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GDH and Collaborations,
J. Ahrens,
S. Altieri,
J. R. M. Annand,
H. -J. Arends,
R. Beck,
M. A. Blackston,
C. Bradtke,
A. Braghieri,
N. d'Hose, [......],
M. Rost,
T. Rostomyan,
D. Ryckbosch,
M. Schumacher,
B. Seitz,
G. Tamas,
A. Thomas,
R. Van de Vyver,
H. R. Weller,
F. Zapadtka
[show abstract]
[hide abstract]
ABSTRACT: The helicity dependence of the total cross-section and the invariant-mass distributions in the (pπ±) and (π+π-) final states for the γp → pπ+π- reaction have been measured for the first time at incident photon energies from 400 to 800MeV. The measurement was performed
with the large-acceptance detector DAPHNE at the tagged photon beam facility of the MAMI accelerator in Mainz. Although this
channel is found to be predominantly excited by the intermediate production of a Δπ state, both the measured unpolarized and
the helicity-dependent observables are generally not well described by the existing theoretical models.
European Physical Journal A 04/2012; 34(1):11-21. · 2.19 Impact Factor
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J Ahrens,
S Altieri,
J R M Annand,
H-J Arends,
R Beck,
C Bradtke,
A Braghieri,
N d'Hose,
H Dutz,
S Goertz, [......],
G Rosner,
M Rost,
T Rostomyan,
D Ryckbosch,
M Schumacher,
B Seitz,
G Tamas,
A Thomas,
R Van de Vyver,
F Zapadtka
[show abstract]
[hide abstract]
ABSTRACT: A measurement of the helicity dependence of the total inclusive photoabsorption cross section on the deuteron was carried out at MAMI (Mainz) in the energy range 200<Egamma<800 MeV. The experiment used a 4pi detection system, a circularly polarized tagged photon beam and a frozen-spin target which provided longitudinally polarized deuterons. The contribution to the Gerasimov-Drell-Hearn sum rule for the deuteron determined from the data is 407+/-20(stat)+/-24(syst) mu b for 200<Egamma<800 MeV.
Physical Review Letters 11/2006; 97(20):202303. · 7.37 Impact Factor
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J. Ahrens,
S. Altieri,
J. R. M. Annand,
H. -J. Arends,
R. Beck,
A. Braghieri,
N. d'Hose,
H. Dutz,
S. Goertz,
P. Grabmayr, [......],
M. Rost,
T. Rostomyan,
D. Ryckbosch,
M. Schumacher,
B. Seitz,
G. Tamas,
A. Thomas,
R. van de Vyver,
Th. Walcher,
F. Zapadtka
[show abstract]
[hide abstract]
ABSTRACT: The G asymmetry of the γp↦Nπ reaction has been measured for the first time for Eγ = 340±14 MeV. This observable, for which very scarce published data exist, plays an important role to disentangle the contributions
of the various nucleon resonances. The experiment, performed at the Mainz microtron MAMI, used a 4π-detector system, a linearly
polarized, tagged photon beam, and a longitudinally polarized proton target.
European Physical Journal A 09/2005; 26(1):135-140. · 2.19 Impact Factor
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H Dutz,
K Helbing,
J Krimmer,
T Speckner,
G Zeitler,
J Ahrens,
S Altieri,
J R M Annand,
G Anton,
H-J Arends, [......],
C Rohlof,
T Rostomyan,
M Sauer,
B Schoch,
M Schumacher,
G Tamas,
A Thomas,
R van de Vyver,
W Weihofen,
F Zapadtka
[show abstract]
[hide abstract]
ABSTRACT: Helicity-dependent total photoabsorption cross sections on the deuteron have been measured for the first time at ELSA (Bonn) in the photon energy range from 815 to 1825 MeV. Circularly polarized tagged photons impinging on a longitudinally polarized LiD target have been used together with a highly efficient 4pi detector system. The data around 1 GeV are not compatible with predictions from existing multipole analyses. From the measured energy range an experimental contribution to the GDH integral on the neutron of [33.9 +/- 5.5(stat) +/- 4.5(syst)] microb is extracted.
Physical Review Letters 05/2005; 94(16):162001. · 7.37 Impact Factor
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H Dutz,
K Helbing,
J Krimmer,
T Speckner,
G Zeitler,
J Ahrens,
S Altieri,
J R M Annand,
G Anton,
H-J Arends, [......],
C Rohlof,
T Rostomyan,
M Sauer,
B Schoch,
M Schumacher,
G Tamas,
A Thomas,
R van de Vyver,
W Weihofen,
F Zapadtka
[show abstract]
[hide abstract]
ABSTRACT: For the first time we checked the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the proton experimentally in the photon energy range from 0.2-2.9 GeV with the tagged photon facilities at MAMI (Mainz) and ELSA (Bonn). New data of the doubly polarized total cross section difference are presented in the energy range from 1.6 to 2.9 GeV. The contribution to the GDH integral from 0.2-2.9 GeV yields [254+/-5(stat)+/-12(syst)] microb with negative contributions in the Regge regime at photon energies above 2.1 GeV. This trend supports the validity of the GDH sum rule.
Physical Review Letters 08/2004; 93(3):032003. · 7.37 Impact Factor
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H Dutz,
K Helbing,
J Krimmer,
T Speckner,
G Zeitler,
J Ahrens,
S Altieri,
J R M Annand,
G Anton,
H-J Arends, [......],
C Rohlof,
T Rostomyan,
M Sauer,
B Schoch,
M Schumacher,
G Tamas,
A Thomas,
R van de Vyver,
W Weihofen,
F Zapadtka
[show abstract]
[hide abstract]
ABSTRACT: To verify the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the first time experimentally, we measured the helicity dependent total photoabsorption cross section with circularly polarized real photons and longitudinally polarized nucleons in the photon energy range 0.68-1.82 GeV with the tagged photon facility at ELSA. The experiment was carried out with a 4pi detection system, a circularly polarized tagged photon beam, and a frozen spin polarized proton target. The contribution to the GDH sum rule in this photon energy range is [49.9+/-2.4(stat)+/-2.2(syst)] microb.
Physical Review Letters 12/2003; 91(19):192001. · 7.37 Impact Factor
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The GDH and Collaborations,
J. Ahrens,
S. Altieri,
J.R.M. Annand,
G. Anton,
H.-J. Arends,
K. Aulenbacher,
R. Beck,
C. Bradtke,
A. Braghieri, [......],
T. Speckner,
N. Takabayashi,
G. Tamas,
A. Thomas,
R. van de Vyver,
A. Wakai,
W. Weihofen,
F. Wissmann,
F. Zapadtka,
G. Zeitler
[show abstract]
[hide abstract]
ABSTRACT: The helicity dependence of the γ
p↦pη reaction has been measured for the first time at a center-of-mass angle θ*
η = 70° in the photon energy range from 780 MeV to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4π-detector
system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. The helicity 3/2 cross-section
is found to be small and the results for helicity 1/2 agree with predictions from the MAID analysis.
European Physical Journal A 05/2003; 17(2):241-244. · 2.19 Impact Factor
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J Ahrens,
S Altieri,
J R M Annand,
G Anton,
H-J Arends,
K Aulenbacher,
R Beck,
C Bradtke,
A Braghieri,
N Degrande, [......],
N Takabayashi,
G Tamas,
A Thomas,
L Tiator,
R Van Vyver,
A Wakai,
W Weihofen,
F Wissmann,
F Zapadtka,
G Zeitler
[show abstract]
[hide abstract]
ABSTRACT: The helicity dependence of the gamma-->p-->-->ppi(0) reaction has been measured for the first time in the photon-energy range from 550 to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. These data are predominantly sensitive to the D13(1520) resonance and are used to determine its helicity amplitudes.
Physical Review Letters 07/2002; 88(23):232002. · 7.37 Impact Factor
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J Ahrens,
S Altieri,
J R Annand,
G Anton,
H Arends,
K Aulenbacher,
R Beck,
C Bradtke,
A Braghieri,
N Degrande, [......],
D Menze,
W Meyer,
T Michel,
J Naumann,
R O Owens,
A Panzeri,
P Pedroni,
T Pinelli,
I Preobrajenski,
E Radtke
[show abstract]
[hide abstract]
ABSTRACT: The helicity dependence of the single pion photoproduction on the proton has been measured in the energy range from 200 to 450 MeV for the first time. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a frozen-spin target. The data obtained provide new information for multipole analyses of pion photoproduction and determine the main contributions to the Gerasimov-Drell-Hearn sum rule and the forward spin polarizability gamma(0).
Physical Review Letters 07/2000; 84(26 Pt 1):5950-4. · 7.37 Impact Factor
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J ROCHE,
J Berthot,
P Y Bertin,
V. Breton,
W Böglin,
R Böhm,
N D'Hose,
G De Meyer,
N. Degrande,
M. Distler, [......],
H. Schmieden,
G. Tamas,
L. Van Hoorebeke,
R. Van de Vyver,
J. Van de Wiele,
M. Vanderhaeghen,
P. Vernin,
A Wagner,
T Walcher,
S Wolf
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D. Lhuillier,
J Berthot,
P Y Breton,
V Berton,
W Böglin,
R Böhm,
N D'Hose,
M. Distler,
J.E. Ducret,
R Edelhoff, [......],
S Schardt,
G. Tamas,
M. Vanderhaeghen,
L. Van Hoorebeke,
R. Van de Vyver,
J. Van de Wiele,
P. Vernin,
A Wagner,
T Walcher,
S Wolf
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J ROCHE,
P. Bartsch,
J Berthot,
P Y Bertin,
V. Breton,
W Böglin,
R Böhm,
T. Caprano,
N D'Hose,
G De Meyer, [......],
G. Tamas,
M H G Tytgat,
L. Van Hoorebeke,
R. Van de Vyver,
J. Van de Wiele,
M. Vanderhaeghen,
P. Vernin,
A Wagner,
T Walcher,
S Wolf
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J. Ahrens,
S Altieri,
JRM Annand,
HJ Arends,
R. Beck,
MA Blackston,
C. Bradtke,
A. Braghieri,
N. dHose,
H. Dutz, [......],
M Rost,
T. Rostomyan,
D. Ryckbosch,
M Schumacher,
B Seitz,
G. Tamas,
A Thomas,
RV de Vyver,
HR Weller,
F. Zapadtka
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L. Van Hoorebeke,
J Berthot,
V Bertin,
W Böglin,
R Böhm,
N D'Hose,
G De Meyer,
N. Degrande,
M. Distler,
J.E. Ducret, [......],
S Schardt,
H. Schmieden,
G. Tamas,
J Van de Vyver,
J. Van de Wiele,
T Vanderhaeghen,
P. Vernin,
A Wagner,
T Walcher,
S Wolf
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N D'Hose,
P. Bartsch,
J Berthot,
P Y Bertin,
V. Breton,
W Böglin,
R Böhm,
T. Caprano,
G De Meyer,
N. Degrande, [......],
G. Tamas,
M H G Tytgat,
L. Van Hoorebeke,
R. Van de Vyver,
J. Van de Wiele,
M. Vanderhaeghen,
P. Vernin,
A Wagner,
T Walcher,
S Wolf
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J. Ahrens,
S Altieri,
J. R. M. Annand,
G. Anton,
H.J. Arends,
K. Aulenbacher,
R. Beck,
C. Bradtke,
A. Braghieri,
N. Degrande, [......],
N Takabayashi,
G. Tamas,
A Thomas,
L. Tiator,
R. Van de Vyver,
A. Wakai,
W. Weihofen,
F. Wissmann,
F. Zapadtka,
G. Zeitler
[show abstract]
[hide abstract]
ABSTRACT: A high-quality double-polarization data set for the helicity dependence of the total and differential cross-sections for both γp→Nπ channels in the Δ region has been obtained in the framework of the GDH experiment. The experiment, performed at the Mainz microtron MAMI, used a 4 π detection system, a circularly polarized photon beam, and a longitudinally polarized frozen-spin target. These data are included in the database to perform a multipole analysis to determine the properties of the Δ(1232) -resonance. For the resonant Δ(1232) multipoles we find a very good agreement with previous analyses, while the nonresonant ones show significant deviations.
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J. Ahrens,
S Altieri,
J. R. M. Annand,
G. Anton,
H.J. Arends,
K. Aulenbacher,
R. Beck,
C. Bradtke,
A. Braghieri,
N. Degrande, [......],
T. Speckner,
N Takabayashi,
G. Tamas,
A Thomas,
R. Van de Vyver,
A. Wakai,
W. Weihofen,
F. Wissmann,
F. Zapadtka,
G. Zeitler
[show abstract]
[hide abstract]
ABSTRACT: The helicity dependence of the total cross section for the γp→pπ<sup>0</sup>π<sup>0</sup> reaction has been measured for the first time at incident photon energies from 400 to 800 MeV. The measurement, performed at the tagged photon beam facility of the MAMI accelerator in Mainz, used the large acceptance detector DAPHNE and a longitudinally polarized frozen-spin target. This channel is found to be excited predominantly when the photon and proton have a parallel spin orientation, most likely due to the intermediate production of the D<sub>13</sub>(1520) resonance. However, the contribution of the antiparallel spin configuration, arising from other reaction mechanisms, is also not negligible. This result gives important new information to resolve the existing model discrepancies in the identification of the nucleon resonances contributing to this channel.
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J. Ahrens,
S Altieri,
JRM Annand,
HJ Arends,
R. Beck,
A. Braghieri,
N. dHose,
H. Dutz,
S Goertz,
P. Grabmayr, [......],
M Rost,
T. Rostomyan,
D. Ryckbosch,
M Schumacher,
B Seitz,
G. Tamas,
A Thomas,
RV de Vyver,
T Walcher,
F. Zapadtka
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J. Ahrens,
S Altieri,
J. R. M. Annand,
H.J. Arends,
R. Beck,
C. Bradtke,
A. Braghieri,
N. dHose,
H. Dutz,
S Goertz, [......],
M Rost,
T. Rostomyan,
D. Ryckbosch,
M Schumacher,
B Seitz,
G. Tamas,
A Thomas,
L. Tiator,
R.V. de Vyver,
F. Zapadtka
[show abstract]
[hide abstract]
ABSTRACT: The helicity dependence of the γp→nπ<sup>+</sup> reaction has been measured for the first time in the photon energy range from 450 to 790 MeV. The experiment, performed at the Mainz Microtron (MAMI), used a 4π-detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. Although these polarized data are mainly sensitive to mechanisms involving the D<sub>13</sub>(1520) resonance, a cusp structure at the η production threshold can be clearly observed. These data are significantly different from the predictions of the existing multipole analyses and are used to determine the helicity amplitudes of the D<sub>13</sub>(1520) and S<sub>11</sub>(1535) resonances with improved accuracy.
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J. Ahrens,
S Altieri,
J. R. M. Annand,
H.J. Arends,
R. Beck,
C. Bradtke,
A. Braghieri,
N. dHose,
H. Dutz,
S Goertz, [......],
G Rosner,
M Rost,
T. Rostomyan,
D. Ryckbosch,
M Schumacher,
B Seitz,
G. Tamas,
A Thomas,
R. Van de Vyver,
F. Zapadtka
[show abstract]
[hide abstract]
ABSTRACT: A measurement of the helicity dependence of the total inclusive photoabsorption cross section on the deuteron was carried out at MAMI (Mainz) in the energy range 200<Eγ<800 MeV. The experiment used a 4π detection system, a circularly polarized tagged photon beam and a frozen-spin target which provided longitudinally polarized deuterons. The contribution to the Gerasimov-Drell-Hearn sum rule for the deuteron determined from the data is 407±20(stat)±24(syst) μb for 200<Eγ<800 MeV.
