Hybrid phenomenology in a chiral approach
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Hybrid phenomenology in a chiral approach Walaa I. Eshraim1,2 , Christian S. Fischer1,3 , Francesco Giacosa2,4,a Denis Parganlija5,6
,
1 Institute for Theoretical Physics, Justus-Liebig University, Heinrich-Buff-Ring 16, 35392 Giessen,
Germany
2 Institute for Theoretical Physics, Goethe University, Max-von-Laue-Str. 1, 60438 Frankfurt am Main,
Germany
3 Helmholtz Forschungsakademie Hessen für FAIR (HFHF), GSI Helmholtzzentrum für
Schwerionenforschung, Campus Gießen, 35392 Gießen, Germany
4 Institute of Physics, Jan Kochanowski University, ul. Uniwersytecka 7, 25-406 Kielce, Poland 5 Institute for Theoretical Physics, Vienna University of Technology, Wiedner Hauptstr. 8-10, 1040 Vienna,
Austria
6 Verbund AG, Information Security and Digitalisation, Am Hof 6a, 1010 Vienna, Austria
Received: 20 January 2020 / Accepted: 29 October 2020 © Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2021
Abstract We calculate masses and decays of the (lightest) hybrid nonet with exotic quantum numbers J PC = 1−+ and the nonet of their chiral partners with J PC = 1+− in the framework hyb of the extended Linear Sigma Model (eLSM). As an input, we identify π1 = π1 (1600) as a low-lying hybrid. We investigated interaction terms which fulfill chiral symmetry. For what hyb hyb hyb concerns π1 , the most important decays are π1 → b1 π, π1 (1600) → ρπη, π1 → ρπ, hyb hyb hyb and π1 → K K ∗ (892). The decays π1 → ηπ and π1 → η π are expected to be small but nonzero: they follow from a chirally symmetric interaction term that breaks explicitly the axial anomaly. For all the other members of the two hybrid nonets (for which no experimental candidates exist yet), we report decay ratios that may guide ongoing and future experiments.
1 Introduction The search for hybrids is an important part of experimental as well as theoretical hadronic physics, see, e.g., Refs. [1,2] for reviews. Lattice QCD predicts a rich spectrum of hybrids below 5 GeV [3–8] , but up to now no predominantly hybrid state could be unambiguously assigned to one of the mesons listed in the PDG [9]. Yet, two states with “exotic”1 quantum numbers J PC = 1−+ are listed below 2 GeV: π1 (1400) and π1 (1600). Recent results by COMPASS confirmed the state π1 (1600) and led to a revival of interest in this topic [10]. At the Jefferson Lab (JLAB), the GlueX [11] and CLAS12 [12] experiments are actively searching for more states. At the ongoing BESIII experiment [13–15], hybrids can be deter-
a e-mail: [email protected] (corresponding author) 1 Here and in the following we use the term “exotic” to indicate quantum numbers that are not possible for
quark–antiquark states in the nonrelativistic quark model. The term “crypto-exotic” is reserved for mesons with non-exotic quantum numbers, but valence content is beyond the nonrelativistic quark model, such as hybrids, glueballs, and tetraquarks. 0123456789().: V,-vol
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mined through decays of charmonia. In the future, one expects n
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