TAPS Collaboration, 27The CBELSA/TAPS Collaboration, 28The CBELSA/TAPS Collaboration, 29The CBELSA/TAPS Collaboration, 30The CBELSA/TAPS Collaboration, 31The CBELSA/TAPS Collaboration, 32The CBELSA/TAPS Collaboration, 33The CBELSA/TAPS Collaboration, 34The CBELSA/TAPS Collaboration, 35The CBELSA/TAPS Collaboration, 36The CBELSA/TAPS Collaboration, 37The CBELSA/TAPS Collaboration, 38The CBELSA/TAPS Collaboration, 39The CBELSA/TAPS Collaboration, 40The CBELSA/TAPS Collaboration, 41The CBELSA/TAPS Collaboration, 42The CBELSA/TAPS Collaboration, 43The CBELSA/TAPS Collaboration, 44The CBELSA/TAPS Collaboration, 45The CBELSA/TAPS Collaboration, 46The CBELSA/TAPS Collaboration, 47The CBELSA/TAPS Collaboration, 48The CBELSA/TAPS Collaboration, 49The CBELSA/TAPS Collaboration, 50The CBELSA/TAPS Collaboration, 51The CBELSA/TAPS Collaboration, 52The CBELSA/TAPS Collaboration, 53The CBELSA/TAPS Collaboration, 54The CBELSA/TAPS Collaboration, 55The CBELSA/TAPS Collaboration, 56The CBELSA/TAPS Collaboration, 57The CBELSA/TAPS Collaboration, 58The CBELSA/TAPS Collaboration, 59The CBELSA/TAPS Collaboration, 60The CBELSA/TAPS Collaboration, 61The CBELSA/TAPS Collaboration, 62The CBELSA/TAPS Collaboration

The excitation function and momentum distribution of $\eta^\prime$ mesons have been measured in photon induced reactions on $^{12}{}$C in the energy range of 1250-2600 MeV. The experiment was performed with tagged photon beams from the ELSA electron accelerator using the Crystal Barrel and TAPS detectors. The data are compared to model calculations to extract information on the sign and magnitude of the real part of the $\eta^\prime$-nucleus potential. Read More

Ambiguities of the signs of $N\to \Sigma K$ coupling constants are studied in a multichannel partial wave analysis of a large body of pion and photo-induced reactions. It is shown that the signs are not free from some ambiguities, and further experimental data are needed. Data on the reactions $\pi^+p\to \Sigma^+K^+$ and $\gamma p\to K^+\Sigma^0$ define rather well the isospin 3/2 contributions to these channels. Read More

Amplitudes for the reaction $\pi^-p\to \Lambda K^0$ are reconstructed from data on the differential cross section $d\sigma/d\Omega$, the recoil polarization $P$, and on the spin rotation parameter $\beta$. At low energies, no data on $\beta$ exist, resulting in ambiguities. An approximation using $S$ and $P$ waves leads only to a fair description of the data on $d\sigma/d\Omega$ and $P$; in this case, there are two sets of amplitudes. Read More

The helicity amplitudes $A^{1/2}_n$ and $A^{3/2}_n$ for the photoexcitation of nucleon resonances off neutrons are determined in a multi-channel partial-wave analysis. Read More

The first measurement is reported of the double-polarization observable G in 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. Read More

New results on the spectrum of nucleon resonances from the Bonn-Gatchina partial wave analysis are presented, and possible interpretations are discussed. Read More

Pion and photo-induced inelastic reactions off protons are studied in a multichannel partial-wave analysis. Properties of nucleon and $\Delta$ resonances are derived and compared to previous analyses. Amplitudes are shown for transitions to $N\eta$, $\Lambda K$, and $\Sigma K$ final states. Read More

The photoproduction of \eta'-mesons off different nuclei has been measured with the CBELSA/TAPS detector system for incident photon energies between 1500 - 2200 MeV. The transparency ratio has been deduced and compared to theoretical calculations describing the propagation of \eta'-mesons in nuclei. The comparison indicates a width of the \eta' -meson of the order of \Gamma= 15-25 MeV at \rho =\rho_0 for an average momentum p_{\eta'} = 1050 MeV/c, at which the \eta'-meson is produced in the nuclear rest frame. Read More

Properties of nucleon and $\Delta$ resonances are derived from a multichannel partial wave analysis. The statistical significance of pion and photo-induced inelastic reactions off protons are studied in a multichannel partial-wave analysis. Read More

Results from a multi-channel partial wave analysis of elastic and inelastic $\pi N$ and $\gamma N$ induced reactions are presented. The analysis evidences the existence of a spin-quartet of nucleon resonances with total angular momenta $J^P=1/2^+,.. Read More

Evidence is reported for two nucleon resonances with spin-parity $J^P=1/2^-$ and $J^P=3/2^-$ at a mass just below 1.9\,GeV. The evidence is derived from a coupled-channel analysis of a large number of pion and photo-produced reactions. Read More

Data are presented on the reaction pbar-p -> omega-omega-pizero at rest from the Crystal Barrel detector. These data identify a strong signal due to f2(1565) -> omega-omega. The relative production from initial pbar-p states 3P2, 3P1 and 1S0 is well determined from omega-omega decay angular correlations; P-state annihilation dominates strongly. Read More

Nucleon and $\Delta$ resonances in the fourth resonance region are studied in a multichannel partial-wave analysis which includes nearly all available data on pion- and photo-induced reactions off protons. In the high-mass range, above 1850\,MeV, several alternative solutions yield a good description of the data. For these solutions, masses, widths, pole residues and photo-couplings are given. Read More

Results of a partial wave analysis of new high-statistics data on $\gamma p\to p\eta$ from MAMI are presented. A fit using known broad resonances and only standard background amplitudes can not describe the relatively narrow peaking structure in the cross section in the mass region of 1660-1750 MeV which follows a minimum. An improved description of the data can be reached by either assuming the existence of a narrow resonance at a mass of about 1700 MeV with small photo-coupling or by a threshold effect. Read More

Based on a thorough comparison of the nucleon and $\Delta$ excitation spectrum with models we show that parity doublets observed in the mass spectra do not entail the consequence that highly excited $N$ or $\Delta$ resonances are insensitive to chiral symmetry breaking. Instead, the mechanism of mass generation in excited states is suggested to be the same as for the baryon ground states: the mass is assigned to fluctuating gluon fields and their strong attraction. In excited baryons, the field energy has to be integrated over a larger volume, and the total mass increases. Read More

The reaction $\gamma p \TO K^+\Lambda(1520)$ was measured in the energy range from threshold to 2.65 GeV with the SAPHIR detector at the electron stretcher facility ELSA in Bonn. The $\Lambda(1520)$ production cross section was analyzed in the decay modes $pK^-$, $n \bar{K}^0$, $\Sigma^{\pm}\pi^{\mp}$, and $\Lambda\pi^+\pi^-$ as a function of the photon energy and the squared four-momentum transfer $t$. Read More

The reactions $\gamma p \rightarrow K^{+}\Sigma^{\pm}\pi^{\mp}$ were studied with the SAPHIR detector using a tagged photon beam at the electron stretcher facility ELSA in Bonn. The decays $\Sigma^{-} \rightarrow n\pi^{-}$ and $\Sigma^{+} \rightarrow n\pi^{+}, p\pi^0$ were fully reconstructed. Reaction cross sections were measured as a function of the photon energy from threshold up to $2. Read More

We report evidence for $N(1710)P_{11}$, $N(1875)P_{11}$, $N(1900)P_{13}$, $\Delta(1600)P_{33}$, $\Delta(1910)P_{31}$, and $\Delta(1920)P_{33}$, and find indications that $N(1900)P_{13}$ might have a companion state at 1970\,MeV. The controversial $\Delta(1750)P_{31}$ is not seen. The evidence is derived from a study of data on pion- and photo-induced hyperon production, but other data are included as well. Read More

The photoproduction of $\omega$ mesons on LH_2, C and Nb has been studied for incident photon energies from 900 to 1300 MeV using the CB/TAPS detector at ELSA. The $\omega$ line shape does not show any significant difference between the LH_2 and the Nb targets. The data are compared with results of transport calculations that predict a sensitivity of the $\omega$ line shape to in-medium modifications near the production threshold on a free nucleon of $E_{\gamma}^{lab}$ = 1109 MeV. Read More

The proton mass arises from spontaneous breaking of chiral symmetry and the formation of constituent quarks. Their dynamics cannot be tested by proton tomography but only by studying excited baryons. However, the number of excited baryons is much smaller than expected within quark models; even worse, the existence of many known states has been challenged in a recent analysis which includes - compared to older analyses - high-precision data from meson factories. Read More

The mass pattern of nucleon and $\Delta$ resonances is compared with predictions based on quark models, the Skyrme model, AdS/QCD, and the conjecture of chiral symmetry restoration. Read More

The polarization observable I^s, a feature exclusive to the acoplanar kinematics of multi-meson final states produced via linearly polarized photons, has been measured for the first time. Results for the reaction g p -> p pi0 eta are presented for incoming photon energies between 970 MeV and 1650 MeV along with the beam asymmetry I^c. The comparably large asymmetries demonstrate a high sensitivity of I^s to the dynamics of the reaction. Read More

Masses, widths and photocouplings of baryon resonances are determined in a coupled-channel partial wave analysis of a large variety of data. The Bonn-Gatchina partial wave formalism is extended to include a decomposition of t- and u-exchange amplitudes into individual partial waves. The multipole transition amplitudes for $\gamma p\to p\pi^0$ and $\gamma p\to n\pi^+$ are given and compared to results from other analyses. Read More

About 120 baryons and baryon resonances are known, from the abundant nucleon with $u$ and $d$ light-quark constituents up to the recently discovered $\Omega_b^-=bss$, and the $\Xi_b^-=bsd$ which contains one quark of each generation. In spite of this impressively large number of states, the underlying mechanisms leading to the excitation spectrum are not yet understood. Heavy-quark baryons suffer from a lack of known spin-parities. Read More