Measurement of the beam-helicity asymmetry in photoproduction of π0η pairs on carbon, aluminum, and lead

Sokhoyan, V.; Prakhov, S.; Fix, A.; Abt, S.; Achenbach, P.; Adlarson, P.; Afzal, F.; Aguar-Bartolome, P.; Ahmed, Z.; Altangerel, K.; Annand, J. R. M.; Arends, H. J.; Bantawa, K.; Bashkanov, M.; Beck, R.; Biroth, M.; Borisov, N. S.; Braghieri, A.; Briscoe, W. J.; Cherepnya, S.; Cividini, F.; Collicott, C.; Costanza, S.; Denig, A.; Dieterle, M.; Downie, E. J.; Drexler, P.; Ferretti Bondy, M. I.; Fil'Kov, L. V.; Gardner, S.; Garni, S.; Glazier, D. I.; Gorodnov, I.; Gradl, W.; Gunther, M.; Gurevich, G. M.; Heijkenskjold, L.; Hornidge, D.; Huber, G. M.; Kaser, A.; Kashevarov, V. L.; Kay, S.; Keshelashvili, I.; Kondratiev, R.; Korolija, M.; Krusche, B.; Lazarev, A.; Livingston, K.; Lutterer, S.; Macgregor, I. J. D.; Macrae, R.; Manley, D. M.; Martel, P. P.; Mcgeorge, J. C.; Middleton, D. G.; Miskimen, R.; Mornacchi, E.; Mullen, C.; Mushkarenkov, A.; Neganov, A.; Neiser, A.; Oberle, M.; Ostrick, M.; Otte, P. B.; Paudyal, D.; Pedroni, P.; Powell, A.; Rickert, E.; Ron, G.; Rostomyan, T.; Sarty, A.; Sfienti, C.; Spieker, K.; Steffen, O.; Strakovsky, I. I.; Strandberg, B.; Strub, T.; Supek, I.; Thiel, A.; Thiel, M.; Thomas, A.; Unverzagt, M.; Usov, Y. A.; Wagner, S.; Walford, N. K.; Watts, D. P.; Werthmuller, D.; Wettig, J.; Witthauer, L.; Wolfes, M.; Zachariou, N.

doi:10.1016/j.physletb.2020.135243

The beam-helicity asymmetry was measured, for the first time, in photoproduction of π0η pairs on carbon, aluminum, and lead, with the A2 experimental setup at MAMI. The results are compared to an earlier measurement on a free proton and to the corresponding theoretical calculations. The Mainz model is used to predict the beam-helicity asymmetry for the nuclear targets. The present results indicate that the photoproduction mechanism for π0η pairs on nuclei is similar to photoproduction on a free nucleon. This process is dominated by the D33 partial wave with the ηΔ(1232) intermediate state.