Kavli Affiliate: Jonathan L. Rosner
| First 5 Authors: Marek Karliner, Jonathan L. Rosner, , ,
| Summary:
Structure in the di-$J/psi$ mass spectrum observed by the LHCb experiment
around 6.9 and 7.2 GeV is interpreted in terms of $J^{PC}=0^{++}$ and $2^{++}$
resonances between a $cc$ diquark and a $bar c bar c$ antidiquark, using a
recently confirmed string-junction picture to calculate tetraquark masses. The
main peak around 6.9 GeV is likely dominated by the $0^{++}(2S)$ state, a
radial excitation of the $cc$-$bar c bar c$ tetraquark, which we predict at
$6.871pm 0.025$ GeV. The dip around 6.75 GeV is ascribed to the opening of the
Swave di-$chi_{c0}$ channel, while the dip around 7.2 GeV could be
correlated with the opening of the di-$eta_c(2S)$ or $Xi_{cc} bar Xi_{cc}$
channel. The low-mass part of the di-$J/psi$ structure appears to require a
broad resonance consistent with a predicted $2^{++}(1S)$ state with invariant
mass around $M_{rm inv} = 6400$ MeV. Implications for $bb bar b bar b$
tetraquarks are discussed.
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