Triangle Singularity as the Origin of the $a_1(1420)$
Creators: name: Alexeev, G. D.
name: Alexeev, M. G.
name: Amoroso, A.
name: Andrieux, V.
name: Anosov, V.
name: Antoshkin, A.
name: Augsten, K.
name: Augustyniak, W.
name: Azevedo, C. D. R.
name: Badelek, B.
name: Balestra, F.
name: Ball, M.
name: Barth, J.
name: Beck, R.
name: Bedfer, Y.
name: Antequera, J. Berenguer
name: Bernhard, J.
name: Bodlak, M.
name: Bradamante, F.
name: Bressan, A.
name: Burtsev, V. E.
name: Chang, W. -C.
name: Chatterjee, C.
name: Chiosso, M.
name: Chumakov, A. G.
name: Chung, S. -U.
name: Cicuttin, A.
name: Correia, P. M. M.
name: Crespo, M. L.
name: D'Ago, D.
name: Torre, S. Dalla
name: Dasgupta, S. S.
name: Dasgupta, S.
name: Denisenko, I.
name: Denisov, O. Yu.
name: Donskov, S. V.
name: Doshita, N.
name: Dreisbach, Ch.
name: Duennweber, W.
name: Dusaev, R. R.
name: Efremov, A.
name: Eversheim, P. D.
name: Faccioli, P.
name: Faessler, M.
name: Finger, M.
name: Finger, M.
name: Fischer, H.
name: Franco, C.
name: Friedrich, J. M.
name: Frolov, V.
name: Gautheron, F.
name: Gavrichtchouk, O. P.
name: Gerassimov, S.
name: Giarra, J.
name: Gnesi, I.
name: Gorzellik, M.
name: Grasso, A.
name: Gridin, A.
name: Perdekamp, M. Grosse
name: Grube, B.
name: Guskov, A.
name: von Harrach, D.
name: Heitz, R.
name: Herrmann, F.
name: Horikawa, N.
name: d'Hose, N.
name: Hsieh, C. -Y.
name: Huber, S.
name: Ishimoto, S.
name: Ivanov, A.
name: Iwata, T.
name: Jandek, M.
name: Jary, T.
name: Joosten, R.
name: Joerg, P.
name: Kabuss, E.
name: Kaspar, F.
name: Kerbizi, A.
name: Ketzer, B.
name: Khaustov, G. V.
name: Khokhlov, Yu. A.
name: Kisselev, Yu.
name: Klein, F.
name: Koivuniemi, J. H.
name: Kolosov, V. N.
name: Kondo, K.
name: Konorov, I.
name: Konstantinov, V. F.
name: Kotzinian, A. M.
name: Kouznetsov, O. M.
name: Koval, A.
name: Kral, Z.
name: Krinner, F.
name: Kulinich, Y.
name: Kunne, F.
name: Kurek, K.
name: Kurjata, R. P.
name: Kveton, A.
name: Lavickova, K.
name: Levorato, S.
name: Lian, Y. -S.
name: Lichtenstadt, J.
name: Lin, P. -J.
name: Longo, R.
name: Lyubovitskij, V. E.
name: Maggiora, A.
name: Magnon, A.
name: Makins, N.
name: Makke, N.
name: Mallot, G. K.
name: Maltsev, A.
name: Mamon, S. A.
name: Marianski, B.
name: Martin, A.
name: Marzec, J.
name: Matousek, J.
name: Matsuda, T.
name: Mattson, G.
name: Meshcheryakov, G. V.
name: Meyer, M.
name: Meyer, W.
name: Mikhailov, Yu. V.
name: Mikhasenko, M.
name: Mitrofanov, E.
name: Mitrofanov, N.
name: Miyachi, Y.
name: Moretti, A.
name: Nagaytsev, A.
name: Naim, C.
name: Neyret, D.
name: Novy, J.
name: Nowak, W. -D.
name: Nukazuka, G.
name: Nunes, A. S.
name: Olshevskiy, A. G.
name: Ostrick, M.
name: Panzieri, D.
name: Parsamyan, B.
name: Paul, S.
name: Pekeler, H.
name: Peng, J. -C.
name: Pesek, M.
name: Peshekhonov, D. V.
name: Peskova, M.
name: Pierre, N.
name: Platchkov, S.
name: Pochodzalla, J.
name: Polyakov, V. A.
name: Pretz, J.
name: Quaresma, M.
name: Quintans, C.
name: Reicherz, G.
name: Riedl, C.
name: Rudnicki, T.
name: Ryabchikov, D. I.
name: Rybnikov, A.
name: Rychter, A.
name: Samoylenko, V. D.
name: Sandacz, A.
name: Sarkar, S.
name: Savin, I. A.
name: Sbrizzai, G.
name: Schmieden, H.
name: Selyunin, A.
name: Sinha, L.
name: Slunecka, M.
name: Smolik, J.
name: Srnka, A.
name: Steffen, D.
name: Stolarski, M.
name: Subrt, O.
name: Sulc, M.
name: Suzuki, H.
name: Sznajder, P.
name: Tessaro, S.
name: Tessarotto, F.
name: Thiel, A.
name: Tomsa, J.
name: Tosello, F.
name: Townsend, A.
name: Tskhay, V.
name: Uhl, S.
name: Vasilishin, B. I.
name: Vauth, A.
name: Veit, B. M.
name: Veloso, J.
name: Ventura, B.
name: Vidon, A.
name: Virius, M.
name: Wagner, M.
name: Wallner, S.
name: Zaremba, K.
name: Zavada, P.
name: Zavertyaev, M.
name: Zemko, M.
name: Zemlyanichkina, E.
name: Zhao, Y.
name: Ziembicki, M.
Publisher: name: arXiv
Year: 2020
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: The COMPASS experiment recently discovered a new isovector resonance-like signal with axial-vector quantum numbers, the $a_1(1420)$, decaying to $f_0(980)π$. 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 resonance-like signal fully matching the experimental data is produced by the decay of the $a_1(1260)$ resonance into $K^\ast(\to Kπ)\bar{K}$ and subsequent rescattering through a triangle singularity into the coupled $f_0(980)π$ 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 less 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 light-meson sector that a resonance-like structure in the experimental data can be described by rescattering through a triangle singularity, providing evidence for a genuine three-body effect.
description: 7 pages, 5 figures