Exotic meson <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn></mml:mrow></mml:msub><mml:mo stretchy="false">(</mml:mo><mml:mn>1600</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:math> with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>J</mml:mi><mml:mrow><mml:mi>P</mml:mi><mml:mi>C</mml:mi></mml:mrow></mml:msup><mml:mo>=</mml:mo><mml:msup><mml:mn>1</mml:mn><mml:mrow><mml:mo>−</mml:mo><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:math> and its decay into <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>ρ</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>770</mml:mn><mml:mo stretchy="false">)</mml:mo><mml:mi>π</mml:mi></mml:mrow></mml:math>
G. D. Alexeev, M. Alexeev, A. Amoroso, V. Andrieux, V. Anosov, K. Augsten, W. Augustyniak, C.D.R. Azevedo, B. Badełek, F. Balestra, M. Ball, J. Barth, R. Beck, Y. Bedfer, J. Berenguer Antequera, J. Bernhard, M. Bodlak, F. Bradamante, A. Bressan, V. E. Burtsev, W. C. Chang, C. Chatterjee, M. Chiosso, A. G. Chumakov, S. U. Chung, A. Cicuttin, P. M. M. Correia, M.L. Crespo, D. D’Ago, S. Dalla Torre, S. Dasgupta, S. Dasgupta, I. Denisenko, O.Yu. Denisov, S. V. Donskov, N. Doshita, Ch. Dreisbach, W. Dünnweber, R. R. Dusaev, A. Efremov, D. Eremeev, P.D. Eversheim, P. Faccioli, M. Faessler, M. Finger, M. Finger, H. Fischer, K. Floethner, C. Franco, J. M. Friedrich, V. Frolov, L.G. Garcia Ordòñez, F. Gautheron, O.P. Gavrichtchouk, S. Gerassimov, D. Giordano, D. Giordano, M. Gorzellik, A. Grasso, A. Gridin, M. Große Perdekamp, B. Grube, M. Grüner, A. Guskov, F. Haas, D. von Harrach, R. Heitz, M. Hoffmann, N. Horikawa, N. d’Hose, C.-Y. Hsieh, S. Huber, S. Ishimoto, A. Ivanov, T. Iwata, M. Jandek, V. Jary, R. Joosten, E. Kabuß, F. Kaspar, A. Kerbizi, B. Ketzer, G. V. Khaustov, Yu.A. Khokhlov, Yu. Kisselev, F. Klein, J.H. Koivuniemi, J.H. Koivuniemi, I. Konorov, V. F. Konstantinov, A.M. Kotzinian, O. M. Kouznetsov, A. Koval, Zdeněk Král, F. Krinner, F. Kunne, K. Kurek, R. Kurjata, A. Kveton, K Lavickova
Abstract
We study the spin-exotic J PC 1 - amplitude in single-diffractive dissociation of 190 GeV=c pions into - - using a hydrogen target and confirm the 1 1600 770 amplitude, which interferes with a nonresonant 1 - amplitude. We demonstrate that conflicting conclusions from previous studies on these amplitudes can be attributed to different analysis models and different treatment of the dependence of the amplitudes on the squared four-momentum transfer and we thus reconcile these experimental findings. We study the nonresonant contributions to the - - final state using pseudodata generated on the basis of a Deck model. Subjecting pseudodata and real data to the same partial-wave analysis, we find good agreement concerning the spectral shape and its dependence on the squared four-momentum transfer for the J PC 1 - amplitude and also for amplitudes with other J PC quantum numbers. We investigate for the first time the amplitude of the - subsystem with J PC 1 --in the 3 amplitude with J PC 1 - employing the novel freed-isobar analysis scheme. We reveal this - amplitude to be dominated by the 770 for both the 1 1600 and the nonresonant contribution. These findings largely confirm the underlying assumptions for the isobar model used in all previous partial-wave analyses addressing the J PC 1 - amplitude.