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

(A2 Collaboration MAMI) 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, Milorad; 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, Th.; Supek, Ivan; Thiel, A.; Thiel, M.; Thomas, A.; Unverzagt, M.; Usov, Yu.A.; Wagner, S.; Walford, N.K.; Watts, D.P.; Werthmüller, D.; Wettig, J.; Wolfes, M.; Zana, L. (2018) First measurement of helicity-dependent cross sections in π0η photoproduction from quasi-free nucleons. Physics Letters B, 786 . pp. 305-312. ISSN 0370-2693

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Abstract

The helicity-dependent cross sections for the photoproduction of pi(0)eta pairs 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 sigma(1/2)(photon and target spinantiparallel) and sigma(3/2) (parallel spins) components to be measured for quasi-free production of pi(0)n pairs 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, A(1/2)(n, p) and A(3/2)(n, p) Identical couplings for protons and neutrons are typical for Delta resonances and identical A(1/2) and A(3/2)components are only possible for J >= 3/2 states, which constrains possible contributions of nucleon resonances.

Item Type: Article
Uncontrolled Keywords: reaction gamma-p ; polarization ; eta ; mesons ; mami ; Pi(0)-pairs ; photon ; proton ; pairs
Subjects: NATURAL SCIENCES > Physics
Divisions: Division of Experimental Physics
Depositing User: Milorad Korolija
Date Deposited: 11 May 2020 14:34
Last Modified: 11 May 2020 14:34
URI: http://fulir.irb.hr/id/eprint/5789
DOI: 10.1016/j.physletb.2018.10.006

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