First measurement of the polarization observable $E$ and helicity-dependent cross sections in single $π^{0}$ photoproduction from quasi-free nucleons
Creators: name: Dieterle, M.
name: Witthauer, L.
name: Cividini, F.
name: Abt, S.
name: Achenbach, P.
name: Adlarson, P.
name: Afzal, F.
name: Ahmed, Z.
name: Akondi, C. S.
name: Annand, J. R. M.
name: Arends, H. J.
name: Bashkanov, M.
name: Beck, R.
name: Biroth, M.
name: Borisov, N. S.
name: Braghieri, A.
name: Briscoe, W. J.
name: Costanza, S.
name: Collicott, C.
name: Denig, A.
name: Downie, E. J.
name: Drexler, P.
name: Ferretti-Bondy, M. I.
name: Gardner, S.
name: Garni, S.
name: Glazier, D. I.
name: Glowa, D.
name: Gradl, W.
name: Günther, M.
name: Gurevich, G. M.
name: Hamilton, D.
name: Hornidge, D.
name: Huber, G. M.
name: Käser, A.
name: Kashevarov, V. L.
name: Kay, S.
name: Keshelashvili, I.
name: Kondratiev, R.
name: Korolija, M.
name: Krusche, B.
name: Lazarev, A. B.
name: Linturi, J. M.
name: Lisin, V.
name: Livingston, K.
name: Lutterer, S.
name: MacGregor, I. J. D.
name: Mancell, J.
name: Manley, D. M.
name: Martel, P. P.
name: Metag, V.
name: Meyer, W.
name: Miskimen, R.
name: Mornacchi, E.
name: Mushkarenkov, A.
name: Neganov, A. B.
name: Neiser, A.
name: Oberle, M.
name: Ostrick, M.
name: Otte, P. B.
name: Paudyal, D.
name: Pedroni, P.
name: Polonski, A.
name: Prakhov, S. N.
name: Rajabi, A.
name: Reicherz, G.
name: Ron, G.
name: Rostomyan, T.
name: Sarty, A.
name: Sfienti, C.
name: Sikora, M. H.
name: Sokhoyan, V.
name: Spieker, K.
name: Steffen, O.
name: Strakovsky, I. I.
name: Strub, Th.
name: Supek, I.
name: Thiel, A.
name: Thiel, M.
name: Thomas, A.
name: Unverzagt, M.
name: Usov, Yu. A.
name: Wagner, S.
name: Watts, N. K. Walford D. P.
name: Werthmüller, D.
name: Wettig, J.
name: Wolfes, M.
name: Zana, L.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: 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.
description: accepted for publication in Phys. Lett. B