Regular Article - Theoretical Physics
Deciphering the recently discovered tetraquark candidates around 6.9 GeV
The Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Ramat Aviv, 69978, Tel Aviv, Israel
2 Okinawa Institute of Science and Technology, 1919-1 Tancha, Onna-son, 904-0495, Okinawa, Japan
Accepted: 28 December 2020
Published online: 13 January 2021
Recently a novel hadronic state of mass 6.9 GeV, that decays mainly to a pair of charmonia, was observed in LHCb. The data also reveals a broader structure centered around 6490 MeV and suggests another unconfirmed resonance centered at around 7240 MeV, very near to the threshold of two doubly charmed baryons. We argue in this note that these exotic hadrons are genuine tetraquarks and not molecules of charmonia. It is conjectured that they are V-baryonium , namely, have an inner structure of a baryonic vertex with a cc diquark attached to it, which is connected by a string to an anti-baryonic vertex with a anti-diquark. We examine these states as the analogs of the V-baryonium states and Y(4630)/ which are charmonium-like tetraquarks. One way to test these claims is by searching for a significant decay of the state at 7.2 GeV into . Such a decay would be the analog of the decay of the state Y(4630) into to . We further argue that there should be trajectories of both orbital and radial excited states of the X(6900). We predict their masses. It is possible that a few of these states have already been seen by LHCb.
© The Author(s) 2021
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