Zooming in on Multiquark Hadrons within QCD Sum-Rule Approaches

¹ Institute for High Energy Physics, Austrian Academy of Sciences, Nikolsdorfergasse 18, A-1050 Vienna, Austria
² D. V. Skobeltsyn Institute of Nuclear Physics, M. V. Lomonosov Moscow State University, 119991 Moscow, Russia
³ Joint Institute for Nuclear Research, 141980 Dubna, Russia
⁴ Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria
⁵ Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France

^* e-mail: Wolfgang.Lucha@oeaw.ac.at
^** e-mail: dmitri_melikhov@gmx.de
^*** e-mail: sazdjian@ijclab.in2p3.fr

Published online: 22 December 2022

Abstract

Aiming at self-consistent descriptions of multiquark hadrons (such as tetraquarks, pentaquarks, hexaquarks) by means of QCD sum rules, we note that the totality of contributions to two-point or three-point correlation functions that involve, respectively, either two or just a single operator capable of interpolating the particular multiquark under study can be straightforwardly disentangled into two disjoint classes defined by unambiguously identifiable members. The first is formed by so-called multiquark-phile contributions which indeed might support multiquarks. In the case of flavour-exotic tetraquarks, by definition composed of four (anti–) quarks of mutually different flavours, a tetraquark-phile contribution has to exhibit two or more gluon exchanges of appropriate topology. The second consists of contributions evidently not bearing any relation to multiquarks; these must be discarded when studying multiquarks by QCD sum rules. The first class only should enter the “multiquark-adequate” QCD sum rules for exotic hadrons.