Photoproduction of $\eta$ η mesons from the neutron: Cross sections and double polarization observable E

Witthauer, L.; Dieterle, M.; Afzal, F.; Anisovich, A. V.; Bantes, B.; Bayadilov, D.; Beck, R.; Bichow, M.; Brinkmann, K.-Th.; Böse, S.; Challand, Th.; Credé, V.; Dutz, H.; Eberhardt, H.; Elsner, D.; Ewald, R.; Fornet-Ponse, K.; Friedrich, S.; Frommberger, F.; Funke, Ch.; Goertz, S.; Gottschall, M.; Gridnev, A.; Grüner, M.; Gutz, E.; Hammann, D.; Hammann, Ch.; Hannappel, J.; Hartmann, J.; Hillert, W.; Hoffmeister, P.; Honisch, Christiane; Jude, Thomas; Kaiser, David; Kalinowsky, H.; Kalischewski, F.; Kammer, S.; Käser, A.; Keshelashvili, I.; Klassen, P.; Kleber, V.; Klein, Frank; Koop, K.; Krusche, B.; Lang, Μ.; Lopatin, I.; Mahlberg, P.; Makónyi, K.; Metag, V.; Meyer, W.; Müller, J.; Müllers, J.; Nanova, M.; Nikonov, V. A.; Piontek, D.; Reicherz, G.; Rostomyan, T.; Sarantsev, A.; Schmidt, Ch.; Schmieden, H.; Seifen, T.; Sokhoyan, V.; Spieker, K.; Thiel, A.; Thoma, U.; Urban, M.; Pee, H. van; Walford, N. K.; Walther, Dirk; Wendel, Ch.; Werthmüller, D.; Wilson, A.; Winnebeck, A.

doi:10.1140/epja/i2017-12247-0

Cited by 19 publications

(8 citation statements)

References 74 publications

(187 reference statements)

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“…The magnitude and the energy and angular dependence of FSI can differ significantly between reactions. Previous experiments have shown that FSI for η photoproduction off deuterons in the energy range discussed here is negligible for cross sections and also for polarization observables [43,57,60,[74][75][76]. Also for photoproduction of η ′ mesons, no significant effects were observed [44].…”

Section: H Correction Of Final State Interaction Effectsmentioning

confidence: 53%

Photoproduction of π0 mesons off protons and neutrons in the second and third nucleon resonance regions

Dieterle¹,

Werthmüller²,

Abt³

et al. 2018

Phys. Rev. C

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Background: Photoproduction of mesons off quasi-free nucleons bound in the deuteron allows to study the electromagnetic excitation spectrum of the neutron and the isospin structure of the excitation of nucleon resonances. The database for such reactions is much more sparse than for free proton targets.Purpose: Study experimentally single π 0 photoproduction off quasi-free nucleons from the deuteron. Investigate nuclear effects by a comparison of the results for free protons and quasi-free protons. Use the quasi-free neutron data (corrected for nuclear effects) to test the predictions of reaction models and partial wave analysis (PWA) for γn → nπ 0 derived from the analysis of the other isospin channels.Methods: High statistics angular distributions and total cross sections for the photoproduction of π 0 mesons off the deuteron with coincident detection of recoil nucleons have been measured for the first time. The experiment was performed at the tagged photon beam of the Mainz MAMI accelerator for photon energies between 0.45 GeV and 1.4 GeV, using an almost 4π electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. A complete kinematic reconstruction of the final state removed the effects of Fermi motion.Results: Significant effects from final state interactions (FSI) were observed for participant protons in comparison to free proton targets (between 30% and almost 40%). The data in coincidence with recoil neutrons were corrected for such effects under the assumption that they are identical for participant protons and neutrons. Reaction model predictions and PWA for γn → nπ 0 , based on fits to data for the other isospin channels, disagreed between themselves and no model provided a good description of the new data. Conclusions:The results demonstrate clearly the importance of a mesurement of the fully neutral final state for the isospin decmposition of the cross section. Model refits, for example from the Bonn-Gatchina analysis, show that the new and the previous data for the other three isospin channels can be simultaneously described when the contributions of several partial waves are modified. The results are also relevant for the suppression of the higher resonance bumps in total photoabsorption on nuclei, which are not well understood.The photoproduction of mesons is a prime tool for the study of the excitation spectrum of the nucleon, which is a major testing ground for the properties of the strong interaction in the non-perturbative regime. The pion is the lightest meson and has a strong coupling to many nucleon excited states. Although recent years have provided new photoproduction data for many different final states, pion scattering and photoproduction of pions are still central to most analyses which aim to identify and characterize the excited states of nucleons. Many theoretical frameworks are employed to extract this information. They include the SAID multipole analysis [1,2], the MAID unitary isobar model [3,4], the Dubna-Mainz-Taipei (DMT) dynamical model [5], the Bonn-Gatchi...

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Section: H Correction Of Final State Interaction Effectsmentioning

confidence: 53%

Photoproduction of π0 mesons off protons and neutrons in the second and third nucleon resonance regions

Dieterle¹,

Werthmüller²,

Abt³

et al. 2018

Phys. Rev. C

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“…No significant effects were found for ππ and πη pairs. Also, for the helicity asymmetry E, as defined in this paper, no effects were found for single π 0 [37] and η production [33][34][35], although the effects on absolute cross sections for π 0 production are substantial. For πη production also shapes of invariant mass distributions of meson-meson and mesonnucleon pairs are basically unaffected [24].…”

Section: Complications For Quasi-free Production Off Bound Nucleonsmentioning

confidence: 65%

First measurement of helicity-dependent cross sections in π0η photoproduction from quasi-free nucleons

et al. 2018

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“…This observable allows the separation of the unpolarized cross section into the helicity-1/2 and helicity-3/2 parts. Results for η production became recently available [35][36][37] and this paper summarizes the first results for this observable for single π 0 production off the neutron.…”

Section: Introductionmentioning

confidence: 98%

First measurement of the polarization observable E and helicity-dependent cross sections in single π0 photoproduction from quasi-free nucleons

et al. 2017

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The double-polarization observable E and the helicity-dependent cross sections σ 1/2 and σ 3/2 have been measured for the first time for single π 0 photoproduction from protons and neutrons bound in the deuteron at the electron accelerator facility MAMI in Mainz, Germany. The experiment used a circularly polarized photon beam and a longitudinally polarized deuterated butanol target. The reaction products, recoil nucleons and decay photons from the π 0 meson were detected with the Crystal Ball and TAPS electromagnetic calorimeters. Effects from nuclear Fermi motion were removed by a kinematic reconstruction of the π 0 N final state. A comparison to data measured with a free proton target showed that the absolute scale of the cross sections is significantly modified by nuclear final-state interaction (FSI) effects. However, there is no significant effect on the asymmetry E since the σ 1/2 and σ 3/2 components appear to be influenced in a similar way. Thus, the best approximation of the two helicity-dependent cross sections for the free neutron is obtained by combining the asymmetry E measured with quasi-free neutrons and the unpolarized cross section corrected for FSI effects under the assumption that the FSI effects are similar for neutrons and protons.

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Photoproduction of $\eta$ η mesons from the neutron: Cross sections and double polarization observable E

Cited by 19 publications

References 74 publications

Photoproduction of π0 mesons off protons and neutrons in the second and third nucleon resonance regions

Photoproduction of π0 mesons off protons and neutrons in the second and third nucleon resonance regions

First measurement of helicity-dependent cross sections in π0η photoproduction from quasi-free nucleons

First measurement of the polarization observable E and helicity-dependent cross sections in single π0 photoproduction from quasi-free nucleons

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