supported by

Collaborative Research Centre 16

Subnuclear Structure of Matter
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A1. Spectroscopy of baryon resonances

R. Beck, U. Thoma

This project aims at a detailed understanding of the spectrum and the properties of baryon resonances being the bound states of strong QCD. With the Crystal Barrel / TAPS experiment at ELSA, the photoproduction of single- and multi-meson final states is investigated. Precise data for the extraction of resonance properties will be obtained by performing further single and double polarization experiments off the proton and the neutron. The experiments will use a circularly / linearly polarized photon beam and a longitudinally / transversely polarized target

Publications

Published and accepted papers
A. Thiel et al. [CBELSA/TAPS Collaboration]
„Double-polarization observable G in neutral-pion photoproduction off the proton″,
[arXiv:1604.02922 [nucl-ex]].
A. Wilson et al. [CBELSA/TAPS Collaboration]
„Photoproduction of ω mesons off the proton″,
Phys. Lett. B 749 (2015) 407, [arXiv:1508.01483 [nucl-ex]].
V. Sokhoyan et al. [CBELSA/TAPS Collaboration]
„High-statistics study of the reaction γ p → p 2π0″,
Eur. Phys. J. A 51 (2015) no.8, 95 , Erratum: Eur. Phys. J. A 51 (2015) no.12, 187, [arXiv:1507.02488 [nucl-ex]].
J. Hartmann et al. [CBELSA/TAPS Collaboration]
„The polarization observables T , P , and H and their impact on γ p → p π0 multipoles″,
Phys. Lett. B 748 (2015) 212, [arXiv:1506.06226 [nucl-ex]].
V. Sokhoyan et al. [CBELSA/TAPS Collaboration]
„Data on Is and Ic in γ p → p π0 π0 reveal cascade decays of N(1900) via N(1520)π″,
Phys. Lett. B 746 (2015) 127
A. Thiel et al. [CBELSA/TAPS Collaboration]
„Three-body nature of N* and Δ* resonances from sequential decay chains″,
Phys. Rev. Lett. 114 (2015) no.9, 091803, [arXiv:1501.02094 [nucl-ex]].
J. Hartmann et al. [CBELSA/TAPS Collaboration]
„The N(1520) 3/2- helicity amplitudes from an energy-independent multipole analysis based on new polarization data on photoproduction of neutral pions″,
Phys. Rev. Lett. 113 (2014) 062001, [arXiv:1407.2163 [nucl-ex]].
E. Gutz et al. [CBELSA/TAPS Collaboration]
„High statistics study of the reaction γp → pπ0η″,
Eur. Phys. J. A 50 (2014) 74, [arXiv:1402.4125 [nucl-ex]].
M. Gottschall et al. [CBELSA/TAPS Collaboration]
„First measurement of the helicity asymmetry for γp → pπ0 in the resonance region″,
Phys. Rev. Lett. 112 (2014) 012003, [arXiv:1312.2187 [nucl-ex]].
A. Thiel et al. [CBELSA/TAPS Collaboration]
„Well-established nucleon reconances revisited by double-polarization measurements″,
Phys. Rev. Lett. 109(2012) 102001, [arXiv:1207.2686 [nucl-ex]].
V. Crede et al. [CBELSA/TAPS Collaboration]
„Photoproduction of Neutral Pions off Protons″,
Phys. Rev. C 84 (2011) 055203, [arXiv:1107.2151 [nucl-ex]].
I. Jaegle et al. [CBELSA/TAPS Collaboration]
„Quasi-free photoproduction of η-mesons off the deuteron″,
Eur. Phys. J. A 47 (2011) 89, [arXiv:1107.2046 [nucl-ex]].
I. Jaegle et al. [CBELSA/TAPS Collaboration]
„Photoproduction of η′-mesons off the deuteron″,
Eur. Phys. J. A 47 (2011) 11, [arXiv:1012.1021 [nucl-ex]].
E. Gutz et al. [CBELSA/TAPS Collaboration]
„Photoproduction of meson pairs: First measurement of the polarization observable Is″,
Phys. Lett. B 687 (2010) 11, [arXiv:0912.2632 [nucl-ex]].
N. Sparks et al. [CBELSA/TAPS Collaboration]
„Measurement of the Beam Asymmetry Σ in the Forward Direction for γ→p → pπ0 Photoproduction″,
Phys. Rev. C 81 (2010) 065210, [arXiv:1003.1346 [nucl-ex]].
V. Crede et al. [CBELSA/TAPS Collaboration]
„Photoproduction of η and η′ mesons off protons″,
Phys. Rev. C 80 (2009) 055202, [arXiv:0909.1248 [nucl-ex]].
T. Mertens et al. [CBELSA/TAPS Collaboration]
„Photoproduction of η-mesons off nuclei for Eγ <= 2.2 GeV″,
Eur. Phys. J. A 38 (2008) 195, [arXiv:0810.2678 [nucl-ex]].
I. Horn et al. [CB-ELSA Collaboration]
„Study of the reaction γp → pπ0η″,
Eur. Phys. J. A 38 (2008) 173, [arXiv:0806.4251 [nucl-ex]].
M. Nanova et al. [CBELSA/TAPS Collaboration]
„K0 π0 Σ+ and K*0Σ+ photoproduction off the proton″,
Eur. Phys. J. A 35 (2008) 333, [arXiv:0803.2146 [nucl-ex]].
E. Gutz et al. [CBELSA/TAPS Collaboration]
„Measurement of the beam asymmetry Σ in π0η production off the proton with the CBELSA/TAPS experiment″,
Eur. Phys. J. A 35 (2008) 291.
I. Horn et al. [CB-ELSA Collaboration]
„Evidence for a Parity Doublet Δ(1920)P33 and Δ(1940)D33 from γp → pπ0 η″,
Phys. Rev. Lett. 101 (2008) 202002, [arXiv:0711.1138 [nucl-ex]].
I. Jaegle et al. [CBELSA/TAPS Collaboration]
„Quasi-free photoproduction of η-mesons of the neutron″,
Phys. Rev. Lett. 100 (2008) 252002, [arXiv:0804.4841 [nucl-ex]].
A.V. Sarantsev, M. Fuchs, M. Kotulla, U. Thoma et al. [CB-ELSA and A2-TAPS Collaborations]
„New results on the Roper resonance and the P11 partial wave″,
Phys. Lett. B 659 (2008) 94-100, [arXiv:0707.3591 [hep-ph]].
U. Thoma, M. Fuchs et al. [CB-ELSA Collaboration]
„N* and Δ* decays into Nπ0π0″,
Phys. Lett. B 659 (2008) 87-93, [arXiv:0707.3592 [hep-ph]].
O. Bartholomy, V. Crede et al. [CB-ELSA Collaboration]
„Photoproduction of η mesons off protons″,
Eur. Phys. J. A 33 (2007) 133.
J. Junkersfeld et al. [CB-ELSA Collaboration]
„Photoproduction of π0ω off protons for Eγ ≤ 3 GeV″,
Eur. Phys. J. A 31 (2007) 365, [arXiv:0704.0710 [nucl-ex]].
H. van Pee, O. Bartholomy, V. Crede et al. [CB-ELSA Collaboration]
„Photoproduction of π0-mesons off protons from the Δ(1232) region to Eγ = 3 GeV″,
Eur. Phys. J. A 31 (2007) 61, [arXiv:0704.1776 [nucl-ex]].
O. Bartholomy, V. Crede, H. van Pee et al. [CB-ELSA Collaboration]
„Neutral pion photoproduction off protons in the energy range 0.3 GeV < Eγ < 3 GeV″,
Phys. Rev. Lett. 94 (2005) 012003, [arXiv:hep-ex/0407022].
V. Crede, O. Bartholomy et al. [CB-ELSA Collaboration]
„Photoproduction of η mesons off protons for 0.75 GeV < Eγ < 3 GeV″,
Phys. Rev. Lett. 94 (2005) 012004, [arXiv:hep-ex/0311045].

Related review articles
E. Klempt, J.-M. Richard, and U. Thoma
„Baryon spectroscopy″,
Review commissioned for Rev. Mod. Phys. (2008).,

List of further relevant publications
D.P. Watts, J.R.M. Annand, R. Beck, D. Branford, D. Glazier, P. Grabmayr, K. Livingston, I.J.D. MacGregor, J.C. McGeorge, R.O. Owens (A2 Collaboration)
„Dependence of the 12C(γ,pd) reaction on photon linear polarisation″,
Phys. Lett. B 647 (2007) 88.
R. K. Bradford, R. A. Schumacher et al. [CLAS Collaboration]
„First measurement of beam-recoil observables C(x) and C(z) in hyperon photoproduction″,
Phys. Rev. C 75 (2007) 035205, [arXiv:nucl-ex/0611034].
J. Ahrens et al. [A2- and GDH-Collaborations]
„Measurement of the helicity dependence for the γ p→ nπ+ channel in the second resonance region″,
Phys. Rev. C. 74 (2006) 045204.
R. Bradford, R. A. Schumacher, J. W. C. McNabb, L. Todor et al. [CLAS Collaboration]
„Differential cross sections for γ + p → K+ + Y for Λ and Σ0 hyperons″,
Phys. Rev. C 73 (2006) 035202, [arXiv:nucl-ex/0509033].
M. Battaglieri, R. De Vita, V. Kubarovsky, L. Guo, G. S. Mutchler, P. Stoler, D. P. Weygand et al. [CLAS Collaboration]
„Search for Θ+(1540) pentaquark in high statistics measurement of γ p → K0– K+n at CLAS″,
Phys. Rev. Lett. 96 (2006) 042001, [arXiv:hep-ex/0510061].
S. Strauch, B. L. Berman et al. [CLAS Collaboration]
„Beam-helicity asymmetries in double charged pion photoproduction on the proton″,
Phys. Rev. Lett. 95 (2005) 162003, [arXiv:hep-ex/0508002].
J. Ahrens et al. [A2- and GDH-Collaborations]
„Measurement of the G asymmetry for the γp → Nπ channels in the Δ(1232) resonance region″,
Eur. Phys. J. A 26 (2005) 135.
J. Ahrens et al.
„Measurement of the π+ meson polarizabilities via the γp → γπ+ n reaction″,
Eur. Phys. J. A 23 (2005) 113.
J.D. Kellie, P. Clive, R. Beck, K. Livingston, I.J.D. MacGregor, J.C. McGeorge, A. Schmidt, D.P. Watts
„The selection and performance of diamond radiators used in coherent bremsstrahlung experiments″,
NIM A 545 (2005) 164-180.
J. Ahrens et al. [GDH- and A2-Collaborations]
„Intermediate resonance excitation in the γp → pπ0π0 reaction″,
Phys. Lett. B 624 (2005) 173.
J. W. C. McNabb, R. A. Schumacher, L. Todor et al. [CLAS Collaboration]
„Hyperon photoproduction in the nucleon resonance region″,
Phys. Rev. C 69 (2004) 042201, [arXiv:nucl-ex/0305028].
B. Krusche, J. Lehr et al.
„Photoproduction of π0-mesons from nuclei″,
Eur. Phys. J. A 22(2004) 277-291.
J. Ahrens et al. [GDH- and A2-Collaborations]
„Helicity dependence of the γp → Nπ channels and multipole analysis in the Delta region″,
Eur. Phys. J. A 21 (2004) 323.
K. Kossert, M. Camen, F. Wissmann et al.
„Quasi-free π0 photoproduction from the bound nucleon″,
Eur. Phys. J. A 19 (2004) 391.
M. Pfeiffer et al.
„Photoproduction of η 3He″,
Phys. Rev. Lett. 92 (2004) 252001.

last updated Mon Mar 18 14:26:00 UTC 2013