Measurement of the Helicity Asymmetry $E$ for the reaction $ \gamma p\to \pi^0 p$

The CBELSA/TAPS collaboration Gottschall, M. ; Afzal, F. ; Anisovich, A.V. ; et al.
Eur.Phys.J.A 57 (2021) 40, 2021.
Inspire Record 1731795 DOI 10.17182/hepdata.100433

A measurement of the double-polarization observable $E$ for the reaction $\gamma p\to \pi^0 p$ 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 $E_\gamma =600$~MeV to $E_\gamma =2310$~MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses.

1 data table

Double-polarization observable E for different beam energies from 600 to 2310 MeV


Measurement of polarization observables $\textbf{T}$, ${\textbf{P}}$, and ${\textbf{H}}$ in $\mathbf {\pi ^0}$ and $\mathbf {\eta }$ photoproduction off quasi-free nucleons

The CBELSA/TAPS collaboration Jermann, N. ; Krusche, B. ; Metag, V. ; et al.
Eur.Phys.J.A 59 (2023) 232, 2023.
Inspire Record 2712592 DOI 10.17182/hepdata.145075

The target asymmetry T, recoil asymmetry P, and beam-target double polarization observable H were determined in exclusive $\pi ^0$ and $\eta $ photoproduction off quasi-free protons and, for the first time, off quasi-free neutrons. The experiment was performed at the electron stretcher accelerator ELSA in Bonn, Germany, with the Crystal Barrel/TAPS detector setup, using a linearly polarized photon beam and a transversely polarized deuterated butanol target. Effects from the Fermi motion of the nucleons within deuterium were removed by a full kinematic reconstruction of the final state invariant mass. A comparison of the data obtained on the proton and on the neutron provides new insight into the isospin structure of the electromagnetic excitation of the nucleon. Earlier measurements of polarization observables in the $\gamma p \rightarrow \pi ^0 p$ and $\gamma p \rightarrow \eta p$ reactions are confirmed. The data obtained on the neutron are of particular relevance for clarifying the origin of the narrow structure in the $\eta n$ system at $W = 1.68\ \textrm{GeV}$. A comparison with recent partial wave analyses favors the interpretation of this structure as arising from interference of the $S_{11}(1535)$ and $S_{11}(1650)$ resonances within the $S_{11}$-partial wave.

4 data tables

Target asymmetry T, recoil asymmetry P, and polarization observable H for $\gamma p \to \pi^0 p$ as a function of the polar center-of-mass angle for bins at the given centroid c.m. energies.

Target asymmetry T, recoil asymmetry P, and polarization observable H for $\gamma n \to \pi^0 n$ as a function of the polar center-of-mass angle for bins at the given centroid c.m. energies.

Target asymmetry T, recoil asymmetry P, and polarization observable H for $\gamma p \to \eta p$ as a function of the polar center-of-mass angle for bins at the given centroid c.m. energies.

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Single photoproduction of neutral π-mesons on hydrogen at small angles between 1.3 and 3 GeV

Braunschweig, M. ; Husmann, D. ; Lübelsmeyer, K. ; et al.
Phys.Lett. 22 (1966) 705-708, 1966.
Inspire Record 1389452 DOI 10.17182/hepdata.753

The differential cross section of the reaction γ + p → p + πo has been measured at the Deutsches Elektronen- Synchrotron, Hamburg, at mean phonon energies of 1.36, 2.0 and 3.0 GeV and pion center of mass angles between 0o and 70o. The results are compared with some theoretical calculations based on elementary and reggeized 1- meson exchange.

4 data tables

Axis error includes +- 12/12 contribution.

Axis error includes +- 12/12 contribution.

Axis error includes +- 12/12 contribution.

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POLARIZATION OF RECOIL PROTONS IN THE REACTION GAMMA P ---> PI0 P IN THE PHOTON ENERGY INTERVAL 500-MEV - 800-MEV. (IN RUSSIAN)

Bratashevsky, A.S. ; Derebchinsky, A.I. ; Zybalov, A.A. ; et al.
Yad.Fiz. 32 (1980) 667-670, 1980.
Inspire Record 159788 DOI 10.17182/hepdata.18935

None

3 data tables

No description provided.

No description provided.

No description provided.


No description provided.

No description provided.


MEASUREMENT OF POLARIZATION OF RECOIL PROTONS IN PI0 PHOTOPRODUCTION FOR THETA* (PI0) = 60-degrees IN RESONANCE REGION. (IN RUSSIAN)

Avakian, R.O. ; Avakian, E.O. ; Avetisian, A.E. ; et al.
Sov.J.Nucl.Phys. 37 (1983) 199-201, 1983.
Inspire Record 183972 DOI 10.17182/hepdata.17739

None

1 data table

Axis error includes +- 0.0/0.0 contribution (?////NO DISCUSSION OF ERRORS AT ALL).


MEASUREMENT OF POLARIZATION OF PROTONS IN THE REACTION GAMMA P ---> P PI0 IN A PHOTON LINEARLY POLARIZED BEAM. (IN RUSSIAN)

Avakian, R.O. ; Avakian, E.O. ; Avetisian, A.E. ; et al.
Yad.Fiz. 36 (1982) 393-399, 1982.
Inspire Record 183654 DOI 10.17182/hepdata.17730

None

1 data table

Axis error includes +- 0.0/0.0 contribution (?////ERROR IN POLARIZATION OF INITIAL GAMMAS IS NOT GIVEN).


POLARIZATION OF THE RECOIL PROTONS IN GAMMA P ---> P PI0 REACTION FOR E (GAMMA) = 0.65-GEV - 1.4-GEV AT THETA (PI) = 70-DEGREES CM (IN RUSSIAN)

Bratashevsky, A.S. ; Derebchinsky, A.I. ; Zybalov, A.A. ; et al.
Yad.Fiz. 35 (1982) 56-58, 1982.
Inspire Record 178208 DOI 10.17182/hepdata.17740

None

1 data table

No description provided.


MEASUREMENT OF ASYMMETRY IN CROSS-SECTION OF GAMMA P ---> P PI0 REACTION IN THE RESONANCE REGION. (IN RUSSIAN)

Avakian, R.O. ; Avetisian, A.E. ; Bagdasaryan, A.S. ; et al.
Yad.Fiz. 38 (1983) 1196-1198, 1983.
Inspire Record 200187 DOI 10.17182/hepdata.17731

None

1 data table

Axis error includes +- 0.0/0.0 contribution (?////DUE TO ERRORS IN PHOTON POLARIZATION).


THETA IS THETA(P=4,RF=CM) IN DEG.