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

Dieterle, M. et al. (2017) First measurement of the polarization observable E and helicity-dependent cross sections in single π0 photoproduction from quasi-free nucleons. Physics Letters B, 770, pp. 523-531. (doi: 10.1016/j.physletb.2017.04.079)

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The double-polarization observable E and the helicity-dependent cross sections σ1/2 and σ3/2 have been measured for the first time for single π0 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 π0 meson were detected with the Crystal Ball and TAPS electromagnetic calorimeters. Effects from nuclear Fermi motion were removed by a kinematic reconstruction of the π0N 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 σ1/2 and σ3/2 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.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Glazier, Dr Derek and Werthmueller, Dr Dominik and MacGregor, Professor Douglas and Livingston, Dr Kenneth and Gardner, Mr Simon and Annand, Dr John and Hamilton, Dr David
Authors: Dieterle, M., Witthauer, L., Cividini, F., Abt, S., Achenbach, P., Adlarson, P., Afzal, F., Ahmed, Z., Akondi, C.S., Annand, J.R.M., Arends, H.J., Bashkanov, M., Beck, R., Biroth, M., Borisov, N.S., Braghieri, A., Briscoe, W.J., Costanza, S., Collicott, C., Denig, A., Downie, E.J., Drexler, P., Ferretti-Bondy, M.I., Gardner, S., Garni, S., Glazier, D.I., Glowa, D., Gradl, W., Günther, M., Gurevich, G.M., Hamilton, D., Hornidge, D., Huber, G.M., Käser, A., Kashevarov, V.L., Kay, S., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lazarev, A.B., Linturi, J.M., Lisin, V., Livingston, K., Lutterer, S., MacGregor, I.J.D., Mancell, J., Manley, D.M., Martel, P.P., Metag, V., Meyer, W., Miskimen, R., Mornacchi, E., Mushkarenkov, A., Neganov, A.B., Neiser, A., Oberle, M., Ostrick, M., Otte, P.B., Paudyal, D., Pedroni, P., Polonski, A., Prakhov, S.N., Rajabi, A., Reicherz, G., Ron, G., Rostomyan, T., Sarty, A., Sfienti, C., Sikora, M.H., Sokhoyan, V., Spieker, K., Steffen, O., Strakovsky, I.I., Strub, T., Supek, I., Thiel, A., Thiel, M., Thomas, A., Unverzagt, M., Usov, Y.A., Wagner, S., Walford, N.K., Watts, D.P., Werthmüller, D., Wettig, J., Wolfes, M., and Zana, L.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Physics Letters B
Published Online:10 May 2017
Copyright Holders:Copyright © 2017 The Authors
First Published:First published in Physics Letters B 770: 523-531
Publisher Policy:Reproduced under a Creative Commons license

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
570711Nuclear Physics GroupDavid IrelandScience & Technology Facilities Council (STFC)ST/J000175/1P&A - PHYSICS & ASTRONOMY
507271Illuminating strongly interacting matterI MacgregorScience & Technology Facilities Council (STFC)ST/G008604/1P&A - PHYSICS & ASTRONOMY