Doubly-hidden scalar heavy molecules and tetraquarks states from QCD at NLO
Résumé
Alerted by the recent LHCb discovery of exotic hadrons in the range (6.2 6.9) GeV, we present new results for the doubly-hidden scalar heavy (Q¯Q)(QQ¯) charm and beauty molecules using the inverse Laplace transform sum rule (LSR) within stability criteria and including the next-to-leading order (NLO) factorized perturbative and ⟨G3⟩ gluon condensate corrections. We also critically revisit and improve existing lowest order (LO) QCD spectral sum rules (QSSR) estimates of the (Q¯Q¯)(QQ) tetraquarks analogous states. In the example of the antiscalar-scalar molecule, we separate explicitly the contributions of the factorized and nonfactorized contributions to LO of perturbative QCD and to the ⟨αsG2⟩ gluon condensate contributions in order to disprove some criticisms on the (mis)uses of the sum rules for four-quark currents. We also reemphasize the importance to include PT radiative corrections for heavy quark sum rules in order to justify the (ad hoc) definition and value of the heavy quark mass used frequently at LO in the literature. Our LSR results for tetraquark masses summarized in Table II are compared with the ones from ratio of moments (MOM) at NLO and results from LSR and ratios of MOM at LO (Table IV). The LHCb broad structure around (6.2–6.7) GeV can be described by the η¯cηc, J/ψ¯J/ψ and χ¯c1χc1 molecules or/and their analogue tetraquark scalar-scalar, axial-axial and vector-vector lowest mass ground states. The peak at (6.8–6.9) GeV can be likely due to a χ¯c0χc0 molecule or/and a pseudoscalar-pseudoscalar tetraquark state. Similar analysis is done for the scalar beauty states whose masses are found to be above the η¯bηb and ϒ¯(1S)ϒ(1S) thresholds.
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