Single $\pi^0$ Production Off Neutrons Bound in Deuteron with Linearly Polarized Photons

The A2 at MAMI collaboration Mullen, C. ; Gardner, S. ; Glazier, D.I. ; et al.
Eur.Phys.J.A 57 (2021) 205, 2021.
Inspire Record 1851649 DOI 10.17182/hepdata.127968

The quasifree $\overrightarrow{\gamma} d\to\pi^0n(p)$ photon beam asymmetry, $\Sigma$, has been measured at photon energies, $E_\gamma$, from 390 to 610 MeV, corresponding to center of mass energy from 1.271 to 1.424 GeV, for the first time. The data were collected in the A2 hall of the MAMI electron beam facility with the Crystal Ball and TAPS calorimeters covering pion center-of-mass angles from 49 to 148$^\circ$. In this kinematic region, polarization observables are sensitive to contributions from the $\Delta (1232)$ and $N(1440)$ resonances. The extracted values of $\Sigma$ have been compared to predictions based on partial-wave analyses (PWAs) of the existing pion photoproduction database. Our comparison includes the SAID, MAID, and Bonn-Gatchina analyses; while a revised SAID fit, including the new $\Sigma$ measurements, has also been performed. In addition, isospin symmetry is examined as a way to predict $\pi^0n$ photoproduction observables, based on fits to published data in the channels $\pi^0p$, $\pi^+n$, and $\pi^-p$.

12 data tables

Photon beam asymmetry Sigma at W= 1.2711 GeV

Photon beam asymmetry Sigma at W= 1.2858 GeV

Photon beam asymmetry Sigma at W= 1.3003 GeV

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Cross Section for $\gamma n \to \pi^0 n$ measured at Mainz/A2

The A2 collaboration Briscoe, W.J. ; Hadžimehmedović, M. ; Kudryavtsev, A.E. ; et al.
Phys.Rev.C 100 (2019) 065205, 2019.
Inspire Record 1748263 DOI 10.17182/hepdata.116236

The $\gamma n \to \pi^0 n$ differential cross section evaluated for 27 energy bins span the photon-energy range 290-813 MeV (W = 1.195-1.553 GeV) and the pion c.m. polar production angles, ranging from 18 deg to 162 deg, making use of model-dependent nuclear corrections to extract pi0 production data on the neutron from measurements on the deuteron target. Additionally, the total photoabsorption cross section was measured. The tagged photon beam produced by the 883-MeV electron beam of the Mainz Microtron MAMI was used for the 0-meson production. Our accumulation of 3.6 x 10^6 $\gamma n \to \pi^0 n$ events allowed a detailed study of the reaction dynamics. Our data are in reasonable agreement with previous A2 measurements and extend them to lower energies. The data are compared to predictions of previous SAID, MAID, and BnGa partial-wave analyses and to the latest SAID fit MA19 that included our data. Selected photon decay amplitudes $N^* \to \gamma n$ at the resonance poles are determined for the first time.

21 data tables

Excitation function at pion c.m. angle THETA=18 deg as function of incident photon energy E. The uncertainties are statistical and systematic, combined in quadrature.

Excitation function at pion c.m. angle THETA=32 deg as function of incident photon energy E. The uncertainties are statistical and systematic, combined in quadrature.

Excitation function at pion c.m. angle THETA=41 deg as function of incident photon energy E. The uncertainties are statistical and systematic, combined in quadrature.

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Measurement of the transverse target and beam-target asymmetries in $\eta$ meson photoproduction at MAMI

The A2 at MAMI collaboration Akondi, C.S. ; Annand, J.R.M. ; Arends, H.J. ; et al.
Phys.Rev.Lett. 113 (2014) 102001, 2014.
Inspire Record 1310837 DOI 10.17182/hepdata.116552

We present new data for the transverse target asymmetry T and the very first data for the beam-target asymmetry F in the $\vec \gamma \vec p\to\eta p$ reaction up to a center-of-mass energy of W=1.9 GeV. The data were obtained with the Crystal-Ball/TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. All existing model predictions fail to reproduce the new data indicating a significant impact on our understanding of the underlying dynamics of $\eta$ meson photoproduction. The peculiar nodal structure observed in existing T data close to threshold is not confirmed.

24 data tables

Target asymmetry T for c.m. energy W= 1.4969 GeV

Target asymmetry T for c.m. energy W= 1.5156 GeV

Target asymmetry T for c.m. energy W= 1.5341 GeV

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Quasifree photoproduction of $\eta$ mesons off protons and neutrons

The A2 collaboration Werthmüller, D. ; Witthauer, L. ; Keshelashvili, I. ; et al.
Phys.Rev.C 90 (2014) 015205, 2014.
Inspire Record 1308107 DOI 10.17182/hepdata.130235

Differential and total cross sections for the quasifree reactions $\gamma p\rightarrow\eta p$ and $\gamma n\rightarrow\eta n$ have been determined at the MAMI-C electron accelerator using a liquid deuterium target. Photons were produced via bremsstrahlung from the 1.5 GeV incident electron beam and energy-tagged with the Glasgow photon tagger. Decay photons of the neutral decay modes $\eta\rightarrow 2\gamma$ and $\eta\rightarrow 3\pi^0 \rightarrow 6\gamma$ and coincident recoil nucleons were detected in a combined setup of the Crystal Ball and the TAPS calorimeters. The $\eta$-production cross sections were measured in coincidence with recoil protons, recoil neutrons, and in an inclusive mode without a condition on recoil nucleons, which allowed a check of the internal consistency of the data. The effects from nuclear Fermi motion were removed by a kinematic reconstruction of the final-state invariant mass and possible nuclear effects on the quasifree cross section were investigated by a comparison of free and quasifree proton data. The results, which represent a significant improvement in statistical quality compared to previous measurements, agree with the known neutron-to-proton cross-section ratio in the peak of the $S_{11}(1535)$ resonance and confirm a peak in the neutron cross section, which is absent for the proton, at a center-of-mass energy $W = (1670\pm 5)$ MeV with an intrinsic width of $\Gamma\approx 30$ MeV.

90 data tables

Total cross section as a function of c.m. energy W.

Total cross section as a function of c.m. energy W.

Differential cross section at W= 1.4925 GeV

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PHASE SHIFT ANALYSIS OF THE p p AMPLITUDES IN THE ENERGY RANGE 380-MeV TO 1000-MeV

Shklyarevsky, G.M. ;
Sov.J.Nucl.Phys. 47 (1988) 76-82, 1988.
Inspire Record 231081 DOI 10.17182/hepdata.17359
2 data tables

THE PHASES IN THIS TABLE WERE FIXED AT INITIAL STAGE OF PWA.

No description provided.


AZIMUTHAL CORRELATIONS BETWEEN SHOWER PARTICLES FROM PROTON - NUCLEAR INTERACTIONS IN THE ENERGY REGION 20-GeV - 400-GeV

Azimov, S.A. ; Gulamov, K.G. ; Navotnyi, V.Sh. ; et al.
Sov.J.Nucl.Phys. 34 (1981) 717, 1981.
Inspire Record 164983 DOI 10.17182/hepdata.19306

None

6 data tables

No description provided.

No description provided.

No description provided.

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