Deciphering the recently discovered tetraquark candidates around 6.9 GeV

Jacob Sonnenschein, Dorin Weissman*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

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 Ξ cc 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 c¯ c¯ anti-diquark. We examine these states as the analogs of the V-baryonium states Ψ (4360) and Y(4630)/Ψ (4660) 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 Ξ ccΞ ¯ cc. Such a decay would be the analog of the decay of the state Y(4630) into to Λ cΛ ¯ c. 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.

Original languageEnglish
Article number25
JournalEuropean Physical Journal C
Volume81
Issue number1
DOIs
StatePublished - Jan 2021

Funding

FundersFunder number
Israel Science Foundation2289/18
Okinawa Institute of Science and Technology Graduate University

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