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    Adlarson, P.; Augustyniak, W.; Bardan, W.; Bashkanov, M.; Bergmann, F.S.; Berłowski, M.; Bondar, A.; Büscher, M.; Calén, H.; Ciepał, I.; Clement, H.; Czerwiński, E.; Demmich, K.; Engels, R.; Erven, A.; Erven, W.; Eyrich, W.; Fedorets, P.; Föhl, K.; Fransson, K.; Goldenbaum, F.; Goswami, A.; Grigoryev, K.; Gullström, C.-O.; Hanhart, C.; Heijkenskjöld, L.; Hejny, V.; Hüsken, N.; Jarczyk, L.; Johansson, T.; Kamys, B.; Kemmerling, G.; Khatri, G.; Khoukaz, A.; Khreptak, O.; Kirillov, D.A.; Kistryn, S.; Kleines, H.; Kłos, B.; Krzemień, W.; Kulessa, P.; Kupść, A.; Kuzmin, A.; Lalwani, K.; Lersch, D.; Lorentz, B.; Magiera, A.; Maier, R.; Marciniewski, P.; Mariański, B.; Morsch, H.-P.; Moskal, P.; Ohm, H.; Parol, W.; Perez del Rio, E.; Piskunov, N.M.; Prasuhn, D.; Pszczel, D.; Pysz, K.; Pyszniak, A.; Ritman, J.; Roy, A.; Rudy, Z.; Rundel, O.; Sawant, S.; Schadmand, S.; Schätti-Ozerianska, I.; Sefzick, T.; Serdyuk, V.; Shwartz, B.; Sitterberg, K.; Skorodko, T.; Skurzok, M.; Smyrski, J.; Sopov, V.; Stassen, R.; Stepaniak, J.; Stephan, E.; Sterzenbach, G.; Stockhorst, H.; Ströher, H.; Szczurek, A.; Trzciński, A.; Wolke, M.; Wrońska, A.; Wüstner, P.; Yamamoto, A.; Zabierowski, J.; Zieliński, M.J.; Złomańczuk, J.; Żuprański, P.; Żurek, M.

    Physics letters. B, 06/2018, Letnik: 781
    Journal Article

    This letter reports a first quantitative analysis of the contribution of higher partial waves in the charge symmetry breaking reaction dd→4Heπ0 using the WASA-at-COSY detector setup at an excess energy of Q=60MeV. The determined differential cross section can be parametrized as dσ/dΩ=a+bcos2⁡θ⁎, where θ⁎ is the production angle of the pion in the center-of-mass coordinate system, and the results for the parameters are a=(1.55±0.46(stat)+0.32−0.8(syst))pb/sr and b=(13.1±2.1(stat)−2.7+1.0(syst))pb/sr. The data are compatible with vanishing p-waves and a sizable d-wave contribution. This finding should strongly constrain the contribution of the Δ isobar to the dd→4Heπ0 reaction and is, therefore, crucial for a quantitative understanding of quark mass effects in nuclear production reactions.