Abstract
Constituent mass predictions for axial vector (i.e., $J^P=1^+$) $cc$ and $bb$ colour antitriplet diquarks are generated using QCD Laplace sum-rules. We calculate the diquark correlator within the operator product expansion to NLO, including terms proportional to the four- and six-dimensional gluon and six-dimensional quark condensates. The sum-rules analyses stabilize, and we find that the mass of the $cc$ diquark is 3.51~GeV and the mass of the $bb$ diquark is 8.67~GeV. Using these diquark masses as inputs, we calculate several tetraquark masses within the Type-II diquark-antidiquark tetraquark model.
Highlights
Outside-the-quark-model hadrons consisting of four valence quarks have been theorized for decades
The sum-rule analyses stabilize, and we find that the constituent mass of the cc diquark is ð3.51 Æ 0.35Þ GeV and the constituent mass of the bb diquark is ð8.67 Æ 0.69Þ GeV
These hadrons, collectively referred to as the XYZ resonances, are difficult to explain within the quark model [8]
Summary
Outside-the-quark-model hadrons consisting of four (or more) valence quarks have been theorized for decades. Since more and more of these hadrons have been discovered in the heavy quarkonium spectra These hadrons, collectively referred to as the XYZ resonances, are difficult to explain within the quark model [8]. Color antitriplet pairs of quarks within a hadron. We use QCD Laplace sum rules (LSRs) to calculate the constituent masses of axial vector (i.e., JP 1⁄4 1þ) cc and bb diquarks. We use the operator product expansion (OPE) [38] to compute the correlation function between a pair of diquark currents (1) and (2) In this calculation, in addition to leading-order (LO) pertubative contributions, we include next-to-leading-order (NLO) perturbative contributions and nonperturbative corrections proportional to the four-dimensional (4D) and 6D gluon condensates as well as the 6D quark condensate.
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