Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8188731 | Physics Letters B | 2013 | 7 Pages |
Abstract
Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of neutral pion pairs in the reactions γâpâpÏ0Ï0 and γâdâ(n)pÏ0Ï0, γâdâ(p)nÏ0Ï0 off free protons and off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow magnetic spectrometer. Decay photons from the Ï0 mesons, recoil protons, and recoil neutrons were detected in the 4Ï covering electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. After kinematic reconstruction of the final state, excellent agreement was found between the results for free and quasi-free protons. This demonstrates that the free-nucleon behavior of such observables can be extracted from measurements with quasi-free nucleons, which is the only possibility for the neutron. Contrary to expectations, the measured asymmetries are very similar for reactions off protons and neutrons. The results are compared to the predictions from the Two-Pion MAID reaction model and (for the proton) also to the Bonn-Gatchina coupled channel analysis.
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Nuclear and High Energy Physics
Authors
M. Oberle, B. Krusche, J. Ahrens, J.R.M. Annand, H.J. Arends, K. Bantawa, P.A. Bartolome, R. Beck, V. Bekrenev, H. Berghäuser, A. Braghieri, D. Branford, W.J. Briscoe, J. Brudvik, S. Cherepnya, B. Demissie, M. Dieterle, E.J. Downie, F. Zehr,