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ISSN - 03702693, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2017, vol. 770, p. 418-425

Measurement of the ω → π<sup>+</sup>π<sup>−</sup>π<sup>0</sup> Dalitz plot distribution

Adlarson P., Augustyniak W., Bardan W., Bashkanov M., Bergmann F. S., Berłowski M., Bhatt H., 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., Heijkenskjöld L., Hejny V., Hüsken N., Jarczyk L., Johansson T., Kamys B., Kemmerling G., Khan F. A., 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., 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.

© 2017 The Author Using the production reactions pd→He3ω and pp→ppω, the Dalitz plot distribution for the ω→π + π − π 0 decay is studied with the WASA detector at COSY, based on a combined data sample of (4.408±0.042)×10 4 events. The Dalitz plot density is parametrised by a product of the P-wave phase space and a polynomial expansion in the normalised polar Dalitz plot variables Z and ϕ. For the first time, a deviation from pure P-wave phase space is observed with a significance of 4.1σ. The deviation is parametrised by a linear term 1+2αZ, with α determined to be +0.147±0.036, consistent with the expectations of ρ-meson-type final-state interactions of the P-wave pion pairs.