Triangle Singularity as the Origin of the a(1) (1420)

Alexeev, G. D.; Alexeev, M. G.; Amoroso, A.; Andrieux, V.; Anosov, V.; Antoshkin, A.; Augsten, K.; Augustyniak, W.; Azevedo, C. D. R.; Badelek, B.; Balestra, F.; Ball, M.; Barth, J.; Beck, R.; Bedfer, Y.; Antequera, J. Berenguer; Bernhard, J.; Bodlak, M.; Bradamante, F.; Bressan, A.; Burtsev, V. E.; Chang, W.-C.; Chatterjee, C.; Chiosso, M.; Chumakov, A. G.; Chung, S.-U.; Cicuttin, A.; Correia, P. M. M.; Crespo, M. L.; D'Ago, D.; Dalla Torre, S.; Dasgupta, S. S.; Dasgupta, S.; Denisenko, I.; Denisov, O. Yu.; Donskov, S. V.; Doshita, N.; Dreisbach, Ch.; Duennweber, W.; Dusaev, R. R.; Efremov, A.; Eversheim, P. D.; Faccioli, P.; Faessler, M.; Finger, M.; Finger, M.; Fischer, H.; Franco, C.; Friedrich, J. M.; Frolov, V.; Gautheron, F.; Gavrichtchouk, O. P.; Gerassimov, S.; Giarra, J.; Gnesi, I.; Gorzellik, M.; Grasso, A.; Gridin, A.; Perdekamp, M. Grosse; Grube, B.; Guskov, A.; von Harrach, D.; Heitz, R.; Herrmann, F.; Horikawa, N.; d'Hose, N.; Hsieh, C.-Y.; Huber, S.; Ishimoto, S.; Ivanov, A.; Iwata, T.; Jandek, M.; Jary, V.; Joosten, R.; Joerg, P.; Kabuss, E.; Kaspar, F.; Kerbizi, A.; Ketzer, B.; Khaustov, G. V.; Khokhlov, Yu. A.; Kisselev, Yu.; Klein, F.; Koivuniemi, J. H.; Kolosov, V. N.; Horikawa, K. Kondo; Konorov, I.; Konstantinov, V. F.; Kotzinian, A. M.; Kouznetsov, O. M.; Koval, A.; Kral, Z.; Krinner, F.; Kulinich, Y.; Kunne, F.; Kurek, K.; Kurjata, R. P.; Kveton, A.; Lavickova, K.; Levorato, S.; Lian, Y. -S.; Lichtenstadt, J.; Lin, P.-J.; Longo, R.; Lyubovitskij, V. E.; Maggiora, A.; Magnon, A.; Makins, N.; Makke, N.; Mallot, G. K.; Maltsev, A.; Mamon, S. A.; Marianski, B.; Martin, A.; Marzec, J.; Matousek, J.; Matsuda, T.; Mattson, G.; Meshcheryakov, G. V.; Meyer, M.; Meyer, W.; Mikhailov, Yu. V.; Mikhasenko, M.; Mitrofanov, E.; Mitrofanov, N.; Miyachi, Y.; Moretti, A.; Nagaytsev, A.; Naim, C.; Neyret, D.; Novy, J.; Nowak, W.-D.; Nukazuka, G.; Nunes, A. S.; Olshevsky, A. G.; Ostrick, M.; Panzieri, D.; Parsamyan, B.; Paul, S.; Pekeler, H.; Peng, J.-C.; Pesek, M.; Peshekhonov, D. V.; Peskova, M.; Pierre, N.; Platchkov, S.; Pochodzalla, J.; Polyakov, V. A.; Pretz, J.; Quaresma, M.; Quintans, C.; Reicherz, G.; Riedl, C.; Rudnicki, T.; Ryabchikov, D. I.; Rybnikov, A.; Rychter, A.; Samoylenko, V. D.; Sandacz, A.; Sarkar, S.; Savin, I. A.; Sbrizzai, G.; Schmieden, H.; Selyunin, A.; Sinha, L.; Slunecka, M.; Smolik, J.; Srnka, A.; Steffen, D.; Stolarski, M.; Subrt, O.; Sulc, M.; Suzuki, H.; Sznajder, P.; Tessaro, S.; Tessarotto, F.; Thiel, A.; Tomsa, J.; Tosello, F.; Townsend, A.; Tskhay, V.; Uhl, S.; Vasilishin, B. I.; Vauth, A.; Veit, B. M.; Veloso, J.; Ventura, B.; Vidon, A.; Virius, M.; Wagner, M.; Wallner, S.; Zaremba, K.; Zavada, P.; Zavertyaev, M.; Zemko, M.; Zemlyanichkina, E.; Zhao, Y. und Ziembicki, M. (2021): Triangle Singularity as the Origin of the a(1) (1420). In: Physical Review Letters, Bd. 127, Nr. 8, 82501

Abstract

The COMPASS Collaboration experiment recently discovered a new isovector resonancelike signal with axial-vector quantum numbers, the a(1)(1420), decaying to f(0)(980)(pi). With a mass too close to and a width smaller than the axial-vector ground state a(1)(1260), it was immediately interpreted as a new light exotic meson, similar to the X, Y, Z states in the hidden-charm sector. We show that a resonancelike signal fully matching the experimental data is produced by the decay of the a(1) (1260) resonance into K* (-> K pi) (K) over bar and subsequent rescattering through a triangle singularity into the coupled f(0)(980)p channel. The amplitude for this process is calculated using a new approach based on dispersion relations. The triangle-singularity model is fitted to the partial-wave data of the COMPASS experiment. Despite having fewer parameters, this fit shows a slightly better quality than the one using a resonance hypothesis and thus eliminates the need for an additional resonance in order to describe the data. We thereby demonstrate for the first time in the lightmeson sector that a resonancelike structure in the experimental data can be described by rescattering through a triangle singularity, providing evidence for a genuine three-body effect.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Physik
• Themengebiete: 500 Naturwissenschaften und Mathematik > 530 Physik
• ISSN: 0031-9007
• Sprache: Englisch