First measurement of helicity-dependent cross sections in π0η photoproduction from quasi-free nucleons

Käser, A. et al. (2018) First measurement of helicity-dependent cross sections in π0η photoproduction from quasi-free nucleons. Physics Letters B, 786, pp. 305-312. (doi: 10.1016/j.physletb.2018.10.006)

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The helicity-dependent cross sections for the photoproduction of π0ηpairs have been measured for the first time. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with the combined Crystal Ball – TAPS calorimeter. The experiment used a polarized deuterated butanol target and a circularly polarized photon beam. This arrangement allowed the σ1/2(photon and target spin antiparallel) and σ3/2(parallel spins) components to be measured for quasi-free production of π0ηpairs off protons and neutrons. The main finding is that the two helicity components contribute identically, within uncertainties, for both participant protons and neutrons. The absolute couplings for protons and neutrons are also identical. This means that nucleon resonances contributing to this reaction in the investigated energy range have almost equal electromagnetic helicity couplings, An,p1/2and An,p3/2. Identical couplings for protons and neutrons are typical for Δ resonances and identical A1/2and A3/2components are only possible for J≥3/2states, which constrains possible contributions of nucleon resonances.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Glazier, Dr Derek and Werthmueller, Dr Dominik and MacGregor, Professor Douglas and Livingston, Dr Kenneth and Annand, Dr John
Authors: Käser, A., Dieterle, M., Witthauer, L., Abt, S., Achenbach, P., Adlarson, P., Afzal, F., Ahmed, Z., Ahrens, J., Annand, J.R.M., Arends, H.J., Bashkanov, M., Beck, R., Biroth, M., Borisov, N.S., Braghieri, A., Briscoe, W.J., Cividini, F., Collicott, C., Costanza, S., Denig, A., Downie, E.J., Drexler, P., Fix, A., Garni, S., Glazier, D.I., Gorodnov, I., Gradl, W., Günther, M., Gurevich, G.M., Heijkenskjöld, L., Hornidge, D., Huber, G.M., Kashevarov, V.L., Kay, S., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lazarev, A.B., Lisin, V., Livingston, K., Lutterer, S., MacGregor, I.J.D., 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., Reicherz, G., Ron, G., Rostomyan, T., Sarty, A., Sfienti, C., 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
ISSN (Online):1873-2445
Published Online:08 October 2018
Copyright Holders:Copyright © 2018 Elsevier B.V.
First Published:First published in Physics Letters B 786: 305-312
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
165582Nuclear Physics GroupDavid IrelandScience and Technology Facilities Council (STFC)ST/J000175/1P&S - Physics & Astronomy
162615Illuminating strongly interacting matterI MacgregorScience and Technology Facilities Council (STFC)ST/G008604/1P&S - Physics & Astronomy