{"paper":{"title":"Observation of a new narrow axial-vector meson $a_1(1420)$","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"hep-ex","authors_text":"A.A. Lednev, A. Amoroso, A. Austregesilo, A. Bressan, A. Cicuttin, A. Efremov, A. Ferrero, A.G. Olshevsky, A. Grasso, A. Guskov, A. Ivanov, A. Lehmann, A. Maggiora, A. Magnon, A. Martin, A.M. Kotzinian, A. Nagaytsev, A. Rychter, A. Sandacz, A. Selyunin, A.S. Nunes, A. Srnka, A. Szabelski, A. Zink, B. Badelek, B. Grube, B. Ketzer, B. Parsamyan, C. Adolph, C. Azevedo, C. Braun, C. Franco, C. Marchand, C. Quintans, C. Regali, C. Riedl, C. Santos, C.-Yu Hsieh, D. Hahne, D.I. Ryabchikov, D. Neyret, D. Panzieri, D. von Harrach, D.V. Peshekhonov, E. Burtin, E. Kabuss, E. R. Bielert, E. Rocco, E. Zemlyanichkina, F. Balestra, F. Bradamante, F. Gautheron, F. Haas, F. Herrmann, F.H. Heinsius, F. Hinterberger, F. Klein, F. Krinner, F. Kunne, F. Nerling, F. Pereira, F. Sozzi, F. Tessarotto, F. Thibaud, G.D. Alexeev, G.K. Mallot, G. Meshcheryakov, G. Reicherz, G. Sbrizzai, G.V. Khaustov, H. Fischer, H. Matsuda, H. Schmieden, H. Suzuki, I.A. Savin, I. Choi, I. Gnesi, I. Konorov, I. Orlov, J. Barth, J. Bernhard, J. Bisplinghoff, J.-C. Peng, J.H. Koivuniemi, J. Lichtenstadt, J. Marzec, J. Matousek, J.M. Friedrich, J. Novy, J. Pochodzalla, J. Pretz, J. Ter Wolbeek, J. Veloso, K. Bicker, K. Klimaszewski, K. Koenigsmann, K. Kondo, K. Kurek, K. Schmidt, K. Schoenning, K. Zaremba, L. Dhara, L. Silva, L. Sinha, M. Bodlak, M. Boer, M. Buechele, M. Chiosso, M. Dziewiecki, M. Faessler, M. Finger, M. Finger Jr., M.G. Alexeev, M. Gorzellik, M. Grosse-Perdekamp, M. Kraemer, M.L. Crespo, M. Levillain, M. Ostrick, M. Pesek, M. Quaresma, M. Slunecka, M. Stolarski, M. Sulc, M. Virius, M. Wilfert, M. Zavertyaev, M. Ziembicki, N. d'Hose, N. Doshita, N. du Fresne von Hohenesche, N. Horikawa, N. Kuchinski, N. Makins, N. Makke, N.S. Rossiyskaya, O. Kouznetsov, O.P. Gavrichtchouk, O.Yu. Denisov, O.Yu. Shevchenko, P. Bordalo, P.D. Eversheim, P. Joerg, P. Kremser, P. Schiavon, P. Sznajder, Q. Curiel, R. Akhunzyanov, R. Beck, R. Birsa, R. Hashimoto, R. Jahn, R. Joosten, R.P. Kurjata, S. Dalla Torre, S. Dasgupta, S. Gerassimov, S. Grabmueller, S. Huber, S. Ishimoto, S. Levorato, S. Paul, S. Platchkov, S. Ramos, S. Sarkar, S. Schopferer, S.S. Dasgupta, S. Sirtl, S. Takekawa, S. Tessaro, S.U. Chung, S. Uhl, S.V. Donskov, S. Wallner, T. Grussenmeyer, T. Iwata, T. Matsuda, T. Michigami, T. Nagel, T. Schlueter, T. Szameitat, T. Weisrock, V. Andrieux, V. Anosov, V.A. Polyakov, V.D. Samoylenko, V. Duic, V.F. Konstantinov, V. Frolov, V.I. Nikolaenko, V. Jary, V.N. Kolosov, V. Tskhay, W.-C. Chang, W.-D. Nowak, W Duennweber, W. Eyrich, W. Meyer, Y. Bedfer, Y. Miyachi, Yu.A. Khokhlov, Yu. Ivanshin, Yu. Kisselev, Yu.V. Mikhailov, Z.V. Kroumchtein","submitted_at":"2015-01-23T07:55:11Z","abstract_excerpt":"The COMPASS collaboration at CERN has measured diffractive dissociation of 190 GeV/$c$ pions into the $\\pi^-\\pi^-\\pi^+$ final state using a stationary hydrogen target. A partial-wave analysis (PWA) was performed in bins of $3\\pi$ mass and four-momentum transfer using the isobar model and the so far largest PWA model consisting of 88 waves. A narrow $J^{PC} = 1^{++}$ signal is observed in the $f_0(980)\\,\\pi$ channel. We present a resonance-model study of a subset of the spin-density matrix selecting $3\\pi$ states with $J^{PC} = 2^{++}$ and $4^{++}$ decaying into $\\rho(770)\\,\\pi$ and with $J^{PC"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1501.05732","kind":"arxiv","version":3},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}